Outbreaks | Equine Disease Communication Center

Updates on current disease outbreaks are listed here as they occur and will include the date listed, disease name, location and current status. Specific premises will not be named but the general location by town, county and state will be listed. When locations, events or horses are at risk they will be listed. Updates will be posted as they are received.

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Equine Herpesvirus- Neurologic

Sonoma County, CA

Outbreak Identifier: 6882

Alert ID: 4391

June 04, 2025

Confirmed Case(s) - Official Quarantine

Source: California Department of Food and Agriculture

Number Confirmed: 1;
Number Exposed: 36;
Number Euthanized: 1;

Horse 1:
Age: 23; Gender: Mare; Breed: Pony; Onset of Clinical Signs: 6/1/2025; Clinical Signs: ataxia; Confirmation Date: 6/3/2025; Horse Status: Euthanized;

Comments: A 23-year-old retired Pony mare from Sonoma County displaying neurologic signs was confirmed positive for Equine Herpesvirus Myeloencephalopathy (EHM) secondary to Equine Herpesvirus-1 (EHV-1). The mare was euthanized due to severity of clinical signs. Thirty-six (36) potentially exposed horses at the home premises in Sonoma County were quarantined with enhanced biosecurity measures implemented. CDFA has been onsite and will continue to actively monitor the situation.;

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