In many horses, the only sign of EHV-1 infection is fever, which can go undetected. | Photo: Alexandra Beckstett/The Horse

A second Union County, New Jersey, horse has tested positive for equine herpesvirus-1 (EHV-1), the New Jersey Department of Agriculture announced March 20.

That horse resides on the same property quarantined last week after a horse developed equine herpesvirus myeloencephalopathy (EHM, the neurologic form EHV-1).

The second horse developed an elevated temperature and exhibited respiratory signs of disease, but the attending veterinarian did not note any neurologic signs. That horse was placed in the farm’s isolation barn and the entire property remains quarantined.

Personnel continue to take temperatures twice daily on all horses on the property. No horses have moved on or off the property in approximately a month, therefore officials consider exposure to outside horses unlikely.

This second EHV-1-positive horse has reset the quarantine clock and, at this point, will delay the release date another three days. These are the first reported EHV-1 cases in New Jersey in 2018.

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. 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.

Officials note that EHM is a reportable disease in New Jersey. If an owner has a horse exhibiting neurologic signs or suspects EHV-1, he or she is directed to call their veterinarian immediately.