ACVIM issues consensus statement on EHV-1

Report calls for more research

June 12, 2009
By Jennifer Fiala

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The American College of Veterinary Internal Medicine (ACVIM) has released a consensus statement on equine herpesvirus-1 (EHV-1), as experts perceive an increase in North American cases of equine herpesvirus myeloencephalopathy, a rare neurologic version of the disease.

The 12-page report, published in the Journal of Veterinary Internal Medicine, pulls together the latest information on EHV-1 pathogenesis, strain variation, epidemiology, diagnostic testing, vaccination, outbreak prevention and control and treatment.

EHV-1 is ubiquitous in most horse populations in the world, although infections are particularly common in young performance horses. The renewed focus on EHV-1 infection and its control stems from new research developments and viral detection technologies, the report says.

Dr. David Powell, an equine epidemiologist at the University of Kentucky College of Agriculture Gluck Equine Center explains that while there have been recent outbreaks, the number of animals involved has been small compared to previous years.

Powell, whose office tracks EHV-1 cases, refers to a 2003 outbreak at the University of Findley in Ohio, which resulted in the death of 10 horses and illnesses in at least 10 more.

“The losses were quite severe,” Powell recalls. “Subsequent to that outbreak, we haven’t seen a repetition of when an outbreak has occurred and a large number of animals have become paralyzed and have had to be put down.”

That’s because there’s now a rapid test and, often, increased baseline biosecurity, Powell says. Those developments are key, he adds, because EHV-1 spreads fast with an overall fatality rate of 30 percent.

“It’s very sporadic,” Powell says of the virus. “Outbreaks tend to occur in the winter months, but that doesn’t mean they don’t happen in the summer. There’s no standard pattern from year-to-year.”

That’s one reason why the statement’s authors call for more research.

“Our understanding of the features of EHV-1 is increasing, but there is more to learn before we can best address the challenges that this virus prevents,” the statement says. “In almost every area of this paper we repeatedly encounter limitations of our understanding, that depend principally on our lack of understanding of the pathogenesis of the diseases EHV-1 causes. The clear message is that future progress will be dependent on research into viral pathogenesis and epidemiology.”

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