EHV-1 Reported in Washington State

Four horses have tested positive for a non-neurologic strain of equine herpesvirus-1 (EHV-1), according a March 29 statement from the Snohomish, Wash.-based Pilchuck Veterinary Hospital. The statement cites the Washington State Veterinarian as the source of information.

According to the statement, the four EHV-1 positive horses are from two separate facilities, both of which are under voluntary quarantine. Potentially exposed horses at both facilities are being monitored closely for signs of disease, the statement said.

The statement noted that three of the four affected horses attended the HITS Thermal Horse Show March 5-11, 2012, in Thermal, Calif., that also saw three California horses sickened. The fourth horse is being considered a "secondary exposure," the statement said.

No further information regarding the horses' conditions was immediately available. Phone calls to the Washington State Veterinarian's office seeking further information on the confirmed cases have not yet been returned, as of press time (1:30 p.m. EDT).

The California Department of Food and Agriculture (CDFA) recommends owners of horses that were stabled in tents 22 and 34 during the last week of the Thermal show observe their animals closely and check their temperatures twice daily.

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 in California) is responsible for the more common respiratory EHV-1 cases," the CDFA said in a previous 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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