Chlamydia pecorum prevalence in South Australian koala (Phascolarctos cinereus) populations: Identification and modelling of a population free from infection

• DOI: 10.1038/s41598-019-42702-z
• Publication Date: 2019-04-18T10:08:13Z
• Authors: Jessica Fabijan; Charles Caraguel; Martina Jelocnik; Adam Polkinghorne; Wayne S. J. Boardman; Elisa Nishimoto; Greg Johnsson; Robyn Molsher; Lucy Woolford; Peter Timms; Greg Simmons; Farhid Hemmatzadeh; Darren J. Trott; Natasha Speight
• Keywords: Male; Pathological Features; Epidemiology; Eye Infections; Models, Biological; Polymerase Chain Reaction; Article; Eye Infections, Bacterial; Mount Lofty Ranges; 03 medical and health sciences; Models; South Australia; Prevalence; Animals; Urinary; Chlamydia; Tract Disease; 0303 health sciences; Bacterial; Chlamydia Infections; Conjunctivitis; Biological; FoR multidisciplinary; Female Urogenital Diseases; Fertility; Infertility; 1000 General; Cattle; Load; Female; Phascolarctidae; Kangaroo-Island

AbstractChlamydia pecorum is an established and prevalent infection that produces severe clinical disease in many koala populations, contributing to dramatic population declines. In wild South Australian koala populations, C. pecorum occurrence and distribution is unknown. Here, C. pecorum-specific real-time quantitative PCR (qPCR) was applied to ocular and urogenital swabs from targeted surveys of wild koalas from the mainland Mount Lofty Ranges (MLR) (n = 75) and Kangaroo Island (KI) (n = 170) populations. Historical data from 13,081 KI koalas (1997–2018) provided additional evidence for assessing the absence of C. pecorum infection. In the MLR population, 46.7% (CI: 35.1–58.6%) of koalas were C. pecorum positive by qPCR but only 4% had grade 3 clinical disease. MLR koala fertility was significantly reduced by C. pecorum infection; all reproductively active females (n = 16) were C. pecorum negative, whereas 85.2% of inactive females (n = 23) were positive (P < 0.001). KI koalas were C. pecorum negative and the population was demonstrated to be free of C. pecorum infection with 95% confidence. C. pecorum is a real threat for the sustainability of the koala and KI is possibly the last isolated, large C. pecorum-free population remaining in Australia. These koalas could provide a safeguard against this serious disease threat to an iconic Australian species.