Disease and Pathological Conditions of an Endangered Rodent, Microtus Californicus Scirpensis, in a Captive-Rearing Facility and in the Wild
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DISEASE AND PATHOLOGICAL CONDITIONS OF AN ENDANGERED RODENT, MICROTUS CALIFORNICUS SCIRPENSIS, IN A CAPTIVE-REARING FACILITY AND IN THE WILD Authors: Foley, Janet, Allan, Nora, Pesapane, Risa, Johnson, Amanda, Woods, Leslie, et. al. Source: Journal of Zoo and Wildlife Medicine, 50(4) : 758-768 Published By: American Association of Zoo Veterinarians URL: https://doi.org/10.1638/2018-0117 BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access titles in the biological, ecological, and environmental sciences published by nonprofit societies, associations, museums, institutions, and presses. Your use of this PDF, the BioOne Complete website, and all posted and associated content indicates your acceptance of BioOne’s Terms of Use, available at www.bioone.org/terms-of-use. Usage of BioOne Complete content is strictly limited to personal, educational, and non - commercial use. Commercial inquiries or rights and permissions requests should be directed to the individual publisher as copyright holder. BioOne sees sustainable scholarly publishing as an inherently collaborative enterprise connecting authors, nonprofit publishers, academic institutions, research libraries, and research funders in the common goal of maximizing access to critical research. Downloaded From: https://bioone.org/journals/Journal-of-Zoo-and-Wildlife-Medicine on 17 Jan 2020 Terms of Use: https://bioone.org/terms-of-use Access provided by Ohio State University DOI: 10.1638/2018-0117 Journal of Zoo and Wildlife Medicine 50(4): 758–768, 2019 Copyright 2019 by American Association of Zoo Veterinarians DISEASE AND PATHOLOGICAL CONDITIONS OF AN ENDANGERED RODENT, MICROTUS CALIFORNICUS SCIRPENSIS, IN A CAPTIVE-REARING FACILITY AND IN THE WILD Janet Foley, DVM, PhD, Nora Allan, MS, Risa Pesapane, MS, Amanda Johnson, DVM, Leslie Woods, DVM, PhD, Laurie Brignolo, DVM, Abigail Luce, BS, Deana L. Clifford, DVM, PhD, and Denise M. Imai, DVM, PhD Abstract: Causes of morbidity and mortality and a survey of infectious disease agents were collated from wild and colony-raised endangered Amargosa voles (Microtus californicus scirpensis). Six voles from the wild and 295 voles in the captive-breeding colony were included in the study upon identification of an infectious agent during screening, identification of clinical signs of disease, or finding a pathological condition or infectious agent on necropsy. Findings included 28 significant or incidental pathological conditions of seven organ systems and 19 parasitic, viral, bacterial, or fungal agents. Several voles captured in the wild had fungal osteomyelitis of the tail that disseminated systemically in a vole brought from the wild to the colony and may have been caused by a Penicillium sp. Three voles reintroduced from the colony to the wild experienced inanition and subsequent severe hepatic and moderate renal tubular lipidosis. The most common significant pathological conditions in colony- reared voles were chronic interstitial nephritis with proteinosis; cardiomyopathy; trichobezoars that, in intestines or cecocolic junctions, sometimes induced local rupture or infarction with peritonitis; multifocal gastrointestinal ulceration and colibacillosis; acute renal tubular necrosis or nephritis; sepsis; hepatic and renal lipidosis; molar apical elongation sometimes progressing to invasion of the calvarium; and mammary tumors. Uncommon diagnoses included intervertebral disc disease; microvascular dysplasia; and multifocal bacterial abscessation. Common or clinically important infectious agents included Demodex sp. mites in hair follicles, Demodex sp. in esophageal mucosa, and an outbreak of tropical rat mites thought to have been introduced via the straw bedding; gastrointestinal Helicobacter sp.; attaching and effacing Escherichia coli; and Citrobacter braakii, a possible zoonotic bacterium. This survey of species-specific diseases and pathogens was possible because the established health surveillance program that is part of the species recovery plan allowed for monitoring of voles throughout the duration of their natural life spans in captivity. Key words: Amargosa vole, endangered species, Microtus californicus scirpensis, mites, rodent, trichobezoar. INTRODUCTION identified in the formal recovery plan included loss of genetic variability and predation.28 In The Amargosa vole (Microtus californicus scir- 2013, the U.S. Department of the Interior char- pensis) is a Mojave Desert-endemic, Pleistocene tered an ad hoc Amargosa vole team that added relict subspecies of California vole found only in disease considerations to the list of concerns. marshes near the Amargosa River in Inyo