Two Illinois horses diagnosed with the equine herpes virus (EHV-1) have been euthanized, according to state health officials. The infected horses were stabled at the same farm in Frankfort.
The horses confirmed with EHV-1 tested positive via a nasal swab test. Both euthanized horses exhibited neurological symptoms.
Additional horses at the stable have exhibited fevers and one is exhibiting neurological symptoms. The horses are under a state mandated quarantine.
The source of the initial exposure has not been identified. Several horses from the stable attended the Midwest Classic, which is a Midwest Reining Horse Association show, in Gifford, Illinois May 2-3, 2015. The competition’s organizers have notified exhibitors.
EHV-1 may lie dormant for long periods of time and then re-activate during a period of stress, which can result in clinical disease.
The incubation period of EHV-1 is 1-10 days and signs are typically seen within 1-3 days. Viral shedding of the virus occurs for 7-10 days, but can occur up to 28 days from the onset of signs.
The neurologic signs include ataxia, urinary bladder atony and reduced tail tone. In severe cases, horses will be unable to stand; these cases have a very poor prognosis.
The EHV-1 vaccine does not protect against the neurological infection.