Treatment of inflammatory airway disease in young standardbreds with interferon alpha

The effect of oral treatment with natural or recombinant human interferon alpha (HIA) on inflammatory airway disease in young standardbreds was assessed in a double-blind, randomized clinical trial. A total of 34 horses with nasal discharge, excess mucus in the trachea, and a persistent cough of at least 2 weeks' duration that interfered with training completed the trial. Horses were rested for 1 week and received oral treatment with either a saline placebo, recombinant human interferon alpha (rHIA; 90 U/horse/day), or natural human interferon alpha (nHIA: 50 U/horse/day) for 5 days. There was a significant decline in nasal discharge and cough scores in all groups and the apparent response rate was similar. However, significantly fewer horses relapsed within 2 weeks once treatment was ceased when interferon rather than placebo was used (P = 0.012). Seventeen of 22 horses treated with rHIA or nHIA were cough-free 4 weeks after treatment, compared with only 4 of 12 after treatment with the placebo. Treatment with oral interferon is a useful adjunct to rest in standardbreds with inflammatory airway disease.