Respiratory disease in thoroughbred horses in training: the relationships between disease and viruses, bacteria and environment.

This research investigates the relationship between different infectious agents, environmental conditions, and respiratory disease in thoroughbred racehorses. The study found that a bacterial infection, equine herpesvirus, and certain housing conditions were significant factors in the development of these respiratory issues.

Objectives of the Research

• The primary goal of this study was to understand the correlation between different infectious pathogens and respiratory disease in racehorses. The researchers also sought to evaluate the impact of the horses’ environment on their health.
• The investigators also analyzed the connection between symptoms such as coughing, nasal discharge, pyrexia (fever), and lower respiratory tract disease, aiming to enhance clinical diagnoses mainly concerning lower respiratory tract diseases.

Key Findings

• Infections with Streptococcus zooepidemicus, a bacteria, were closely linked to lower airway disease.
• Equine herpesvirus seroconversions and infections with S. pneumoniae were independently associated with the development of nasal discharge in the equine subjects.
• Coughing, although being a specific indicator of lower respiratory tract disease, was found to lack sensitivity, meaning that not all horses with lower respiratory tract disease manifested coughing. The research found that when coughing did occur, it was likely the horse had been experiencing lower respiratory tract disease for over a month.
• Environmental conditions, particularly the housing conditions of the horses, played a significant role in their health. Horses living on straw in loose boxes demonstrated twice the likelihood of contracting lower airway disease compared to those housed on shredded paper in American barns.

Implications of the Study

• This research helped to better define the issue of respiratory disease in racehorses by recognizing the trends in the relationships between bacterial and viral infections, the environment, and the manifestation of respiratory disease.
• The study was not large enough to assess the significance of rarer infections, calling for larger studies to further elucidate these relationships.