The Idaho State Department of Agriculture (ISDA) has received confirmation of equine herpesvirus myeloencephalopathy (EHM) diagnosed in horses on a premises in Jerome County and a premises in Gooding County. Both premises are privately owned and now are under quarantine.

EHM is caused by a neuropathogenic strain of equine herpes virus (EHV-1) infection and results in neurological symptoms. One additional premises in Gem County also is under quarantine due to a confirmed EHV abortion in a pregnant mare. An epidemiological investigation is under way for the three premises, but no connection between the operations is apparent. The EHV strain affecting the mare in Gem County was a non-neuropathogenic form, which is known to commonly cause respiratory disease as well as abortion in mares.

EHV-1 is highly contagious among horses. The virus poses no health threat to humans. EHV-1 is present in the environment and found in most horse populations around the world. Horses are typically exposed to the virus at a young age with no serious side effects. Research has not yet determined conclusively why horses with EHV-1 can develop the neuropathogenic strain, EHM.

Symptoms frequently associated with EHM infection in horses include a fever greater than 101.5 F, incoordination, hindquarter weakness, lethargy, incontinence and diminished tail tone. The virus is easily spread by airborne transmission, horse-to-horse contact and contact with nasal secretions on tack, feed and other surfaces. People can spread the virus to horses through contaminated hands, clothing, shoes and vehicles. There is no licensed equine vaccine to protect against EHM.

“We encourage owners to contact their veterinarian immediately if they observe any symptoms of illness in their horses,” said Dr. Bill Barton, ISDA State Veterinarian. EHM/EHV is a Notifiable Disease to the State Veterinarian in Idaho. Anyone suspecting or confirming a case of EHM/EHV should call (208) 332-8540 or (208) 332-8570 to report cases.

Horses that may have been exposed to EHV often take several days to demonstrate clinical illness and run the risk of shedding the virus undetected. Exposed horses that travel to shows or exhibitions could expose other horses before disease containment can be implemented.

ISDA urges horse owners to incorporate preventative biosecurity measures while transporting or boarding horses at facilities with regular traffic on and off the grounds and especially where horses are likely to come in contact with new horses such as at a racetrack, rodeo or fairgrounds. Several preventative biosecurity measures are important in minimizing a horse’s risk of contracting the virus:

• Disinfect stalls before use,
• Never share water or feed buckets and tack or grooming equipment,
• Avoid unnecessary contact with other horses.

Additionally, people who work at multiple equine facilities should practice biosecurity measures by washing hands and changing footwear and clothing before entering each facility.

Contacting ISDA

Dr. Bill Barton, Dr. Scott Leibsle or Chanel Tewalt

(208) 332-8540

info@isda.idaho.gov

Resources

https://aaep.org/sites/default/files/Documents/DiseaseFactsheetEHV.pdf

https://aaep.org/sites/default/files/Guidelines/EHM%20-%20EHV-1%20FAQ1.pdf

https://aaep.org/sites/default/files/Guidelines/BiosecurityGuidelinesFinal1.pdf