Cryptosporidium-associated enteritis in captive koalas (Phascolarctos cinereus)

Cryptosporidium spp. sporadically infect a range of Australian native mammals including koalas, red kangaroos, eastern grey kangaroos, bilbies and brush tailed possums and can range from asymptomatic to fatal infections. Traditionally considered a disease of the young or immuno-compromised, and resulting in profuse diarrhoea in other species, here we report an atypical clinical syndrome associated with Cryptosporidium in a captive population of koalas. All affected animals were in-contact adults, and demonstrated anorexia, dehydration and abdominal pain in the absence of diarrhoea. Following euthanasia on welfare grounds, Cryptosporidium infection was confirmed postmortem in three of four symptomatic animals via faecal floatation and/or intestinal histopathology, with enteritis also diagnosed in the fourth koala. Further screening of the captive colony found the outbreak had been contained. Based on sequencing the cause of the infection was C. fayeri, but the source was undetermined. In conclusion, Cryptosporidium should be considered as a possible cause of generalised illness in koalas.