Project snapshot: Understanding the epidemiology of Chlamydia psittaci infections in mares and their newborn foals

  • 6 pages

  • Published: 10 Aug 2022

  • Author(s): Martina Jelocnik, Susan Anstey, Joan Carrick, Peter Timms

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Foal loss causes significant economic losses to the Australian thoroughbred industry. Chlamydia psittaci (C. psittaci) has been recognised as a pathogen causing late-term foetal loss in Australia. The objective of this project was to improve understanding of C. psittaci infections in pregnant mares and healthy newborn foals, as well as in foetal loss cases, and to determine reservoirs for this pathogen.

The study demonstrated that C. psittaci foetal loss occurs yearly on a single or several farms as a single case or multiple cases. In all cases, the same C. psittaci ST24 strain was detected in high loads, a strain found in previous foetal loss cases and in parrots such as galahs, sulphur-crested cockatoos, rosellas and budgerigars across Australia. This strain poses risks to human health.

The research showed healthy mares and foals can be infected with low levels of C. psittaci, however the impact of this low-level infection on equine health remains unknown. No specific risk factors were found for C. psittaci related to the pregnant mare. However, detection of this pathogen in both healthy animals and foetal loss cases was consistently higher in winter.

A range of birds (parrots, ibis, ducks and others) found on farms can shed this pathogen, however parrots carry the strain involved in foetal loss. Farms should develop a protocol for suspected C. psittaci foetal loss, with C. psittaci included in foetal loss and/or foal disease laboratory diagnosis.

* An academic journal paper, ‘Suspected chlamydial foetal loss highlights the need for standardised on-farm protocols’, developed as part of this project was published in the Australian Veterinary Journal: Anstey, S. I., Jenkins, C. and Jelocnik, M. (2022). Suspected chlamydial foetal loss highlights the need for standardised on-farm protocols. Aust Vet J. 1–5.