Officials at the New York Racing Association (NYRA) and the New York State Gaming Commission have placed Barn 10 at Belmont Park, in Elmont, New York, under quarantine after a suspected case of equine herpes myeloencephalopathy (EHM) developed in that barn. The quarantine is effective immediately.

The affected horse, a 4-year-old filly trained by Tom Albertrani, developed a fever on Feb. 12 and started treatment under the care of a private veterinarian. On Thursday evening, the filly began exhibiting clear neurologic symptoms.

At 7 p.m. on Thursday, and in consultation with the New York State Gaming Commission, Anthony Verderosa, DVM, director of NYRA’s Veterinary Department, placed Barn 10 at Belmont Park under a 21-day quarantine.

By Friday, the filly’s health had continued to worsen, and the decision was made to euthanize her. The horse will be taken to Cornell University College of Veterinary Medicine in Ithaca, New York, for a full necropsy.

All standard precautions and biosecurity measures are in place for the quarantine, and at this time no other horses in the barn have developed fever or exhibited clinical signs.

The 20 remaining horses stabled in Barn 10 will be monitored daily for fever and other signs of illness. During the quarantine period, these horses will not be permitted to run or enter races. They will have isolated training hours following the normal closure of the training track at 10 a.m.

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 EHM (the neurologic form). In many horses, the 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 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.