Chlamydia Psittaci ST24: Clonal Strains of One Health Importance Dominate in Australian Horse, Bird and Human Infections

Abstract

Chlamydia psittaci is traditionally regarded as a globally distributed avian pathogen that can cause zoonotic spill-over. Molecular research has identified an extended global host range and significant genetic diversity. However, Australia has reported a reduced host range (avian, horse, and human) with a dominance of clonal strains, denoted ST24. To better understand the widespread of this strain type in Australia, multilocus sequence typing (MLST) and ompA genotyping were applied on samples from a range of hosts (avian, equine, marsupial, and bovine) from Australia. MLST confirms that clonal ST24 strains dominate infections of Australian psittacine and equine hosts (82/88; 93.18%). However, this study also found novel hosts (Australian white ibis, King parrots, racing pigeon, bovine, and a wallaby) and demonstrated that strain diversity does exist in Australia. The discovery of a C. psittaci novel strain (ST306) in a novel host, the Western brush wallaby, is the first detection in a marsupial. Analysis of the results of this study applied a multidisciplinary approach regarding Chlamydia infections, equine infectious disease, ecology, and One Health. Recommendations include an update for the descriptive framework of C. psittaci disease and cell biology work to inform pathogenicity and complement molecular epidemiology.

Emerging and well‐characterized chlamydial infections detected in a wide range of wild Australian birds

“…psittaci is considered to have the broadest host range amongst all Chlamydiaceae, highlighting its effectiveness in infecting genetically diverse hosts, including humans and causing zoonotic disease (Borel et al, 2018;Knittler & Sachse, 2015;Radomski et al, 2016). Prelimi-nary strain characterization using ompA genotyping from five parrots, an Australian bustard, masked lapwing and sacred kingfisher from this study revealed ompA genotype A, commonly detected in highly virulent, clonal, globally distributed psittacine, livestock and human ST24type strains (Anstey et al, 2021;Vorimore et al, 2021) (Figure 5a).…”

“…These findings indicate that the Australian avian host range of C. psittaci is grossly underestimated (Anstey et al., 2021; Stokes et al., 2021, 2020; Sutherland et al., 2019). Furthermore, these infections were only described in a handful of surveillance studies conducted in one distinct Australian region, in the state of Victoria (Amery‐Gale et al., 2020; Stokes et al., 2019, 2020; Sutherland et al., 2019) or as a discrete part of genotyping or equine/human infection studies (Anstey et al., 2021; Branley et al., 2016; Jelocnik et al., 2017; Jenkins et al., 2018). Regarding other avian chlamydial species in Australia, to date, only a single report describes C. gallinaceae in free‐range chickens and a single wild galah (Stokes et al., 2019), starkly contrasting global avian chlamydial species and host diversity.…”

“…Infections have also been detected in non-psittacine species, mainly in single hosts, including a superb lyrebird (Menura novaehollandiae), Australian white ibis (Threskiornis molucca) and introduced species such as a domestic pigeon (Columba livia domestica) and a spotted dove (Spilopelia chinensis). These findings indicate that the Australian avian host range of C. psittaci is grossly underestimated (Anstey et al, 2021;Stokes et al, 2021Stokes et al, , 2020Sutherland et al, 2019). Furthermore, these infections were only described in a handful of surveillance studies conducted in one distinct Australian region, in the state of Victoria (Amery-Gale et al, 2020;Stokes et al, 2019Stokes et al, , 2020Sutherland et al, 2019) or as a discrete part of genotyping or equine/human infection studies (Anstey et al, 2021;Branley et al, 2016;Jelocnik et al, 2017;Jenkins et al, 2018).…”

Animal Chlamydiae: A Concern for Human and Veterinary Medicine

“…The prevalence and role of the Chlamydiaceae in sympatric wild and domesticated animals is also of interest due to the potential for cross-host infections [ 17 ]. Specifically, a study investigating mountain habitats in northern Spain showed that 0.6% of the free-range Pyrenean chamois ( Rupicapra pyrenaica ) and 1.4% of the domestic sheep, from a total of 893 animals evaluated, were positive for Chlamydiaceae , with C. pecorum being the only species identified.…”

“…These ST24/ omp A genotype A strains pose a documented zoonotic risk to humans. The authors further discovered a novel strain (ST306) in the Western brush wallaby, a novel host of C. psittaci [ 17 ]. The multidisciplinary approach in this study ranging from equine infectious disease to ecology is in line with the “One Health” perspective [ 21 ].…”