An epizootic of Chlamydia psittaci equine reproductive loss associated with suspected spillover from native Australian parrots

Abstract

Chlamydia psittaci is an avian pathogen capable of spill-over infections to humans. A parrot C. psittaci strain was recently detected in an equine reproductive loss case associated with a subsequent cluster of human C. psittaci infections. In this study, we screened for C. psittaci in cases of equine reproductive loss reported in regional New South Wales, Australia during the 2016 foaling season. C. psittaci specific-PCR screening of foetal and placental tissue samples from cases of equine abortion (n = 161) and foals with compromised health status (n = 38) revealed C. psittaci positivity of 21.1% and 23.7%, respectively. There was a statistically significant geographical clustering of cases ~170 km inland from the mid-coast of NSW (P < 0.001). Genomic analysis and molecular typing of C. psittaci positive samples from this study and the previous Australian equine index case revealed that the equine strains from different studs in regional NSW were clonal, while the phylogenetic analysis revealed that the C. psittaci strains from both Australian equine disease clusters belong to the parrot-associated 6BC clade, again indicative of spill-over of C. psittaci infections from native Australian parrots. The results of this work suggest that C. psittaci may be a more significant agent of equine reproductive loss than thought. A range of studies are now required to evaluate (a) the exact role that C. psittaci plays in equine reproductive loss; (b) the range of potential avian reservoirs and factors influencing infection spill-over; and (c) the risk that these equine infections pose to human health.

Detection of a range of genetically diverse chlamydiae in Australian domesticated and wild ungulates

“…Nevertheless, the question remains whether the livestock animals are indeed commonly infected with this pathogen or if C. psittaci detection is a result of environmental exposure. Potential C. psittaci contamination from bird excretions was suggested for the recent C. psittaci horse epizootic (Borel et al, ; Jenkins et al, ). To date, the reports of C. psittaci infections in Australian sheep and cattle were unclear and inconclusive (Seaman, Cockram, & Scrivener, ), in contrast to the global studies recognizing the significant role of C. psittaci in livestock infection and disease (Borel et al, , ; Ostermann et al, ).…”

“…(a) the host range for this species in Australia is broader than previ- (Borel et al, 2018;Jenkins et al, 2018). To date, the reports of C. psittaci infections in Australian sheep and cattle were unclear and inconclusive (Seaman, Cockram, & Scrivener, 1986), in contrast to the global studies recognizing the significant role of C. psittaci in livestock infection and disease (Borel et al, 2018(Borel et al, , 2006Ostermann et al, 2013).…”

“…In Australia, the two chlamydial species that remain in the spotlight are the endemic sheep pathogen C. pecorum, infamous for its role in koala blindness and reproductive disease (Polkinghorne, Hanger, & Timms, 2013;Walker et al, 2018), and C. psittaci, an emerging cause of equine reproductive loss associated with zoonotic events (Jelocnik, Jenkins, O'Rourke, Barnwell, & Polkinghorne, 2018;Jenkins et al, 2018). Little is known about infections caused by other chlamydial organisms in Australian livestock or wildlife (Burnard et al, 2017), despite studies elsewhere describing genetically diverse chlamydial infections in a range of hosts (Borel et al, 2018).…”

Recent history of psittacosis in Australia: expanding our understanding of the epidemiology of this important globally distributed zoonotic disease

“…To the authors' surprise, in one season, over 20% of cases of equine pregnancy loss and/or foal death were found to be C. psittaci positive suggesting that non-avian animal hosts may be more common than previously thought. 14 Notably, this expansion of the host range of C. psittaci in Australian animals was recently expanded with the detection of DNA of this pathogen in Australian domesticated sheep and cattle. 15 While environmental contamination cannot be excluded in the latter cases, these veterinary studies nevertheless highlight that a history of contact with animals beyond birds should be considered in clinical investigations of patients with psittacosis.…”

New evidence for domesticated animals as reservoirs of Chlamydia-associated community-acquired pneumonia

“…New reports of unusual presentations of chlamydiosis are not limited to humans. A recent study found that >20% of pregnancy losses and early foal deaths in horses were positive for Chlamydia psittaci [4]. C. psittaci is an avian pathogen that can also cause serious atypical pneumonia in humans, known as psittacosis.…”