EFFECT OF MODERATE EXERCISE ON THE SEVERITY OF CLINICAL SIGNS ASSOCIATED WITH INFLUENZA-VIRUS INFECTION IN HORSES

The purpose of this experiment was to determine if exercising horses, infected with influenza virus, exacerbates the severity of clinical di sease. Eight horses were trained on a treadmill for 42 days and then c hallenged with aerosolised influenza A/equine/Kentucky/91 (H3N8). Foll owing challenge, 4 horses (exercise group) continued training for 28 d ays, while the other 4 horses (nonexercise group) were confined to the ir stalls. All horses developed clinical signs within 36 h of challeng e (fever, coughing, and mucopurulent nasal discharge) and clinical sco res were greater in the exercise group. Horses developed fever from Da ys 1-11 post challenge (PC) and were tachypnoeic and tachycardic from Days 1-14 PC. All horses lost weight within 4 days PC, but the exercis e group lost an average of 20 kg more than the nonexercise group. All horses developed pneumonia, and ultrasonography revealed pulmonary con solidation and oedema by Day 7 PC that was resolving by Day 14 PC. End oscopy and transtracheal aspirates showed airway inflammation for up t o 21 days PC, While the exercise group; exhibited more severe signs of clinical disease, resolution occurred for both groups on approximatel y Day 14 PC, and no adverse effects were noted at the end of the study . However, the potential long term effects of exercising horses acutel y infected with influenza virus are unknown. Until further research is conducted in this area, it appears prudent not to exercise affected h orses.