On May 27, 2020, the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA) was notified of the fourth confirmed cases of equine herpes myeloencephalopathy (EHM) due to equine herpes virus-1 (EHV-1) at a farm in Dufferin County.
This was the fourth horse on the farm to be confirmed with the disease between May 23 and May 27.
Two of the horses have been euthanized due to severe and progressive neurological signs. The other two horses are receiving treatment at a referral hospital.
A fifth horse on the farm was euthanized on May 23 due to severe and progressive neurological signs, but testing to confirm EHV-1 was not conducted.
The farm manager along with the attending veterinarian restricted movement for horses and people on and off the property on May 17 and instituted strict biosecurity procedures at that time. The disease has been contained to the main barn on the property.
The outbreak at this farm has an epidemiological link to Woodbine Racetrack in Ontario, where an outbreak of EHM was first reported on May 18. Four horses from the racing facility were confirmed with EHM and referred to an equine hospital for treatment and a fifth horse, also presumed to have EHM, was euthanized.
Information for this report was provided by the Equine Disease Communication Center.
The Alcohol and Gaming Commission of Ontario (AGCO) announced on June 2 that horses not currently in isolation can now exit Woodbine Racetrack. There have been no EHV-1 transmissions outside of Barn 12 in the past 14 days.
One horse in Barn 10 had tested positive and was isolated. All of the remaining horses in Barn 10 tested negative multiple times over the past 14 days. The restrictions on these horses have been lifted.
On June 1, all horses in Barn 12 had tested negative for the first time. The negative results in Barn 12 are an encouraging sign that mitigation strategies appear to have been effective in isolating this neuropathogenic form of EHV-1.
Testing of Barn 12 horses will continue. These horses and others in isolation still have movement restrictions in place, which the AGCO will review on an ongoing basis. New significant developments will be reported as needed.