The Pennsylvania Department of Agriculture announced May 18 the quarantine of a barn in Tionesta, in Forest County, after a horse residing there tested positive for equine herpesvirus-1 (EHV-1) on May 13.

A horse from the Forest County barn was used in the Tionesta Wounded Warrior Horseback Scavenger Hunt, where 94 horses—including horses from Ohio and West Virginia—took part.

Another barn in Shippenville, in Clarion County, housing an exposed horse that showed clinical signs of EHV-1 was put under precautionary quarantine on May 14, until the pending laboratory results are confirmed. Two additional horses from the Forest County barn have shown signs of illness after being exposed to the positive horse.

The Pennsylvania Department of Agriculture is in the process of tracing the horses that participated in the scavenger hunt, and has notified animal health officials in Ohio and West Virginia.

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

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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 a