Academic Appointments

Administrative Appointments

  • Associate Director, Veterinary Service Center, Comparative Medicine Department (2019 - Present)
  • Director, Animal Biosafety Level-3 Facility, Comparative Medicine Department (2023 - Present)
  • Director, Laboratory Animal Medicine Residency Program, Comparative Medicine Department (2023 - Present)
  • Director, Diagnostic Laboratory, Comparative Medicine Department (2019 - 2023)

Honors & Awards

  • Laboratory Animal Medicine Consultant to the U.S. Army Surgeon General, U.S. Army Surgeon General (2017)
  • U.S. Army Surgeon General's "A" Proficiency Designator, U.S. Army Surgeon General (2016)
  • Order of Military Medical Merit, U.S. Army Medical Department (2016)

Boards, Advisory Committees, Professional Organizations

  • Faculty Fellow, Stanford Center for Innovation in Global Health (2019 - Present)
  • Council on Accreditation, AAALAC, International (2018 - Present)
  • Committee Member, ACLAM/ASLAP Program Committee (2015 - 2018)
  • Certified Professional in IACUC Administration, PRIM&R (2012 - Present)
  • Chairman, ACLAM Exam Resources Committee (2012 - 2013)
  • Ad hoc Specialist, AAALAC, International (2011 - 2018)
  • Committee Member, ACLAM Exam Resources Committee (2010 - 2013)
  • Diplomate, American College of Laboratory Animal Medicine (2005 - Present)
  • Member, American Association for Laboratory Animal Science (2005 - Present)
  • Diplomate, American College of Veterinary Preventive Medicine (2003 - Present)

Professional Education

  • MSS, U.S. Army War College, Strategic Studies (2014)
  • MPH, Uniformed Services University of the Health Sciences, Public Health (2003)
  • VMD, University of Pennsylvania School of Veterinary Medicine, Veterinary Medicine (1996)
  • BS, The Pennsylvania State University, Animal Bioscience (1992)

Community and International Work

  • Peru Earthquake Disaster Response Team (2007), Ica Region, Peru


    Health Surveillance

    Partnering Organization(s)

    Naval Medical Research Center Detachment and Peruvian Ministry of Health

    Populations Served

    Effected population of Ica region

    Ongoing Project


    Opportunities for Student Involvement


All Publications

  • Effect of Home Cage Bedding in the Induction Chamber on Serum Cortisol and Corticosterone Levels in Response to Isoflurane-induced Anesthesia in C57BL/6J Mice. Journal of the American Association for Laboratory Animal Science : JAALAS Reiter, C. P., Christy, A. C., Olsen, C. H., Bentzel, D. E. 2017; 56 (2): 118-121


    Mice are routinely anesthetized with isoflurane in an induction chamber. The AVMA Guidelines for the Euthanasia of Animals states that distress should be minimized during euthanasia but does not address this point in regard to induction of anesthesia. Here we evaluated the potential for familiar surroundings to reduce the adrenocortical response of mice during anesthesia induction with isoflurane. However, adding bedding from the animals' home cage to the induction chamber failed to significantly reduce serum cortisol or corticosterone levels in male and female C57BL/6J mice. These results indicate that familiar surroundings do not appear sufficient to reduce the adrenocortical response of mice during anesthesia induction with isoflurane.

    View details for PubMedID 28315639

    View details for PubMedCentralID PMC5361035

  • Evaluation of Consumption of Self-Administered Acetaminophen in Drinking Water and Two Gel Delivery Systems in C57BL/6 Mice. Internet Journal of Veterinary Medicine Brunell, M. K., Olsen, C. H., Christy, A. C., Maxwell, B. M., Bentzel, D. E. 2017; 14 (1): 1 - 11

    View details for DOI 10.5580/IJVM.52393

  • Comparison of Digital Rectal and Microchip Transponder Thermometry in Ferrets (Mustela putorius furo). Journal of the American Association for Laboratory Animal Science : JAALAS Maxwell, B. M., Brunell, M. K., Olsen, C. H., Bentzel, D. E. 2016; 55 (3): 331-5


    Body temperature is a common physiologic parameter measured in both clinical and research settings, with rectal thermometry being implied as the 'gold standard.' However, rectal thermometry usually requires physical or chemical restraint, potentially causing falsely elevated readings due to animal stress. A less stressful method may eliminate this confounding variable. The current study compared 2 types of digital rectal thermometers-a calibrated digital thermometer and a common digital thermometer-with an implantable subcutaneous transponder microchip. Microchips were implanted subcutaneously between the shoulder blades of 16 ferrets (8 male, 8 female), and temperatures were measured twice from the microchip reader and once from each of the rectal thermometers. Results demonstrated the microchip temperature readings had very good to good correlation and agreement to those from both of the rectal thermometers. This study indicates that implantable temperature-sensing microchips are a reliable alternative to rectal thermometry for monitoring body temperature in ferrets.

