Abstract
Red-backed voles (Myodes gapperi; order Rodentia, family Cricetidae, subfamily Arvicolinae) are a relatively uncommon laboratory animal useful as a model for prion diseases. The red-backed vole dental formula is I 1/1, C 0/0, P 0/0, M 3/31 with elodont incisor teeth. Voles were obtained by live-trapping in Wisconsin and Pennsylvania during the fall of 2006 and were kept in the National Wildlife Health Center Research Facility. They were maintained in pairs or same-sex groups in rat boxes, on a 14-hour light 10-hour dark cycle. A mixture of six parts commercial rabbit diet, one-part rodent diet, one part in-shell black sunflower seeds, one part cracked corn, one-part whole oats, and apples, were provided. Five red-backed voles of the first generation of the wild caught breeding colony presented with lesions of the maxillary incisors consistent with elodontomas.
Affected animals presented with a history of chronic weight loss. Voles affected had ages over 499 days and were siblings. Examination of the oral cavity revealed overgrown mandibular incisor teeth, and absence of visible maxillary incisor teeth with a gingival ulcer. Radiologic findings indicated irregular mineral density masses at the apices of the maxillary incisors. Microscopically, these masses were composed of well-differentiated but disorganized dental tissue, including odontogenic epithelium, dentin, cementum, and enamel matrix, and were consistent with elodontomas. Elodontomas are hamartomas of odontogenic tissues at the apex of elodont teeth.2-4 This condition has been described in degu,2 prairie dogs and other squirrel-like rodents3,4. Clinical signs in the voles did not include severe respiratory signs as described in prairie dogs, degus and tree squirrels.2,4,5 Voles were observed chewing on metallic water bottle hardware, so persistent trauma and genetic factors are considered predisposing factors.
Literature Cited
1. Long, C.A. 2008. The Wild Mammals of Wisconsin. Faunistica 68. Pensoft, Bulgaria. 262 pp.
2. Jekl, V., K. Hauptman, M. Skoric, E. Jeklova, P. Fictum, and Z. Knotek. 2008. Elodontoma in a Degu (Octodon degus). J. Exotic Pet. Med. 17: 216–220.
3. Boy, S.C., and G. Steenkamp. 2006. Odontoma-like tumours of squirrel elodont incisors-elodontomas. J. Comp. Pathol. 135: 56–61.
4. Capello, V., and M. Gracis. 2005. Rabbit and Rodent Dentistry Handbook Zoological Education Network, Inc., Florida.
5. Phalen, D.N., N. Antinoff, and M.E. Fricke. 2000. Obstructive respiratory disease in prairie dogs with odontomas. Vet. Clin. North Am. Exotic Anim. Pract. 3: 513–517, viii.