All British race meetings have been cancelled until next Wednesday at the earliest because of an outbreak of equine flu. The decision by the British Horseracing Authority (BHA) comes after three vaccinated horses in the Cheshire yard of leading jumps trainer Donald McCain tested positive for the illness, leading initially to the cancellation of all four meetings yesterday.

The incubation period for an infected horse is typically a matter of days, but recovery can take weeks, or even months. There are no known consequences for humans exposed to it.

A BHA statement warned that the “full extent of potential exposure is unknown”, but the fact that the cases have been identified in vaccinated horses is a “cause for significant concern over welfare and the potential spread” of the highly-contagious airborne disease. It stated that cancelling racing is viewed as “necessary in order to restrict, as far as possible, the risk of further spread”.

A decision about racing can continue is set to be made on Monday.

Eighteen years ago, British and Irish racing was shaken by the outbreak of foot and mouth disease in the UK. Racing was stopped for a while, and the 2001 Cheltenham Festival was called off altogether.

An outbreak in of equine flu Australia in August 2007 infected horses on 10,651 premises in three months despite the imposition of movement controls. The disease was eradicated, but the cost of treatments and cancellation of events cost the industry a reported A$1 billion.