Canine Distemper Virus Outbreak in Captive Linnaeus’s Two-Toed Sloths (Choloepus didactylus): Clinical and Pathologic Findings and Response to Vaccination
American Association of Zoo Veterinarians Conference 2017

Julie D. Sheldon1, DVM; Andrew C. Cushing1, BVSc, CertAVP (ZM), DACZM; Rebecca P. Wilkes2, DVM, PhD, DACVM; Eman Amis2, BVSc, PhD; Edward J. Dubovi3, MS, PhD

1Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Tennessee, Knoxville, TN, USA; 2Veterinary Diagnostic and Investigational Laboratory, College of Veterinary Medicine, University of Georgia, Tifton, GA, USA; 3Animal Health Diagnostic Center, College of Veterinary Medicine, Cornell University, Ithaca, NY, USA; Present address (Sheldon): Illinois Zoological and Aquatic Animal Residency Program, College of Veterinary Medicine, University of Illinois, Urbana, IL, USA


An outbreak of canine distemper virus (CDV) caused the death of five adult Linnaeus’s two-toed sloths (Choloepus didactylus) living in separate enclosures in a building at a private zoo in eastern Tennessee during a 2-wk period. Clinical signs included oral and nasal discharge and ulcerations, diarrhea, lethargy, and anorexia. Diagnosis was confirmed via necropsy, histopathology, immunohistochemistry, virus isolation, and PCR. Viral sequencing identified the strain to be consistent with a new CDV lineage currently affecting domestic dogs and wildlife in Tennessee.3,4 Canine distemper has not been previously reported in any species in the super order Xenarthra.1,2 Seven sloths (three surviving the outbreak, and four animals added after the outbreak) were sedated, examined, and vaccinated with a recombinant CDV vaccine (Recombitek C3, Merial, 1 ml s.c.) on day 0, and again on day 21. Blood was collected and CDV antibody titers were measured prior to initial vaccination in all seven sloths and on day 49 in four sloths (two sloths died of non-CDV disease before day 49 and an adequate sample could not be obtained in one sloth). Serology revealed negative titers (<1:32) on day 0 in six of seven sloths, and titers increased by day 49 in three of four sloths with seroconversion in two sloths and a 32-fold increase in one sloth. No adverse effects of vaccination were observed. Based on this outbreak and serologic findings post vaccination without adverse effects, the authors recommend recombinant CDV vaccination in sloths exposed to known carriers of CDV.


The authors would like to thank the animal care staff of the Bright’s Zoo, Drs. Linden Craig and Allison Watson of the Anatomic Pathology service at the University of Tennessee College of Veterinary Medicine, and the technical staff of the Cornell virology lab.

Literature Cited

1.  Deem SL, Spelman LH, Yates RA, Montali RJ. Canine distemper in terrestrial carnivores: a review. J Zoo Wildl Med. 2009;31:441–451.

2.  Martinez-Gutierrez M, Ruiz-Saenz J. Diversity of susceptible hosts in canine distemper virus infection: a systematic review and data synthesis. BMC Vet Res. 2nd ed. 2016;12:1489–1489.

3.  Pope JP, Miller DL, Riley MC, Anis E, Wilkes RP. Characterization of a novel canine distemper virus causing disease in wildlife. J Vet Diagn Invest. 2016;28:506–513.

4.  Riley MC, Wilkes RP. Sequencing of emerging canine distemper virus strain reveals new distinct genetic lineage in the United States associated with disease in wildlife and domestic canine populations. Virol J. 2015;12:219–229.


Speaker Information
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Julie D. Sheldon, DVM
Department of Small Animal Clinical Sciences
College of Veterinary Medicine
University of Tennessee
Knoxville, TN, USA

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