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.

Disease

Outbreak States

Start Date

End Date

Search by Alert ID

Search by Outbreak ID

West Nile Virus

Yolo County, CA

Outbreak Identifier: 7087

Alert ID: 4607

September 24, 2025

Confirmed Case(s) - No Quarantine

Source: California Department of Food and Agriculture

Number Confirmed: 1;

Horse 1:
Age: 9; Gender: Stallion; Breed: Dutch Warmblood; Onset of Clinical Signs: 9/15/2025; Clinical Signs: ataxia (worse in hind end), hyperreactive, muscle fasciculations in face; Confirmation Date: 9/23/2025; Horse Status: Affected And Alive; Vaccination Status: Undervaccinated;

Comments: The fourth (4th) case of West Nile Virus in California in 2025 was confirmed in Yolo County. On September 23, 2025, a partially vaccinated 9-year-old Dutch Warmblood stallion in Yolo County displaying neurologic signs was confirmed positive for West Nile Virus. The stallion is alive and recovering.;

Search for County

Disease Alerts