Following the April 6 confirmation of a horse at a boarding facility in Northumberland County, Ontario, Canada, with equine herpesvirus myeloencephalopathy  (EHM, the neurologic condition arising from equine herpesvirus-1, or EHV-1), a horse that left the index horse’s Northumberland County facility on April 1 was referred to an equine hospital for treatment of suspected EHM on April 10 in Durham County.

The second horse is now at a private farm under veterinary care including biosecurity measures. Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA) officials have enacted restrictions for voluntary animal movement on or off the property.

On April 13, OMAFRA was notified of a confirmed case of EHM at the index facility. That mare presented with ataxia (incoordination) and is isolated at the facility where she is receiving veterinary care.

 

EHV 101

Herpesvirus is highly contagious among horses and can cause a variety of ailments in equids, including rhinopneumonitis (a respiratory disease usually found in young horses), abortion in broodmares, and equine herpesvirus myeloencephalitis (EHM, the neurologic form).

In many horses, the first or only sign of EHV-1 infection is fever, which can go undetected. In addition to fever, other common signs of EHV-1 infection in young horses include cough, decreased appetite, depression, and a nasal discharge. Pregnant mares typically show no signs of infection before they abort, and abortions usually occur late in gestation (around eight months) but can be earlier. Abortions can occur anywhere from two weeks to several months following infection with EHV-1.

Horses with EHM usually have a fever at the onset of the disease and might show signs of a respiratory infection. A few days later, neurologic signs such as ataxia (incoordination), weakness or paralysis of the fore- and hind limbs, urine retention and dribbling, loss of tail tone, and recumbency (inability to rise) develop.

Herpesvirus is easily spread by nose-to-nose or close contact with an infectious horse; sharing contaminated equipment including bits, buckets, and towels; or clothing, hands, or equipment of people who have recently had contact with an infectious horse. Routine biosecurity measures, including hygiene and basic cleaning and disinfection practices, should be in place at all times to help prevent disease spread.

Current EHV-1 vaccines might reduce viral shedding but are not protective against the neurologic form of the disease. Implementing routine biosecurity practices is the best way to minimize viral spread, and the best method of disease control is disease prevention.