A Retrospective Study of Mortality in Captive Pygmy Hippopotamus (Choeropsis liberiensis)
American Association of Zoo Veterinarians Conference 2015
Gabriella L. Flacke1, DVM, MVSc; Suzana Tkalcic2, DVM, PhD; Beatrice L. Steck3; Kristin Warren4, BVMS, PhD, DECZM; Monique C. Paris1,5,6,7, PhD
1School of Animal Biology, University of Western Australia, Crawley, WA, Australia; 2Western University of Health Sciences, College of Veterinary Medicine, Pomona, CA, USA; 3Zoo Basel, Basel, Switzerland; 4College of Veterinary Medicine, School of Veterinary and Life Sciences, Murdoch University, Murdoch, WA, Australia; 5College of Public Health, Medical and Veterinary Services, James Cook University, Townsville, QLD, Australia; 6Institute for Breeding of Rare and Endangered African Mammals (IBREAM), Edinburgh, Scotland; 7Mammal Research Institute, University of Pretoria, Hatfield, Pretoria, South Africa
The pygmy hippopotamus (Choeropsis liberiensis), an IUCN Red List Endangered species (CITES Appendix II), has been housed in zoological collections since 1912. Our study is the first comprehensive review of mortality in captive pygmy hippopotamus that has been conducted since 1982 and significantly expands on previous data.1 We solicited necropsy reports from 129/187 zoological institutions worldwide currently or previously holding pygmy hippopotamus. Cause of mortality was determined for a total of 404 animals: 177 male, 220 female, and 7 of unknown sex. Reports were grouped into three age categories: neonate (0–30 days); juvenile (30 days–3 yr); adult (3+ yr). Causes of mortality were grouped according to body system and etiology. Our data indicate that mortality in neonates is primarily due to perinatal causes (failure to thrive, weakness, poor suckling reflex, maternal neglect) or parent-inflicted trauma. Common causes of mortality or euthanasia in adult pygmy hippopotamus include cardiovascular disease, degenerative musculoskeletal conditions, and renal insufficiency, the latter frequently associated with advanced polycystic kidney disease (PKD). The prevalence of PKD in pygmy hippopotamus 10+ yr of age exceeds 30%, and the condition exhibits a familial inheritance pattern. Infectious diseases causing mortality in pygmy hippopotamus include leptospirosis and encephalomyocarditis virus (EMCV), the latter usually presenting as acute, unexpected death. Our data significantly expand on the first reports of PKD in this species2,3 and indicate that the condition is of possible concern for long-term viability of the captive population given the limited number of remaining founder genomes.
We thank all of the zoological institutions that responded to our enquiries for their time and effort in assisting us with our research and for providing data essential to this retrospective study.
1. Jarofke D, Klös HG. Immobilisierung und Krankheiten von Zwergflusspferden: Auswertung einer Umfrage bei mehr als 100 Zoologischen Gärten. Erkrankg Zootiere: Verhandlungsbericht. 1982;24:361–374.
2. Nees S, Schade B, Clauss M, Steinmetz HW, Ehrensperger F, Steck B, Hatt J-M. Polycystic kidney disease in the pygmy hippopotamus (Hexaprotodon liberiensis). J Zoo Wildl Med. 2009;40:529–535.
3. Raymond JT, Eaton KA, Montali RJ. A disease in captive pygmy hippopotamuses (Choeropsis liberiensis liberiensis) anatomically resembling polycystic kidney disease. Proc Am Assoc Zoo Vet, Int Assoc Aquat Anim Med; 2000. p. 302.