European zoos have housed koalas (Phascolarctos cinereus) for almost 25 years. From the time the first individual arrived on the old continent to the present population of 30 (15.15) animals, medical knowledge has improved significantly. During this time, 57 koala deaths have been recorded. With the discovery of the koala endogenous retrovirus (KoRV), the question remains whether it is involved in the various diseases found in captive population and specifically whether it was involved in the

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... deaths. This question is unfortunately difficult to answer as no real time tests were performed before and during the course of the diseases. A study of the detailed information of these records shows that almost half of them concern very young animals probably mainly because of joeys falling from the pouch and maternal neglect. A few deaths have no recorded information or are clearly not related to any infectious cause. 44% are due to neoplastic and opportunistic or non-opportunistic bacterial infectious process. While KoRV is thought to cause immunosuppression and tumour induction (mainly lymphomas), the link between disease and the virus has not been clearly established.