    View details for PubMedID 27177569

    View details for PubMedCentralID PMC4865697

  • Susceptibility and lack of evidence for a viremic state of rabies in the night owl monkey, Aotus nancymaae. Virology journal Reaves, E. J., Salmón-Mulanovich, G., Guevara, C., Kochel, T. J., Steinbach, T. J., Bentzel, D. E., Montgomery, J. M. 2012; 9: 95


    Rabies causes an acute fatal encephalomyelitis in most mammals following infection with rhabdovirus of the genus Lyssavirus. Little is known about rabies virus infection in species of New World non-human Primates (NHP). To investigate the suitability of the owl monkey Aotus nancymaae asissue sections examined were unremarkable for inflammation or other histologic signs of rabies a viable animal model for rabies virus candidate vaccine testing, we used clinical presentation, serology, viral isolation, and PCR to evaluate the incubation period, immunity, and pathogenesis of infected animals. We tested the hypothesis that no viremic state exists for rabies virus.Eight monkeys divided into two equal groups were inoculated intramuscularly either in the neck or footpad with 105 pfu of rabies virus (Pasteur/V-13R) and observed for >130 days. Oral and blood samples were collected and analyzed.Two monkeys inoculated in the neck displayed classic paralytic rabies. The mean incubation period was 11.5 days. The average maximum IgG response (antibody titer >0.200 O.D.) was achieved at day 10.0 and 62.3 in the clinical rabies and non-clinical rabies cases, respectively (p = 0.0429). No difference in IgM or IgG time to seroconversion or average maximum IgM level was observed between neck versus footpad inoculation groups. No viremia or viral shedding was detected by PCR or viral isolation during the observation period, including within the two symptomatic animals three days after disease onset. Tissue sections examined were unremarkable for inflammation or other histologic signs of rabies within the asymptomatic animal. Similarly none of the brain sections exhibited immunoreactivity for rabies virus antibody.This study demonstrates there is no difference in time to immune response between inoculation sites and distance to the brain; however, immune response tends to be more rapid in cases of clinically apparent disease and prolonged in cases infected at sites further from the brain.Our findings support the hypothesis that a viremic state for rabies does not exist in the New World Monkey, Aotus nancymaae, and it appears that this species may be refractory to infection. The species does provide a suitable model to assess post infection immune responses. Additional studies that address the limitations of sample size, length of observation, and lack of measurable infection should be conducted.

    View details for DOI 10.1186/1743-422X-9-95

    View details for PubMedID 22612895

    View details for PubMedCentralID PMC3522049

  • Epidemiology of spotted fever group and typhus group rickettsial infection in the Amazon basin of Peru. The American journal of tropical medicine and hygiene Forshey, B. M., Stewart, A., Morrison, A. C., Gálvez, H., Rocha, C., Astete, H., Eza, D., Chen, H. W., Chao, C. C., Montgomery, J. M., Bentzel, D. E., Ching, W. M., Kochel, T. J. 2010; 82 (4): 683-90


    A seroprevalence study for IgG antibodies against spotted fever group (SFGR) and typhus group (TGR) Rickettsia among humans and domestic pets was conducted in the city of Iquitos, located in the Amazon basin of Peru. Of 1,195 human sera analyzed, 521 (43.6%) and 123 (10.3%) were positive for SFGR and TGR antibodies, respectively. District of residence and participant age were associated with antibody positivity for both groups, whereas rodent sightings in the home were associated with TGR antibody positivity. Of the 71 canines tested, 42 (59.2%) were positive for SFGR antibodies, and two (2.8%) were positive for TGR antibodies; one active SFGR infection was detected by polymerase chain reaction. An uncharacterized SFGR species was detected in 95.9% (71/74) of Ctenocephalides felis pools collected from domestic pets. These data suggest that rickettsial transmission is widespread in Iquitos. Rickettsia species should be further explored as potential causes of acute febrile illnesses in the region.

