Suspected chlamydial foetal loss highlights the need for standardised on-farm protocols.

Chlamydia psittaci is a recognised cause of late-term equine foetal loss and poses a zoonotic risk in Australia. However, a management strategy is lacking to protect at-risk humans handling infected aborted material and pregnant mares. This study proposes a protocol for approaching C. psittaci foetal loss after investigating four foetal losses that occurred on a horse stud in the Hunter Valley, Australia in 2021. Swabs from the foetal loss cases (n = 4), close contact mares (n = 59), and foals of the close contact mares (n = 33) were collected and tested for C. psittaci using both isothermal points of care and quantitative polymerase chain reaction (qPCR) laboratory-based testing. Genotyping was performed utilising C. psittaci multilocus sequence typing and ompA sequencing from C. psittaci positive pooled foetal and placental (n = 3) DNA. Foetal and placental samples from the four foetal loss cases were all positive for C. psittaci with 100% agreement between the isothermal swab testing on the farm and qPCR DNA testing at an external laboratory. Genotyping revealed the clonal and identical sequence type 24 (ST24) C. psittaci strains in all samples. C. psittaci was not detected in close contact with mares or their foals. There was no statistically significant difference in foal survival between the close contact mare groups that did and did not receive antimicrobial intervention (P > 0.05). The proposed protocol is intended to raise awareness and begin a discussion for guidelines around handling of chlamydial foetal loss cases in late pregnant mares which pose a zoonotic threat to farm workers and veterinarians.

Epidemiology of Chlamydia psittaci infections in pregnant Thoroughbred mares and foals.

Late-term foal loss due to the traditional avian pathogen Chlamydia psittaci recently emerged as a threat to the Australian Thoroughbred industry. A longitudinal study of 14 stud farms was undertaken to better understand C. psittaci infection in pregnant mares and their foals by evaluating C. psittaci prevalence, equine herpesvirus-1 (EHV-1) co-infection, avian reservoirs, and potential risk factors. Mucosal swabs taken from 228 healthy pregnant mares and their foals were tested for C. psittaci and EHV-1 using species-specific qPCR assays. No foal loss was recorded due to either pathogen, and no mare tested positive to either C. psittaci or EHV-1. However, healthy newborn foals tested positive to both pathogens, at low levels, with 13.2% (n = 30/228) and 14.5% (n = 33/228) prevalence for C. psittaci and EHV-1, respectively. Co-infection occurred in 1.3% (n = 3/228) of foals. In avian environmental faecal samples collected from the same studs, C. psittaci was detected at 5.3% (n = 5/94). Multiple logistic regression modelling found that foals born in winter were more likely to be infected with C. psittaci (adjusted odds ratio = 15.83; P < 0.001; Confidence Interval 5.12-48.49). Being a maiden mare, absence of prophylactic vaginal suture, interventions in the last trimester and residing on a farm with prior history of C. psittaci abortion posed no higher risk to infection in the newborn. Analysis of all reported C. psittaci abortion cases (Hunter Valley, 2016-2019) revealed a dominant C. psittaci sequence type (denoted ST24) and a significant correlation with frost events (Spearmans' rho = 0.44; P = 0.002).

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

Chlamydial infections in dairy cattle are common and have been sporadically associated with reduced performance and severe disease manifestations. While chlamydial infections are well described in sheep, very little is known about the epidemiology of these infections in dairy cattle in Australia. In this study, we screened for chlamydial infections and assessed on-farm risks in dairy cattle herds from Southeast Queensland (SE Qld) region of Australia. In total, 228 paired vaginal and rectal swabs were collected from 114 visually healthy dairy cows from four farms in SE Qld. Risk factors were rated by observational study and included: hygiene and cleanliness of cows, walkway and parlour, incidence of perinatal mortality, external replacements, mode of breeding, calving pen management, heat reduction strategies, and feed ration usage. Testing for chlamydial pathogens (Chlamydia pecorum, Chlamydia psittaci and Chlamydia abortus) was done using species-specific quantitative polymerase chain reaction (qPCR) assays. Detected rates of chlamydial infection were evaluated against the on-farm risk factors. C. pecorum infection was widespread in all four farms, with 56.1% (64/114) of individual animals shedding this organism from vaginal and rectal, or both sites. C. abortus and C. psittaci were not detected in any animals. No association was found to exist with risk factors and C. pecorum infection rates in our study, however the number of Chlamydia positive animals was statistically different between the herds. This study suggests that subclinical chlamydial infections may impact on dairy herd health at the production level rather than affecting individual animal.

Detection of Chlamydiaceae in ocular swabs from Australian pre-export feedlot sheep.

Infectious Ovine Keratoconjunctivitis (IOK) is a contagious ocular disease of sheep. A range of organisms have been observed as the aetiological agents of IOK. In this study, the presence of chlamydial pathogens (C. pecorum, C. abortus, C. psittaci) in conjunctival swabs was tested for. The swabs were collected from sheep with varying grades of IOK in an Australian pre-export feedlot. The sheep had been rejected from a shipment because of the eye disease. The relative contribution of chlamydial pathogens to IOK and the rejection of animals was evaluated. In total, 149 conjunctival swabs were taken from rejected sheep (IOK Grades 1 to 6; n = 126) as well as those with healthy eyes (Grade 0; n = 23). Screening for chlamydial pathogens was done using species-specific qPCR assays. Chlamydial DNA was detected in 35.6% (53/149) of conjunctival samples. C. pecorum was the most predominant species with an overall prevalence of 28.9% (43/149). C. psittaci prevalence was 6.7% (10/149). Both organisms were detected in healthy as well as IOK-affected eyes. All swabs tested negative for C. abortus. The results from this study demonstrate that Chlamydia spp can be readily detected in sheep presenting with IOK. The zoonotic C. abortus was not detected in any of the samples in this study, providing further evidence to the suggestion that this pathogen remains absent from Australia. Although the exact contribution of Chlamydia spp in the IOK pathogenesis is unclear, such studies are anticipated to be of benefit to Australian domestic and live export production systems.

Molecular evidence to suggest pigeon-type Chlamydia psittaci in association with an equine foal loss.

Chlamydia psittaci is an important avian pathogen with spillover from infected wild and domesticated birds also posing a risk to human health. We recently reported a case of C. psittaci equine placentitis associated with further spillover to humans. Molecular typing of this case revealed it belonged to the 6BC clade of C. psittaci, a globally distributed highly virulent set of strains, typically linked to infection spillover from parrots. Equine chlamydiosis associated with C. psittaci infection has previously been reported elsewhere in countries where parrots are not endemic, however, raising questions over the identity of infecting C. psittaci strains and the potential infection reservoirs. In this study, we describe the detection and molecular characterization of C. psittaci in a case of equine abortion in southern Queensland. Equine placenta and fresh liver and lung tissue from the necropsied foetus were positive by C. psittaci-specific qPCR. Chlamydia psittaci-specific multilocus sequence typing and ompA genotyping were used to further characterize the detected equine strains and an additional strain obtained from a dove from a different geographic region presenting with psittacosis. Molecular typing of this case revealed that the infecting equine strains were closely related to the C0sittaci detected in dove, all belonging to an evolutionary lineage of C. psittaci strains typically associated with infections of pigeons globally. This finding suggests a broader diversity of C. psittaci strains may be detected in horses and in association with reproductive loss, highlighting the need for an expansion of surveillance studies globally to understand the epidemiology of equine chlamydiosis and the associated zoonotic risk.