I am a theoretical ecologist by formation, I am generally interested in investigating factors and processes driving the dynamics of natural and harvested populations and in understanding how to use this knowledge to inform practical management.
In recent years I have been particularly interested in investigating factors and processes that provide resilience of natural or managed population to natural and anthropogenic stressors, environmental shocks and climate change. I study resilience from two very different points of view: on the one hand, I have focused my attention on populations that prove to be resilient despite our effort to control or eradicate them, namely parasitic and infectious diseases. On the other hand, I have been working extensively to understand how to increase resilience of population of commercial or conservation interest to extensive harvesting, environmental shocks, climate change and land use change.
I have been working on a number of theoretical and applied problems ranging from the conservation of the European eel to the sustainable management of the abalone fishery in Baja California in the face of climate change, the biocontrol of schistososmiasis in west Africa and the relationship between resource exploitation, infectious diseases and poverty traps.
In the last five years, I focused most of my effort on building the Program for Disease Ecology Health and the Environment as a pillar of Human and Planetary Health at Stanford University, with the ultimate goal of discovering novel ecological solutions that can improve human wellbeing and the health of the environment that underpins it.
Professor, Earth System Science
Senior Fellow, Stanford Woods Institute for the Environment
Professor (By courtesy), Biology
Faculty Affiliate, Institute for Human-Centered Artificial Intelligence (HAI)
Senior Fellow, Stanford Woods Institute for the Environment
Boards, Advisory Committees, Professional Organizations
Faculty Fellow, Stanford Center for Innovation in Global Health (2015 - Present)
Ph.D., University of Parma & University of Ferrara, Ecology (1993)
B.E. & M.Sc., Politecnico di Milano, Civil and Environmental Engineering (1989)
Current Research and Scholarly Interests
I am a population biologist and my primary research interest is the use of ecological theory, particularly life history-based models, in population dynamics and management. I make use of advanced mathematical and computational techniques to analyse a wide variety of ecological problems ranging from the identification of basic first-principles in the ecology of infectious diseases, to the analysis of costs and benefits of alternative policies for natural resource management in a multi-objective, multi-attribute framework, to the investigation of population dynamics and extinction risk in endangered populations. I dedicated a considerable effort to assess the effect of anthopogenic pressures as well as of ecological and environmental heterogeneities - including temperature, oxygen and pH anomalies - on population dynamics and management of marine resources and to estimate key parameters that may be incorporated into population models useful for decision-making. I have been working for more than two decades on the demography and management of the European eel (A. anguilla) and, more recently, the conservation of marble trout (S. marmoratus), the optimal bioeconomic management of mollusc farming, the problem of algal bloom control in Adriatic coastal lagoons and the development of Rapid Assessment Methods to assess the status of coastal lagoons. I am currently investigating how the interaction between networks of Marine Protected Areas and different schemes of fishery management might impact the resilience, productivity and persistence of the abalone fisheries in Baja California, Mexico under alternative scenarios of climate change, including increase frequency and intensity of low oxygen, low pH and variable temperature.
I recently started to work on the bio-control of schistosomiasis in Senegal with dr. Sanna Sokolow and I keep working with Luca Bolzoni on the optimal control of infectious diseases in the wildlife and in farmed animals.
My interest for pursuing solutions for a more sustainable world brought me to take a non-academic, governmental job from 2001 to 2004 as director of the Program for Technological Innovation and Sustainable Development for the Environmental Protection Agency of the Lombardy region (Italy), where I developed agreements with business and industrial associations to foster the adoption of environmental management schemes and to improve corporate environmental performances.
I am currently associated editor of Ecology Letters and reviewers for several ecological journals. From 1999 to 2005 I was president of the Italian Association of Environmental Engineering (AIAT), member of the administration board of WWF Italy (2005-2007) and, from 2007 to 2012, chair of the Ethics and Sustainability Committee of Eurizon Capital, the investment management company of Intesa SanPaolo, the first Italian Bank. In the effort to increase awareness about the threats imposed by climate change and to foster actions to curb emissions, increase energy efficiency and saving, I wrote a book “Energia e Salute della Terra” (Energy and Planet Health, Fondazione Boroli publisher) that was distributed to 40 thousands students in high schools and colleges in Italy.
I hold a BE in Civil Engineering and a MS in Environmental Engineering from Politecnico di Milano (1989, Italy), a PhD in Applied Ecology from the Universities of Ferrara and Parma (1993, Italy) a three years research experience at Princeton University (1994-1996) and three more years (1996-1998) back to Politecnico di Milano . After more than a decade at the University of Parma, in 2012 I happily moved to Stanford as full time faculty.
- Catalyzing Solutions for a Sustainable Ocean: Learning with Local Communities
BIO 123, OCEANS 123H, OCEANS 223H (Spr)
- Get to Know Your Oceans
OCEANS 300A (Aut)
- Get to Know Your Oceans
OCEANS 300B (Win)
- Human and Planetary Health
MED 103, PUBLPOL 183, SOC 103, SUSTAIN 103 (Aut)
- Introduction to Scientific Reading and Writing
OCEANS 302 (Spr)
- Managing Your PhD
OCEANS 301 (Aut)
- Quantitative Methods for Marine Ecology and Conservation
BIO 143, BIO 243, CEE 164, CEE 264H, OCEANS 143 (Win)
Independent Studies (9)
- Directed Instruction or Reading
OCEANS 198H (Aut, Win, Spr)
- Directed Investigation
BIOE 392 (Aut, Win, Spr, Sum)
- Directed Reading in Environment and Resources
ENVRES 398 (Aut, Win, Spr, Sum)
- Directed Research in Environment and Resources
ENVRES 399 (Aut, Win, Spr, Sum)
- Graduate Research
ESS 400 (Aut, Spr, Sum)
- Out-of-Department Advanced Research Laboratory in Bioengineering
BIOE 191X (Aut, Win, Spr, Sum)
OCEANS 300 (Aut, Win, Spr)
- Teaching Practicum in Biology
OCEANS 290H (Win, Spr)
- Undergraduate Research
OCEANS 199H (Aut, Win, Spr)
- Directed Instruction or Reading
Prior Year Courses
- Catalyzing Solutions for a Sustainable Ocean: Learning with Local Communities
BIO 123, BIOHOPK 123H, BIOHOPK 223H, OCEANS 123, OCEANS 223 (Spr)
- Environmental Humanities: Finding Our Place on a Changing Planet
BIO 184, ENGLISH 140D, SUSTAIN 140 (Aut)
- Human and Planetary Health
BIO 103, BIO 203, SOC 103, SUSTAIN 103 (Aut)
- Human and Planetary Health
BIO 103, BIO 203, SOC 103 (Aut)
- Managing Your PhD
BIO 305 (Aut)
- People and Nature of Monterey Bay
BIOHOPK 119H, BIOHOPK 219H (Spr)
- Quantitative methods for marine ecology and conservation
BIO 143, BIO 243, BIOHOPK 143H, BIOHOPK 243H, CEE 164H, CEE 264H, EARTHSYS 143H, EARTHSYS 243H (Win)
- Current Topics and Concepts in Quantitative Fish Dynamics and Fisheries Management
BIOHOPK 153H, BIOHOPK 253H (Win)
- HUMAN AND PLANET HEALTH
BIO 103, BIO 203 (Aut)
- Managing Your PhD
BIO 305 (Aut, Spr)
- Quantitative methods for marine ecology and conservation
BIOHOPK 143H, BIOHOPK 243H, CEE 164H, CEE 264H, EARTHSYS 143H, EARTHSYS 243H (Win)
- Catalyzing Solutions for a Sustainable Ocean: Learning with Local Communities
Graduate and Fellowship Programs
Biology (School of Humanities and Sciences) (Phd Program)
Reframing Optimal Control Problems for Infectious Disease Management in Low-Income Countries.
Bulletin of mathematical biology
2023; 85 (4): 31
Optimal control theory can be a useful tool to identify the best strategies for the management of infectious diseases. In most of the applications to disease control with ordinary differential equations, the objective functional to be optimized is formulated in monetary terms as the sum of intervention costs and the cost associated with the burden of disease. We present alternate formulations that express epidemiological outcomes via health metrics and reframe the problem to include features such as budget constraints and epidemiological targets. These alternate formulations are illustrated with a compartmental cholera model. The alternate formulations permit us to better explore the sensitivity of the optimal control solutions to changes in available budget or the desired epidemiological target. We also discuss some limitations of comprehensive cost assessment in epidemiology.
View details for DOI 10.1007/s11538-023-01137-4
View details for PubMedID 36907932
Climatic, land-use and socio-economic factors can predict malaria dynamics at fine spatial scales relevant to local health actors: Evidence from rural Madagascar.
PLOS global public health
2023; 3 (2): e0001607
While much progress has been achieved over the last decades, malaria surveillance and control remain a challenge in countries with limited health care access and resources. High-resolution predictions of malaria incidence using routine surveillance data could represent a powerful tool to health practitioners by targeting malaria control activities where and when they are most needed. Here, we investigate the predictors of spatio-temporal malaria dynamics in rural Madagascar, estimated from facility-based passive surveillance data. Specifically, this study integrates climate, land-use, and representative household survey data to explain and predict malaria dynamics at a high spatial resolution (i.e., by Fokontany, a cluster of villages) relevant to health care practitioners. Combining generalized linear mixed models (GLMM) and path analyses, we found that socio-economic, land use and climatic variables are all important predictors of monthly malaria incidence at fine spatial scales, via both direct and indirect effects. In addition, out-of-sample predictions from our model were able to identify 58% of the Fokontany in the top quintile for malaria incidence and account for 77% of the variation in the Fokontany incidence rank. These results suggest that it is possible to build a predictive framework using environmental and social predictors that can be complementary to standard surveillance systems and help inform control strategies by field actors at local scales.
View details for DOI 10.1371/journal.pgph.0001607
View details for PubMedID 36963091
View details for PubMedCentralID PMC10021226
Modeling the efficacy of CRISPR gene drive for snail immunity on schistosomiasis control.
PLoS neglected tropical diseases
2022; 16 (10): e0010894
CRISPR gene drives could revolutionize the control of infectious diseases by accelerating the spread of engineered traits that limit parasite transmission in wild populations. Gene drive technology in mollusks has received little attention despite the role of freshwater snails as hosts of parasitic flukes causing 200 million annual cases of schistosomiasis. A successful drive in snails must overcome self-fertilization, a common feature of host snails which could prevents a drive's spread. Here we developed a novel population genetic model accounting for snails' mixed mating and population dynamics, susceptibility to parasite infection regulated by multiple alleles, fitness differences between genotypes, and a range of drive characteristics. We integrated this model with an epidemiological model of schistosomiasis transmission to show that a snail population modification drive targeting immunity to infection can be hindered by a variety of biological and ecological factors; yet under a range of conditions, disease reduction achieved by chemotherapy treatment of the human population can be maintained with a drive. Alone a drive modifying snail immunity could achieve significant disease reduction in humans several years after release. These results indicate that gene drives, in coordination with existing public health measures, may become a useful tool to reduce schistosomiasis burden in selected transmission settings with effective CRISPR construct design and evaluation of the genetic and ecological landscape.
View details for DOI 10.1371/journal.pntd.0010894
View details for PubMedID 36315503
- Shifting fish distributions impact predation intensity in a sub-Arctic ecosystem ECOGRAPHY 2022
- Modelling the effect of habitat and fishing heterogeneity on the performance of a Total Allowable Catch-regulated fishery ICES JOURNAL OF MARINE SCIENCE 2022
- Rapid recovery of depleted abalone in Isla Natividad, Baja California, Mexico ECOSPHERE 2022; 13 (3)
Concomitant Immunity and Worm Senescence May Drive Schistosomiasis Epidemiological Patterns: An Eco-Evolutionary Perspective.
Frontiers in immunology
2020; 11: 160
In areas where human schistosomiasis is endemic, infection prevalence and egg output are known to rise rapidly through childhood, reach a peak at 8-15 years of age, and decline thereafter. A similar peak ("overshoot") followed by return to equilibrium infection levels sometimes occurs a year or less after mass drug administration. These patterns are usually assumed to be due to acquired immunity, which is induced by exposure, directed by the host's immune system, and develops slowly over the lifetime of the host. Other explanations that have been advanced previously include differential exposure of hosts, differential mortality of hosts, and progressive pathology. Here we review these explanations and offer a novel (but not mutually exclusive) explanation, namely that adult worms protect the host against larval stages for their own benefit ("concomitant immunity") and that worm fecundity declines with worm age ("reproductive senescence"). This explanation approaches schistosomiasis from an eco-evolutionary perspective, as concomitant immunity maximizes the fitness of adult worms by reducing intraspecific competition within the host. If correct, our hypothesis could have profound implications for treatment and control of human schistosomiasis. Specifically, if immunity is worm-directed, then treatment of long-standing infections comprised of old senescent worms could enable infection with new, highly fecund worms. Furthermore, our hypothesis suggests revisiting research on therapeutics that mimic the concomitant immunity-modulating activity of adult worms, while minimizing pathological consequences of their eggs. We emphasize the value of an eco-evolutionary perspective on host-parasite interactions.
View details for DOI 10.3389/fimmu.2020.00160
View details for PubMedID 32161583
View details for PubMedCentralID PMC7053360
Development, environmental degradation, and disease spread in the Brazilian Amazon.
2019; 17 (11): e3000526
The Amazon is Brazil's greatest natural resource and invaluable to the rest of the world as a buffer against climate change. The recent election of Brazil's president brought disputes over development plans for the region back into the spotlight. Historically, the development model for the Amazon has focused on exploitation of natural resources, resulting in environmental degradation, particularly deforestation. Although considerable attention has focused on the long-term global cost of "losing the Amazon," too little attention has focused on the emergence and reemergence of vector-borne diseases that directly impact the local population, with spillover effects to other neighboring areas. We discuss the impact of Amazon development models on human health, with a focus on vector-borne disease risk. We outline policy actions that could mitigate these negative impacts while creating opportunities for environmentally sensitive economic activities.
View details for DOI 10.1371/journal.pbio.3000526
View details for PubMedID 31730640
Precision mapping of snail habitat provides a powerful indicator of human schistosomiasis transmission.
Proceedings of the National Academy of Sciences of the United States of America
Recently, the World Health Organization recognized that efforts to interrupt schistosomiasis transmission through mass drug administration have been ineffective in some regions; one of their new recommended strategies for global schistosomiasis control emphasizes targeting the freshwater snails that transmit schistosome parasites. We sought to identify robust indicators that would enable precision targeting of these snails. At the site of the world's largest recorded schistosomiasis epidemic-the Lower Senegal River Basin in Senegal-intensive sampling revealed positive relationships between intermediate host snails (abundance, density, and prevalence) and human urogenital schistosomiasis reinfection (prevalence and intensity in schoolchildren after drug administration). However, we also found that snail distributions were so patchy in space and time that obtaining useful data required effort that exceeds what is feasible in standard monitoring and control campaigns. Instead, we identified several environmental proxies that were more effective than snail variables for predicting human infection: the area covered by suitable snail habitat (i.e., floating, nonemergent vegetation), the percent cover by suitable snail habitat, and size of the water contact area. Unlike snail surveys, which require hundreds of person-hours per site to conduct, habitat coverage and site area can be quickly estimated with drone or satellite imagery. This, in turn, makes possible large-scale, high-resolution estimation of human urogenital schistosomiasis risk to support targeting of both mass drug administration and snail control efforts.
View details for DOI 10.1073/pnas.1903698116
View details for PubMedID 31659025
Ecological interventions to prevent and manage zoonotic pathogen spillover.
