2023 Equine West Nile Virus (WNV) Updates:

No cases Equine WNV have been confirmed in California in 2023. The last detection in California was in Los Angeles County on October 26, 2022.

 

2022 Equine WNV Summary: Sixteen Confirmed Cases

For 2022, a total of sixteen (16) horses were confirmed positive for WNV in California. The first case was confirmed on July 13, 2022 and the last case on October 26, 2022. Horses ranged in age from under 1 year to 15 years (mean 6, median 5), with 10 males and 6 females affected, with multiple breeds reprsesented, but an overrepresentation of Quarter Horse breeds/crosses (over half of confirmed cases).

The positive horses were located in Kern County (3), Kings County (1), Los Angeles (1), Nevada County (1), Sacramento County (2), San Luis Obispo County (1), San Joaquin County (1), Stanislaus County (1), Tehama County (2), and Tulare County (3). Ten (10) horses were unvaccinated, four (4) horses had unknown vaccine history, and two (2) were vaccinated. Eleven (11) horses recovered, one (1) horse died, and four (4) horses were euthanized. 

2021 Equine WNV Summary: Thirteen Confirmed Cases

For 2021, a total of thirteen (13) horses were confirmed positive for West Nile Virus in California. The first case was confirmed on June 28, 2021 and the last case was confirmed on October 6, 2021. Horses ranged in age from 1 to 14 years old (mean 4 years, median 3 years), with 9 females and 4 males affected, and multiple breeds represented.

The positive horses were located in Amador County (1), Fresno County (2), Kings County (1), Merced County (1), Sacramento County (2), San Joaquin County (3), Stanislaus County (1), and Yuba County (2). Nine (9) horses were unvaccinated, two (2) horses had unknown vaccine history and two (2) were vaccinated. Eleven (11) horses are alive, one (1) horse died, and one (1) horse was euthanized. CDFA continually monitors and investigates equine neurologic cases for the presence of WNV in California. CDFA urges horse owners to consult their veterinarian concerning a WNV vaccination program to ensure maximum protection of their horses.