Maryland EHV-1 Contained to One Farm, State Vet Says

Maryland EHV-1 Contained to One Farm, State Vet Says

In many horses, fever is the only sign of EHV-1 infection, which can go undetected.

Photo: Stephanie L. Church, Editor-in-Chief

The Maryland Department of Agriculture confirmed April 7 that there have been no new cases of equine herpesvirus-1 (EHV-1) reported since April 4, when one horse stabled in Anne Arundel County tested positive for the non-neuropathogenic strain of the virus.

The farm was placed on 21-day investigational hold when the first case was confirmed on April 4 and strict biosecurity measures are in place to ensure that no visitors or vendors carry the disease onto other farms. There has been no movement of horses on or off the farm since that date.

The farm’s attending veterinarian and animal health inspectors from the Maryland Department of Agriculture have been closely monitoring all horses on the farm and have found no new cases of the virus. Epidemiologic links to the sick horse have been notified of the situation and owners are cautioned to monitor horses at their premises carefully.

“We have received many calls from concerned stable owners and event organizers since the original case was confirmed earlier this week,” said State Veterinarian Michael Radebaugh, DVM. “We have no reason to believe that the disease has spread beyond this specific farm. Horses are latent carriers of the EHV-1 virus, and under certain conditions, (carriers can) breakout with this disease. In Maryland, we experience a few isolated cases of EHV-1 every year.”

Health Alert: Equine Herpesvirus

Recent cancellations of equine events around the state have led to a heightened level of concern; however, these were precautionary measures taken by the event organizers, and not by the Department.

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.

The Department of Agriculture’s Animal Health Program is monitoring the situation closely. Though the virus appears to be contained, the department reminds all horse owners to remain vigilant in protecting the health of their animals. If a horse exhibits significant temperature elevations or neurologic signs, veterinarians should call the department’s Animal Health program at 410/841-5810 or 410/841-5971 (after hours). EHV-1 is a reportable disease in Maryland

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