Our understanding of koala retrovirus (KoRV) has advanced dramatically in recent years. Cross-sectional studies examining hundreds of wild koalas (Phascolarctos cinereus) from populations across their natural Australian range (Queensland–New South Wales–Victoria) have shed new light on KoRV abundance and diversity in the wild. A single strain of KoRV (the originally characterized Hanger strain from 2000) appears to be the dominant KoRV strain within koalas, endogenous in northern populations and the predominant exogenous strain in southern populations. Alongside this strain are potentially exogenous variants representing both intact and defective versions of some of the many recognized KoRV subtypes (KoRV-A to KoRV-M). The patterns of these may suggest a transition from endogenous KoRV in the north to exogenous KoRV in the south, occurring in southern New South Wales. They also highlight how actively the hypervariable region of the envelope gene of KoRV is diversifying, with fragmented koala populations across the country containing unique and distinctive KoRV proviral profiles. As more koala populations are examined with increasingly sensitive and specific genetic tools, our understanding of KoRV is poised to continue to evolve as quickly as the virus itself.
Quigley, Bonnie L., and Peter Timms. 2023. Endogenous and exogenous koala retrovirus patterns in wild koalas across Australia. In Proceedings of the Second Koala Retrovirus Workshop, ed. D. E. Alquezar-Planas, D. P. Higgins, C. L. Singleton, and A. D. Greenwood. Technical Reports of the Australian Museum Online 38: 7–9.