There have been no additional cases of horses infected with equine herpesvirus-1 (EHV-1) since the June 1 reported infection of a 14-year old Quarter Horse gelding in Marion County.

The horse was treated at Oregon State University College of Veterinary Medicine’s Large Animal Hospital and returned to his stable, which remains under quarantine. All horses located at the stable remain under active observation by owners and their veterinarians for clinical signs of disease.

All eight quarantines associated with previous EHV-1 cases in Oregon have 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. 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.

The virus is spread by direc