Disease Alerts

Number Confirmed: 1; 
Number Euthanized: 1; 

Horse 1: 
Age: 2; Gender: Stallion; Breed: Friesian; Onset of Clinical Signs: 9/5/2026; Clinical Signs: Ataxia, muscle fasciculations; Confirmation Date: 9/10/2026; Horse Status: Euthanized; Vaccination Status: Unvaccinated;

Comments: The eleventh (11th) equine case of West Nile Virus in California in 2026 was confirmed in Amador County. On September 10, 2026, a 2-year-old unvaccinated Friesian stallion in Amador County displaying neurologic signs was confirmed positive for West Nile Virus. The stallion was euthanized due to severity of clinical signs.;

Number Confirmed: 1; 
Number Exposed: Unknown; 
Facility Type: Private Facility; 

Horse 1: 
Age: 2; Gender: Gelding; Breed: Mustang; Usage: Pleasure Riding; Onset of Clinical Signs: 8/31/2026; Clinical Signs: Horse apprearaed off and increasingly reactive after a short trailer ride with mild muscle fasiculations. Progressively worse muscle tremors over the follwoing 3 days. 9/3/26 began dexamethason treatment and improvement was seen.; Confirmation Date: 9/4/2026; Horse Status: Recovering; Vaccination Status: Vaccinated;

Number Confirmed: 1; 
Number Exposed: 1; 

Horse 1: 
Age: 7; Gender: Gelding; Breed: Quarter Horse (QH); 

Comments: A 7–year–old Quarter Horse gelding in San Benito County was confirmed positive for Equine Infectious Anemia (EIA). One (1) potentially exposed horse on the home premises has initially tested negative for EIA and will remain under quarantine until the sixty (60) day retest as per CDFA and USDA program requirements. CDFA has been on site with continued monitoring of the situation. Epidemiological tracing determined that the positive horse is directly linked to other recent EIA positive premises in California.;

Number Confirmed: 1; 
Facility Type: Farm;

Comment: This is the first case of New World Screwworm in a horse this century. For additional information, please see the USDA NWS dashboard page https://www.aphis.usda.gov/animals/animal-health/livestock-and-poultry-disease/stop-screwworm/current-status/confirmed. Additional information about NWS can be found at  https://equinediseasecc.org/new-world-screwworm

Number Confirmed: 1; 
Number Exposed: 4; 
Facility Type: Private Facility; 

Horse 1: 
Age: 17; Gender: Gelding; Breed: Quarter Horse (QH); Usage: Pleasure Riding; Onset of Clinical Signs: 9/2/2026; Clinical Signs: mild to moderate acute ataxia and pyrexia improving with supportive care; Confirmation Date: 9/3/2026; Horse Status: Recovering; Vaccination Status: Unvaccinated;

Number Confirmed: 1; 
Number Exposed: Unknown; 

Horse 1: 
Age: 13; Gender: Gelding; Breed: Mustang; Clinical Signs: Fever; Confirmation Date: 8/26/2026; Horse Status: Affected And Alive; Vaccination Status: Status Unknown;

Number Confirmed: 1; 
Number Exposed: Unknown; 
Facility Type: Stable; 

Horse 1: 
Age: 2; Gender: Mare; Breed: Quarter Horse (QH); Usage: Farm/Ranch; Onset of Clinical Signs: 9/2/2026; Clinical Signs: Ataxia Anorexia Abnormal Mentation; Confirmation Date: 9/9/2026; Horse Status: Affected And Alive; Vaccination Status: Status Unknown;

Number Confirmed: 1; 
Number Exposed: Unknown; 
Facility Type: Private Facility; 

Horse 1: 
Age: 4; Gender: Gelding; Breed: Quarter Horse (QH); Usage: Farm/Ranch; Onset of Clinical Signs: 9/2/2026; Clinical Signs: Weakness Ataxia Teeth Grinding Fasciculation; Confirmation Date: 9/9/2026; Horse Status: Affected And Alive; Vaccination Status: Unvaccinated;

Number Confirmed: 1; 
Number Exposed: 3; 
Facility Type: Private Facility; 
Comments: Horse recently purchased in TX with another horse. 2 others on property have been secluded after dx. Under vet care and recovering.;

Number Confirmed: 1; 
Number Exposed: Unknown; 
Facility Type: Farm; 

Horse 1: 
Age: 19; Gender: Gelding; Breed: Draft; Onset of Clinical Signs: 8/25/2026; Clinical Signs: This gelding developed acute neurologic signs (ataxia, falling down) on Aug 25, 2026 and was euthanized. Serum was positive for WNV IgM.; Horse Status: Euthanized; Vaccination Status: Unvaccinated;

Comments: This is the third confirmed case of equine WNV in Ontario this year . To see past and present WNV cases in Ontario go to: https://www.oahn.ca/resources/ontario-equine-disease-alerts/ and enter the disease surveillance portal.;