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Equine Herpesvirus confirmed in Colorado PDF Print E-mail
Written by Darci Tomky   

Nine cases of Equine Herpesvirus (EHV-1) have been confirmed in Colorado, reported Colorado Department of Agriculture last week.

Gale Wiebers said Holyoke’s CJRA rodeo set for June 4-5 has been canceled and will not be rescheduled due to the risk of spreading the disease.

EHV-1 is a contagious viral disease of horses that can cause respiratory disease, abortion and occasionally neurologic disease.

The neurologic disease, which is less common but more serious than the other two forms, is what has now appeared in Colorado.

Some of the confirmed EHV-1 positive horses had recently attended the National Cutting Horse Association’s Western National Championships in Ogden, Utah.

Numerous other suspect cases include horses that are believed to have been exposed to the disease.

All horse owners who attended the Ogden event should notify a veterinarian and isolate and monitor their horses for clinical signs of the disease.

Local veterinarian Dr. Darrell Tomky said EHV-1 is spread most commonly by nose to nose contact, but it can be spread by aerosol (airborne) and fomites (feed, clothing, boots, hands, etc.).

The disease cannot spread to humans or other animals except llamas and alpacas.

“It’s our recommendation to reduce exposure to other animals,” said Tomky who is urging all horse owners to stop all travel with their horses.

“While travel of horses is not prohibited at this time, we would urge owners to be prudent and avoid any unnecessary travel,” he said.

Those horses which are totally isolated will not be at as much risk of getting EHV-1, a disease which can result in death.

Any new horses at a site should be isolated for a period of three weeks with no sharing of feed, equipment, tack, etc.

“Viral infections are a lot like fires,” said Tomky, noting a virus needs new victims to keep going.

“This could spread like wildfire or it could die out for lack of fuel,” he said. “This fire will burn out if these horses don’t go anywhere.”

Two types of EHV-1 vaccine include one for the respiratory form and one for the abortion-causing form. Tomky said neither one directly protects for the neurologic form, but those vaccinated are at less risk of contracting the disease.

“It appears the vaccine for the abortion form is the most protective,” he added. “We are recommending horses be vaccinated with both products.”

Vaccinations should be repeated every six months and as often as every three months for horses who travel frequently. It may be helpful to give a booster immunization in a previously vaccinated, unexposed horse. These vaccinations could help reduce the severity of an EHV-1 outbreak.

Symptoms of EHV-1 include fever, decreased coordination, nasal discharge, urine dribbling, loss of tail tone, hind limb weakness, leaning against a wall or fence to maintain balance, lethargy and the inability to rise. While there is no cure, the symptoms of the disease may be treatable.

Any sick horses should be isolated, and a veterinarian should be immediately contacted.

Additional information is posted at the Colorado Department of Agriculture website at

Tomky may be contacted at Holyoke Veterinary Service, 970-854-3800.

Many rodeos and other events are being canceled or postponed due to the risk of spreading EHV-1, so be sure to check with organizers about the status of upcoming events.

Holyoke Enterprise May 26, 2011