Philosophical transactions of the Royal Society of London. Series B, Biological sciences
2019; 374 (1782): 20180342
Spillover of a pathogen from a wildlife reservoir into a human or livestock host requires the pathogen to overcome a hierarchical series of barriers. Interventions aimed at one or more of these barriers may be able to prevent the occurrence of spillover. Here, we demonstrate how interventions that target the ecological context in which spillover occurs (i.e. ecological interventions) can complement conventional approaches like vaccination, treatment, disinfection and chemical control. Accelerating spillover owing to environmental change requires effective, affordable, durable and scalable solutions that fully harness the complex processes involved in cross-species pathogen spillover. This article is part of the theme issue 'Dynamic and integrative approaches to understanding pathogen spillover'.
View details for DOI 10.1098/rstb.2018.0342
View details for PubMedID 31401951
Unavoidable Risks: Local Perspectives on Water Contact Behavior and Implications for Schistosomiasis Control in an Agricultural Region of Northern Senegal.
The American journal of tropical medicine and hygiene
Human schistosomiasis is a snail-borne parasitic disease affecting more than 200 million people worldwide. Direct contact with snail-infested freshwater is the primary route of exposure. Water management infrastructure, including dams and irrigation schemes, expands snail habitat, increasing the risk across the landscape. The Diama Dam, built on the lower basin of the Senegal River to prevent saltwater intrusion and promote year-round agriculture in the drought-prone Sahel, is a paradigmatic case. Since dam completion in 1986, the rural population-whose livelihoods rely mostly on agriculture-has suffered high rates of schistosome infection. The region remains one of the most hyperendemic regions in the world. Because of the convergence between livelihoods and environmental conditions favorable to transmission, schistosomiasis is considered an illustrative case of a disease-driven poverty trap (DDPT). The literature to date on the topic, however, remains largely theoretical. With qualitative data generated from 12 focus groups in four villages, we conducted team-based theme analysis to investigate how perception of schistosomiasis risk and reported preventive behaviors may suggest the presence of a DDPT. Our analysis reveals three key findings: 1) rural villagers understand schistosomiasis risk (i.e., where and when infections occur), 2) accordingly, they adopt some preventive behaviors, but ultimately, 3) exposure persists, because of circumstances characteristic of rural livelihoods. These findings highlight the capacity of local populations to participate actively in schistosomiasis control programs and the limitations of widespread drug treatment campaigns. Interventions that target the environmental reservoir of disease may provide opportunities to reduce exposure while maintaining resource-dependent livelihoods.
View details for DOI 10.4269/ajtmh.19-0099
View details for PubMedID 31452497
- Modelled effects of prawn aquaculture on poverty alleviation and schistosomiasis control NATURE SUSTAINABILITY 2019; 2 (7): 611–20
Gene drives for schistosomiasis transmission control.
PLoS neglected tropical diseases
2019; 13 (12): e0007833
Schistosomiasis is one of the most important and widespread neglected tropical diseases (NTD), with over 200 million people infected in more than 70 countries; the disease has nearly 800 million people at risk in endemic areas. Although mass drug administration is a cost-effective approach to reduce occurrence, extent, and severity of the disease, it does not provide protection to subsequent reinfection. Interventions that target the parasites' intermediate snail hosts are a crucial part of the integrated strategy required to move toward disease elimination. The recent revolution in gene drive technology naturally leads to questions about whether gene drives could be used to efficiently spread schistosome resistance traits in a population of snails and whether gene drives have the potential to contribute to reduced disease transmission in the long run. Responsible implementation of gene drives will require solutions to complex challenges spanning multiple disciplines, from biology to policy. This Review Article presents collected perspectives from practitioners of global health, genome engineering, epidemiology, and snail/schistosome biology and outlines strategies for responsible gene drive technology development, impact measurements of gene drives for schistosomiasis control, and gene drive governance. Success in this arena is a function of many factors, including gene-editing specificity and efficiency, the level of resistance conferred by the gene drive, how fast gene drives may spread in a metapopulation over a complex landscape, ecological sustainability, social equity, and, ultimately, the reduction of infection prevalence in humans. With combined efforts from across the broad global health community, gene drives for schistosomiasis control could fortify our defenses against this devastating disease in the future.
View details for DOI 10.1371/journal.pntd.0007833
View details for PubMedID 31856157
THE ROLE OF IRRIGATED AGRICULTURE IN SCHISTOSOMIASIS RISK IN A DAMMED LANDSCAPE IN WEST AFRICA
AMER SOC TROP MED & HYGIENE. 2019: 11
View details for Web of Science ID 000507364502035
Potential Biological Control of Schistosomiasis by Fishes in the Lower Senegal River Basin.
The American journal of tropical medicine and hygiene
More than 200 million people in sub-Saharan Africa are infected with schistosome parasites. Transmission of schistosomiasis occurs when people come into contact with larval schistosomes emitted from freshwater snails in the aquatic environment. Thus, controlling snails through augmenting or restoring their natural enemies, such as native predators and competitors, could offer sustainable control for this human disease. Fishes may reduce schistosomiasis transmission directly, by preying on snails or parasites, or indirectly, by competing with snails for food or by reducing availability of macrophyte habitat (i.e., aquatic plants) where snails feed and reproduce. To identify fishes that might serve as native biological control agents for schistosomiasis in the lower Senegal River basin-one of the highest transmission areas for human schistosomiasis globally-we surveyed the freshwater fish that inhabit shallow, nearshore habitats and conducted multivariate analyses with quantitative diet data for each of the fish species encountered. Ten of the 16 fish species we encountered exhibited diets that may result in direct (predation) and/or indirect (food competition and habitat removal) control of snails. Fish abundance was low, suggesting limited effects on schistosomiasis transmission by the contemporary fish community in the lower Senegal River basin in the wild. Here, we highlight some native species-such as tilapia, West African lungfish, and freshwater prawns-that could be aquacultured for local-scale biological control of schistosomiasis transmission.
View details for PubMedID 30479247
Estimating the elimination feasibility in the 'end game' of control efforts for parasites subjected to regular mass drug administration: Methods and their application to schistosomiasis.
PLoS neglected tropical diseases
2018; 12 (11): e0006794
Progress towards controlling and eliminating parasitic worms, including schistosomiasis, onchocerciasis, and lymphatic filariasis, is advancing rapidly as national governments, multinational NGOs, and pharmaceutical companies launch collaborative chemotherapeutic control campaigns. Critical questions remain regarding the potential for achieving elimination of these infections, and analytical methods can help to quickly estimate progress towards-and the probability of achieving-elimination over specific timeframes. Here, we propose the effective reproduction number, Reff, as a proxy of elimination potential for sexually reproducing worms that are subject to poor mating success at very low abundance (positive density dependence, or Allee effects). Reff is the number of parasites produced by a single reproductive parasite at a given stage in the transmission cycle, over the parasite's lifetime-it is the generalized form of the more familiar basic reproduction number, R0, which only applies at the beginning of an epidemic-and it can be estimated in a 'model-free' manner by an estimator ('epsilon'). We introduce epsilon, demonstrate its estimation using simulated data, and discuss how it may be used in planning and evaluation of ongoing elimination efforts for a range of parasitic diseases.
View details for PubMedID 30418968
Agrochemicals increase risk of human schistosomiasis by supporting higher densities of intermediate hosts
2018; 9: 837
Schistosomiasis is a snail-borne parasitic disease that ranks among the most important water-based diseases of humans in developing countries. Increased prevalence and spread of human schistosomiasis to non-endemic areas has been consistently linked with water resource management related to agricultural expansion. However, the role of agrochemical pollution in human schistosome transmission remains unexplored, despite strong evidence of agrochemicals increasing snail-borne diseases of wildlife and a projected 2- to 5-fold increase in global agrochemical use by 2050. Using a field mesocosm experiment, we show that environmentally relevant concentrations of fertilizer, a herbicide, and an insecticide, individually and as mixtures, increase densities of schistosome-infected snails by increasing the algae snails eat and decreasing densities of snail predators. Epidemiological models indicate that these agrochemical effects can increase transmission of schistosomes. Identifying agricultural practices or agrochemicals that minimize disease risk will be critical to meeting growing food demands while improving human wellbeing.
View details for PubMedID 29483531
LOCAL PERCEPTIONS OF SEASONALITY AND REPORTED WATER CONTACT BEHAVIOR IN THE SAHEL: IMPLICATIONS FOR SCHISTOSOMIASIS TRANSMISSION
AMER SOC TROP MED & HYGIENE. 2018: 418–19
View details for Web of Science ID 000461386604031
- Ecological control of schistosomiasis in Sub-Saharan Africa: restoration of predator-prey dynamics to reduce transmission ECOLOGY AND EVOLUTION OF INFECTIOUS DISEASES: PATHOGEN CONTROL AND PUBLIC HEALTH MANAGEMENT IN LOW-INCOME COUNTRIES 2018: 236–51
AN ECO-EVOLUTIONARY PERSPECTIVE ON SCHISTOSOMIASIS
AMER SOC TROP MED & HYGIENE. 2018: 418
View details for Web of Science ID 000461386604028
COMPUTER VISION AND MACHINE LEARNING ENABLE ENVIRONMENTAL DIAGNOSTICS FOR TARGETING SCHISTOSOMIASIS CONTROL
AMER SOC TROP MED & HYGIENE. 2018: 418
View details for Web of Science ID 000461386604029
To Reduce the Global Burden of Human Schistosomiasis, Use 'Old Fashioned' Snail Control
TRENDS IN PARASITOLOGY
2018; 34 (1): 23–40
Control strategies to reduce human schistosomiasis have evolved from 'snail picking' campaigns, a century ago, to modern wide-scale human treatment campaigns, or preventive chemotherapy. Unfortunately, despite the rise in preventive chemotherapy campaigns, just as many people suffer from schistosomiasis today as they did 50 years ago. Snail control can complement preventive chemotherapy by reducing the risk of transmission from snails to humans. Here, we present ideas for modernizing and scaling up snail control, including spatiotemporal targeting, environmental diagnostics, better molluscicides, new technologies (e.g., gene drive), and 'outside the box' strategies such as natural enemies, traps, and repellants. We conclude that, to achieve the World Health Assembly's stated goal to eliminate schistosomiasis, it is time to give snail control another look.
View details for PubMedID 29126819
View details for PubMedCentralID PMC5819334
The spatial spread of schistosomiasis: A multidimensional network model applied to Saint-Louis region, Senegal
ADVANCES IN WATER RESOURCES
2017; 108: 406–15
Schistosomiasis is a parasitic, water-related disease that is prevalent in tropical and subtropical areas of the world, causing severe and chronic consequences especially among children. Here we study the spatial spread of this disease within a network of connected villages in the endemic region of the Lower Basin of the Senegal River, in Senegal. The analysis is performed by means of a spatially explicit metapopulation model that couples local-scale eco-epidemiological dynamics with spatial mechanisms related to human mobility (estimated from anonymized mobile phone records), snail dispersal and hydrological transport of schistosome larvae along the main water bodies of the region. Results show that the model produces epidemiological patterns consistent with field observations, and point out the key role of spatial connectivity on the spread of the disease. These findings underline the importance of considering different transport pathways in order to elaborate disease control strategies that can be effective within a network of connected populations.
View details for PubMedID 29056816
View details for PubMedCentralID PMC5637889
General ecological models for human subsistence, health and poverty
NATURE ECOLOGY & EVOLUTION
2017; 1 (8): 1153–59
The world's rural poor rely heavily on their immediate natural environment for subsistence and suffer high rates of morbidity and mortality from infectious diseases. We present a general framework for modelling subsistence and health of the rural poor by coupling simple dynamic models of population ecology with those for economic growth. The models show that feedbacks between the biological and economic systems can lead to a state of persistent poverty. Analyses of a wide range of specific systems under alternative assumptions show the existence of three possible regimes corresponding to a globally stable development equilibrium, a globally stable poverty equilibrium and bistability. Bistability consistently emerges as a property of generalized disease-economic systems for about a fifth of the feasible parameter space. The overall proportion of parameters leading to poverty is larger than that resulting in healthy/wealthy development. All the systems are found to be most sensitive to human disease parameters. The framework highlights feedbacks, processes and parameters that are important to measure in studies of rural poverty to identify effective pathways towards sustainable development.
View details for PubMedID 29046570
Nearly 400 million people are at higher risk of schistosomiasis because dams block the migration of snail-eating river prawns
PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY B-BIOLOGICAL SCIENCES
2017; 372 (1722)
Dams have long been associated with elevated burdens of human schistosomiasis, but how dams increase disease is not always clear, in part because dams have many ecological and socio-economic effects. A recent hypothesis argues that dams block reproduction of the migratory river prawns that eat the snail hosts of schistosomiasis. In the Senegal River Basin, there is evidence that prawn populations declined and schistosomiasis increased after completion of the Diama Dam. Restoring prawns to a water-access site upstream of the dam reduced snail density and reinfection rates in people. However, whether a similar cascade of effects (from dams to prawns to snails to human schistosomiasis) occurs elsewhere is unknown. Here, we examine large dams worldwide and identify where their catchments intersect with endemic schistosomiasis and the historical habitat ranges of large, migratory Macrobrachium spp. prawns. River prawn habitats are widespread, and we estimate that 277-385 million people live within schistosomiasis-endemic regions where river prawns are or were present (out of the 800 million people who are at risk of schistosomiasis). Using a published repository of schistosomiasis studies in sub-Saharan Africa, we compared infection before and after the construction of 14 large dams for people living in: (i) upstream catchments within historical habitats of native prawns, (ii) comparable undammed watersheds, and (iii) dammed catchments beyond the historical reach of migratory prawns. Damming was followed by greater increases in schistosomiasis within prawn habitats than outside prawn habitats. We estimate that one third to one half of the global population-at-risk of schistosomiasis could benefit from restoration of native prawns. Because dams block prawn migrations, our results suggest that prawn extirpation contributes to the sharp increase of schistosomiasis after damming, and points to prawn restoration as an ecological solution for reducing human disease.This article is part of the themed issue 'Conservation, biodiversity and infectious disease: scientific evidence and policy implications'.
View details for DOI 10.1098/rstb.2016.0127
View details for Web of Science ID 000399956400008
View details for PubMedID 28438916
Disease ecology, health and the environment: a framework to account for ecological and socio-economic drivers in the control of neglected tropical diseases
PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY B-BIOLOGICAL SCIENCES
2017; 372 (1722)
Reducing the burden of neglected tropical diseases (NTDs) is one of the key strategic targets advanced by the Sustainable Development Goals. Despite the unprecedented effort deployed for NTD elimination in the past decade, their control, mainly through drug administration, remains particularly challenging: persistent poverty and repeated exposure to pathogens embedded in the environment limit the efficacy of strategies focused exclusively on human treatment or medical care. Here, we present a simple modelling framework to illustrate the relative role of ecological and socio-economic drivers of environmentally transmitted parasites and pathogens. Through the analysis of system dynamics, we show that periodic drug treatments that lead to the elimination of directly transmitted diseases may fail to do so in the case of human pathogens with an environmental reservoir. Control of environmentally transmitted diseases can be more effective when human treatment is complemented with interventions targeting the environmental reservoir of the pathogen. We present mechanisms through which the environment can influence the dynamics of poverty via disease feedbacks. For illustration, we present the case studies of Buruli ulcer and schistosomiasis, two devastating waterborne NTDs for which control is particularly challenging.This article is part of the themed issue 'Conservation, biodiversity and infectious disease: scientific evidence and policy implications'.
