Koala retrovirus genetic diversity and transmission: advice for breeders. In Proceedings of the Second Koala Retrovirus Workshop, ed. D. E. Alquezar-Planas, D. P. Higgins, C. L. Singleton, and A. D. Greenwood

Abstract

The rapid spread of koala retrovirus (KoRV) across Australia and international zoo populations has necessitated appropriate control measures. Along with pathogenicity, the genetic diversity of the virus and how it transmits between animals also needs to be considered when deciding the most suitable measures. Next generation sequencing has become the gold standard approach for KoRV diversity studies due to the high sensitivity, accuracy, and throughput. This approach has identified a large proportion of known KoRV diversity and has provided a broader understanding of KoRV prevalence and abundance within koala (Phascolarctos cinereus) populations, specifically identifying individuals with low diversity. Recent evidence has demonstrated that exogenous KoRV transmits from mother to joey, likely through the ingestion of milk and/or pap, and that koalas are not likely to acquire additional KoRV subtypes/sequences later in life. This finding strongly indicates that breeding with KoRV negative or endogenous KoRV-A positive only females is the best chance at alleviating exogenous KoRV from koala populations worldwide. Captive breeders are therefore urged to determine the KoRV profile of all animals included in their breeding program through deep sequencing methods (where feasible) and use this to inform their future breeding regimes.