County, When the single known sustainable marsh in 3 California. It is endangered, with only several which Amargosa voles persisted showed advanc- hundred individuals remaining in the wild and in ing drying, vegetation collapse, and vole popula- captivity.6,9. Potential long-standing stressors tion reduction, a captive breeding colony was initiated in 2014 at the University of California Davis from 20 voles from the wild.5 From the Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Initially captive voles were reluctant to eat and 1 Davis, CA 95616, USA (Foley, Allan, Pesapane, and breed, but over time they accepted a high-fiber, Luce); Wildlife Investigations Lab, California Department commercial rabbit diet and exhibited species- of Fish and Wildlife, 1701 Nimbus Road, Rancho appropriate behaviors when provided with open Cordova, CA 95670, USA (Allan and Clifford); California water bowls and deep straw to mimic the bulrush Animal Health and Food Safety Laboratory System, Davis litter they utilize in marshes. Some colony voles Branch, University of California, Davis, CA 95616, USA have achieved life spans of 32 mo, compared with (Woods); Comparative Pathology Laboratory, School of the longest known life span of a wild Amargosa Veterinary Medicine, University of California, Davis, CA 95616, USA (Johnson and Imai); and UC Davis Campus vole of 18 mo. During this time, comprehensive Veterinary Services, University of California, Davis, CA medical records and a full pathological examina- 95616, USA (Brignolo). Correspondence should be directed tion of voles to determine causes of morbidity and to Dr. Foley ([email protected]). mortality have informed our understanding of 758 Downloaded From: https://bioone.org/journals/Journal-of-Zoo-and-Wildlife-Medicine on 17 Jan 2020 Terms of Use: https://bioone.org/terms-of-use Access provided by Ohio State University FOLEY ET AL—PATHOLOGY OF MICROTUS CALIFORNICUS SCIRPENSIS 759 natural and infectious disease processes in this they were released into the marsh and monitored species. The goal of this study was to determine with a radio collar and remotely triggered camera the relative frequencies of the causes of morbidity set near the release cage throughout the battery and mortality, including reports on rare patho- life of the collar (approximately 1 mo). All work logical conditions. We hope that this information was in compliance with U.S. Fish and Wildlife will help identify conditions that may be associ- Service Endangered Species Recovery Permit ated either with husbandry or highly specific TE54614A, California Department of Fish and adaptations of this species to its environment. Wildlife Scientific Collecting Permit 000854, and UC Davis Institutional Animal Care oversight. MATERIALS AND METHODS The latter incorporates oversight of animal care and work as well as personnel training and Study animals occupational health and safety. The study population included free-ranging Amargosa voles from marshes near Tecopa, CA Diagnostic pathology and disease screening and captive animals in a colony maintained in Results of pathological evaluation and infec- Davis, CA captured or bred between 2014 and tious disease testing were compiled from the 2017. Free-ranging voles live in marshes where following sources: (1) ante-mortem findings from three-square bulrush (Schoenoplectus americanus), animals captured in the wild before release, a flowering plant, predominates as a primary during quarantine after removal from the wild to source of their nutrition. A thick litter of dead bring into the colony, or currently residing in the bulrush provides sites for nesting and protection colony during physical examinations; (2) on gross from predators. They were trapped and sampled necropsy of five animals assessed only for tricho- 6 as previously described. Captive voles are main- bezoars and external lesions; (3) as needed to tained individually or in mated pairs in polycar- diagnose and treat a documented veterinary bonate rodent cages with a wire top (model medical condition; and (4) on animals submitted R70PC, Ancare, Bellmore, NY 11710, USA) and for full necropsy. In the latter case, any animals thick straw to mimic bulrush litter, open water that were found dead or moribund, or that had bowls, and rodent chow (Teklad 2018, Envigo, very low body condition scores (BCS, 1 or less on Hayward, CA 94540, USA) replaced between a scale of 1 to 529), or that had a nontreatable April and October 2016 with LabDiet 5326 rabbit medical condition associated with suffering or chow (Purina, Largo, FL 33779, USA, milled into being unsuitable for continued breeding in the large pellets by Stewart’s Feed Service, Lawrence- colony were candidates for euthanasia and sub- ville, GA 30043, USA). Day : night light cycles mitted for comprehensive pathological examina- were 12