    View details for DOI 10.4269/ajtmh.2010.09-0355

    View details for PubMedID 20348519

    View details for PubMedCentralID PMC2844554

  • Cutaneous lesions in a pig. Diagnosis: Porcine juvenile pustular psoriaform dermatitis. Lab animal Bentzel, D., Betterton, L., Carroll, E. E. 2009; 38 (10): 319-21

    View details for DOI 10.1038/laban1009-319

    View details for PubMedID 19773773

  • Capsule polysaccharide conjugate vaccine against diarrheal disease caused by Campylobacter jejuni. Infection and immunity Monteiro, M. A., Baqar, S., Hall, E. R., Chen, Y. H., Porter, C. K., Bentzel, D. E., Applebee, L., Guerry, P. 2009; 77 (3): 1128-36


    The capsule polysaccharide (CPS) of Campylobacter jejuni is one of the few identified virulence determinants of this important human pathogen. Since CPS conjugate vaccines have been so effective against other mucosal pathogens, we evaluated this approach using CPSs from two strains of C. jejuni, 81-176 (HS23 and HS36 serotype complex) and CG8486 (HS4 serotype complex). The CPSs of 81-176 and CG8486 were independently linked to the carrier protein CRM(197) by reductive amination between an aldehyde(s), strategically created at the nonreducing end of each CPS, and accessible amines of CRM(197). In both cases, the CPS:CRM(197) ratio used was 2:1 by weight. Mass spectrometry and gel electrophoresis showed that on average, each glycoconjugate preparation contained, at least in part, two to five CPSs attached to one CRM(197). When administered subcutaneously to mice, these vaccines elicited robust immune responses and significantly reduced the disease following intranasal challenge with the homologous strains of C. jejuni. The CPS(81-176)-CRM(197) vaccine also provided 100% protection against diarrhea in the New World monkey Aotus nancymaae following orogastric challenge with C. jejuni 81-176.

    View details for DOI 10.1128/IAI.01056-08

    View details for PubMedID 19114545

    View details for PubMedCentralID PMC2643618

  • Rapid response to a case of mumps: implications for preventing transmission at a medical research facility. Salud publica de Mexico Salmón-Mulanovich, G., Utz, G., Lescano, A. G., Bentzel, D. E., Blazes, D. L. 2008; 51 (1): 34-8


    To prevent transmission among the staff and potentially among the non-human primate (NHP) colony at the U.S. Naval Medical Research Center Detachment in Peru, where an active case of mumps was discovered in a senior laboratory technician in Sep 03, 2007.Subjects at the research facility were interviewed and potentially susceptible contacts were tested for mumps IgG.In total, 81 out of 106 staff members (76%) had close contact with the case. Only 6/81 (7%) had MMR, 33 (41%) reported having had mumps, and 8 of 45 (18%) of the potentially susceptible individuals did not have immunity (IgG > 20.0). All the susceptible, exposed individuals received MMR vaccine. There were no secondary cases and access to the NHP colony was restricted.Immediate and thorough investigation and occupational health response were imperative in preventing secondary cases of mumps among humans and NHP.

    View details for PubMedID 19180311

    View details for PubMedCentralID PMC4080888

  • Susceptibility of owl monkeys (Aotus nancymaae) to experimental infection with Bartonella bacilliformis. Comparative medicine Bentzel, D. E., Espinosa, B. J., Canal, E., Blazes, D. L., Hall, E. R. 2008; 58 (1): 76-80


    Bartonellosis, caused by Bartonella bacilliformis, is a clinically significant disease in parts of South America, where it is characterized by fever and hemolytic anemia during the often-fatal acute stage and warty skin eruptions during chronic disease. In this study, we evaluated owl monkeys (Aotus nancymaae) as a potential model for studying the immunogenicity and pathology of bartonellosis. Two groups of animals (n = 3 per group) received either 9.5 x 10(7) CFU B. bacilliformis by the ID route or 1.1 x 10(6) CFU by the IV route and were followed for 140 d. Animals were evaluated by physical exam, complete blood count or hematocrit (or both); infection was confirmed by Giemsa staining of blood smears, PCR amplification, and blood culture. On days 7 and 21, Giemsa-stained blood smears from both groups contained organisms (1% to 4% of erythrocytes). All blood cultures and PCR tests were negative. Complete blood counts and chemistry panels showed no difference from baseline. Serology revealed a greater than 4-fold increase in the IgM titer (compared with baseline levels) in the 3 animals from the ID group and 1 animal from the IV group. On day 35, a dermal lesion was excised from the inguinal region of 1 monkey from each group, with a second lesion excised on day 84 from the same monkey in the IV group. However the histopathology and immunostaining of these samples were not consistent with B. bacilliformis. The present study shows that owl monkeys can be infected with B. bacilliformis, but additional dosage studies are necessary to evaluate the usefulness of this species as a disease model for human bartonellosis.

