The Equine Disease Communication Center (EDCC) has confirmed that an Ingham County, Michigan, horse has tested positive for equine herpesvirus-1 (EHV-1).

“On Feb. 8, a horse from a small stable in Ingham County, Michigan, was diagnosed with EHV-1,” the EDCC said Feb. 10. “The horse had only mild clinical signs and is recovering. The farm is under quarantine until all horses are free from clinical signs, including fever, for 21 days. Horses at this farm rarely travel and there have been no recent movements.”

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.

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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 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.