Effect of moderate exercise on the severity of clinical signs associated with influenza virus infection in horses.

This study investigates the impact of moderate exercise on the severity of symptoms in horses infected with influenza virus. It concludes that exercising horses during the acute phase of infection could worsen their clinical conditions, though the long-term effects remain uncertain.

Objectives of the Research

• The main objective of this research was to explore whether moderate exercise intensifies a horse’s clinical symptoms when infected with the influenza virus.
• The research sought to investigate the development and severity of symptoms in two groups of horses: those exercised post-infection and those confined to their stalls.

Methodology

• Eight horses were initially trained on a treadmill for 42 days, and subsequently infected with the aerosolised influenza A/equine/Kentucky/91 (H3N8) virus.
• Post infection, one group of 4 horses continued with their exercise regimen, while the other 4 were confined to their stalls.

Findings

• All the horses presented with clinical signs within 36 hours after infection, which included fever, coughing, and mucopurulent nasal discharge.
• The severity scores of clinical symptoms were higher in the group that continued to exercise after infection.
• The infected horses exhibited fever, increased respiratory and heart rates between Day 1 and 14 post-infection.
• All the horses were found to have lost weight by the fourth day, but the exercise group experienced a significantly higher average weight loss (20kg) compared to the non-exercise group.
• Pulmonary complications like pneumonia, consolidation, and oedema were observed in all horses. Ultrasonography showed these conditions usually started improving by Day 14 post-infection.
• All the horses showed signs of airway inflammation for up to 21 days.
• Though the exercising group exhibited severe signs of clinical disease, recovery occurred for both groups on approximately Day 14, and no adverse effects were noted at the end of the study.

Implications and Recommendations

• The research implies that moderate exercise can potentially worsen the clinical symptoms in horses infected with the influenza virus.
• Despite the short-term study indicating no adverse effects post recovery, the potential long-term effects of exercising during the acute phase of infection remain unknown.
• The study concludes with the recommendation that until further research is conducted, it seems judicious to avoid exercising horses affected by an influenza virus infection.