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Chlamydia psittaci infection in horses: results of a prevalence survey and experimental challenge
1Department of Veterinary Medicine, University of Bristol, School of Veterinary Science, Langford, Avon.
Abstract:
Nasal and conjunctival swabs were obtained from 300 horses and Chlamydia psittaci was isolated from 15 of them (5 per cent). Eleven nasal swabs and six conjunctival swabs were positive on culture, but there was no association between the isolation of the organism and the presence of clinical ocular or respiratory disease. Six ponies were challenged with an equine isolate of C psittaci into the eye, nasal cavity or bronchial tree. The organism could be isolated from nasal and conjunctival swabs taken from the ponies for up to 17 days after challenge, but there was no clinical evidence of disease.
Insights
Chlamydia psittaci was isolated from 5% of horses without clinical signs. Experimental infection in ponies showed organism shedding for 17 days, but no disease development.
Area of Science:
- Veterinary Microbiology
- Equine Infectious Diseases
- Ocular and Respiratory Pathogens
Background:
- Chlamydia psittaci is an important bacterial pathogen affecting various animal species, including horses.
- Understanding the prevalence and pathogenicity of C. psittaci in equine populations is crucial for disease control.
- Previous studies have indicated potential roles in equine respiratory and ocular conditions.
Purpose of the Study:
- To determine the prevalence of Chlamydia psittaci in a cohort of horses.
- To investigate the association between C. psittaci isolation and clinical signs of ocular or respiratory disease.
- To evaluate the pathogenicity of an equine C. psittaci isolate in ponies through experimental challenge.
Main Methods:
- Nasal and conjunctival swabs were collected from 300 horses for bacterial culture.
- Isolation of C. psittaci was performed using standard microbiological techniques.
- Six ponies were experimentally infected via ocular, nasal, or bronchial routes with an equine C. psittaci isolate.
- Post-challenge monitoring included serial swabbing and clinical observation.
Main Results:
- Chlamydia psittaci was isolated from 15 out of 300 horses (5%), with positive cultures from nasal and conjunctival swabs.
- No significant association was found between C. psittaci isolation and the presence of clinical ocular or respiratory disease in the surveyed horses.
- Following experimental challenge, C. psittaci was re-isolated from ponies up to 17 days post-infection, yet no clinical signs of disease were observed.
Conclusions:
- Chlamydia psittaci is present in the equine population, but its isolation does not correlate with overt clinical disease in the studied horses.
- Experimental challenge with an equine C. psittaci isolate demonstrated the organism's ability to establish infection and be shed, but without inducing clinical manifestations in ponies.
- Further research is warranted to understand the subclinical dynamics and potential transmission of C. psittaci in horses.