Koala populations across Australia have been listed as endangered, with disease being a key threat. Chlamydia pecorum (Cpec) is one the most important, widely researched, and highly prevalent pathogens of koalas, with ocular and urogenital infections leading to debilitating disease. Chlamydial disease remains a major threat to vulnerable koala populations [1]. In contrast, much less is known about koala herpesvirus 1 (KHV-1) infections, and their impact in coinfection with chlamydia [2,3]. To better understand impacts of these infections, we investigated the prevalence Cpec and KHV-1 infecting wild koalas from Queensland.
We screened 739 samples collected from 311 different wild koalas admitted to the Australia Zoo Wildlife Hospital from February 2023 to March 2024 for Cpec and KHV-1. Paired ocular (n=311) and urogenital/ cloacal/ penile (n=311) swabs were obtained from the same koalas (n=311). Of those, 53 koalas were sampled over different time points. Using species-specific qPCR assays, the estimated true and apparent prevalence of Cpec and KHV-1 infections from testing results using a test of known sensitivity (0.95) and specificity (0.99) within a 95% CI was determined.
We revealed an overall Cpec and KHV-1 prevalence of 49% (146/311; CI 0.4305 – 0.5478), and 33% (95/297; CI 0.2760 – 0.3882), respectively, in tested koalas. Cpec and KHV-1 coinfections were detected in 23% (68/297; CI 0.1860 – 0.2873) koalas. When assessing 53 individual koalas over several sampling events, we observed dynamic changes in KHV-1 shedding, including: no shedding after treatment for chlamydial infection (n= 23 koalas), continuous shedding even with treatment (n= 17 koalas), shedding after initial negative testing (n= 7 koalas) and the rest remained negative (n=6 koalas).
This study provides additional evidence that Cpec and KHV-1 are prevalent in koalas across Southeast Queensland, and that co-infections are common. Going forward, we need to further characterise the impacts of co-infections on koala health, and factors that may influence disease development [4].