The strain of equine influenza involved in the outbreak in the UK has been identified as the “Florida Clade 1” strain, which the British Horseracing Authority explains is endemic to North and South America and different from the “Clade 2” strain which is endemic to Europe. British horses are reported to be vaccinated against both strains of the virus, but the BHA states that the strain involved in the current outbreak is “clearly more virulent than the European strain and therefore able to affect vaccinated horses, though the vaccine will provide some protection.”
According to Sky News, this Clade 1 strain is the same culprit behind a three-month shutdown of Australian racing in 2007. That incident involved more than 10,000 horses, but horses in Australia were not vaccinated against that strain at that time because the virus was “completely alien to that continent.”
Conversely, European horses do have some measure of protection against the Claude 1 strain of influenza.
The Animal Health Trust can provide more detailed information about equine influenza here.
The AHT has informed the BHA that it has received approximately 2,100 nasal swabs and tested and reported on 720. So far, other than the six at the yard of Donald McCain already identified, there have been no further positive samples returned.
This includes the swabs taken from horses at the yard of Rebecca Menzies, which various reports had previously pointed to as a potential new threat to UK racing. One horse – which tested negative – had previously been identified as suspicious and high risk after testing at a different laboratory. All these horses will remain under close surveillance, analysis of tests from the yard is ongoing and testing of the suspicious horses will be repeated.
Wider analysis is continuing with thousands more swabs expected to be received and tested over the coming days.
The BHA is continuing to follow its process of assessment, analysis and containment of the highly infectious equine influenza virus, ahead of a decision being made on Monday about the program of upcoming race-meetings.
“We are very grateful to all those trainers whose horses may have come into contact with those from the infected yard for working so rapidly with us and the Animal Health Trust to test their horses,” said David Sykes, BHA's Director of Equine Health and Welfare.
“There are many more tests to analyse and the nature of the incubation period means that a negative test now does not mean that horse has never had this flu virus. So these yards continue to remain locked down and their horses kept under observation.
“Though hundreds of tests have been completed already, there are many hundreds more to be analysed over the weekend before we will have a fuller picture. The nature of disease control means that if a positive did emerge elsewhere, that could lead to more yards being locked down.
“I would advise against anyone drawing any conclusions or making any predictions based on this set of results. Our focus remains on containing the virus through the strict adherence to biosecurity measures we are seeing across the industry”
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