The worst is over in an equine herpesvirus type 1 (EHV-1) outbreak that thus far has caused the death of 12
horses, and scientists are still studying the virus to see if it is somehow different from the normal EHV-1 strain. The outbreak, which began Jan. 12, quarantined the entire equine population of 138 horses at the University of Findlay’s English riding facility in Findlay, Ohio. It has not been detected outside that facility. As of Feb. 3, veterinarians had not diagnosed any new cases of the neurological form of the illness since Jan. 24. Eight horses had presented with fevers since Jan. 28, but none of these horses had exhibited neurologic signs. Several horses with neurologic signs remained stable and under treatment at Findlay. Two horses that had been in critical condition at The Ohio State University’s veterinary teaching hospital could not be saved.

Epidemiological studies are being completed to figure out where the virus came from, and scientists are comparing the strain to others found in past outbreaks.

The EHV-1 organism can spread quickly from horse to horse through aerosol droplets (in the air) or contact with equipment used by affected horses. The virus does not live in the environment for long. Herpesviruses can cause three different forms of disease, including rhinopneumonitis (a respiratory disease mostly of young horses), abortions in pregnant mares, and neurologic disease. The stricken horses in Findlay showed clinical signs of the respiratory and neurological forms. (See article #32 at www.TheHorse.com for more on herpesviruses.)

According to Steve Reed, DVM, Dipl. ACVIM, of The Ohio State University, the high degree of mortality made this strain of EHV-1 unusual. The morbidity (sickness rate) of those horses with the neurologic form of EHV-1 was a little higher than in other outbreaks, he said