Bonnie Chaban1, Vanissa A. Ong1, Jonathan Hanger2, Peter Timms1

1Faculty of Science, Health, Education and Engineering, University of the Sunshine Coast, 90 Sippy Downs Drive, Sippy Downs, Queensland, 4556, Australia

2Endeavour Veterinary Ecology, 1695 Pumicestone Road, Toorbul, Queensland, 4510, Australia

Koala retrovirus (KoRV) is a new virus that has created new opportunities for retroviral research and new challenges for koala conservation. There are currently two major types of KoRV; KoRV-A, which we believe has added itself to koala DNA and is now passed from parents to joeys in the northern part of Australia, and KoRV-B, which appears to be passed from koala to koala like other viruses in the environment. KoRV is in the same virus family as human immunodeficiency virus (HIV, leading to AIDS in people) and feline leukemia virus (FeLV, which causes cancer in cats). To understand how much of each KoRV type is present in Queensland, what it might be doing to koalas and how it might be spreading between koalas, we studied a wild Moreton Bay koala population of 290 koalas over a five year period. We found that all the koalas we tested were KoRV-A positive (100%) and they all had the same surface protein (meaning KoRV-A is not changing much in this group). By comparison, we found that only 24% of koalas tested KoRV-B positive and within these koalas, we found 21 different versions of the surface protein (meaning KoRV-B is actively changing and adapting as it moves from koala to koala). When we looked at whether having KoRV made a difference to getting another serious disease, we found significant links between koalas having KoRV-B and developing chlamydial disease and/or cancer. So, to figure out how KoRV-B was being spread through the population, we followed 49 adult koalas over several years, as well as 25 new joeys being born into the group. We found that if a koala was KoRV-B negative when he/she became independent, he/she only had a 3% chance each year of getting KoRV-B from another koala. However, we found that if a koala was KoRV-B positive when she started having joeys, all her joeys would have KoRV-B (100%) and if she was KoRV-B negative when she had a joey, her joey would be KoRV-B free (0%). This told us that mothers infecting their joeys is the most significant way KoRV-B is being spread through the group. Overall, this study helped us learn that KoRV-B is the virus type that is contributing to chlamydial disease and cancer in the koala population, making it an imminent threat to this already vulnerable species. We also learned that if we can stop KoRV-B spreading from mother-to-joey, we can have a major impact on how much KoRV-B infection is in the wild. Both of these outcomes are now helping our group develop the first KoRV vaccine to combat this new threat to koala health.

Written by Bonnie Chaban