Veterinary advisory: Equine herpes myeloencephalopathy
Update and information about equine herpes myeloencephalopathy in horses. (Issued August 12, 2022)
Current situation
Equine herpes myeloencephalopathy case confirmed in a horse in Wellington County
The Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA) was notified of a confirmed case of equine herpes myeloencephalopathy (EHM) caused by equine herpesvirus-1 (EHV-1) infection at an equine facility in Wellington County. EHV-1 does not pose a threat to public health or food safety.
A mature gelding was euthanized after showing incoordination, which rapidly progressed. This gelding had not been off the property for several years. The facility is under veterinary supervision and biosecurity protocols and voluntary movement restrictions have been implemented by the facility manager. Other horses from the facility had recently competed at an eventing competition in Simcoe County. None of these horses have shown signs of EHM. The risk to other horses competing at the event is considered low given that the horses from the affected facility were maintained at their trailers with limited interaction with other horses or competitors during the event. Out of an abundance of caution, owners or custodians of horses attending the event should monitor the health of their horses, including rectal temperature, and contact their veterinarian if concerned. Health monitoring should be done for all competition horses regardless of discipline.
EHV-1 infection is immediately notifiable by laboratories to OMAFRA under the Animal Health Act. Attending veterinarians concerned about potential cases of EHV-1 infection may contact an OMAFRA veterinarian through the Agricultural Information Contact Centre at
Clinical signs
A fever (greater than 101.5°F or 38.6°C) may be the first indication of infection, therefore, the temperature of potentially exposed animals should be monitored and recorded twice daily for 21 days and any abnormalities discussed with a veterinarian. Neurological signs, if they develop, may include loss of balance, hind-limb weakness, difficulty urinating, decreased tail tone, depression and being down and unable to rise. It is important that a veterinarian assess horses demonstrating neurological signs since it can be difficult to distinguish this from other serious diseases such as rabies.
Biosecurity
EHV-1 infection is easily spread to other horses by nose-to-nose or close contact with an infected horse, by sharing contaminated equipment including bits, buckets and towels or by the clothing and hands of people who have recently had contact with an infected horse. It is important, therefore, to restrict movement for 21 days of both people and horses where EHV-1 has been diagnosed. Any person moving between equine facilities should change their clothes, shoes/boots and wash their hands. Facility owners should also inform all service providers that have attended the facility within the previous week, including, but not restricted to, veterinarians, farriers, feed suppliers and transporters, of the presence of the virus at the facility so they can take appropriate precautions.
Prevention
Biosecurity is key to preventing spread of EHV-1. Implementing routine biosecurity measures is the best way to minimize viral spread and should be in place at all times to prevent a disease outbreak. Such measures include hand hygiene and basic cleaning and disinfection practices. Horses that have been shipped long distances any new horse to the facility should be segregated for 14 days prior to entering the general population.
EHV-1 vaccines marketed for prevention of respiratory disease may reduce viral shedding but are not protective against developing the neurological form of the disease in the vaccinated animal.
For additional information
OMAFRA
Preventing Disease Spread - Personal Hygiene and Disinfectants around Horse Barns
Horses - Health Management and Biosecurity
CFIA
National Farm and Facility Level Biosecurity Standard for the Equine Sector
Equine Guelph
Equine Biosecurity Risk Calculator