ANALYSIS OF STATUS OF VACCINATION AND DEVELOPMENT OF FEVER IN TROTTERS IN SWEDEN DURING AN OUTBREAK OF INFLUENZA TYPE-A2 (H3N8)

An outbreak of influenza type A2 affecting a population of 603 vaccina ted trotters in three different trotting tracks in Sweden during the s pring of 1990 was investigated using logistic regression. The analyses were performed with data from the entire population and with data fro m a subpopulation consisting of 150 horses which had been vaccinated s olely with Isovac Flu vet, and who had had at least four such vaccinat ions. The results from analysis of the entire population showed differ ences between tracks, and lower risk for geldings and for horses 4 yea rs or older. The risk of developing clinical signs was increased for h orses vaccinated more than 119 days before the outbreak. The results f rom analysis of Iscovac Flu vet-vaccinated horses also showed differen ces between tracks, lower risk for geldings, and increased risk for ho rses vaccinated more than 119 days before the outbreak.