The Idaho State Department of Agriculture has confirmed a case of the contagious equine herpes virus myeloencephalopathy in Ada County, in the Boise area.
The horse tested positive for the non-neuropathogenic strain of EHV-1 but still showed neurologic symptoms. ISDA said in a news release that the horse traveled from Arizona to Idaho in February and then was transported to the Salty Dash Futurity in South Jordan, Utah, from March 15 to 17.
The horse has not traveled since returning to Idaho and is under veterinary care at a private facility that is under quarantine.
The decision to cancel equine events and competitions remains with coordinators at the host facilities. ISDA said owners transporting or boarding horses, and people who work at multiple facilities, should follow biosecurity measures.
Neuropathogenic and non-neuropathogenic strains of the virus have both been known to cause neurologic, respiratory and reproductive symptoms. The neurologic strain is more frequently associated with neurologic disease outbreaks and typically causes higher levels of the virus in the blood.
The common virus is spread by airborne transmission, horse-to-horse contact, and contact with nasal secretions on tack, feed and other surfaces. It has no licensed vaccine. Symptoms may include fever, incoordination, hindquarter weakness, lethargy, incontinence and diminished tail tone.
Exposed horses may take several days to demonstrate illness. They run the risk of spreading the virus to other horses undetected.
ISDA State Veterinarian Bill Borton said owners should contact their veterinarian if they detect symptoms. The virus must be reported to the agency at 208-332-8560.