Determining the endpoint of an outbreak of equine influenza in a large population of racing Thoroughbreds

Abstract

Outbreaks of equine influenza (EI) cause major disruption to the racing industry, resulting in cessation of racing until affected horses have recovered from the disease. The introduction of EI to a large population of Thoroughbred horses stabled at a Sydney racecourse provided the opportunity to observe clinical signs and monitor the spread of EI in this predominantly naïve population and to assist in determining an endpoint to infection spread to allow resumption of racing events.

Clinical outcomes and virology of equine influenza in a naïve population and in horses infected soon after receiving one dose of vaccine

“…The clinical signs and incidence of infection in the unvaccinated Warwick Farm horses were similar to those observed in other large, intensively managed populations during this outbreak 6–8 . Almost all horses became infected in a very short time period and most showed clinical signs.…”

“…The clinical signs and incidence of infection in the unvaccinated Warwick Farm horses were similar to those observed in other large, intensively managed populations during this outbreak. [6][7][8] Almost all horses became infected in a very short time period and most showed clinical signs. Although no deaths were recorded in the study popu- lations, a number of horses in the unvaccinated Warwick Farm population were severely affected and required intensive treatment, in some cases for a lengthy period.…”

The first five days: field and laboratory investigations during the early stages of the equine influenza outbreak in Australia, 2007

“…Most horses recovered uneventfully, but disease appeared to be more severe, and often required treatment, in large aggregations of horses (especially in large stable complexes) compared with individual horses on pasture. Detailed clinical descriptions are provided elsewhere in this supplement 7–9 …”

“…Detailed clinical descriptions are provided elsewhere in this supplement. [7][8][9] During the early stages of the outbreak, among large groups of horses, often only a few were clinically affected at the initial investigation. However, subsequently infection spread rapidly, with clinical signs observed in most horses.…”