The Washington State Veterinarian’s Office has received a report of a case of non-neuropathogenic equine herpesvirus-1 (EHV-1) in a King County horse, the Equine Disease Communication Center (EDCC) reported June 13.

“The horse is in isolation and the facility is currently under quarantine,” the EDCC said. “Strict equine biosecurity is in place.”

Earlier this year, several other facilities in King County were quarantined after resident horses tested positive for EHV-1. Those quarantines have since been released.

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 myeloencephalopathy (the neurologic form). In many horses, fever is the only sign of EHV-1 infection, 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 the neurologic form 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.