The New Mexico Livestock Board (NMLB) reported Jan. 26 that additional horses residing at a racetrack in New Mexico have tested positive for equine herpesvirus-1 (EHV-1), bringing the total case count to 18.

“These horses are from 13 different barns within Sunland Park racetrack; at present, horses in surrounding areas have tested negative,” the report stated. “Of these 18, one horse has been euthanized for neurologic symptoms.”

No movement of horses is being allowed in or out of Sunland Park. Officials with the NMLB, New Mexico Racing Commission, and Sunland Park will continue to work together to resolve the issue, the statement said.

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 an