California EHV-1: One New Case Confirmed

The California Department of Food and Agriculture (CDFA) has reported one additional confirmed case of neurologic equine herpesvirus-1 (EHV-1) at the Orange County facility quarantined since Jan. 11. No additional cases have been confirmed at the Riverside County facility that saw an EHV-1 positive horse euthanized Jan. 24.

The newly confirmed Orange County case brings the total to 16 confirmed cases. Only one horse--the index case--has displayed neurologic signs and is reportedly recovering, the statement indicated. One horse was euthanized on Jan. 18 after becoming recumbent; however, a necropsy led veterinarians to believe the recumbency was unrelated to the EHV-1, the CDFA said.

In Riverside County the CDFA reported that a necropsy on the euthanized horse found histologic lesions compatible with EHV-1. The CDFA also noted that the "large multidiscipline equine premises" where the horse was residing has been quarantined as a result of the confirmed EHV-1 case.

"Based on the initial investigation, there is no evidence to link this case to the Orange County premises," the department 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).

Myeloencephalopathy is characterized by fever, ataxia (incoordination), weakness or paralysis of the hind limbs, and incontinence. Should a horse with potential EHV-1 exposure display any of the aforementioned clinical signs, a veterinarian should be called to obtain samples and test for the disease. will continue to provide updates as new 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 eventing with her OTTB, Dorado.

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