View details for DOI 10.1098/rstb.2016.0128
View details for PubMedID 28438917
Big-data-driven modeling unveils country-wide drivers of endemic schistosomiasis
Schistosomiasis is a parasitic infection that is widespread in sub-Saharan Africa, where it represents a major health problem. We study the drivers of its geographical distribution in Senegal via a spatially explicit network model accounting for epidemiological dynamics driven by local socioeconomic and environmental conditions, and human mobility. The model is parameterized by tapping several available geodatabases and a large dataset of mobile phone traces. It reliably reproduces the observed spatial patterns of regional schistosomiasis prevalence throughout the country, provided that spatial heterogeneity and human mobility are suitably accounted for. Specifically, a fine-grained description of the socioeconomic and environmental heterogeneities involved in local disease transmission is crucial to capturing the spatial variability of disease prevalence, while the inclusion of human mobility significantly improves the explanatory power of the model. Concerning human movement, we find that moderate mobility may reduce disease prevalence, whereas either high or low mobility may result in increased prevalence of infection. The effects of control strategies based on exposure and contamination reduction via improved access to safe water or educational campaigns are also analyzed. To our knowledge, this represents the first application of an integrative schistosomiasis transmission model at a whole-country scale.
View details for DOI 10.1038/s41598-017-00493-1
View details for Web of Science ID 000397528600021
View details for PubMedID 28352101
The Potential Role of Direct and Indirect Contacts on Infection Spread in Dairy Farm Networks.
PLoS computational biology
2017; 13 (1)
Animals' exchanges are considered the most effective route of between-farm infectious disease transmission. However, despite being often overlooked, the infection spread due to contaminated equipment, vehicles, or personnel proved to be important for several livestock epidemics. This study investigated the role of indirect contacts in a potential infection spread in the dairy farm network of the Province of Parma (Northern Italy). We built between-farm contact networks using data on cattle exchange (direct contacts), and on-farm visits by veterinarians (indirect contacts). We compared the features of the contact structures by using measures on static and temporal networks. We assessed the disease spreading potential of the direct and indirect network structures in the farm system by using data on the infection state of farms by paratuberculosis. Direct and indirect networks showed non-trivial differences with respect to connectivity, contact distribution, and super-spreaders identification. Furthermore, our analyses on paratuberculosis data suggested that the contributions of direct and indirect contacts on diseases spread are apparent at different spatial scales. Our results highlighted the potential role of indirect contacts in between-farm disease spread and underlined the need for a deeper understanding of these contacts to develop better strategies for prevention of livestock epidemics.
View details for DOI 10.1371/journal.pcbi.1005301
View details for PubMedID 28125610
View details for PubMedCentralID PMC5268397
Global Assessment of Schistosomiasis Control Over the Past Century Shows Targeting the Snail Intermediate Host Works Best.
PLoS neglected tropical diseases
2016; 10 (7)
Despite control efforts, human schistosomiasis remains prevalent throughout Africa, Asia, and South America. The global schistosomiasis burden has changed little since the new anthelmintic drug, praziquantel, promised widespread control.We evaluated large-scale schistosomiasis control attempts over the past century and across the globe by identifying factors that predict control program success: snail control (e.g., molluscicides or biological control), mass drug administrations (MDA) with praziquantel, or a combined strategy using both. For data, we compiled historical information on control tactics and their quantitative outcomes for all 83 countries and territories in which: (i) schistosomiasis was allegedly endemic during the 20th century, and (ii) schistosomiasis remains endemic, or (iii) schistosomiasis has been "eliminated," or is "no longer endemic," or transmission has been interrupted.Widespread snail control reduced prevalence by 92 ± 5% (N = 19) vs. 37 ± 7% (N = 29) for programs using little or no snail control. In addition, ecological, economic, and political factors contributed to schistosomiasis elimination. For instance, snail control was most common and widespread in wealthier countries and when control began earlier in the 20th century.Snail control has been the most effective way to reduce schistosomiasis prevalence. Despite evidence that snail control leads to long-term disease reduction and elimination, most current schistosomiasis control efforts emphasize MDA using praziquantel over snail control. Combining drug-based control programs with affordable snail control seems the best strategy for eliminating schistosomiasis.
View details for DOI 10.1371/journal.pntd.0004794
View details for PubMedID 27441556
View details for PubMedCentralID PMC4956325
Infection with schistosome parasites in snails leads to increased predation by prawns: implications for human schistosomiasis control
JOURNAL OF EXPERIMENTAL BIOLOGY
2015; 218 (24): 3962-3967
Schistosomiasis - a parasitic disease that affects over 200 million people across the globe - is primarily transmitted between human definitive hosts and snail intermediate hosts. To reduce schistosomiasis transmission, some have advocated disrupting the schistosome life cycle through biological control of snails, achieved by boosting the abundance of snails' natural predators. But little is known about the effect of parasitic infection on predator-prey interactions, especially in the case of schistosomiasis. Here, we present the results of laboratory experiments performed on Bulinus truncatus and Biomphalaria glabrata snails to investigate: (i) rates of predation on schistosome-infected versus uninfected snails by a sympatric native river prawn, Macrobrachium vollenhovenii, and (ii) differences in snail behavior (including movement, refuge-seeking and anti-predator behavior) between infected and uninfected snails. In predation trials, prawns showed a preference for consuming snails infected with schistosome larvae. In behavioral trials, infected snails moved less quickly and less often than uninfected snails, and were less likely to avoid predation by exiting the water or hiding under substrate. Although the mechanism by which the parasite alters snail behavior remains unknown, these results provide insight into the effects of parasitic infection on predator-prey dynamics and suggest that boosting natural rates of predation on snails may be a useful strategy for reducing transmission in schistosomiasis hotspots.
View details for DOI 10.1242/jeb.129221
View details for Web of Science ID 000366645500015
View details for PubMedID 26677260
- Reconciling predator conservation with public safety FRONTIERS IN ECOLOGY AND THE ENVIRONMENT 2015; 13 (8): 412-417
A Theoretical Analysis of the Geography of Schistosomiasis in Burkina Faso Highlights the Roles of Human Mobility and Water Resources Development in Disease Transmission
PLOS NEGLECTED TROPICAL DISEASES
2015; 9 (10)
We study the geography of schistosomiasis across Burkina Faso by means of a spatially explicit model of water-based disease dynamics. The model quantitatively addresses the geographic stratification of disease burden in a novel framework by explicitly accounting for drivers and controls of the disease, including spatial information on the distributions of population and infrastructure, jointly with a general description of human mobility and climatic/ecological drivers. Spatial patterns of disease are analysed by the extraction and the mapping of suitable eigenvectors of the Jacobian matrix subsuming the stability of the disease-free equilibrium. The relevance of the work lies in the novel mapping of disease burden, a byproduct of the parametrization induced by regional upscaling, by model-guided field validations and in the predictive scenarios allowed by exploiting the range of possible parameters and processes. Human mobility is found to be a primary control at regional scales both for pathogen invasion success and the overall distribution of disease burden. The effects of water resources development highlighted by systematic reviews are accounted for by the average distances of human settlements from water bodies that are habitats for the parasite's intermediate host. Our results confirm the empirical findings about the role of water resources development on disease spread into regions previously nearly disease-free also by inspection of empirical prevalence patterns. We conclude that while the model still needs refinements based on field and epidemiological evidence, the proposed framework provides a powerful tool for large-scale public health planning and schistosomiasis management.
View details for DOI 10.1371/journal.pntd.0004127
View details for Web of Science ID 000364459600033
View details for PubMedID 26513655
View details for PubMedCentralID PMC4625963
ECOLOGICAL THEORY. A general consumer-resource population model.
2015; 349 (6250): 854-857
Food-web dynamics arise from predator-prey, parasite-host, and herbivore-plant interactions. Models for such interactions include up to three consumer activity states (questing, attacking, consuming) and up to four resource response states (susceptible, exposed, ingested, resistant). Articulating these states into a general model allows for dissecting, comparing, and deriving consumer-resource models. We specify this general model for 11 generic consumer strategies that group mathematically into predators, parasites, and micropredators and then derive conditions for consumer success, including a universal saturating functional response. We further show how to use this framework to create simple models with a common mathematical lineage and transparent assumptions. Underlying assumptions, missing elements, and composite parameters are revealed when classic consumer-resource models are derived from the general model.
View details for DOI 10.1126/science.aaa6224
View details for PubMedID 26293960
- A general consumer-resource population model SCIENCE 2015; 349 (6250): 854-857
Epidemiological modelling for the assessment of bovine tuberculosis surveillance in the dairy farm network in Emilia-Romagna (Italy)
2015; 11: 62-70
Assessing the performance of a surveillance system for infectious diseases of domestic animals is a challenging task for health authorities. Therefore, it is important to assess what strategy is the most effective in identifying the onset of an epidemic and in minimizing the number of infected farms. The aim of the present work was to evaluate the performance of the bovine tuberculosis (bTB) surveillance system in the network of dairy farms in the Emilia-Romagna (ER) Region, Italy. A bTB-free Region since 2007, ER implements an integrated surveillance strategy based on three components, namely routine on-farm tuberculin skin-testing performed every 3 years, tuberculin skin-testing of cattle exchanged between farms, and post-mortem inspection at slaughterhouses. We assessed the effectiveness of surveillance by means of a stochastic network model of both within-farm and between-farm bTB dynamics calibrated on data available for ER dairy farms. Epidemic dynamics were simulated for five scenarios: the current ER surveillance system, a no surveillance scenario that we used as the benchmark to characterize epidemic dynamics, three additional scenarios in which one of the surveillance components was removed at a time so as to outline its significance in detecting the infection. For each scenario we ran Monte Carlo simulations of bTB epidemics following the random introduction of an infected individual in the network. System performances were assessed through the comparative analysis of a number of statistics, including the time required for epidemic detection and the total number of infected farms during the epidemic. Our analysis showed that slaughterhouse inspection is the most effective surveillance component in reducing the time for disease detection, while routine surveillance in reducing the number of multi-farms epidemics. On the other hand, testing exchanged cattle improved the performance of the surveillance system only marginally.
View details for DOI 10.1016/j.epidem.2015.02.007
View details for Web of Science ID 000354403100008
View details for PubMedID 25979283
React or wait: which optimal culling strategy to control infectious diseases in wildlife
JOURNAL OF MATHEMATICAL BIOLOGY
2014; 69 (4): 1001-1025
We applied optimal control theory to an SI epidemic model to identify optimal culling strategies for diseases management in wildlife. We focused on different forms of the objective function, including linear control, quadratic control, and control with limited amount of resources. Moreover, we identified optimal solutions under different assumptions on disease-free host dynamics, namely: self-regulating logistic growth, Malthusian growth, and the case of negligible demography. We showed that the correct characterization of the disease-free host growth is crucial for defining optimal disease control strategies. By analytical investigations of the model with negligible demography, we demonstrated that the optimal strategy for the linear control can be either to cull at the maximum rate at the very beginning of the epidemic (reactive culling) when the culling cost is low, or never to cull, when culling cost is high. On the other hand, in the cases of quadratic control or limited resources, we demonstrated that the optimal strategy is always reactive. Numerical analyses for hosts with logistic growth showed that, in the case of linear control, the optimal strategy is always reactive when culling cost is low. In contrast, if the culling cost is high, the optimal strategy is to delay control, i.e. not to cull at the onset of the epidemic. Finally, we showed that for diseases with the same basic reproduction number delayed control can be optimal for acute infections, i.e. characterized by high disease-induced mortality and fast dynamics, while reactive control can be optimal for chronic ones.
View details for DOI 10.1007/s00285-013-0726-y
View details for Web of Science ID 000342173300008
View details for PubMedID 24057080
Does biodiversity protect humans against infectious disease?
2014; 95 (4): 817-832
Control of human infectious disease has been promoted as a valuable ecosystem service arising from the conservation of biodiversity. There are two commonly discussed mechanisms by which biodiversity loss could increase rates of infectious disease in a landscape. First, loss of competitors or predators could facilitate an increase in the abundance of competent reservoir hosts. Second, biodiversity loss could disproportionately affect non-competent, or less competent reservoir hosts, which would otherwise interfere with pathogen transmission to human populations by, for example, wasting the bites of infected vectors. A negative association between biodiversity and disease risk, sometimes called the "dilution effect hypothesis," has been supported for a few disease agents, suggests an exciting win-win outcome for the environment and society, and has become a pervasive topic in the disease ecology literature. Case studies have been assembled to argue that the dilution effect is general across disease agents. Less touted are examples in which elevated biodiversity does not affect or increases infectious disease risk for pathogens of public health concern. In order to assess the likely generality of the dilution effect, we review the association between biodiversity and public health across a broad variety of human disease agents. Overall, we hypothesize that conditions for the dilution effect are unlikely to be met for most important diseases of humans. Biodiversity probably has little net effect on most human infectious diseases but, when it does have an effect, observation and basic logic suggest that biodiversity will be more likely to increase than to decrease infectious disease risk.
View details for DOI 10.1890/13-1041.1
View details for Web of Science ID 000334573600004
View details for PubMedID 24933803
Data-poor ecological risk assessment of multiple stressors
View details for DOI 10.1016/j.ecoinf.2023.102198
Pyrethroid insecticides pose greater risk than organophosphate insecticides to biocontrol agents for human schistosomiasis.
Environmental pollution (Barking, Essex : 1987)
Use of agrochemicals, including insecticides, is vital to food production and predicted to increase 2-5 fold by 2050. Previous studies have shown a positive association between agriculture and the human infectious disease schistosomiasis, which is problematic as this parasitic disease infects approximately 250 million people worldwide. Certain insecticides might runoff fields and be highly toxic to invertebrates, such as prawns in the genus Macrobrachium, that are biocontrol agents for snails that transmit the parasites causing schistosomiasis. We used a laboratory dose-response experiment and an observational field study to determine the relative toxicities of three pyrethroid (esfenvalerate, λ-cyhalothrin, and permethrin) and three organophosphate (chlorpyrifos, malathion, and terbufos) insecticides to Macrobrachium prawns. In the lab, pyrethroids were consistently several orders of magnitude more toxic than organophosphate insecticides, and more likely to runoff fields at lethal levels according to modeling data. At 31 water contact sites in the lower basin of the Senegal River where schistosomiasis is endemic, we found that Macrobrachium prawn survival was associated with pyrethroid but not organophosphate application rates to nearby crop fields after controlling for abiotic and prawn-level factors. Our laboratory and field results suggest that widely used pyrethroid insecticides can have strong non-target effects on Macrobrachium prawns that are biocontrol agents where 400 million people are at risk of human schistosomiasis. Understanding the ecotoxicology of high-risk insecticides may help improve human health in schistosomiasis-endemic regions undergoing agricultural expansion.
View details for DOI 10.1016/j.envpol.2022.120952
View details for PubMedID 36586553
Ecological and socioeconomic factors associated with the human burden of environmentally mediated pathogens: a global analysis
LANCET PLANETARY HEALTH
2022; 6 (11): E870-E879
View details for Web of Science ID 000960726200008
Evidence gaps and diversity among potential win-win solutions for conservation and human infectious disease control
LANCET PLANETARY HEALTH
2022; 6 (8): E694-E705
View details for Web of Science ID 000863508500010
Evidence gaps and diversity among potential win-win solutions for conservation and human infectious disease control.
The Lancet. Planetary health
2022; 6 (8): e694-e705
As sustainable development practitioners have worked to "ensure healthy lives and promote well-being for all" and "conserve life on land and below water", what progress has been made with win-win interventions that reduce human infectious disease burdens while advancing conservation goals? Using a systematic literature review, we identified 46 proposed solutions, which we then investigated individually using targeted literature reviews. The proposed solutions addressed diverse conservation threats and human infectious diseases, and thus, the proposed interventions varied in scale, costs, and impacts. Some potential solutions had medium-quality to high-quality evidence for previous success in achieving proposed impacts in one or both sectors. However, there were notable evidence gaps within and among solutions, highlighting opportunities for further research and adaptive implementation. Stakeholders seeking win-win interventions can explore this Review and an online database to find and tailor a relevant solution or brainstorm new solutions.
