WHEN EHV-1 TURNS DEADLY

There’s no sure-fire way of stopping an equine herpesvirus infection from developing into a potentially devastating neurological disease. But you can take steps to protect your horse.

- Heather Smith Thomas with Laurie Prinz

In this age of pandemic, everyone has become familiar with, if not expert in, measures that control the spread of disease: Social distancing. Disinfection. Quarantine. These fundamentals of biosecurity might once have been abstractions but now have taken on practical importance in our lives. Of course, the horse world has long made the control of certain diseases a priority. And thanks to another pillar of disease prevention---vaccination---we’ve largely been successful in protecting horses from rabies, equine encephalomyelitis, West Nile virus and other infectious scourges.

Yet some pathogens continue to pose a threat despite even the most stringent hygiene measures and vaccination programs. Equine herpesvirus-1 (EHV-1) is one such organism. Even without physical contact, this highly contagious respiratory virus can spread rapidly from horse to horse through nasal discharge or aerosol droplets.

Although most cases cause mild-to-moderate respiratory illness (rhinopneumonitis), EHV-1 infection occasionally leads to a life-threatening neurologic disease known as equine herpesvirus myeloencephalopathy (EHM). The mechanisms through which EHV-1, and even more rarely EHV-4, produce neurologic disease are not yet understood. So your best bet is to reduce your horse’s exposure to pathogens in general.