The Ontario Ministry of Agriculture Food and Rural Affairs (OMAFRA) has been notified of a confirmed case of Equine Herpes Myeloencephalopathy (EHM), caused by equine herpes virus 1 (EHV-1), in Southern Ontario. A blood sample from a horse with severe neurological signs tested positive for EHV-1 in early January. The horse was euthanized after its condition deteriorated. On a second farm in the same area, another horse with similar signs was euthanized in late December. No samples were collected from that horse.
In 2011, there was one laboratory-confirmed case and one suspect case of EHM in Ontario. EHV-1 infection in horses can cause respiratory disease, abortion, neonatal foal death, and/or neurological disease. EHV-1 is not a federally Reportable Disease.
Because infected horses may show no clinical signs, but still shed the virus, the temperature of suspect animals should be monitored twice daily for 14 -21 days and any abnormalities discussed with a veterinarian. Neurological signs include loss of muscle coordination, lethargy, inability to urinate, reduced tail tone and/or head tilt. It is important that a veterinarian assess suspect cases of EHM, since it can be difficult to distinguish between this and other serious diseases, such as rabies, that can affect the nervous system in horses.