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

Abstract

Summary Chlamydiae are globally widespread obligate intracellular bacteria, which several species are a well‐recognized threat to human and animal health. In Australia, the most successful chlamydial species are the infamous koala pathogen C. pecorum, and C. psittaci, an emerging pathogen associated with zoonotic events. Little is known about infections caused by other chlamydial organisms in Australian livestock or wildlife. Considering that these hosts can be encountered by humans at the animal/human interface, in this study, we investigated genetic diversity of chlamydial organisms infecting Australian domesticated and wild ungulates. A total of 185 samples from 129 domesticated (cattle, horses, sheep, and pigs) and 29 wild (deer) ungulate hosts were screened with C. pecorum and C. psittaci species‐specific assays, followed by a screen with pan‐Chlamydiales assay. Overall, chlamydial DNA was detected in 120/185 (65%) samples, including all ungulate hosts. Species‐specific assays further revealed that C. pecorum and C. psittaci DNA were detected in 27% (50/185) and 6% (11/185) of the samples, respectively, however from domesticated hosts only. A total of 46 “signature” 16S rRNA sequences were successfully resolved by sequencing and were used for phylogenetic analyses. Sequence analyses revealed that genetically diverse novel as well as traditional chlamydial organisms infect an expanded range of ungulate hosts in Australia. Detection of the C. psittaci and C. pecorum in livestock, and novel taxa infecting horses and deer raises questions about the genetic make‐up and pathogenic potential of these organisms, but also concerns about risks of spill‐over between livestock, humans, and native wildlife.

Chlamydial infection and on‐farm risk factors in dairy cattle herds in South East Queensland

“…C. pecorum detection rates were high in all the tested animals from the four farms, with rates ranging from 30.0% to 69.6%. This is consistent with other research from Europe and re‐iterates the global distribution for this species in healthy dairy cows . Second, no evidence of C. abortus and C. psittaci could be found in this study, however, taking into account that we have only assessed four farms from one region.…”

“…While C. pecorum is considered one of the major Australian sheep polyarthritis pathogens, less is understood about chlamydial infections in cattle . C. abortus is currently considered exotic to Australia, whereas reports of C. psittaci have been rarely documented in Australian livestock . There is currently a lack of studies on chlamydial infections in cattle and on‐farm risk factors in the Australian setting.…”

“…C. abortus is currently considered exotic to Australia, while C. psittaci status in both beef and dairy cattle in Australia warrants further in‐depth investigations. Recent molecular study did detect C. psittaci in limited number of rectal samples taken from a beef cattle herd from Central New South Wales where animals were presenting with sporadic bovine encephalomyelitis (SBE) . As C. pecorum was also detected in the same herd and due to its association with disease in cattle, the ‘true clinical impact of C. psittaci ’ remains unclear but it does not exclude that C. psittaci may also cause a disease.…”

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

“…The cluster of human psittacosis cases came from a university veterinary teaching hospital with individuals revealed to have been in contact with the unusual foetal membranes of a mare who had delivered a foal that died prematurely. 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. 13 Given very little was otherwise known about the frequency of C. psittaci infection in horses and the risks posed to human health, studies examining the prevalence of C. psittaci infections in association with equine pregnancy loss were recently completed in regional New South Wales.…”

“…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.…”