Koala retrovirus genetic diversity and transmission dynamics within captive koala populations

Koala populations are currently in rapid decline across Australia, with infectious diseases being a contributing cause. The koala retrovirus (KoRV) is a gammaretrovirus present in both captive and wild koala colonies that presents an additional challenge for koala conservation in addition to habitat...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 2021-09, Vol.118 (38), p.1-7
Main Authors: Joyce, Briony A., Blyton, Michaela D. J., Johnston, Stephen D., Young, Paul R., Chappell, Keith J.
Format: Article
Language:English
Subjects:
Animals
Antiretroviral agents
Biological Sciences
Climate change
Colonies
Disease transmission
Evolution, Molecular
Female
Genetic analysis
Genetic diversity
Genetic Variation - genetics
Habitat loss
Infectious diseases
Male
Phascolarctidae
Populations
Queensland
Retroviridae - genetics
Retroviridae Infections - transmission
Retroviridae Infections - virology
Sequences
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Summary:Koala populations are currently in rapid decline across Australia, with infectious diseases being a contributing cause. The koala retrovirus (KoRV) is a gammaretrovirus present in both captive and wild koala colonies that presents an additional challenge for koala conservation in addition to habitat loss, climate change, and other factors. Currently, nine different subtypes (A to I) have been identified; however, KoRV genetic diversity analyses have been limited. KoRV is thought to be exogenously transmitted between individuals, with KoRV-A also being endogenous and transmitted through the germline. The mechanisms of exogenous KoRV transmission are yet to be extensively investigated. Here, deep sequencing was employed on 109 captive koalas of known pedigree, housed in two institutions from Southeast Queensland, to provide a detailed analysis of KoRV transmission dynamics and genetic diversity. The final dataset included 421 unique KoRV sequences, along with the finding of an additional subtype (KoRV-K). Our analysis suggests that exogenous transmission of KoRV occurs primarily between dam and joey, with evidence provided for multiple subtypes, including nonendogenized KoRV-A. No evidence of sexual transmission was observed, with mating partners found to share a similar number of sequences as unrelated koala pairs. Importantly, both distinct captive colonies showed similar trends. These findings indicate that breeding strategies or antiretroviral treatment of females could be employed as effective management approaches in combating KoRV transmission.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.2024021118