View details for DOI 10.1016/S2542-5196(22)00148-6
View details for PubMedID 35932789
- Deep Learning Segmentation of Satellite Imagery Identifies Aquatic Vegetation Associated with Snail Intermediate Hosts of Schistosomiasis in Senegal, Africa REMOTE SENSING 2022; 14 (6)
- The Potential for Aquaculture to Reduce Poverty and Control Schistosomiasis in Cote d'Ivoire (Ivory Coast) during an Era of Climate Change: A Systematic Review REVIEWS IN FISHERIES SCIENCE & AQUACULTURE 2022
Ecological and socioeconomic factors associated with the human burden of environmentally mediated pathogens: a global analysis.
The Lancet. Planetary health
2022; 6 (11): e870-e879
BACKGROUND: Billions of people living in poverty are at risk of environmentally mediated infectious diseases-that is, pathogens with environmental reservoirs that affect disease persistence and control and where environmental control of pathogens can reduce human risk. The complex ecology of these diseases creates a global health problem not easily solved with medical treatment alone.METHODS: We quantified the current global disease burden caused by environmentally mediated infectious diseases and used a structural equation model to explore environmental and socioeconomic factors associated with the human burden of environmentally mediated pathogens across all countries.FINDINGS: We found that around 80% (455 of 560) of WHO-tracked pathogen species known to infect humans are environmentally mediated, causing about 40% (129 488 of 359 341 disability-adjusted life years) of contemporary infectious disease burden (global loss of 130 million years of healthy life annually). The majority of this environmentally mediated disease burden occurs in tropical countries, and the poorest countries carry the highest burdens across all latitudes. We found weak associations between disease burden and biodiversity or agricultural land use at the global scale. In contrast, the proportion of people with rural poor livelihoods in a country was a strong proximate indicator of environmentally mediated infectious disease burden. Political stability and wealth were associated with improved sanitation, better health care, and lower proportions of rural poverty, indirectly resulting in lower burdens of environmentally mediated infections. Rarely, environmentally mediated pathogens can evolve into global pandemics (eg, HIV, COVID-19) affecting even the wealthiest communities.INTERPRETATION: The high and uneven burden of environmentally mediated infections highlights the need for innovative social and ecological interventions to complement biomedical advances in the pursuit of global health and sustainability goals.FUNDING: Bill & Melinda Gates Foundation, National Institutes of Health, National Science Foundation, Alfred P. Sloan Foundation, National Institute for Mathematical and Biological Synthesis, Stanford University, and the US Defense Advanced Research Projects Agency.
View details for DOI 10.1016/S2542-5196(22)00248-0
View details for PubMedID 36370725
Environmental Persistence of the World's Most Burdensome Infectious and Parasitic Diseases.
Frontiers in public health
2022; 10: 892366
Humans live in complex socio-ecological systems where we interact with parasites and pathogens that spend time in abiotic and biotic environmental reservoirs (e.g., water, air, soil, other vertebrate hosts, vectors, intermediate hosts). Through a synthesis of published literature, we reviewed the life cycles and environmental persistence of 150 parasites and pathogens tracked by the World Health Organization's Global Burden of Disease study. We used those data to derive the time spent in each component of a pathogen's life cycle, including total time spent in humans versus all environmental stages. We found that nearly all infectious organisms were "environmentally mediated" to some degree, meaning that they spend time in reservoirs and can be transmitted from those reservoirs to human hosts. Correspondingly, many infectious diseases were primarily controlled through environmental interventions (e.g., vector control, water sanitation), whereas few (14%) were primarily controlled by integrated methods (i.e., combining medical and environmental interventions). Data on critical life history attributes for most of the 150 parasites and pathogens were difficult to find and often uncertain, potentially hampering efforts to predict disease dynamics and model interactions between life cycle time scales and infection control strategies. We hope that this synthetic review and associated database serve as a resource for understanding both common patterns among parasites and pathogens and important variability and uncertainty regarding particular infectious diseases. These insights can be used to improve systems-based approaches for controlling environmentally mediated diseases of humans in an era where the environment is rapidly changing.
View details for DOI 10.3389/fpubh.2022.892366
View details for PubMedID 35875032
- Editorial: Planetary health impacts of pandemic coronaviruses. Frontiers in public health 2022; 10: 987167
BEHAVIORAL RESPONSES TO A SEASONAL ENVIRONMENT REDUCE FREQUENCY BUT INCREASE EXTENT OF WATER CONTACT IN A SCHISTOSOMIASIS-ENDEMIC REGION OF WEST AFRICA
AMER SOC TROP MED & HYGIENE. 2021: 405
View details for Web of Science ID 000778105603359
IDENTIFICATION OF SNAILS AND SCHISTOSOMA OF MEDICAL IMPORTANCE VIA CONVOLUTIONAL NEURAL NETWORKS
AMER SOC TROP MED & HYGIENE. 2021: 295
View details for Web of Science ID 000778105603011
Exposure, hazard, and vulnerability all contribute to Schistosoma haematobium re-infection in northern Senegal.
PLoS neglected tropical diseases
2021; 15 (10): e0009806
BACKGROUND: Infectious disease risk is driven by three interrelated components: exposure, hazard, and vulnerability. For schistosomiasis, exposure occurs through contact with water, which is often tied to daily activities. Water contact, however, does not imply risk unless the environmental hazard of snails and parasites is also present in the water. By increasing reliance on hazardous activities and environments, socio-economic vulnerability can hinder reductions in exposure to a hazard. We aimed to quantify the contributions of exposure, hazard, and vulnerability to the presence and intensity of Schistosoma haematobium re-infection.METHODOLOGY/PRINCIPAL FINDINGS: In 13 villages along the Senegal River, we collected parasitological data from 821 school-aged children, survey data from 411 households where those children resided, and ecological data from all 24 village water access sites. We fit mixed-effects logistic and negative binomial regressions with indices of exposure, hazard, and vulnerability as explanatory variables of Schistosoma haematobium presence and intensity, respectively, controlling for demographic variables. Using multi-model inference to calculate the relative importance of each component of risk, we found that hazard (Ʃwi = 0.95) was the most important component of S. haematobium presence, followed by vulnerability (Ʃwi = 0.91). Exposure (Ʃwi = 1.00) was the most important component of S. haematobium intensity, followed by hazard (Ʃwi = 0.77). Model averaging quantified associations between each infection outcome and indices of exposure, hazard, and vulnerability, revealing a positive association between hazard and infection presence (OR = 1.49, 95% CI 1.12, 1.97), and a positive association between exposure and infection intensity (RR 2.59-3.86, depending on the category; all 95% CIs above 1).CONCLUSIONS/SIGNIFICANCE: Our findings underscore the linkages between social (exposure and vulnerability) and environmental (hazard) processes in the acquisition and accumulation of S. haematobium infection. This approach highlights the importance of implementing both social and environmental interventions to complement mass drug administration.
View details for DOI 10.1371/journal.pntd.0009806
View details for PubMedID 34610025
Identification of Snails and Schistosoma of Medical Importance via Convolutional Neural Networks: A Proof-of-Concept Application for Human Schistosomiasis
FRONTIERS IN PUBLIC HEALTH
2021; 9: 642895
In recent decades, computer vision has proven remarkably effective in addressing diverse issues in public health, from determining the diagnosis, prognosis, and treatment of diseases in humans to predicting infectious disease outbreaks. Here, we investigate whether convolutional neural networks (CNNs) can also demonstrate effectiveness in classifying the environmental stages of parasites of public health importance and their invertebrate hosts. We used schistosomiasis as a reference model. Schistosomiasis is a debilitating parasitic disease transmitted to humans via snail intermediate hosts. The parasite affects more than 200 million people in tropical and subtropical regions. We trained our CNN, a feed-forward neural network, on a limited dataset of 5,500 images of snails and 5,100 images of cercariae obtained from schistosomiasis transmission sites in the Senegal River Basin, a region in western Africa that is hyper-endemic for the disease. The image set included both images of two snail genera that are relevant to schistosomiasis transmission - that is, Bulinus spp. and Biomphalaria pfeifferi - as well as snail images that are non-component hosts for human schistosomiasis. Cercariae shed from Bi. pfeifferi and Bulinus spp. snails were classified into 11 categories, of which only two, S. haematobium and S. mansoni, are major etiological agents of human schistosomiasis. The algorithms, trained on 80% of the snail and parasite dataset, achieved 99% and 91% accuracy for snail and parasite classification, respectively, when used on the hold-out validation dataset - a performance comparable to that of experienced parasitologists. The promising results of this proof-of-concept study suggests that this CNN model, and potentially similar replicable models, have the potential to support the classification of snails and parasite of medical importance. In remote field settings where machine learning algorithms can be deployed on cost-effective and widely used mobile devices, such as smartphones, these models can be a valuable complement to laboratory identification by trained technicians. Future efforts must be dedicated to increasing dataset sizes for model training and validation, as well as testing these algorithms in diverse transmission settings and geographies.
View details for DOI 10.3389/fpubh.2021.642895
View details for Web of Science ID 000678775200001
View details for PubMedID 34336754
View details for PubMedCentralID PMC8319642
- A comparative analysis of European eel's somatic growth in the coastal lagoon Santo Andre (Portugal) with growth in other estuaries and freshwater habitats ENVIRONMENTAL BIOLOGY OF FISHES 2021
Variable coastal hypoxia exposure and drivers across the southern California Current.
2021; 11 (1): 10929
Declining oxygen is one of the most drastic changes in the ocean, and this trend is expected to worsen under future climate change scenarios. Spatial variability in dissolved oxygen dynamics and hypoxia exposures can drive differences in vulnerabilities of coastal ecosystems and resources, but documentation of variability at regional scales is rare in open-coast systems. Using a regional collaborative network of dissolved oxygen and temperature sensors maintained by scientists and fishing cooperatives from California, USA, and Baja California, Mexico, we characterize spatial and temporal variability in dissolved oxygen and seawater temperature dynamics in kelp forest ecosystems across 13° of latitude in the productive California Current upwelling system. We find distinct latitudinal patterns of hypoxia exposure and evidence for upwelling and respiration as regional drivers of oxygen dynamics, as well as more localized effects. This regional and small-scale spatial variability in dissolved oxygen dynamics supports the use of adaptive management at local scales, and highlights the value of collaborative, large-scale coastal monitoring networks for informing effective adaptation strategies for coastal communities and fisheries in a changing climate.
View details for DOI 10.1038/s41598-021-89928-4
View details for PubMedID 34035327
- Redefining risk in data-poor fisheries FISH AND FISHERIES 2021
Land use impacts on parasitic infection: a cross-sectional epidemiological study on the role of irrigated agriculture in schistosome infection in a dammed landscape.
Infectious diseases of poverty
2021; 10 (1): 35
BACKGROUND: Water resources development promotes agricultural expansion and food security. But are these benefits offset by increased infectious disease risk? Dam construction on the Senegal River in 1986 was followed by agricultural expansion and increased transmission of human schistosomes. Yet the mechanisms linking these two processes at the individual and household levels remain unclear. We investigated the association between household land use and schistosome infection in children.METHODS: We analyzed cross-sectional household survey data (n=655) collected in 16 rural villages in August 2016 across demographic, socio-economic and land usedimensions, which were matched to Schistosoma haematobium (n=1232) and S. mansoni (n=1222) infection data collected from school-aged children. Mixed effects regression determined the relationship between irrigated area and schistosome infection presence and intensity.RESULTS: Controlling for socio-economic and demographic risk factors, irrigated area cultivated by a household was associated with an increase in the presence of S. haematobium infection (odds ratio [OR]=1.14; 95% confidence interval [95% CI]: 1.03-1.28) but not S. mansoni infection (OR=1.02; 95% CI: 0.93-1.11). Associations between infection intensity and irrigated area were positive but imprecise (S. haematobium: rate ratio [RR]=1.05; 95% CI: 0.98-1.13, S. mansoni: RR=1.09; 95% CI: 0.89-1.32).CONCLUSIONS: Household engagement in irrigated agriculture increases individual risk of S. haematobium but not S. mansoni infection. Increased contact with irrigated landscapes likely drives exposure, with greater impacts on households relying on agricultural livelihoods.
View details for DOI 10.1186/s40249-021-00816-5
View details for PubMedID 33745442
- Agricultural Innovations to Reduce the Health Impacts of Dams SUSTAINABILITY 2021; 13 (4)
The influence of vector-borne disease on human history: socio-ecological mechanisms.
Vector-borne diseases (VBDs) are embedded within complex socio-ecological systems. While research has traditionally focused on the direct effects of VBDs on human morbidity and mortality, it is increasingly clear that their impacts are much more pervasive. VBDs are dynamically linked to feedbacks between environmental conditions, vector ecology, disease burden, and societal responses that drive transmission. As a result, VBDs have had profound influence on human history. Mechanisms include: (1) killing or debilitating large numbers of people, with demographic and population-level impacts; (2) differentially affecting populations based on prior history of disease exposure, immunity, and resistance; (3) being weaponised to promote or justify hierarchies of power, colonialism, racism, classism and sexism; (4) catalysing changes in ideas, institutions, infrastructure, technologies and social practices in efforts to control disease outbreaks; and (5) changing human relationships with the land and environment. We use historical and archaeological evidence interpreted through an ecological lens to illustrate how VBDs have shaped society and culture, focusing on case studies from four pertinent VBDs: plague, malaria, yellow fever and trypanosomiasis. By comparing across diseases, time periods and geographies, we highlight the enormous scope and variety of mechanisms by which VBDs have influenced human history.
View details for DOI 10.1111/ele.13675
View details for PubMedID 33501751
Visualization of schistosomiasis snail habitats using light unmanned aerial vehicles.
2021; 15 (2)
Schistosomiasis, or "snail fever", is a parasitic disease affecting over 200 million people worldwide. People become infected when exposed to water containing particular species of freshwater snails. Habitats for such snails can be mapped using lightweight, inexpensive and field-deployable consumer-grade Unmanned Aerial Vehicles (UAVs), also known as drones. Drones can obtain imagery in remote areas with poor satellite imagery. An unexpected outcome of using drones is public engagement. Whereas sampling snails exposes field technicians to infection risk and might disturb locals who are also using the water site, drones are novel and fun to watch, attracting crowds that can be educated about the infection risk.
View details for DOI 10.4081/gh.2020.818
View details for PubMedID 33461284
Filamentous Bacteriophages and the Competitive Interaction between Pseudomonas aeruginosa Strains under Antibiotic Treatment: a Modeling Study.
Pseudomonas aeruginosa (Pa) is a major bacterial pathogen responsible for chronic lung infections in cystic fibrosis patients. Recent work has implicated Pf bacteriophages, nonlytic filamentous viruses produced by Pa, in the chronicity and severity of Pa infections. Pf phages act as structural elements in Pa biofilms and sequester aerosolized antibiotics, thereby contributing to antibiotic tolerance. Consistent with a selective advantage in this setting, the prevalence of Pf-positive (Pf+) bacteria increases over time in these patients. However, the production of Pf phages comes at a metabolic cost to bacteria, such that Pf+ strains grow more slowly than Pf-negative (Pf-) strains in vitro. Here, we use a mathematical model to investigate how these competing pressures might influence the relative abundance of Pf+ versus Pf- strains in different settings. Our model suggests that Pf+ strains of Pa cannot outcompete Pf- strains if the benefits of phage production falls onto both Pf+ and Pf- strains for a majority of parameter combinations. Further, phage production leads to a net positive gain in fitness only at antibiotic concentrations slightly above the MIC (i.e., concentrations for which the benefits of antibiotic sequestration outweigh the metabolic cost of phage production) but which are not lethal for Pf+ strains. As a result, our model suggests that frequent administration of intermediate doses of antibiotics with low decay rates and high killing rates favors Pf+ over Pf- strains. These models inform our understanding of the ecology of Pf phages and suggest potential treatment strategies for Pf+ Pa infections. IMPORTANCE Filamentous phages are a frontier in bacterial pathogenesis, but the impact of these phages on bacterial fitness is unclear. In particular, Pf phages produced by Pa promote antibiotic tolerance but are metabolically expensive to produce, suggesting that competing pressures may influence the prevalence of Pf+ versus Pf- strains of Pa in different settings. Our results identify conditions likely to favor Pf+ strains and thus antibiotic tolerance. This study contributes to a better understanding of the unique ecology of filamentous phages in both environmental and clinical settings and may facilitate improved treatment strategies for combating antibiotic tolerance.
