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Disease Alerts

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.



Equine Herpesvirus- Neurologic
Los Angeles County, CA
Outbreak Identifier: 6858
Alert ID: 4362
May 16, 2025
Confirmed Case(s) - Official Quarantine

California Department of Food and Agriculture

Number Confirmed: 2; 
Number Exposed: 95; 

Horse 1: 
Age: 20; Gender: Mare; Breed: Thoroughbred (TB); Clinical Signs: neurologic; Horse Status: Euthanized; 

Horse 2: 
Age: 28; Gender: Mare; Breed: Warmblood (WB); Clinical Signs: fever; 

Comments: A 20-year-old Thoroughbred mare from Los Angeles 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. One additional horse on the premises with a fever, a 28-year-old Warmblood mare, also tested positive for EHV-1. Ninety-five (95) potentially exposed horses at the home premises in Los Angeles County were quarantined with enhanced biosecurity measures implemented. CDFA has been onsite and will continue to actively monitor the situation.;
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