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Home / Equine Research Bank / J Vet Intern Med / Prevalence and Risk Factors of Staphylococcus aureus Nasal C...
Journal of veterinary internal medicine2025; 39(3); e70027; doi: 10.1111/jvim.70027

Prevalence and Risk Factors of Staphylococcus aureus Nasal Colonization in Horses Admitted to a Veterinary Teaching Hospital.

Abstract: Methicillin-resistant Staphylococcus aureus (MRSA) is a major cause of nosocomial infections, including in veterinary settings. Objective: To investigate the prevalence, risk factors for Staphylococcus aureus (SA) and MRSA colonization, and the duration of MRSA colonization. Methods: Elective cases admitted to the Veterinary Teaching Hospital were recruited (228 horses). Methods: A cross-sectional study was conducted over 3 years. Nasal swabs were collected at admission and cultured for SA. Methicillin-resistant isolates were identified using matrix-assisted laser desorption/ionization-time-of-flight (MALDI-TOF) technology, oxacillin minimal inhibitory concentration (MIC), and PCR testing. Horses colonized with MRSA were resampled until two negative cultures were obtained. Stabling management, activity, and medical history were obtained from owners and medical files. Multivariable logistic regressions were used to model associations between risk factors and colonization. Results: The prevalence of SA and of MRSA nasal carriage was 17.5% (95% CI: 12.4-22.7) and 6.2% (95% CI: 2.9-9.4), respectively. Of the 10 horses colonized by MRSA and monitored over time, only one tested positive after 3 months. More than 10 horses on the premises (OR 6.0 - 95% CI 1.1-64.2), previous hospitalization (OR 6.0 - 95% CI 1.0-35.2), and year of admission (2022 vs. 2020-2021; OR 9.0 - 95% CI 1.7-92.2) were associated with MRSA nasal carriage. Conclusions: The prevalence of MRSA nasal colonization is of concern; however, the carriage seems transitory. Apart from the medical risk factors, the importance of social interactions in MRSA transmission needs to be elucidated in horses.
© 2025 The Author(s). Journal of Veterinary Internal Medicine published by Wiley Periodicals LLC on behalf of American College of Veterinary Internal Medicine.
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Publication Date: 2025-03-26 PubMed ID: 40135807PubMed Central: PMC11938290DOI: 10.1111/jvim.70027Google Scholar: Lookup
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  • Journal Article

Summary

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This research investigates the rate of nasal colonization of Staphylococcus aureus (SA) and Methicillin-resistant Staphylococcus aureus (MRSA) in horses in a veterinary hospital, identifies associated risk factors, and measures the duration of MRSA colonization. This study reveals a substantial prevalence of these bacteria and identifies several risk factors, but suggests MRSA carriage is typically temporary.

Methodology

  • This study involved 228 horses admitted to a Veterinary Teaching Hospital over a span of three years. All participants were elective cases.
  • As the study is cross-sectional, samples were collected at different time points to observe variations in SA and MRSA colonization.
  • Nasal swabs were obtained from the horses at the time of their admission and then cultured to grow and identify any SA bacteria.
  • Methicillin-resistant isolate, if present, were recognized using advanced techniques such as MALDI-TOF technology, oxacillin minimal inhibitory concentration (MIC), and PCR testing.
  • Those horses found to be colonized by MRSA were continually resampled until two successive negative results were recorded.
  • Data on horse stabling management, activity, and medical history was also collected to identify potential risk factors.
  • A multivariable logistic regression model was used to find the associations between identified risk factors and colonization.

Results

  • The study found that 17.5% of the horses carried SA, and 6.2% carried MRSA in their nasal cavities.
  • Among those colonized by MRSA, colonization was not persistent, as only one out of ten horses continued to test positive for MRSA after three months.
  • The risk factors found to be associated with MRSA nasal carriage include having more than ten horses at the same location, previous hospitalization of the horse, and the year of admission, with a higher risk identified for 2022 versus 2020-2021.

Conclusion

  • Despite the concern over the considerable rate of MRSA colonization, it was observed that such carriage seems to be temporary in nature.
  • While certain medical and environmental risk factors have been identified, the role of social interactions in the transmission of MRSA amongst horses remains to be further studied and clarified.

Cite This Article

APA
Allano M, Arsenault J, Archambault M, Fairbrother JH, Sauvé F. (2025). Prevalence and Risk Factors of Staphylococcus aureus Nasal Colonization in Horses Admitted to a Veterinary Teaching Hospital. J Vet Intern Med, 39(3), e70027. https://doi.org/10.1111/jvim.70027

Publication

Journal of veterinary internal medicine
ISSN: 1939-1676
NlmUniqueID: 8708660
Country: United States
Language: English
Volume: 39
Issue: 3
Pages: e70027

Researcher Affiliations

Allano, Marion
  • Department of Clinical Sciences, Faculty of Veterinary Medicine, Université de Montréal, Saint-Hyacinthe, Canada.
Arsenault, Julie
  • Research Chair in Antimicrobial Surveillance and Antimicrobial Resistance in Animal Health, Epidemiology of Zoonoses and Public Health Research Unit (GREZOSP) and Department of Pathology and Microbiology, Faculty of Veterinary Medicine, Université de Montréal, Saint-Hyacinthe, Canada.
Archambault, Marie
  • Department of Clinical Sciences, Faculty of Veterinary Medicine, Université de Montréal, Saint-Hyacinthe, Canada.
  • Bacteriology Diagnostic Laboratory, Complexe de Diagnostic et d'Épidémiosurveillance Vétérinaires du Québec, Ministère de l'Agriculture, des Pêcheries et de l'Alimentation du Québec and Faculté de médecine vétérinaire, Université de Montréal, Saint-Hyacinthe, Canada.
Fairbrother, Julie-Hélène
  • Bacteriology Diagnostic Laboratory, Complexe de Diagnostic et d'Épidémiosurveillance Vétérinaires du Québec, Ministère de l'Agriculture, des Pêcheries et de l'Alimentation du Québec and Faculté de médecine vétérinaire, Université de Montréal, Saint-Hyacinthe, Canada.
Sauvé, Frédéric
  • Department of Clinical Sciences, Faculty of Veterinary Medicine, Université de Montréal, Saint-Hyacinthe, Canada.

MeSH Terms

  • Animals
  • Horses
  • Horse Diseases / microbiology
  • Horse Diseases / epidemiology
  • Staphylococcal Infections / veterinary
  • Staphylococcal Infections / epidemiology
  • Staphylococcal Infections / microbiology
  • Risk Factors
  • Prevalence
  • Cross-Sectional Studies
  • Methicillin-Resistant Staphylococcus aureus / isolation & purification
  • Hospitals, Animal
  • Male
  • Female
  • Carrier State / veterinary
  • Carrier State / epidemiology
  • Carrier State / microbiology
  • Staphylococcus aureus / isolation & purification
  • Hospitals, Teaching
  • Nose / microbiology

Grant Funding

  • PPIA-16 / Research Chair in Antimicrobial Surveillance and Antimicrobial Resistance in Animal Health funded by the Agri-Food Innovation Partnership Program under the Canadian Agricultural Partnership Agreement between the governments of Canada and Quebec

Conflict of Interest Statement

The authors declare no conflicts of interest.

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