Ontario Reports Two Confirmed Cases of EHM in Durham Region

Ontario Reports Two Confirmed Cases of EHM in Durham Region

Because some infected horses show no clinical signs of disease, but still shed the virus, exposed or potentially exposed animals’ temperatures should be monitored twice daily for 14 to 21 days and any abnormalities discussed with a veterinarian.

Photo: Kevin Thompson/The Horse

The Ontario Ministry of Agriculture, Food, and Rural Affairs (OMAFRA) has been notified of two confirmed cases of equine herpes myeloencephalopathy (EHM), a neurologic disease caused by equine herpesvirus-1 (EHV-1).

The horses from Durham Region were referred to the University of Guelph’s Ontario Veterinary College with neurologic signs and are receiving treatment. Three other horses on the farm have tested positive for the mutated (neuropathogenic) strain of EHV-1 on nasal swabs but are not demonstrating neurologic signs at this time. The farm owner has voluntarily placed the premises under quarantine to reduce the risk of viral spread.

These are the first cases of EHM diagnosed in Ontario this year; however, cases of EHM have been diagnosed in California, Kentucky, Louisiana, and Michigan since the beginning of the year. In 2015, there were three laboratory-confirmed cases of EHM in Ontario

Equine herpesvirus-1 infection can cause respiratory disease, abortion, neonatal foal death, and/or neurologic disease in horses. It is not a federally reportable disease, but is immediately notifiable by laboratories under the reporting regulation of the provincial Animal Health Act. Attending veterinarians suspicious of EHM should contact OMAFRA as soon as possible.

Health Alert: Equine Herpesvirus

Because some infected horses show no clinical signs of disease, but still shed the virus, exposed or potentially exposed animals’ temperatures should be monitored twice daily for 14 to 21 days and any abnormalities discussed with a veterinarian. Neurologic signs, if they develop, can include loss of balance, hind-limb weakness, recumbency (inability to rise), difficulty urinating, decreased tail tone, and depression. It is important that a veterinarian assess suspect cases of EHM since it can be difficult to distinguish this from other serious neurologic diseases, such as rabies.

Equine herpesvirus-1is easily spread by nose-to-nose or close contact with an infectious horse, by sharing contaminated equipment (such as bits, buckets, towels, etc.) or by the clothing, hands or equipment of people who recently had contact with an infectious horse. This highlights the need for routine biosecurity measures (including hand hygiene and basic cleaning and disinfection practices) to be in place at all times to prevent a disease outbreak. Special attention should be given to cleaning and disinfecting trailers.

Current EHV-1 vaccines can reduce viral shedding but are not licensed to protect against the neurologic form of the disease. Implementing routine biosecurity practices is the best way to minimize viral spread. The best method of disease control is disease prevention.

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