Texas Animal Health Commission (TAHC) officials confirmed that a hunter-jumper horse visiting Katy, Texas, in Harris County from Wyoming for a Jan. 29 competition tested positive for equine herpesvirus-1 (EHV-1). The horse, which had not visited other events in Texas, exhibited ataxia (incoordination) and other neurologic signs and was isolated immediately, then taken to a veterinary hospital in Brazos County, Texas, for care. Horses that had come into direct contact with the affected horse were also quarantined and are being monitored for clinical signs and elevated temperatures.

EHV 101

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 equine herpesvirus myeloencephalitis (EHM, the neurologic form).

In many horses, the first or 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 EHM 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