Pathology, infectious agents and horse- and management-level risk factors associated with signs of respiratory disease in Ethiopian working horses.

Background: Respiratory disease is a common cause for presentation of working horses to clinics in Ethiopia and a priority concern for owners.

Objectives: To identify risk factors for and association of pathogens with respiratory signs in working horses.

Study Design: Unmatched case-control study.

Methods: Cases were those animals recently coughing (last 7 days) or observed with coughing, nasal discharge or altered respiration at the time of examination. A physical exam and respiratory endoscopy were performed including a tracheal wash sample to detect the presence of pathogens and serology performed on blood. An owner questionnaire was administered. Risk factors were determined using multivariable logistic regression.

Results: Data on 108 cases and 93 unmatched control horses were obtained. Case horses often had underlying lower airway pathology and were significantly more likely to have Streptococcus zooepidemicus detected (OR: 12.4, 95% CI: 3.6-42.4). There was no evidence of a major role for viral respiratory pathogens. Risk factors included completion of strenuous work (OR: 2.7, 95% CI: 1.2-6.3), drinking from stagnant water sources (OR: 2.3, 95% CI: 1.0-5.2) or being housed on a cobbled floor (OR: 2.0, 95% CI: 1.1-3.8). There were increased odds of respiratory disease in young and old horses in this population.

Main Limitations: Samples for pathogen detection and cytology were only taken from the trachea.

Conclusion: S. zooepidemicus, a common commensal, may play a role in clinical respiratory disease in this population.