View details for DOI 10.1128/mSystems.00193-21
View details for PubMedID 34156288
Schistosome infection in Senegal is associated with different spatial extents of risk and ecological drivers for Schistosoma haematobium and S. mansoni.
PLoS neglected tropical diseases
2021; 15 (9): e0009712
Schistosome parasites infect more than 200 million people annually, mostly in sub-Saharan Africa, where people may be co-infected with more than one species of the parasite. Infection risk for any single species is determined, in part, by the distribution of its obligate intermediate host snail. As the World Health Organization reprioritizes snail control to reduce the global burden of schistosomiasis, there is renewed importance in knowing when and where to target those efforts, which could vary by schistosome species. This study estimates factors associated with schistosomiasis risk in 16 villages located in the Senegal River Basin, a region hyperendemic for Schistosoma haematobium and S. mansoni. We first analyzed the spatial distributions of the two schistosomes' intermediate host snails (Bulinus spp. and Biomphalaria pfeifferi, respectively) at village water access sites. Then, we separately evaluated the relationships between human S. haematobium and S. mansoni infections and (i) the area of remotely-sensed snail habitat across spatial extents ranging from 1 to 120 m from shorelines, and (ii) water access site size and shape characteristics. We compared the influence of snail habitat across spatial extents because, while snail sampling is traditionally done near shorelines, we hypothesized that snails further from shore also contribute to infection risk. We found that, controlling for demographic variables, human risk for S. haematobium infection was positively correlated with snail habitat when snail habitat was measured over a much greater radius from shore (45 m to 120 m) than usual. S. haematobium risk was also associated with large, open water access sites. However, S. mansoni infection risk was associated with small, sheltered water access sites, and was not positively correlated with snail habitat at any spatial sampling radius. Our findings highlight the need to consider different ecological and environmental factors driving the transmission of each schistosome species in co-endemic landscapes.
View details for DOI 10.1371/journal.pntd.0009712
View details for PubMedID 34570777
Human-mediated impacts on biodiversity and the consequences for zoonotic disease spillover.
Current biology : CB
2021; 31 (19): R1342-R1361
Human-mediated changes to natural ecosystems have consequences for both ecosystem and human health. Historically, efforts to preserve or restore 'biodiversity' can seem to be in opposition to human interests. However, the integration of biodiversity conservation and public health has gained significant traction in recent years, and new efforts to identify solutions that benefit both environmental and human health are ongoing. At the forefront of these efforts is an attempt to clarify ways in which biodiversity conservation can help reduce the risk of zoonotic spillover of pathogens from wild animals, sparking epidemics and pandemics in humans and livestock. However, our understanding of the mechanisms by which biodiversity change influences the spillover process is incomplete, limiting the application of integrated strategies aimed at achieving positive outcomes for both conservation and disease management. Here, we review the literature, considering a broad scope of biodiversity dimensions, to identify cases where zoonotic pathogen spillover is mechanistically linked to changes in biodiversity. By reframing the discussion around biodiversity and disease using mechanistic evidence - while encompassing multiple aspects of biodiversity including functional diversity, landscape diversity, phenological diversity, and interaction diversity - we work toward general principles that can guide future research and more effectively integrate the related goals of biodiversity conservation and spillover prevention. We conclude by summarizing how these principles could be used to integrate the goal of spillover prevention into ongoing biodiversity conservation initiatives.
View details for DOI 10.1016/j.cub.2021.08.070
View details for PubMedID 34637744
Two Homogametic Genotypes - One Crayfish: On the Consequences of Intersexuality.
2020; 23 (11): 101652
In the Australian redclaw crayfish, Cherax quadricarinatus (WZ/ZZ system), intersexuals, although exhibiting both male and female gonopores, are functional males bearing a female genotype (WZ males). Therefore, the occurrence of the unusual homogametic WW females in nature is plausible. We developed W/Z genomic sex markers and used them to investigate the genotypic structure of experimental and native C.quadricarinatus populations in Australia. We discovered, for the first time, the natural occurrence of WW females in crustacean populations. By modeling population dynamics, we found that intersexuals contribute to the growth rate of crayfish populations in the short term. Given the vastly fragmented C.quadricarinatus habitat, which is characterized by drought-flood cycles, we speculate that intersexuals contribute to the fitness of this species since they lead to occasional increment in the population growth rate which potentially supports crayfish population restoration and establishment under extinction threats or colonization events.
View details for DOI 10.1016/j.isci.2020.101652
View details for PubMedID 33103088
- CLIMATE CHANGE AND COMMUNICABLE DISEASES Schistosomiasis and climate change BMJ-BRITISH MEDICAL JOURNAL 2020; 371
- How to identify win-win interventions that benefit human health and conservation NATURE SUSTAINABILITY 2020
Improving rural health care reduces illegal logging and conserves carbon in a tropical forest.
Proceedings of the National Academy of Sciences of the United States of America
Tropical forest loss currently exceeds forest gain, leading to a net greenhouse gas emission that exacerbates global climate change. This has sparked scientific debate on how to achieve natural climate solutions. Central to this debate is whether sustainably managing forests and protected areas will deliver global climate mitigation benefits, while ensuring local peoples' health and well-being. Here, we evaluate the 10-y impact of a human-centered solution to achieve natural climate mitigation through reductions in illegal logging in rural Borneo: an intervention aimed at expanding health care access and use for communities living near a national park, with clinic discounts offsetting costs historically met through illegal logging. Conservation, education, and alternative livelihood programs were also offered. We hypothesized that this would lead to improved health and well-being, while also alleviating illegal logging activity within the protected forest. We estimated that 27.4 km2 of deforestation was averted in the national park over a decade (70% reduction in deforestation compared to a synthetic control, permuted P = 0.038). Concurrently, the intervention provided health care access to more than 28,400 unique patients, with clinic usage and patient visitation frequency highest in communities participating in the intervention. Finally, we observed a dose-response in forest change rate to intervention engagement (person-contacts with intervention activities) across communities bordering the park: The greatest logging reductions were adjacent to the most highly engaged villages. Results suggest that this community-derived solution simultaneously improved health care access for local and indigenous communities and sustainably conserved carbon stocks in a protected tropical forest.
View details for DOI 10.1073/pnas.2009240117
View details for PubMedID 33106399
Cost-effectiveness of combining drug and environmental treatments for environmentally transmitted diseases.
Proceedings. Biological sciences
2020; 287 (1933): 20200966
Control of neglected tropical diseases (NTDs) via mass drug administration (MDA) has increased considerably over the past decade, but strategies focused exclusively on human treatment show limited efficacy. This paper investigated trade-offs between drug and environmental treatments in the fight against NTDs by using schistosomiasis as a case study. We use optimal control techniques where the planner's objective is to treat the disease over a time horizon at the lowest possible total cost, where the total costs include treatment, transportation and damages (reduction in human health). We show that combining environmental treatments and drug treatments reduces the dependency on MDAs and that this reduction increases when the planners take a longer-run perspective on the fight to reduce NTDs. Our results suggest that NTDs with environmental reservoirs require moving away from a reliance solely on MDA to integrated treatment involving investment in both drug and environmental controls.
View details for DOI 10.1098/rspb.2020.0966
View details for PubMedID 32842925
Aquatic macrophytes and macroinvertebrate predators affect densities of snail hosts and local production of schistosome cercariae that cause human schistosomiasis.
PLoS neglected tropical diseases
2020; 14 (7): e0008417
BACKGROUND: Schistosomiasis is responsible for the second highest burden of disease among neglected tropical diseases globally, with over 90 percent of cases occurring in African regions where drugs to treat the disease are only sporadically available. Additionally, human re-infection after treatment can be a problem where there are high numbers of infected snails in the environment. Recent experiments indicate that aquatic factors, including plants, nutrients, or predators, can influence snail abundance and parasite production within infected snails, both components of human risk. This study investigated how snail host abundance and release of cercariae (the free swimming stage infective to humans) varies at water access sites in an endemic region in Senegal, a setting where human schistosomiasis prevalence is among the highest globally.METHODS/PRINCIPAL FINDINGS: We collected snail intermediate hosts at 15 random points stratified by three habitat types at 36 water access sites, and counted cercarial production by each snail after transfer to the laboratory on the same day. We found that aquatic vegetation was positively associated with per-capita cercarial release by snails, probably because macrophytes harbor periphyton resources that snails feed upon, and well-fed snails tend to produce more parasites. In contrast, the abundance of aquatic macroinvertebrate snail predators was negatively associated with per-capita cercarial release by snails, probably because of several potential sublethal effects on snails or snail infection, despite a positive association between snail predators and total snail numbers at a site, possibly due to shared habitat usage or prey tracking by the predators. Thus, complex bottom-up and top-down ecological effects in this region plausibly influence the snail shedding rate and thus, total local density of schistosome cercariae.CONCLUSIONS/SIGNIFICANCE: Our study suggests that aquatic macrophytes and snail predators can influence per-capita cercarial production and total abundance of snails. Thus, snail control efforts might benefit by targeting specific snail habitats where parasite production is greatest. In conclusion, a better understanding of top-down and bottom-up ecological factors that regulate densities of cercarial release by snails, rather than solely snail densities or snail infection prevalence, might facilitate improved schistosomiasis control.
View details for DOI 10.1371/journal.pntd.0008417
View details for PubMedID 32628666
Effects of agrochemical pollution on schistosomiasis transmission: a systematic review and modelling analysis
LANCET PLANETARY HEALTH
2020; 4 (7): E280–E291
View details for Web of Science ID 000582520600011
Effects of agrochemical pollution on schistosomiasis transmission: a systematic review and modelling analysis.
The Lancet. Planetary health
2020; 4 (7): e280–e291
BACKGROUND: Agrochemical pollution of surface waters is a growing global environmental challenge, especially in areas where agriculture is rapidly expanding and intensifying. Agrochemicals might affect schistosomiasis transmission through direct and indirect effects on Schistosoma parasites, their intermediate snail hosts, snail predators, and snail algal resources. We aimed to review and summarise the effects of these agrochemicals on schistosomiasis transmission dynamics.METHODS: We did a systematic review of agrochemical effects on the lifecycle of Schistosoma spp and fitted dose-response models to data regarding the association between components of the lifecycle and agrochemical concentrations. We incorporated these dose-response functions and environmentally relevant concentrations of agrochemicals into a mathematical model to estimate agrochemical effects on schistosomiasis transmission. Dose-response functions were used to estimate individual agrochemical effects on estimates of the agrochemically influenced basic reproduction number, R0, for Schistosoma haematobium. We incorporated time series of environmentally relevant agrochemical concentrations into the model and simulated mass drug administration control efforts in the presence of agrochemicals.FINDINGS: We derived 120 dose-response functions describing the effects of agrochemicals on schistosome lifecycle components. The median estimate of the basic reproduction number under agrochemical-free conditions, was 1·65 (IQR 1·47-1·79). Agrochemical effects on estimates of R0 for S haematobium ranged from a median three-times increase (R0 5·05, IQR 4·06-5·97) to transmission elimination (R0 0). Simulations of transmission dynamics subject to interacting annual mass drug administration and agrochemical pollution yielded a median estimate of 64·82 disability-adjusted life-years (DALYs) lost per 100 000 people per year (IQR 62·52-67·68) attributable to atrazine use. In areas where aquatic arthropod predators of intermediate host snails suppress transmission, the insecticides chlorpyrifos (6·82 DALYs lost per 100 000 people per year, IQR 4·13-8·69) and profenofos (103·06 DALYs lost per 100 000 people per year, IQR 89·63-104·90) might also increase the disability burden through their toxic effects on arthropods.INTERPRETATION: Expected environmental concentrations of agrochemicals alter schistosomiasis transmission through direct and indirect effects on intermediate host and parasite densities. As industrial agricultural practices expand in areas where schistosomiasis is endemic, strategies to prevent increases in transmission due to agrochemical pollution should be developed and pursued.FUNDING: National Science Foundation, National Institutes of Health.
View details for DOI 10.1016/S2542-5196(20)30105-4
View details for PubMedID 32681899
- The IAG gene in the invasive crayfish Procambarus clarkii - towards sex manipulations for biocontrol and aquaculture MANAGEMENT OF BIOLOGICAL INVASIONS 2020; 11 (2): 237–58
Tracking the response of industrial fishing fleets to large marine protected areas in the Pacific Ocean.
Conservation biology : the journal of the Society for Conservation Biology
Large marine protected areas (MPAs) of unprecedented size have recently been established across the global oceans, yet their ability to meet conservation objectives is debated. Key areas of debate include uncertainty over nations' abilities to enforce fishing bans across vast, remote regions and the intensity of human impacts before and after MPA implementation. We used a recently developed vessel tracking data set (produced using Automatic Identification System detections) to quantify the response of industrial fishing fleets to 5 of the largest MPAs established in the Pacific Ocean since 2013. After their implementation, all 5 MPAs successfully kept industrial fishing effort exceptionally low. Detected fishing effort was already low in 4 of the 5 large MPAs prior to MPA implementation, particularly relative to nearby regions that did not receive formal protection. Our results suggest that these large MPAs may present major conservation opportunities in relatively intact ecosystems with low immediate impact to industrial fisheries, but the large MPAs we considered often did not significantly reduce fishing effort because baseline fishing was typically low. It is yet to be determined how large MPAs may shape global ocean conservation in the future if the footprint of human influence continues to expand. Continued improvement in understanding of how large MPAs interact with industrial fisheries is a crucial step toward defining their role in global ocean management.
View details for DOI 10.1111/cobi.13584
View details for PubMedID 33031635
- Modelling marine diseases MARINE DISEASE ECOLOGY 2020: 233–55
- Abundance and distribution of the white shark in the Mediterranean Sea FISH AND FISHERIES 2019
- A demographic model for the conservation and management of the European eel: an application to a Mediterranean coastal lagoon ICES JOURNAL OF MARINE SCIENCE 2019; 76 (7): 2164–78
- Challenges to reconcile conservation and exploitation of the threatened Anguilla anguilla (Linnaeus, 1758) in Santo Andre lagoon (Portugal) OCEAN & COASTAL MANAGEMENT 2019; 181
- Quantifying coconut palm extent on Pacific islands using spectral and textural analysis of very high resolution imagery INTERNATIONAL JOURNAL OF REMOTE SENSING 2019
Catastrophic Mortality, Allee Effects, and Marine Protected Areas
2019; 193 (3): 391–408
For many species, reproductive failure may occur if abundance drops below critical Allee thresholds for successful breeding, in some cases impeding recovery. At the same time, extreme environmental events can cause catastrophic collapse in otherwise healthy populations. Understanding what natural processes and management strategies may allow for persistence and recovery of natural populations is critical in the face of expected climate change scenarios of increased environmental variability. Using a spatially explicit continuous-size fishery model with stochastic dispersal parameterized for abalone-a harvested species with sedentary adults and a dispersing larval phase-we investigated whether the establishment of a system of marine protected areas (MPAs) can prevent population collapse, compared with nonspatial management when populations are affected by mass mortality from environmental shocks and subject to Allee effects. We found that MPA networks dramatically reduced the risk of collapse following catastrophic events (75%-90% mortality), while populations often continued to decline in the absence of spatial protection. Similar resilience could be achieved by closing the fishery immediately following mass mortalities but would necessitate long periods without catch and therefore economic income. For species with Allee effects, the use of protected areas can ensure persistence following mass mortality events while maintaining ecosystem services during the recovery period.
