Poster Presentation Australian Society for Microbiology Annual Scientific Meeting 2022

Developing an on-farm protocol for a suspected Chlamydia psittaci foal loss (#107)

Susan I Anstey 1 , Cheryl Jenkins 2 , Martina Jelocnik 1
  1. Centre for BIoinnovation, University of the Sunshine Coast, Sippy Downs, QLD, Australia
  2. NSW Department of Primary industries, Elizabeth Macarthur Agricultural Institute, Menangle, NSW, Australia

Introduction

Chlamydia psittaci is a recognised cause of late term Thoroughbred foal loss and poses a novel zoonotic risk in Australia. However, a management and diagnostic strategy is still lacking to protect at risk pregnant mares and humans handling infected aborted material. This study describes 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.

Methods

Foetal and placental swabs from the foetal loss cases (n=4), nasal and vaginal swabs of close contact mares (n=59), and their foals (n= 33) were collected and tested for C. psittaci using both recently developed isothermal assay1, and qPCR laboratory-based testing2. Genotyping was performed utilising C. psittaci Multilocus sequence typing (MLST) and ompA sequencing from C. psittaci positive pooled foetal and placental (n=3) DNA3.

Results

Foal and placental samples from the four foal loss cases were all positive for C. psittaci with high loads, and with 100% agreement between the isothermal swab testing on farm and qPCR DNA testing at an external laboratory. No close contact mares and their foals had C. psittaci detected. 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). Genotyping again revealed the clonal sequence type 24 (ST24) C. psittaci strain, a strain detected in all previous equine, psittacine and human hosts.

Conclusion

The proposed protocol is intended to raise awareness and begin a discussion for guidelines for a chlamydial foetal loss in late pregnant mares and a zoonotic threat to farm workers and veterinarians. Furthermore, this study highlights the yearly occurrence of chlamydial foal loss, and endemic nature of this zoonotic pathogen in Australia.

  1. Jelocnik M, Nyari S, Anstey S, et al. Real-time fluorometric and end-point colorimetric isothermal assays for detection of equine pathogens C. psittaci and equine herpes virus 1: validation, comparison and application at the point of care. BMC Vet Res. 2021;17(1):279.
  2. Anstey SI, Kasimov V, Jenkins C, et al. Chlamydia psittaci ST24: Clonal Strains of One Health Importance Dominate in Australian Horse, Bird and Human Infections. Pathogens. 2021;10(8):1015.
  3. Jenkins C, Jelocnik M, Micallef ML, et al. An epizootic of Chlamydia psittaci equine reproductive loss associated with suspected spillover from native Australian parrots. Emerg Microbes Infect. 2018;7(1):88.