The Illinois Department of Agriculture has reported that several horses tested positive for neurologic equine herpesvirus-1 (EHV-1) late last month.

“On January 28, the Bureau of Animal Health and Welfare received notification of laboratory confirmation of EHV-1 (neuropathogenic form) infection in horses being boarded at a private stable in DuPage County,” the department said in a statement. “The stable has been placed under quarantine by state animal health officials. The source of the exposure is unknown. At the time of notification, eight horses were affected with two being subsequently euthanized.”

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