View details for DOI 10.1086/701781
View details for Web of Science ID 000459624900008
View details for PubMedID 30794455
FROM SATELLITES TO SNAILS IN NORTHERN SENEGAL: HONING IN AN HIGHLY PRODUCTIVE SNAIL HABITATS USING REMOTE SENSING TECHNOLOGIES FOR TARGETED AND INTEGRATED VECTOR CONTROL OF SCHISTOSOMIASIS
AMER SOC TROP MED & HYGIENE. 2019: 11
View details for Web of Science ID 000507364502034
- The decline in recruitment of the European eel: new insights from a 40-year-long time-series in the Minho estuary (Portugal) ICES JOURNAL OF MARINE SCIENCE 2018; 75 (6): 1975–83
Heterogeneity in schistosomiasis transmission dynamics
JOURNAL OF THEORETICAL BIOLOGY
2017; 432: 87–99
Simple models of disease propagation often disregard the effects of transmission heterogeneity on the ecological and epidemiological dynamics associated with host-parasite interactions. However, for some diseases like schistosomiasis, a widespread parasitic infection caused by Schistosoma worms, accounting for heterogeneity is crucial to both characterize long-term dynamics and evaluate opportunities for disease control. Elaborating on the classic Macdonald model for macroparasite transmission, we analyze families of models including explicit descriptions of heterogeneity related to differential transmission risk within a community, water contact patterns, the distribution of the snail host population, human mobility, and the seasonal fluctuations of the environment. Through simple numerical examples, we show that heterogeneous multigroup communities may be more prone to schistosomiasis than homogeneous ones, that the availability of multiple water sources can hinder parasite transmission, and that both spatial and temporal heterogeneities may have nontrivial implications for disease endemicity. Finally, we discuss the implications of heterogeneity for disease control. Although focused on schistosomiasis, results from this study may apply as well to other parasitic infections with complex transmission cycles, such as cysticercosis, dracunculiasis and fasciolosis.
View details for PubMedID 28823529
View details for PubMedCentralID PMC5595357
- Assessing the effectiveness of a large marine protected area for reef shark conservation BIOLOGICAL CONSERVATION 2017; 207: 64-71
- The Resilience of Marine Ecosystems to Climatic Disturbances BIOSCIENCE 2017; 67 (3): 208-220
- Ocean warming and the demography of declines in coral body size MARINE ECOLOGY PROGRESS SERIES 2016; 560: 147-158
Body size and meta-community structure: the allometric scaling of parasitic worm communities in their mammalian hosts
2016; 143 (7): 880-893
In this paper we derive from first principles the expected body sizes of the parasite communities that can coexist in a mammal of given body size. We use a mixture of mathematical models and known allometric relationships to examine whether host and parasite life histories constrain the diversity of parasite species that can coexist in the population of any host species. The model consists of one differential equation for each parasite species and a single density-dependent nonlinear equation for the affected host under the assumption of exploitation competition. We derive threshold conditions for the coexistence and competitive exclusion of parasite species using invasion criteria and stability analysis of the resulting equilibria. These results are then used to evaluate the range of parasites species that can invade and establish in a target host and identify the 'optimal' size of a parasite species for a host of a given body size; 'optimal' is defined as the body size of a parasite species that cannot be outcompeted by any other parasite species. The expected distributions of parasites body sizes in hosts of different sizes are then compared with those observed in empirical studies. Our analysis predicts the relative abundance of parasites of different size that establish in the host and suggests that increasing the ratio of parasite body size to host body size above a minimum threshold increases the persistence of the parasite population.
View details for DOI 10.1017/S0031182015001444
View details for Web of Science ID 000376781100008
View details for PubMedID 27001526
- Quantifying 60 years of declining European eel (Anguilla anguilla L., 1758) fishery yields in Mediterranean coastal lagoons ICES JOURNAL OF MARINE SCIENCE 2016; 73 (1): 101-110
- The good, the bad and the ugly of marine reserves for fishery yields PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY B-BIOLOGICAL SCIENCES 2015; 370 (1681)
- A global viability assessment of the European eel GLOBAL CHANGE BIOLOGY 2015; 21 (9): 3323-3335
Reduced transmission of human schistosomiasis after restoration of a native river prawn that preys on the snail intermediate host
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2015; 112 (31): 9650-9655
Eliminating human parasitic disease often requires interrupting complex transmission pathways. Even when drugs to treat people are available, disease control can be difficult if the parasite can persist in nonhuman hosts. Here, we show that restoration of a natural predator of a parasite's intermediate hosts may enhance drug-based schistosomiasis control. Our study site was the Senegal River Basin, where villagers suffered a massive outbreak and persistent epidemic after the 1986 completion of the Diama Dam. The dam blocked the annual migration of native river prawns (Macrobrachium vollenhoveni) that are voracious predators of the snail intermediate hosts for schistosomiasis. We tested schistosomiasis control by reintroduced river prawns in a before-after-control-impact field experiment that tracked parasitism in snails and people at two matched villages after prawns were stocked at one village's river access point. The abundance of infected snails was 80% lower at that village, presumably because prawn predation reduced the abundance and average life span of latently infected snails. As expected from a reduction in infected snails, human schistosomiasis prevalence was 18 ± 5% lower and egg burden was 50 ± 8% lower at the prawn-stocking village compared with the control village. In a mathematical model of the system, stocking prawns, coupled with infrequent mass drug treatment, eliminates schistosomiasis from high-transmission sites. We conclude that restoring river prawns could be a novel contribution to controlling, or eliminating, schistosomiasis.
View details for DOI 10.1073/pnas.1502651112
View details for Web of Science ID 000358930600060
View details for PubMedID 26195752
View details for PubMedCentralID PMC4534245
- A user-friendly tool to assess management plans for European eel fishery and conservation ENVIRONMENTAL MODELLING & SOFTWARE 2015; 64: 9-17
- A risk-based framework for assessing the cumulative impact of multiple fisheries BIOLOGICAL CONSERVATION 2014; 176: 224-235
- A system-wide approach to supporting improvements in seafood production practices and outcomes FRONTIERS IN ECOLOGY AND THE ENVIRONMENT 2014; 12 (5): 297-305
- Rapid estimation of potential yield for data-poor Tapes philippinarum fisheries in North Adriatic coastal lagoons HYDROBIOLOGIA 2014; 724 (1): 267-277
- Understanding the effectiveness of marine protected areas using genetic connectivity patterns and Lagrangian simulations DIVERSITY AND DISTRIBUTIONS 2013; 19 (12): 1531-1542
- REPRODUCTIVE POTENTIAL CAN PREDICT RECRUITMENT RATES IN ABALONE JOURNAL OF SHELLFISH RESEARCH 2013; 32 (1): 161-169
Unexpected Consequences of Culling on the Eradication of Wildlife Diseases: The Role of Virulence Evolution
2013; 181 (3): 301-313
The removal of individuals from an infected population (culling) is a common strategy used to eradicate wildlife diseases. The manipulation of host density can impose strong selective pressures on pathogen virulence by changing the ecological conditions, thus affecting the effectiveness of eradication programs. We present an analysis of the effect of virulence evolution on culling by extending a susceptible-infected model to the case of competing strains with superinfection. To assess both short- and long-term effects, we first carried out the analysis on an ecological timescale, with a two-strain competition model; then we explore the dynamics of a continuum of pathogenic strains on evolutionary timescales using a quantitative genetics approach (when infection and evolutionary processes occur on comparable timescales) and a game-theoretic approach (when evolutionary processes occur on a slower scale). We demonstrate that the competition among pathogenic variants in the presence of superinfection affects outcome of culling campaigns, since increased host mortality may select for less virulent strains able to establish in sparser populations. This can lead to the counterintuitive result that disease abundance and prevalence may even increase with culling, thus making the eradication of infections considerably less likely. This is particularly relevant in the case of zoonoses where higher prevalence and abundance of pathogens in wild reservoirs may increase the risk of spillover in livestock and humans.
View details for DOI 10.1086/669154
View details for Web of Science ID 000315927900004
View details for PubMedID 23448881
Effects of heat recovery for district heating on waste incineration health impact: A simulation study in Northern Italy
SCIENCE OF THE TOTAL ENVIRONMENT
2013; 444: 369-380
The construction of waste incinerators in populated areas always causes substantial public concern. Since the heat from waste combustion can be recovered to power district heating networks and allows for the switch-off of domestic boilers in urbanized areas, predictive models for health assessment should also take into account the potential benefits of abating an important source of diffuse emission. In this work, we simulated the dispersion of atmospheric pollutants from a waste incinerator under construction in Parma (Italy) into different environmental compartments and estimated the potential health effect of both criteria- (PM(10)) and micro-pollutants (PCDD/F, PAH, Cd, Hg). We analyzed two emission scenarios, one considering only the new incinerator, and the other accounting for the potential decrease in pollutant concentrations due to the activation of a district heating network. We estimated the effect of uncertainty in parameter estimation on health risk through Monte Carlo simulations. In addition, we analyzed the robustness of health risk to alternative assumptions on: a) the geographical origins of the potentially contaminated food, and b) the dietary habits of the exposed population. Our analysis showed that under the specific set of assumptions and emission scenarios explored in the present work: (i) the proposed waste incinerator plant appears to cause negligible harm to the resident population; (ii) despite the net increase in PM(10) mass balance, ground-level concentration of fine particulate matter may be curbed by the activation of an extensive district heating system powered through waste combustion heat recovery and the concurrent switch-off of domestic/industrial heating boilers. In addition, our study showed that the health risk caused by waste incineration emissions is sensitive to assumptions about the typical diet of the resident population, and the geographical origins of food production.
View details for DOI 10.1016/j.scitotenv.2012.11.079
View details for Web of Science ID 000316240200040
View details for PubMedID 23280295
A review of exposure assessment methods in epidemiological studies on incinerators.
Journal of environmental and public health
2013; 2013: 129470-?
Incineration is a common technology for waste disposal, and there is public concern for the health impact deriving from incinerators. Poor exposure assessment has been claimed as one of the main causes of inconsistency in the epidemiological literature. We reviewed 41 studies on incinerators published between 1984 and January 2013 and classified them on the basis of exposure assessment approach. Moreover, we performed a simulation study to explore how the different exposure metrics may influence the exposure levels used in epidemiological studies. 19 studies used linear distance as a measure of exposure to incinerators, 11 studies atmospheric dispersion models, and the remaining 11 studies a qualitative variable such as presence/absence of the source. All reviewed studies utilized residence as a proxy for population exposure, although residence location was evaluated with different precision (e.g., municipality, census block, or exact address). Only one study reconstructed temporal variability in exposure. Our simulation study showed a notable degree of exposure misclassification caused by the use of distance compared to dispersion modelling. We suggest that future studies (i) make full use of pollution dispersion models; (ii) localize population on a fine-scale; and (iii) explicitly account for the presence of potential environmental and socioeconomic confounding.
View details for DOI 10.1155/2013/129470
View details for PubMedID 23840228
Contamination, parasitism and condition of Anguilla anguilla in three Italian stocks
2013; 22 (1): 94-108
In conjunction with habitat loss and overfishing, pollution and parasitism are believed to be relevant causes of collapse of Anguilla, as these can affect eel swimming ability and the development of gonads and embryos. The present study investigated Persistent Organic Pollutant (POP) concentrations, infection levels of Anguillicoloides crassus, lipid content and gonad abnormalities in eels sampled in 2007-2008 in three Italian water bodies (Caprolace Lake, Lesina Lagoon and Tevere River) that vary in salinity, trophic condition, contamination level and fishing pressure. Our analysis revealed that low-to-moderate levels of contamination and parasitism were not associated with gonad abnormalities in Caprolace Lake and Lesina Lagoon. On the contrary, POP concentrations and abundances of swim bladder nematodes were remarkably high in eels from the heavily urbanized Tevere River and were associated with significant gonad and swim bladder alterations. Contamination and infestation levels were so high to potentially impair spawner successful migration and reproduction. POP concentrations in Tevere eels also exceeded levels considered safe for food consumption. Though marginally contaminated, eels from the oligotrophic Caprolace Lake were in critical health condition: their lipid reserve was so low as to be considered insufficient to sustain the energetic costs of the transoceanic migration. Lesina eel stock was the only one displaying relatively good quality but here spawner abundance is likely limited by overfishing. Our results suggest that multiple stressors may potentially affect eel reproductive success. More definitive studies are needed to assess whether health effects caused by these multiple stressors are additive, compensatory or synergistic.
View details for DOI 10.1007/s10646-012-1006-0
View details for Web of Science ID 000312659600010
View details for PubMedID 23076840
- Reproductive Potential Can Predict Recruitment Rates in Abalone Journal of Shellfish Research 2013; 32 (1): 162-169
Assessing Dispersal Patterns of Fish Propagules from an Effective Mediterranean Marine Protected Area
2012; 7 (12)
Successfully enforced marine protected areas (MPAs) have been widely demonstrated to allow, within their boundaries, the recovery of exploited species and beyond their boundaries, the spillover of juvenile and adult fish. Little evidence is available about the so-called 'recruitment subsidy', the augmented production of propagules (i.e. eggs and larvae) due to the increased abundance of large-sized spawners hosted within effective MPAs. Once emitted, propagules can be locally retained and/or exported elsewhere. Patterns of propagule retention and/or export from MPAs have been little investigated, especially in the Mediterranean. This study investigated the potential for propagule production and retention/export from a Mediterranean MPA (Torre Guaceto, SW Adriatic Sea) using the white sea bream, Diplodus sargus sargus, as a model species. A multidisciplinary approach was used combining 1) spatial distribution patterns of individuals (post-settlers and adults) assessed through visual census within Torre Guaceto MPA and in northern and southern unprotected areas, 2) Lagrangian simulations of dispersal based on an oceanographic model of the region and data on early life-history traits of the species (spawning date, pelagic larval duration) and 3) a preliminary genetic study using microsatellite loci. Results show that the MPA hosts higher densities of larger-sized spawners than outside areas, potentially guaranteeing higher propagule production. Model simulations and field observation suggest that larval retention within and long-distance dispersal across MPA boundaries allow the replenishment of the MPA and of exploited populations up to 100 km down-current (southward) from the MPA. This pattern partially agrees with the high genetic homogeneity found in the entire study area (no differences in genetic composition and diversity indices), suggesting a high gene flow. By contributing to a better understanding of propagule dispersal patterns, these findings provide crucial information for the design of MPAs and MPA networks effective to replenish fish stocks and enhance fisheries in unprotected areas.
View details for DOI 10.1371/journal.pone.0052108
View details for Web of Science ID 000312794500092
View details for PubMedID 23284887
Evidence That Marine Reserves Enhance Resilience to Climatic Impacts
2012; 7 (7)
Establishment of marine protected areas, including fully protected marine reserves, is one of the few management tools available for local communities to combat the deleterious effect of large scale environmental impacts, including global climate change, on ocean ecosystems. Despite the common hope that reserves play this role, empirical evidence of the effectiveness of local protection against global problems is lacking. Here we show that marine reserves increase the resilience of marine populations to a mass mortality event possibly caused by climate-driven hypoxia. Despite high and widespread adult mortality of benthic invertebrates in Baja California, Mexico, that affected populations both within and outside marine reserves, juvenile replenishment of the species that supports local economies, the pink abalone Haliotis corrugata, remained stable within reserves because of large body size and high egg production of the protected adults. Thus, local protection provided resilience through greater resistance and faster recovery of protected populations. Moreover, this benefit extended to adjacent unprotected areas through larval spillover across the edges of the reserves. While climate change mitigation is being debated, coastal communities have few tools to slow down negative impacts of global environmental shifts. These results show that marine protected areas can provide such protection.
