Equine Herpes Myeloencephalopathy (EHM)
On February 16 and 17, 2021 the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA) was notified of two confirmed cases of equine herpes myeloencephalopathy (EHM) caused by equine herpesvirus-1 (EHV-1) infection at equine facilities in the Regional Municipalities of Peel and Niagara. In the Peel region, an 18-year-old gelding was euthanized at a referral equine hospital after showing incoordination in the hind end which progressed to him being down and unable to rise. In the Niagara region, a 7-year-old mare was first examined for difficulty urinating which then progressed to her being down and unable to rise. Both facilities are under veterinary supervision and the farm managers have implemented biosecurity procedures and movement restrictions. There are now three equine facilities in the province with a confirmed EHV-1 infection causing neurologic disease.
EHV-1 infection in horses can cause respiratory disease, abortion, neonatal foal death, and/or neurological disease.
EHV-1 does not pose a threat to public health or food safety.
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 1-877-424-1300.
Because a fever (greater than 101.5 °F or 38.6 °C) may be the first indication of infection, 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.
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 leaving a facility to care for or be in contact with horses elsewhere should change their clothes, shoes/boots and wash their hands before leaving the property. 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 is the best medicine
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 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:
ALBERTA VETERINARY MEDICAL ASSOCIATION AND ALBERTA EQUESTRIAN FEDERATION