California Non-Neurologic EHV-1: Surveillance Continues

No new cases of equine herpesvirus-1 (EHV-1) have been detected in California, according to a March 16 statement from the California Department of Food and Agriculture (CDFA); however, the organization recommends owners of potentially exposed horses continue monitoring their animals for clinical signs of disease.

Two geldings in California—one in Monterey County and one in San Diego County—tested positive for a non-neurologic strain of EHV-1 last week, according to the CDFA.

The horse in Monterey County displayed hind limb ataxia (incoordination) and was confirmed positive on March 14, the statement said. The San Diego County horse also displayed hind limb ataxia. He was confirmed EHV-1 positive on March 15, the organization noted. Both horses are under veterinary care; however, no further information on their immediate conditions was available.

New information relayed in Friday's statement from the CDFA confirmed that both horses attended the HITS Horse Show in Thermal, Calif., during the event's last week (March 5-11).

"The CDFA recommends that horses stabled in Tents 22 and 34 during the last week of the Thermal show be closely observed and have their temperature monitored twice daily," the CDFA statement noted.

Although it's not transmissible to humans, EHV-1 is highly contagious among horses and camelids, and it is generally passed from horse to horse via aerosol transmission (when affected animals sneeze/cough) and contact with nasal secretions. The disease can cause a variety of ailments in equines, including rhinopneumonitis (a respiratory disease usually found in young horses), abortion in broodmares, and myeloencephalopathy (EHM, the neurologic form).

"(The strain of virus confirmed this week) is responsible for the more common respiratory EHV-1 cases," the CDFA said in the statement. "A small percentage of non-neuropathogenic EHV-1 infected horses can display neurologic signs and are classified as equine herpes myeloencephalopathy cases, which is a reportable condition in California." will continue to provide updates as more information becomes available.

About the Author

Erica Larson, News Editor

Erica Larson, News Editor, holds a degree in journalism with an external specialty in equine science from Michigan State University in East Lansing. A Massachusetts native, she grew up in the saddle and has dabbled in a variety of disciplines including foxhunting, saddle seat, and mounted games. Currently, Erica competes in three-day eventing with her OTTB, Dorado, and enjoys photography in her spare time.

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