    View details for PubMedID 19793460

    View details for PubMedCentralID PMC2703158

  • Evaluation of two fecal examination techniques for detection of Trypanoxyuris spp. infection in owl monkeys (Aotus nancymae). Journal of the American Association for Laboratory Animal Science : JAALAS Bentzel, D. E., Lescano, A. G., Lucas, C., Bacon, D. J. 2007; 46 (5): 50-3


    Infections of Trypanoxyuris spp. pinworms in Aotus nancymae and other New World primates are typically subclinical, but infection during experimental use could confound interpretation of experimental data. Further, Trypanoxyuris species are highly infective, and rapid diagnosis is important to prevent an outbreak in the animal colony. This study sought to determine whether a fecal flotation technique was sensitive enough to replace the perianal tape test for diagnosis of Trypanoxyuris spp., thereby reducing stress to the animal and sample collection time. On days 0 and 3, we collected fecal samples from 45 animals confirmed to be infected with Trypanoxyuris spp. by perianal tape testing. Fecal samples were evaluated by both a commercial analysis system and by sucrose flotation with centrifugation. For both detection methods, no significant difference in sensitivity was detected between tests conducted on day 0 versus day 3. The sensitivity of repeated commercial tests was 80%, significantly higher than the 60% for sucrose flotation. The commercial test was significantly more sensitive than sucrose flotation, indicating that the commercial system was a better method for detecting Trypanoxyuris spp. However, sensitivity of only 80% confers a considerable risk of false negatives, thereby potentially delaying treatment and further contributing to environmental contamination. In our opinion, neither method of fecal analysis was a suitable replacement for the perianal tape test to diagnose Trypanoxyuris spp. in owl monkeys.

    View details for PubMedID 17877329

  • Comparison of various anthelmintic therapies for the treatment of Trypanoxyuris microon infection in owl monkeys (Aotus nancymae). Comparative medicine Bentzel, D. E., Bacon, D. J. 2007; 57 (2): 206-9


    Trypanoxyuris microon is a pinworm that infects New World nonhuman primates, including Aotus nancymae. Although it typically is clinically insignificant, infection may serve as a significant variable during experimental data analysis. In this study we sought to determine the most effective anthelmintic therapy for eradication of T. microon infection in A. nancymae. Animals confirmed to be infected with T. microon by perianal tape test were treated twice (on days 0 and 14) with pyrantel pamoate, ivermectin, or thiabendazole and evaluated for eggs by daily perianal tape test throughout the entire 28-d period. Successful clearance of eggs was defined as 5 consecutive negative perianal tape tests. Pyrantel pamoate and ivermectin were significantly more effective at egg clearance than were thiabendazole and no treatment. Overall, 100% of the pyrantel pamoate and ivermectin treatment groups were cleared of infection after 2 treatments, whereas only 60% of the thiabendazole group became negative for pinworm eggs. In addition, the time after treatment until clearance was 1 to 2 d for pyrantel pamoate, 2 to 4 d for thiabendazole, and 4 to 6.5 d for ivermectin. These results indicate that pyrantel pamoate was the most effective and rapidly acting anthelmintic for the treatment of adult T. microon infection, with ivermectin as a suitable alternative. However because of the potential for continued development of immature stages or reinfection, anthelmintic doses should be repeated after 1 to 2 wk, in combination with effective environmental sanitation.

