Equine abortion due to Chlamydia psittaci in South Australia with zoonotic transmission.

Research Overview

• The study reports the detection of the bacterium Chlamydia psittaci as the cause of abortion in a horse foetus in South Australia for the first time.
• It also documents a case of zoonotic transmission, where the veterinary pathologist who handled the infected equine tissues subsequently contracted C. psittaci infection, confirmed by real-time PCR testing.

Background and Context

• Chlamydia psittaci: A bacterium primarily known for causing psittacosis, typically transmitted from birds to humans, leading to respiratory illness.
• Equine chlamydial abortion: A condition where Chlamydia psittaci infects pregnant mares, leading to abortion of foetuses; previously not documented in South Australia.
• Zoonotic transmission: The process by which an infectious agent passes from animals to humans, often posing occupational hazards for veterinarians and animal handlers.

Methods and Findings

• Specimen collection: Samples were taken from the aborted foetus’s lung, liver, and kidney, as well as placental tissues.
• Diagnostic testing: Real-time polymerase chain reaction (PCR) was utilized to detect Chlamydia psittaci DNA in tissues.
• Microscopic examination: Revealed inflammation (lymphocytic and histiocytic chorionitis), placental necrosis with bacterial presence inside trophoblastic epithelial cells, and multiple microgranulomas in the foetus’s liver.
• Novel identification: This was the first confirmed case of chlamydial abortion in horses in South Australia, expanding geographic and species-specific understanding of C. psittaci infection.

Zoonotic Transmission Incident

• The veterinary pathologist examining the aborted foetus and placenta developed a fever within eight days after handling the infected tissues.
• Hospital admission enabled collection of bronchial washings via bronchoscopy for diagnosis.
• Real-time PCR detected C. psittaci in the patient’s bronchial specimens, confirming human infection derived from the equine source.
• This represents the first laboratory-confirmed case of zoonotic transmission of C. psittaci from horses to a human in Australia, demonstrating a direct occupational health risk.

Significance and Implications

• Clinical awareness: Veterinary and medical professionals must consider Chlamydia psittaci as a potential cause in cases of equine abortions and febrile respiratory illness with relevant exposure.
• Diagnostic advances: The use of sensitive real-time PCR allows for rapid and specific detection, improving diagnosis in animals and humans.
• Occupational hazard: The report emphasizes the risk for veterinarians and laboratory staff when handling potentially infected equine tissues, underscoring the importance of protective measures.
• Public health: This finding expands the known host range and transmission pathways of C. psittaci, suggesting increased surveillance and awareness in equine industries and healthcare settings.