View details for DOI 10.1371/journal.pone.0040832
View details for Web of Science ID 000306548900054
View details for PubMedID 22855690
View details for PubMedCentralID PMC3408031
- Translocation of stream-dwelling salmonids in headwaters: insights from a 15-year reintroduction experience REVIEWS IN FISH BIOLOGY AND FISHERIES 2012; 22 (2): 437-455
Fishery-Induced Selection for Slow Somatic Growth in European Eel
2012; 7 (5)
Both theoretical and experimental studies have shown that fishing mortality can induce adaptive responses in body growth rates of fishes in the opposite direction of natural selection. We compared body growth rates in European eel (Anguilla anguilla) from three Mediterranean stocks subject to different fishing pressure. Results are consistent with the hypotheses that i) fast-growing individuals are more likely to survive until sexual maturity than slow-growing ones under natural conditions (no fishing) and ii) fishing can select for slow-growing individuals by removing fast-growing ones. Although the possibility of human-induced evolution seems remote for a panmictic species like such as the European eel, further research is desirable to assess the implications of the intensive exploitation on this critically endangered fish.
View details for DOI 10.1371/journal.pone.0037622
View details for Web of Science ID 000305345300062
View details for PubMedID 22666373
Allometric scaling of mortality rates with body mass in abalones
2012; 168 (4): 989-996
The existence of an allometric relationship between mortality rates and body mass has been theorized and extensively documented across taxa. Within species, however, the allometry between mortality rates and body mass has received substantially less attention and the consistency of such scaling patterns at the intra-specific level is controversial. We reviewed 73 experimental studies to examine the relationship between mortality rates and body size among seven species of abalone (Haliotis spp.), a marine herbivorous mollusk. Both in the field and in the laboratory, log-transformed mortality rates were negatively correlated with log-transformed individual body mass for all species considered, with allometric exponents remarkably similar among species. This regular pattern confirms previous findings that juvenile abalones suffer higher mortality rates than adult individuals. Field mortality rates were higher overall than those measured in the laboratory, and the relationship between mortality and body mass tended to be steeper in field than in laboratory conditions for all species considered. These results suggest that in the natural environment, additional mortality factors, especially linked to predation, could significantly contribute to mortality, particularly at small body sizes. On the other hand, the consistent allometry of mortality rates versus body mass in laboratory conditions suggests that other sources of mortality, beside predation, are size-dependent in abalone.
View details for DOI 10.1007/s00442-011-2163-1
View details for Web of Science ID 000301604200010
View details for PubMedID 22020817
- Consequences of extreme events on population persistence and evolution of a quantitative trait ECOLOGICAL INFORMATICS 2012; 8: 20-28
Dispersal Patterns of Coastal Fish: Implications for Designing Networks of Marine Protected Areas
2012; 7 (2)
Information about dispersal scales of fish at various life history stages is critical for successful design of networks of marine protected areas, but is lacking for most species and regions. Otolith chemistry provides an opportunity to investigate dispersal patterns at a number of life history stages. Our aim was to assess patterns of larval and post-settlement (i.e. between settlement and recruitment) dispersal at two different spatial scales in a Mediterranean coastal fish (i.e. white sea bream, Diplodus sargus sargus) using otolith chemistry. At a large spatial scale (∼200 km) we investigated natal origin of fish and at a smaller scale (∼30 km) we assessed "site fidelity" (i.e. post-settlement dispersal until recruitment). Larvae dispersed from three spawning areas, and a single spawning area supplied post-settlers (proxy of larval supply) to sites spread from 100 to 200 km of coastline. Post-settlement dispersal occurred within the scale examined of ∼30 km, although about a third of post-settlers were recruits in the same sites where they settled. Connectivity was recorded both from a MPA to unprotected areas and vice versa. The approach adopted in the present study provides some of the first quantitative evidence of dispersal at both larval and post-settlement stages of a key species in Mediterranean rocky reefs. Similar data taken from a number of species are needed to effectively design both single marine protected areas and networks of marine protected areas.
View details for DOI 10.1371/journal.pone.0031681
View details for Web of Science ID 000302741300088
View details for PubMedID 22355388
- Getting a free ride on poultry farms: how highly pathogenic avian influenza may persist in spite of its virulence THEORETICAL ECOLOGY 2012; 5 (1): 23-35
- Integrating habitat restoration and fisheries management: A small-scale case-study to support EEL conservation at the global scale KNOWLEDGE AND MANAGEMENT OF AQUATIC ECOSYSTEMS 2012
The Effect of Recurrent Floods on Genetic Composition of Marble Trout Populations
2011; 6 (9)
A changing global climate can threaten the diversity of species and ecosystems. We explore the consequences of catastrophic disturbances in determining the evolutionary and demographic histories of secluded marble trout populations in Slovenian streams subjected to weather extremes, in particular recurrent flash floods and debris flows causing massive mortalities. Using microsatellite data, a pattern of extreme genetic differentiation was found among populations (global F(ST) of 0.716), which exceeds the highest values reported in freshwater fish. All locations showed low levels of genetic diversity as evidenced by low heterozygosities and a mean of only 2 alleles per locus, with few or no rare alleles. Many loci showed a discontinuous allele distribution, with missing alleles across the allele size range, suggestive of a population contraction. Accordingly, bottleneck episodes were inferred for all samples with a reduction in population size of 3-4 orders of magnitude. The reduced level of genetic diversity observed in all populations implies a strong impact of genetic drift, and suggests that along with limited gene flow, genetic differentiation might have been exacerbated by recurrent mortalities likely caused by flash flood and debris flows. Due to its low evolutionary potential the species might fail to cope with an intensification and altered frequency of flash flood events predicted to occur with climate change.
View details for DOI 10.1371/journal.pone.0023822
View details for Web of Science ID 000294802800009
View details for PubMedID 21931617
- Density-dependent and inter-specific interactions affecting European eel settlement in freshwater habitats HYDROBIOLOGIA 2011; 671 (1): 259-265
- An integrated genetic- demographic model to unravel the origin of genetic structure in European eel (Anguilla anguilla L.) EVOLUTIONARY APPLICATIONS 2011; 4 (4): 517-533
- No apparent genetic bottleneck in the demographically declining European eel using molecular genetics and forward-time simulations CONSERVATION GENETICS 2011; 12 (3): 813-825
- Use of Anguilla anguilla for Biomonitoring Persistent Organic Pollutants (POPs) in Brackish and Riverine Waters in Central and Southern Italy WATER AIR AND SOIL POLLUTION 2011; 217 (1-4): 321-331
- Application of a Random Forest algorithm to predict spatial distribution of the potential yield of Ruditapes philippinarum in the Venice lagoon, Italy ECOLOGICAL MODELLING 2011; 222 (8): 1471-1478
- Body growth and mortality of the spiny lobster Palinurus elephas within and outside a small marine protected area (vol 106, pg 543, 2010) FISHERIES RESEARCH 2011; 108 (2-3): 404-404
Genetic patchiness in European eel adults evidenced by molecular genetics and population dynamics modelling
MOLECULAR PHYLOGENETICS AND EVOLUTION
2011; 58 (2): 198-206
Disentangling the demographic processes that determine the genetic structure of a given species is a fundamental question in conservation and management. In the present study, the population structure of the European eel was examined with a multidisciplinary approach combining the fields of molecular genetics and population dynamics modelling. First, we analyzed a total of 346 adult specimens of known age collected in three separate sample sites using a large panel of 22 EST-linked microsatellite loci. Second, we developed a European eel-specific model to unravel the demographic mechanisms that can produce the level of genetic differentiation estimated by molecular markers. This is the first study that reveals a pattern of genetic patchiness in maturing adults of the European eel. A highly significant genetic differentiation was observed among samples that did not follow an Isolation-by-Distance or Isolation-by-Time pattern. The observation of genetic patchiness in adults is likely to result from a limited parental contribution to each spawning event as suggested by our modelling approach. The value of genetic differentiation found is predicted by the model when reproduction occurs in a limited number of spawning events isolated from each other in time or space, with an average of 130-375 breeders in each spawning event. Unpredictability in spawning success may have important consequences for the life-history evolution of the European eel, including a bet-hedging strategy (distributing reproductive efforts over time) which could in turn guarantee successful reproduction of some adults.
View details for DOI 10.1016/j.ympev.2010.11.019
View details for Web of Science ID 000287888700006
View details for PubMedID 21129491
Intra-specific scaling of natural mortality in fish: the paradigmatic case of the European eel
2011; 165 (2): 333-339
Identifying factors and processes influencing natural mortality is fundamental to the understanding of population dynamics. Metabolic theory of ecology and experimental studies at the cross-species level suggest the existence of general patterns linking natural mortality to body mass and temperature. However, there is scant evidence that similar relationships also hold at the intra-specific scale, possibly because of the relatively narrow range of sizes and temperatures experienced by most species and the effect of local adaptation, which can obscure links between temperature and vital rates. In this sense, the European eel Anguilla anguilla, a panmictic species with a wide distribution range, provides a paradigmatic case. We compiled data published in the past 30 years on eel mortality during the continental phase of the life cycle for 15 eel stocks and calibrated a general model for mortality, considering the effects of body mass, temperature, stock density and gender. Estimated activation energy (E = 1.2 eV) was at the upper extreme reported for metabolic reactions. Estimated mortality rates (ranging between 0.02 year(-1) at 8°C, low density and 0.47 year(-1) at 18°C, high density for a body mass of 100 g) were appreciably lower than those of most fishes, most likely due to the exceptionally low energy-consuming metabolism of eel.
View details for DOI 10.1007/s00442-010-1727-9
View details for Web of Science ID 000286224900008
View details for PubMedID 20665048
Innocent until proven guilty? Stable coexistence of alien rainbow trout and native marble trout in a Slovenian stream
2011; 98 (1): 57-66
To understand the consequences of the invasion of the nonnative rainbow trout Oncorhynchus mykiss on the native marble trout Salmo marmoratus, we compared two distinct headwater sectors where marble trout occur in allopatry (MTa) or sympatry (MTs) with rainbow trout (RTs) in the Idrijca River (Slovenia). Using data from field surveys from 2002 to 2009, with biannual (June and September) sampling and tagging from June 2004 onwards, we analyzed body growth and survival probabilities of marble trout in each stream sector. Density of age-0 in September over the study period was greater for MTs than MTa and very similar between MTs and RTs, while density of trout ≥age-1 was similar for MTa and MTs and greater than density of RTs. Monthly apparent survival probabilities were slightly higher in MTa than in MTs, while RTs showed a lower survival than MTs. Mean weight of marble and rainbow trout aged 0+ in September was negatively related to cohort density for both marble and rainbow trout, but the relationship was not significantly different between MTs and MTa. No clear depression of body growth of sympatric marble trout between sampling intervals was observed. Despite a later emergence, mean weight of RTs cohorts at age 0+ in September was significantly higher than weight of both MTs and MTa. The establishment of a self-sustaining population of rainbow trout does not have a significant impact on body growth and survival probabilities of sympatric marble trout. The numerical dominance of rainbow trout in streams at lower altitudes seem to suggest that while the low summer flow pattern of Slovenian streams is favorable for rainbow trout invasion, the adaptation of marble trout to headwater environments may limit the invasion success of rainbow trout in headwaters.
View details for DOI 10.1007/s00114-010-0741-4
View details for Web of Science ID 000286114800008
View details for PubMedID 21088818
- Body growth and mortality of the spiny lobster Palinurus elephas within and outside a small marine protected area FISHERIES RESEARCH 2010; 106 (3): 543-549
The value of spatial information in MPA network design
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2010; 107 (43): 18294-18299
The science of spatial fisheries management, which combines ecology, oceanography, and economics, has matured significantly. As a result, there have been recent advances in exploiting spatially explicit data to develop spatially explicit management policies, such as networks of marine protected areas (MPAs). However, when data are sparse, spatially explicit policies become less viable, and we must instead rely on blunt policies such as total allowable catches or imprecisely configured networks of MPAs. Therefore, spatial information has the potential to change management approaches and thus has value. We develop a general framework within which to analyze the value of information for spatial fisheries management and apply that framework to several US Pacific coast fisheries. We find that improved spatial information can increase fishery value significantly (>10% in our simulations), and that it changes dramatically the efficient management approach-switching from diffuse effort everywhere to a strategy where fishing is spatially targeted, with some areas under intensive harvest and others closed to fishing. Using all available information, even when incomplete, is essential to management success and may as much as double fishery value relative to using (admittedly incorrect) assumptions commonly invoked.
View details for DOI 10.1073/pnas.0908057107
View details for Web of Science ID 000283677400016
View details for PubMedID 20176962
- Detection of density-dependent growth at two spatial scales in marble trout (Salmo marmoratus) populations ECOLOGY OF FRESHWATER FISH 2010; 19 (3): 338-347
- Individual growth and its implications for the recruitment dynamics of stream-dwelling marble trout (Salmo marmoratus) ECOLOGY OF FRESHWATER FISH 2010; 19 (3): 477-486
- The management of small, isolated salmonid populations: do we have to fix it if it ain't broken? ANIMAL CONSERVATION 2010; 13 (1): 21-23
Genetic variability is unrelated to growth and parasite infestation in natural populations of the European eel (Anguilla anguilla)
2009; 18 (22): 4604-4616
Positive correlations between individual genetic heterozygosity and fitness-related traits (HFCs) have been observed in organisms as diverse as plants, marine bivalves, fish or mammals. HFCs are not universal and the strength and stability of HFCs seem to be variable across species, populations and ages. We analysed the relationship between individual genetic variability and two different estimators of fitness in natural samples of European eel, growth rate (using back-calculated length-at-age 1, 2 and 3) and parasite infestation by the swimbladder nematode Anguillicola crassus. Despite using a large data set of 22 expressed sequence tags-derived microsatellite loci and a large sample size of 346 individuals, no heterozygote advantage was observed in terms of growth rate or parasite load. The lack of association was evidenced by (i) nonsignificant global HFCs, (ii) a Multivariate General Linear Model showing no effect of heterozygosity on fitness components, (iii) single-locus analysis showing a lower number of significant tests than the expected false discovery rate, (iv) sign tests showing only a significant departure from expectations at one component, and, (v) a random distribution of significant single-locus HFCs that was not consistent across fitness components or sampling sites. This contrasts with the positive association observed in farmed eels in a previous study using allozymes, which can be explained by the nature of the markers used, with the allozyme study including many loci involved in metabolic energy pathways, while the expressed sequence tags-linked microsatellites might be located in genes or in the proximity of genes uncoupled with metabolism/growth.
View details for DOI 10.1111/j.1365-294X.2009.04390.x
View details for Web of Science ID 000271468800011
View details for PubMedID 19840264
Genetic composition of Atlantic and Mediterranean recruits of European eel Anguilla anguilla based on EST-linked microsatellite loci
JOURNAL OF FISH BIOLOGY
2009; 74 (9): 2034-2046
Anguilla anguilla glass eels arriving at two Mediterranean and two Atlantic sites were tested for differences in genetic composition between regions using a total of 23 microsatellite loci developed from an expressed sequence tag (EST) library. Hierarchical analysis of molecular variance indicated a non-significant difference between regions (Mediterranean v. Atlantic), which contrasted with the significant differences observed between samples within regions. The existence of a single spawning site for all A. anguilla individuals and extensive migration loop with great opportunity for mixing of individuals might explain the homogeneity in genetic composition found between regions. The observation of a (small-scale) pattern of genetic patchiness among intra-annual samples (arrival waves) within geographic regions does not conflict with the lack of (large-scale) geographic sub-structuring found between the Mediterranean and Atlantic regions, but most likely is a consequence of the strong dependence of A. anguilla on oceanic conditions in the Sargasso Sea that might result in a limited parental contribution to each spawning event. The comparison of Atlantic and Mediterranean A. anguilla glass eel recruits based on EST-linked microsatellite loci provides evidence supporting the hypothesis of panmixia A. anguilla across Europe.