    View details for PubMedID 17536622

  • Antimicrobial therapies for pulmonary Klebsiella pneumoniae infection in B6D2F1/J mice immunocompromised by use of sublethal irradiation. Comparative medicine Bentzel, D. E., Elliott, T. B., Keller, C. E., Brook, I., Shoemaker, M. O., Knudson, G. B. 2004; 54 (2): 185-92


    Klebsiella pneumoniae is a common cause of nosocomially acquired pneumonia in immunocompromised patients. Previously, we established a pneumonia model using Klebsiella pneumoniae in B6D2F1/J mice sublethally irradiated with 7-Gy 60Co gamma-radiation and inoculated intratracheally. In the study reported here, we investigated survival of mice following 10 days of antimicrobial therapy with ceftriaxone, gentamicin, gatifloxacin, and a ceftriaxone-gentamicin combination given once daily. Survival was significantly prolonged in response to all therapies. However, survival of mice was 95% when treated with the ceftriaxone-gentamicin combination followed by ceftriaxone alone (75%), and gatifloxacin (80%), whereas survival for controls was 0%. In addition, resistance to any of the treatments did not develop during the study. We conclude that an immunocompromised status does not alter the Infectious Disease Society of America's primary recommendation for treating community-acquired K. pneumoniae pneumonia using a third-generation cephalosporin, with or without an aminoglycoside.

    View details for PubMedID 15134365

  • Susceptibility of irradiated B6D2F1/J mice to Klebsiella pneumoniae administered intratracheally: a pulmonary infection model in an immunocompromised host. Comparative medicine Keller, C. E., Elliott, T. B., Bentzel, D. E., Mog, S. R., Shoemaker, M. O., Knudson, G. B. 2003; 53 (4): 397-403


    Bacteria such as Klebsiella pneumoniae can invade and colonize an immunocompromised host and complicate clinical recovery. In the study reported here, an experimental model of induced pneumonia was developed in 60Co gamma-photon-irradiated mice for the purpose of evaluating efficacy of therapeutic agents. The model was characterized by use of probit analysis of bacterial dose, and microbiologic, and histopathologic results. Bacterial colony-forming-unit (CFU) values producing 50% mortality within 30 days (LD50/30) and their 95% confidence intervals were 4.0 x 10(4) [1.7 x 10(4) - 8.9 x 10(4)] for 0-Gray (Gy)-irradiated mice, 1.9 x 10(4) [7.0 x 10(3) - 4.8 x 10(4)] for 5-Gy-irradiated mice, and 1.0 x 10(3) [2.8 x 10(2) - 3.3 x 10(3)] for 7-Gy-irradiated mice. Probit regression line fits calculated by use of an iterative, weighted least-squares fit, were used to assess a dose-modifying factor (DMF). The DMFs for mortality, compared with that for the 0-Gy dose, with their 95% confidence intervals, were 2.2 [0.63 - 7.7] for the 5-Gy and 38.9 [9.6 -165.0] for 7-Gy doses. The 5-Gy probit line did not significantly differ (P = 0.21) from the 0-Gy probit line (dose ratios did not significantly differ from 1), whereas the 7-Gy probit line differed significantly from the 0-Gy probit line (P < 0.001). These results demonstrate that 7-Gy 60Co gamma-photon radiation in combination with intratracheal K. pneumoniae challenge induces a valid pulmonary infection model in immunocompromised female B6D2F1/J mice.

    View details for PubMedID 14524416

  • Responsibilities of a veterinary augmentation package in support of a contingency operation. Military medicine Bentzel, D. E., Moloff, A. L. 2000; 165 (7): 533-5


    A veterinary augmentation package (VAP) was assigned to the 212th Medical Treatment Facility supporting Task Force Hawk outside Tirana, Albania, from April 15 to July 4, 1999. The VAP's mission was to provide level I and II veterinary care, including emergency treatment, stabilization, and evacuation of military working dogs, and to ensure food safety and public health. This mission allowed the VAP to act as a force multiplier and to play an integral role in force protection. In the first 30 days of the operation, the VAP was confronted with animal issues concerning housing of the military working dogs, no access to emergency equipment, antiquated sets, kits, and outfits, and stray animal control. The food safety mission initially entailed inspections of operational rations and inspection of local sources for food procurement. Operational rations were replaced by A-rations, which required a central ration breakdown point to facilitate disbursement of food. The final step was to initiate the prime vendor program so that food was delivered directly to the dining facilities. Inspections of the port at which the food was arriving and a close association with preventive medicine personnel ensured a successful prime vendor operation. Veterinarians on future deployments should be prepared to supplement sets, kits, and outfits, pack an aid bag, and work closely with preventive medicine personnel, all while possibly living under the austere conditions of a combat zone.

    View details for PubMedID 10920653