Additional Washington Horses Confirmed With EHM
On April 29 the Washington State Department of Agriculture confirmed that three horses have tested positive for the neurologic form of equine herpesvirus-1 (EHV-1). All three reside at a King County boarding facility.

The newest cases consist of a 17-year-old draft gelding and a 6-year-old crossbreed gelding. The 17-year-old gelding, which was reported as having been vaccinated, presented on April 23 with clinical signs that included ataxia (loss of muscular control), urinary incontinence, and nasal discharge and was confirmed positive on April 24. He is reportedly recovering. The 6-year-old gelding, which was reported as having been vaccinated, presented on April 25 with fever and was confirmed April 29. He is reported as affected and alive.

Thirty horses have been exposed, and the barn is under quarantine, being monitored by a veterinarian.

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, 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.