Why Is There So Much EHV-1 Popping Up This Year?

by | 02.28.2018 | 11:43am

Here at the Paulick Report, it seems as though we have run more alerts about EHV-1 cases at racetracks and other facilities this year than ever before. Positive cases of Equine Herpesvirus Myeloencephalopathy (the neurological form of EHV, which runs a greater risk of fatality) or EHV-1 have been reported in Thoroughbreds in New York, Kentucky, Arizona, Maryland, Oregon, and California so far in 2018.

Much of our information comes from the Equine Disease Communication Center, a centralized source for official reports of infectious disease. The EDCC alerts come directly from state animal health or agriculture officials. Prior to the EDCC's foundation, veterinarians noticed misinformation and confusion spreading in localities as horsemen tried to sort out fact and rumor in the face of an outbreak.

Dr. Nathaniel White, director and administrative consultant for the EDCC, said the appearance of an increase in cases may be deceptive.

For one thing, it's important to remember to distinguish between EHV-1, which may or may not result in neurological symptoms for a horse, and EHM. For another, White says more states have begun reporting to the EDCC as the center has become more established.

“When EDCC started we were only getting a few states reporting diseases, including EHV-1. Those cases were neurologic cases diagnosed as Equine Herpesvirus Myeloencephalopathy, the nervous form of the disease. Now that we have more states using the EDCC alerts it seems like there are more EHM cases,” he said. “Additionally we have had a few alerts for horses with a fever with a positive identification of EHV-1 and no neurologic disease. There may be an increased prevalence, but I suspect some of the increased numbers is having EDCC reporting cases which before the alerts were managed by each state with no national report.”

Dr. Josie Traub-Dargatz, professor of equine internal medicine at Colorado State University, agreed that more data is needed before it's scientifically safe to draw any conclusions about an increase in cases.

“It is difficult to say if prevalence has changed or not as there is more states reporting now than in the past. If we get consistent reporting over next few years it will be more possible to compare across years,” she agreed.

In the meantime, the American Association of Equine Practitioners has compiled a list of frequently-asked questions and control guidelines for horsemen concerned about EHV-1.

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