Retrospective Study of Morbidity in Koalas (Phascolarctos cinereus) Housed at San Diego Zoo Between 1967 and 2013
American Association of Zoo Veterinarians Conference 2014
Andrés Alejandro Castro C.1, DVM; Carmel Witte2, MS; Geoffrey W. Pye3, BVSc, MSc, DACZM
1Unidad de Rescate y Rehabilitación de Animales Silvestres (URRAS), National University of Colombia, Bogotá DC, Colombia; 2Wildlife Disease Laboratories, Institute for Conservation Research, San Diego Zoo Global, Escondido, CA, USA; 3San Diego Zoo Global, San Diego, CA, USA


Recognizing major health problems affecting koalas is key in the conservation of the species. Previous studies have determined the causes of disease in wild koalas presented to wildlife hospitals1,2; however, koalas housed in zoos may present pathologies that differ from their wild relatives.

To identify the most common diseases affecting captive koalas, we reviewed the medical records of 158 koalas housed at the San Diego Zoo between 1967 and 2013. During the 46-year period, clinicopathologic entities and abnormalities that affected the koalas’ health were assessed and listed in the medical records. In total, 382 medical problems were found affecting 120 (120/158; 76%) koalas. 82.9% of females (63/76) and 72.1% of males (57/79) had at least one reported problem; these proportions were not significantly different (p=0.16). Among those with an identified abnormality (n=120), the average number of problems reported over a lifetime was 2.7 (SD=2.4; range=1–15). Problems were further classified into 14 categories, with the highest number of koalas affected in the musculoskeletal category (n=55). Hip and shoulder dysplasia had the highest presentation in this category, with 48 (48/55; 87.3%) and 23 (23/55; 41.8%) koalas affected, respectively. Hip and shoulder dysplasia tended to occur together (kappa=0.53). Other categories with high numbers of koalas affected by disease were ocular (32/158, 20.3%), gastrointestinal (30/158, 19%), and integument (29/158, 18.4%).

This study highlights the most common categories of diseases presented by koalas housed in zoos. Future studies should be performed to understand risk factors associated with the presentation of these diseases.


The authors would like to thank Ms. Donna Vader from the San Diego Zoo for her support during data collection.

Literature Cited

1.  Griffith JE, NK Dhand, MB Krockenberger, DP Higgins. A retrospective study of admission trends of koalas to a rehabilitation facility over 30 years. J Wildl Dis. 2013;49:18–28.

2.  Obendorf DL. Causes of mortality and morbidity of wild koalas, Phascolarctos cinereus (Goldfuss), in Victoria, Australia. J Wildl Dis. 1983;19:123–131.


Speaker Information
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Andrés A. Castro, DVM
Unidad de Rescate y Rehabilitación de Animales Silvestres (URRAS)
National University of Colombia
Bogotá DC, Colombia

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