Epidemiology of Equine Influenza: Risk by Age, Breed and Sex

Abstract

When 360 cases of diagnosed equine influenza reported to VMDP were tested for the independent effects of breed, age and sex, relative to a reference clinic-hospital population of 84,562 equine patients, the quarter horse breed was identified to be at excessive risk, while there were no sex differences. Horses of ages 2-6 months were found to be subject to a significant risk above unity while those at age 7-10 yrs had a risk significantly below unity, indicating a sparing effect on the latter group. A conditional probability of re-infection with equine influenza of 0.05 was identified; and the highest reporting rate was seen to occur in the period April to September. These results should be considered as indicative estimates rather than firm statistics, taking into account the methods used and the type of data available.