Virginia EHV-1 Update: No New Cases Confirmed

Virginia EHV-1 Update: No New Cases Confirmed

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

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

Virginia animal health officials reported Aug. 16 that there have been no new confirmed cases of equine herpesvirus-1 (EHV-1) since two cases were diagnosed earlier this week.

On Aug. 15, the Virginia Department of Agriculture and Consumer Services’ (VDACS) reported that its Animal Health Laboratory in Warrenton confirmed EHV-1 in two horses from Culpeper County. One horse is undergoing supportive therapy at the Marion duPont Scott Equine Medical Center (EMC) in Leesburg and the other was euthanized.

The infected horses originated from a small private farm in Culpeper County. All exposed horses are under quarantine and are being monitored twice daily for fever (temperature over 101.5°F) and other clinical signs. If no new cases occur, the farm will remain quarantined with no equids allowed on or off until Sept. 4. There had been no movement of horses off the premises in the month preceding the first diagnosed case on the farm.

The EMC is not under quarantine. Staff there worked with VDACS earlier to develop a plan to hospitalize infectious horses, specifically EHM (equine herpes myeloencephalopathy, the neurologic form of the virus), following isolation and biosecurity protocols, and those protocols were followed in this case.

The vaccine history of these horses is uncertain. While there are vaccines against the EHV-1 virus, the vaccines are ineffective against the neurologic strain.

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, 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.

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