The Washington State Veterinarian’s office has confirmed a horse at a private boarding facility in Mason County with equine herpesvirus-4 (EHV-4) and strangles. The horse had a runny nose when it was bought from a livestock market, and the owner is working with their veterinarian to monitor its temperature daily and observe biosecurity measures.

Three more horses at the home facility were potentially exposed and are under voluntary quarantine.

EHV-4 Facts

The two most common forms of equine herpesvirus are EHV-1 and EHV-4. EHV-1 is the main cause of viral abortion outbreaks and can also result in fever or respiratory signs, which are sometimes followed by 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). The neurological form, EHV myeloencephalopathy (EHM), is a result of damage to the central nervous system’s vasculature.

EHV-4 usually causes respiratory disease and occasionally can cause abortion or neurologic disease. It is most commonly seen — often in autumn and winter — in weaned foals and yearlings. Older horses with EHV-4 are more likely to spread the virus without showing clinical signs.

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.