Health surveillance representative of koala (Phascolarctos cinereus) distribution in Victoria, Australia.

Health surveillance of wildlife populations is essential for conservation and reduction of the impacts of disease. Population declines and areas of overabundance of koalas (Phascolarctos cinereus) can disrupt the overall survival of the species as well as its habitat. This retrospective study was conducted to describe population distributions, identify areas which need increased surveillance and improve koala health surveillance methodology by Wildlife Health Victoria: Surveillance (WHV:S) at the Veterinary School of The University of Melbourne. Twelve years of Victorian koala observation data from the Atlas of Living Australia combined with surveillance data from WHV:S were used to create choropleth maps, using Quantum Geographic Information Systems of populations and surveillance events, visually representing hot spots. This data was further used to calculate health surveillance efforts between 2008 to the beginning of 2020. Analysis ranked postcodes throughout Victoria from low surveillance efforts to high, using standardised surveillance ratio's 95% confidence interval upper limits which were mapped using a colour gradient. This identified postcodes which need increased surveillance effort, corresponding to areas with high koala observations and low surveillance submissions. This analysis can guide surveillance for postcodes with koalas that were under-represented and inform improved methodology of future surveillance by WHV:S. The specific advice for improvements to WHV:S includes utilisation of citizen science and syndromic surveillance, website improvement, increasing community awareness and more. The limitations of this study were discussed.