View details for DOI 10.1111/j.1095-8649.2009.02267.x
View details for Web of Science ID 000268271100014
View details for PubMedID 20735687
Size selectivity of fyke nets for European eel Anguilla anguilla
JOURNAL OF FISH BIOLOGY
2009; 74 (9): 2178-2186
Size selectivity of fyke nets for European eels Anguilla anguilla was investigated by reviewing the results of published experimental studies. A general size selectivity model was then derived that can be easily incorporated into demographic models to simulate population dynamics, assess and monitor abundance and length structure of eel stocks and forecast the consequences of different management options.
View details for DOI 10.1111/j.1095-8649.2009.02243.x
View details for Web of Science ID 000268271100023
View details for PubMedID 20735696
Assessing Management Plans for the Recovery of the European Eel: A Need for Multi-Objective Analyses
International Symposium on Challenges for Diadromous Fishes in a Dynamic Global Environment
AMER FISHERIES SOC. 2009: 637–647
View details for Web of Science ID 000270598800040
Allometric Scaling and Seasonality in the Epidemics of Wildlife Diseases
2008; 172 (6): 818-828
We present a susceptibles-exposed-infectives (SEI) model to analyze the effects of seasonality on epidemics, mainly of rabies, in a wide range of wildlife species. Model parameters are cast as simple allometric functions of host body size. Via nonlinear analysis, we investigate the dynamical behavior of the disease for different levels of seasonality in the transmission rate and for different values of the pathogen basic reproduction number (R(0)) over a broad range of body sizes. While the unforced SEI model exhibits long-term epizootic cycles only for large values of R(0), the seasonal model exhibits multiyear periodicity for small values of R(0). The oscillation period predicted by the seasonal model is consistent with those observed in the field for different host species. These conclusions are not affected by alternative assumptions for the shape of seasonality or for the parameters that exhibit seasonal variations. However, the introduction of host immunity (which occurs for rabies in some species and is typical of many other wildlife diseases) significantly modifies the epidemic dynamics; in this case, multiyear cycling requires a large level of seasonal forcing. Our analysis suggests that the explicit inclusion of periodic forcing in models of wildlife disease may be crucial to correctly describe the epidemics of wildlife that live in strongly seasonal environments.
View details for DOI 10.1086/593000
View details for Web of Science ID 000261235500011
View details for PubMedID 18947297
- Total population density during the first year of life as a major determinant of lifetime body-length trajectory in marble trout ECOLOGY OF FRESHWATER FISH 2008; 17 (4): 515-519
Parasites in food webs: the ultimate missing links
2008; 11 (6): 533-546
Parasitism is the most common consumer strategy among organisms, yet only recently has there been a call for the inclusion of infectious disease agents in food webs. The value of this effort hinges on whether parasites affect food-web properties. Increasing evidence suggests that parasites have the potential to uniquely alter food-web topology in terms of chain length, connectance and robustness. In addition, parasites might affect food-web stability, interaction strength and energy flow. Food-web structure also affects infectious disease dynamics because parasites depend on the ecological networks in which they live. Empirically, incorporating parasites into food webs is straightforward. We may start with existing food webs and add parasites as nodes, or we may try to build food webs around systems for which we already have a good understanding of infectious processes. In the future, perhaps researchers will add parasites while they construct food webs. Less clear is how food-web theory can accommodate parasites. This is a deep and central problem in theoretical biology and applied mathematics. For instance, is representing parasites with complex life cycles as a single node equivalent to representing other species with ontogenetic niche shifts as a single node? Can parasitism fit into fundamental frameworks such as the niche model? Can we integrate infectious disease models into the emerging field of dynamic food-web modelling? Future progress will benefit from interdisciplinary collaborations between ecologists and infectious disease biologists.
View details for DOI 10.1111/j.1461-0248.2008.01174.x
View details for Web of Science ID 000255552100001
View details for PubMedID 18462196
View details for PubMedCentralID PMC2408649
The role of density-dependent individual growth in the persistence of freshwater salmonid populations
2008; 156 (3): 523-534
Theoretical and empirical models of populations dynamics have paid little attention to the implications of density-dependent individual growth on the persistence and regulation of small freshwater salmonid populations. We have therefore designed a study aimed at testing our hypothesis that density-dependent individual growth is a process that enhances population recovery and reduces extinction risk in salmonid populations in a variable environment subject to disturbance events. This hypothesis was tested in two newly introduced marble trout (Salmo marmoratus) populations living in Slovenian streams (Zakojska and Gorska) subject to severe autumn floods. We developed a discrete-time stochastic individual-based model of population dynamics for each population with demographic parameters and compensatory responses tightly calibrated on data from individually tagged marble trout. The occurrence of severe flood events causing population collapses was explicitly accounted for in the model. We used the model in a population viability analysis setting to estimate the quasi-extinction risk and demographic indexes of the two marble trout populations when individual growth was density-dependent. We ran a set of simulations in which the effect of floods on population abundance was explicitly accounted for and another set of simulations in which flood events were not included in the model. These simulation results were compared with those of scenarios in which individual growth was modelled with density-independent Von Bertalanffy growth curves. Our results show how density-dependent individual growth may confer remarkable resilience to marble trout populations in case of major flood events. The resilience to flood events shown by the simulation results can be explained by the increase in size-dependent fecundity as a consequence of the drop in population size after a severe flood, which allows the population to quickly recover to the pre-event conditions. Our results suggest that density-dependent individual growth plays a potentially powerful role in the persistence of freshwater salmonids living in streams subject to recurrent yet unpredictable flood events.
View details for DOI 10.1007/s00442-008-1012-3
View details for Web of Science ID 000255680000005
View details for PubMedID 18386068
Body-size scaling in an SEI model of wildlife diseases
THEORETICAL POPULATION BIOLOGY
2008; 73 (3): 374-382
A number of wildlife pathogens are generalist and can affect different host species characterized by a wide range of body sizes. In this work we analyze the role of allometric scaling of host vital and epidemiological rates in a Susceptible-Exposed-Infected (SEI) model. Our analysis shows that the transmission coefficient threshold for the disease to establish in the population scales allometrically (exponent = 0.45) with host size as well as the threshold at which limit cycles occur. In contrast, the threshold of the basic reproduction number for sustained oscillations to occur is independent of the host size and is always greater than 5. In the case of rabies, we show that the oscillation periods predicted by the model match those observed in the field for a wide range of host sizes. The population dynamics of the SEI model is also analyzed in the case of pathogens affecting multiple coexisting hosts with different body sizes. Our analyses show that the basic reproduction number for limit cycles to occur depends on the ratio between host sizes, that the oscillation period in a multihost community is set by the smaller species dynamics, and that intermediate interspecific disease transmission can stabilize the epidemic occurrence in wildlife communities.
View details for DOI 10.1016/j.tpb.2007.12.003
View details for Web of Science ID 000255852500006
View details for PubMedID 18241903
- Potential factors controlling the population viability of newly introduced endangered marble trout populations BIOLOGICAL CONSERVATION 2008; 141 (1): 198-210
- A cost analysis of alternative culling strategies for the eradication of classical swine fever in wildlife ENVIRONMENT AND DEVELOPMENT ECONOMICS 2007; 12: 653-671
Multi-objective assessment of conservation measures for the European eel (Anguilla anguilla): an application to the Camargue lagoons
ICES Conference on Is There More to Eels than Slime
OXFORD UNIV PRESS. 2007: 1483–90
View details for Web of Science ID 000250901000023
Transmission Heterogeneity and Control Strategies for Infectious Disease Emergence
2007; 2 (8)
The control of emergence and spread of infectious diseases depends critically on the details of the genetic makeup of pathogens and hosts, their immunological, behavioral and ecological traits, and the pattern of temporal and spatial contacts among the age/stage-classes of susceptible and infectious host individuals.We show that failing to acknowledge the existence of heterogeneities in the transmission rate among age/stage-classes can make traditional eradication and control strategies ineffective, and in some cases, policies aimed at controlling pathogen emergence can even increase disease incidence in the host. When control strategies target for reduction in numbers those subsets of the population that effectively limit the production of new susceptible individuals, then control can produce a flush of new susceptibles entering the population. The availability of a new cohort of susceptibles may actually increase disease incidence. We illustrate these general points using Classical Swine Fever as a reference disease.Negative effects of culling are robust to alternative formulations of epidemiological processes and underline the importance of better assessing transmission structure in the design of wildlife disease control strategies.
View details for DOI 10.1371/journal.pone.0000747
View details for Web of Science ID 000207455300003
View details for PubMedID 17712403
- Early survival of marble trout Salmo marmoratus: evidence for density dependence? ECOLOGY OF FRESHWATER FISH 2007; 16 (2): 116-123
- Density-dependent individual growth of marble trout (Salmo marmoratus) in the Soca and Idrijca river basins, Slovenia HYDROBIOLOGIA 2007; 583: 57-68
A comparative analysis of three habitat suitability models for commercial yield estimation of Tapes philippinarum in a North Adriatic coastal lagoon (Sacca di Goro, Italy)
MARINE POLLUTION BULLETIN
2007; 55 (10-12): 579-590
Habitat Suitability (HS) models have been extensively used by conservation planners to estimate the spatial distribution of threatened species and of species of commercial interest. In this work we compare three HS models for the estimation of commercial yield potential and the identification of suitable sites for Tapes philippinarum rearing in the Sacca di Goro lagoon (Italy) on the basis of six environmental factors. The habitat suitability index (HSI) is based on expert opinion while the habitat suitability conditional (HSC) is calibrated on observational data. The habitat suitability mixed (HSM) model is a two-part model combining expert knowledge and regression analysis: the first component of the model uses logistic regression to identify the areas in which clams are likely to be present; the second part applies the same parameter-specific suitability functions of the HSI model only in the areas previously identified as productive by the logistic component. The HS models were validated on an independent data set and estimates of potential yield of the Goro lagoon were compared. The effectiveness of the three approaches is then discussed in terms of predicted yield and identification of suitable sites for farming.
View details for DOI 10.1016/j.marpolbul.2007.09.016
View details for Web of Science ID 000252169600017
View details for PubMedID 17963792
- Estimating clam yield potential in the Sacca di Goro lagoon (Italy) by using a two-part conditional model AQUACULTURE 2006; 261 (4): 1281-1291
A simulation model of population genetic to unravel the panmictic nature of European eel
WILEY-BLACKWELL. 2006: 242–242
View details for Web of Science ID 000243329400054
- Timing and rate of sexual maturation of European eel in brackish and freshwater environments Annual Symposium of the Fisheries-Society-of-the-British-Isles WILEY-BLACKWELL. 2006: 200–208
A demographic model for the management of eel fisheries in the Camargue lagoons
WILEY-BLACKWELL. 2006: 255–256
View details for Web of Science ID 000243329400082
- Sex differentiation of the European eel in brackish and freshwater environments: a comparative analysis JOURNAL OF FISH BIOLOGY 2006; 69 (4): 1228-1235
- A GIS-based habitat suitability model for commercial yield estimation of Tapes philippinarum in a Mediterranean coastal lagoon (Sacca di Goro, Italy) 1st International Conference on Southern European Coastal Lagoons ELSEVIER SCIENCE BV. 2006: 90–104
Integrating marine protected areas with catch regulation
CANADIAN JOURNAL OF FISHERIES AND AQUATIC SCIENCES
2006; 63 (3): 642-649
View details for Web of Science ID 000237201200015
- Age and growth of Anguilla anguilla in the Camargue lagoons JOURNAL OF FISH BIOLOGY 2006; 68 (3): 876-890
- A preliminary coastal wetland assessment procedure: Designing and testing an environmental sustainability index for Mediterranean lagoons Joint Scientific Meeting of the National-Inter-University-Consortium-for-Marine-Sciences/16th Congress of the Italian-Association-for-Oceanology-and-Limnology TAYLOR & FRANCIS LTD. 2006: 15–35
- A critical review of representative wetland rapid assessment methods in North America AQUATIC CONSERVATION-MARINE AND FRESHWATER ECOSYSTEMS 2004; 14: S103-S113
- The decline of the grey partridge in Europe: comparing demographies in traditional and modern agricultural landscapes ECOLOGICAL MODELLING 2004; 177 (3-4): 313-335
Density and temperature-dependence of vital rates in the Manila clam Tapes philippinarum: a stochastic demographic model
MARINE ECOLOGY PROGRESS SERIES
2004; 272: 153-164
View details for Web of Science ID 000222526900013
Carbon emissions - The economic benefits of the Kyoto Protocol
2001; 413 (6855): 478-479
The third Conference of the Parties in Kyoto set the target of reducing greenhouse-gas emissions by an average of 5.3% with respect to 1990 values by 2008-2012. One of the main objections to the protocol's ratification is that compliance would pose an unbearable economic burden on the countries involved. But we show here that this is not the case if costs apart from the direct costs of energy production are also considered. Costs are also incurred in rectifying damage to human health, material goods, agriculture and the environment related to greenhouse-gas emissions.
View details for Web of Science ID 000171340500034
View details for PubMedID 11586347
A stochastic bioeconomic analysis of silver eel fisheries
2001; 11 (1): 281-294
View details for Web of Science ID 000166749100023
Pricing biodiversity and ecosystem services: The never-ending story
2000; 50 (4): 347-355
View details for Web of Science ID 000086239800013
VVF: integrating modelling and GIS in a software tool for habitat suitability assessment
ENVIRONMENTAL MODELLING & SOFTWARE
2000; 15 (1): 1-12
View details for Web of Science ID 000084361600001
Interspecific competition among macroparasites in a density-dependent host population
JOURNAL OF MATHEMATICAL BIOLOGY
1998; 37 (5): 467-490
View details for Web of Science ID 000077016600004
Trends in vital rates of the European eel: Evidence for density dependence?
1996; 6 (4): 1281-1294
View details for Web of Science ID A1996VR85600028
Allometry and simple epidemic models for microparasites
1996; 379 (6567): 720-722
Simple mathematical models for microparasites offer a useful way to examine the population dynamics of different viral and bacterial pathogens. One constraint in applying these models in free-living host populations is the paucity of data with which to estimate transmission rates. Here we recast a standard epidemiological model by setting the birth and death rates of the host population and its density as simple allometric functions of host body weight. We then use standard threshold theorems for the model in order to estimate the minimum rate of transmission for the parasite to establish itself in a mammalian host population. Transmission rates that produce different comparable values of the parasites' basic reproductive number, RO, are themselves allometric functions of host body size. We have extended the model to show that hosts having different body sizes suffer epidemic outbreaks whose frequency scales with body size. The expected epidemic periods for pathogens in different mammalian populations correspond to cycles observed in free-living populations.
View details for Web of Science ID A1996TW56700050
View details for PubMedID 8602216
A SIZE AND AGE-STRUCTURED MODEL OF THE EUROPEAN EEL (ANGUILLA-ANGUILLA L)
CANADIAN JOURNAL OF FISHERIES AND AQUATIC SCIENCES
1995; 52 (7): 1351-1367
View details for Web of Science ID A1995TD86500002
MANAGEMENT OF SUBSURFACE WATER BODIES - A COMPUTER-AIDED APPROACH TO MODEL CHOICE AND IMPLEMENTATION
JOURNAL OF ENVIRONMENTAL MANAGEMENT
1994; 42 (2): 137-159
View details for Web of Science ID A1994PM93400004
THE INTERACTION BETWEEN SOIL ACIDITY AND FOREST DYNAMICS - A SIMPLE-MODEL EXHIBITING CATASTROPHIC BEHAVIOR
THEORETICAL POPULATION BIOLOGY
1993; 43 (1): 31-51
View details for Web of Science ID A1993KQ07200002
TAXES AND THE DYNAMICS OF OVEREXPLOITED OPEN-ACCESS FISHERIES
25TH EUROPEAN MARINE BIOLOGY SYMP ON EUTROPHICATION OF MARINE ENVIRONMENTS AND POPULATION DYNAMICS OF MARINE ORGANISMS
OLSEN & OLSEN. 1992: 317–322
View details for Web of Science ID A1992BX71B00044