Two mares euthanized after contracting equine herpesvirus

WELLINGTON COUNTY  – Two mares here have died after contracting equine herpesvirus (EHV-1). 

A 24-year-old thoroughbred was euthanized on July 7 and a 25-year-old pony on June 30. 

Equine herpesvirus is a common virus in horses that can lead to myeloencephalopathy (EHM), an often-fatal condition with severe neurological symptoms.

Horses carrying the virus can be asymptomatic and still pass it on. 

The virus does not pose a threat to public health or food safety and there are no other reports of positive cases in the region.

According to a July 2 report from the Ontario Ministry of Agriculture, Food and Agribusiness (OMAFA), a pony developed sudden neurologic signs including ataxia and urine dribbling on the evening of June 29. 

When symptoms progressed the following day, she was euthanized. 

On June 28, the horse was at a schooling show in Peel Region, where she was outside at all times. 

“The risk to other horses competing at the show is considered low. However, out of an abundance of caution, owners of custodians of horses attending the show should monitor the health of their horses over the next 14 days, including rectal temperature, which should be interpreted in the context of the extreme heat wave the region is experiencing,” OMAFA officials state in a notice posted at equinediseasecc.org/alerts. 

“Owners should contact their veterinarian with any concerns about their horse.” 

The thoroughbred had not travelled recently, and developed acute ataxia in all four limbs with muscle fasciculations and hyperesthesia on July 7. 

“Clinical signs progressed and she was euthanized,” OMAFA officials state. 

“Nasal swab and blood samples were positive for EHV-1 by PCR.” 

There was also a thoroughbred gelding who was euthanized in Simcoe County on June 8, two days after developing edema of all four limbs on June 6. 

“His signs progressed to acute hind limb ataxia and gladder paralysis and he was taken to an equine referral hospital that day.

“He became recumbent on June 8 and was euthanized. Nasal swab was positive for EHV-1 by PCR,” OMAFA officials state. 

All three facility owners are working with their veterinarians to institute voluntary animal movement restrictions and biosecurity protocols. 

The virus can be carried on items such as clothing, pails and boots, which should always be disinfected when people travel from one equine facility to another. 

Centre for Public Health and Zoonoses director Dr. Scott Weese previously told the Advertiser most young horses are infected with EHV-1 and then the virus lies dormant, before occasionally reactivating or spreading between horses, sometimes leading to abortion or neurological disease. 

Laboratories must report all confirmed EHV-1 infections to the Office of the Chief Veterinarian for Ontario.