The Texas Animal Health Commission (TAHC) confirmed equine herpes myeloencephalopathy (EHM), the neurologic disease linked to equine herpesvirus-1 (EHV-1), in a Denton County barrel racing horse on Feb. 21.
The horse showed signs of ataxia, loss of coordination in the muscles, and other neurologic signs consistent with EHM when evaluated by a local veterinarian. The horse’s home premises is under quarantine and TAHC staff is working closely with the owner and veterinarian to implement testing protocols and biosecurity measures.
Prior to confirmation, the positive horse attended barrel racing events at the NRS Arena, in Decatur, Texas, on Feb. 15, and Northside Arena, in Fort Worth, Texas, on Feb. 14. The TAHC has been in contact with event management and veterinarians to ensure enhanced biosecurity measures are taken on the premises and event participants are notified.
Owners of horses potentially exposed are encouraged to take precautions. Exposed horses should be isolated and have their temperatures monitored twice daily for at least 14 days after the last known exposure. If an exposed horse develops a fever or other signs consistent with EHM or EHV-1, a veterinarian should perform diagnostic testing. Owners should work with their veterinarian to establish appropriate monitoring and diagnostic plans for any potentially exposed horses.
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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 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.
It is important to remember these signs are not specific to EHM and diagnostic testing is required to confirm EHV-1 infection. Many horses exposed to EHV-1 never develop clinical signs. If you suspect your horse has been exposed to EHV-1, contact your veterinarian.