The thirty-first (31st) case of West Nile Virus in California in 2023 was confirmed in San Mateo County. On November 1, 2023, an 11-year-old Warmblood mare in San Mateo County displaying neurologic signs was confirmed positive for West Nile Virus. The mare is alive and recovering.
The thirtieth (30th) case of West Nile Virus in California in 2023 was confirmed in Riverside County. On October 10, 2023, a 6-year-old Warmblood gelding in Riverside County displaying neurologic signs was confirmed positive for West Nile Virus. The gelding is alive and undergoing treatment.
The twenty-ninth (29th) case of West Nile Virus in California in 2023 was confirmed in San Bernardino County. On October 10, 2023, a 4-year-old Arabian mare in San Bernardino County displaying neurologic signs was confirmed positive for West Nile Virus. The mare is alive and recovering.
The twenty-eighth (28th) case of West Nile Virus in California in 2023 was confirmed in Riverside County. On October 10, 2023, a 6-year-old quarter horse gelding in Riverside County displaying neurologic signs was confirmed positive for West Nile Virus. The gelding is alive and recovering.
The twenty-seventh (27th) case of West Nile Virus in California in 2023 was confirmed in Merced County. On September 25, 2023, a 5-year-old Quarter Horse mare in Merced County displaying neurologic signs was confirmed positive for West Nile Virus. The mare is recovering well at home.
The twenty-sixth (26th) case of West Nile Virus in California in 2023 was confirmed in Riverside County. On September 26, 2023, a 2-year-old Quarter Horse colt in Riverside County displaying neurologic signs was confirmed positive for West Nile Virus. The colt was euthanized due to severity of clinical signs.
The twenty-fifth (25th) case of West Nile Virus in California in 2023 was confirmed in Siskiyou County. On September 20, 2023, a 23-year-old Quarter Horse mare in Siskiyou County displaying neurologic signs was confirmed positive for West Nile Virus.
The twenty-fourth (24th) case of West Nile Virus in California in 2023 was confirmed in Fresno County. On September 18, 2023, a 20-year-old pony mare in Fresno County displaying neurologic signs was confirmed positive for West Nile Virus.
The twenty-third (23rd) case of West Nile Virus in California in 2023 was confirmed in San Joaquin County. On September 21, 2023, a 13-year-old Quarter Horse gelding in San Joaquin County displaying neurologic signs was confirmed positive for West Nile Virus.
The twenty-second (22nd) case of West Nile Virus in California in 2023 was confirmed in Sacramento County. On September 15, 2023, a 4-year-old Andalusian stallion in Sacramento County displaying neurologic signs was confirmed positive for West Nile Virus. The stallion died.
The twenty-first (21st) case of West Nile Virus in California in 2023 was confirmed in Placer County. On September 12, 2023, a 14-year-old Quarter Horse gelding in Placer County displaying neurologic signs was confirmed positive for West Nile Virus. The gelding was euthanized due to severity of clinical signs.
The twentieth (20th) case of West Nile Virus in California in 2023 was confirmed in San Joaquin County. On September 8, 2023, an unvaccinated 5-year-old Westphalian gelding in Sacramento County displaying neurologic signs was confirmed positive for West Nile Virus. The gelding is alive and recovering.
The nineteenth (19th) case of West Nile Virus in California in 2023 was confirmed in San Joaquin County. On September 8, 2023, an unvaccinated 6-year-old Arabian mare in San Joaquin County displaying neurologic signs was confirmed positive for West Nile Virus. The mare is alive and recovering.
The eighteenth (18th) case of West Nile Virus in California in 2023 was confirmed in Madera County. On September 8, 2023, a 5-year-old Quarter Horse mare with unknown vaccine history in Madera County displaying neurologic signs was confirmed positive for West Nile Virus. The mare is alive and recovering.
The seventeenth (17th) case of West Nile Virus in California in 2023 was confirmed in Tulare County. On September 8, 2023, a vaccinated 7-year-old Pony mare in Tulare County displaying neurologic signs was confirmed positive for West Nile Virus. The mare is alive and recovering.
The sixteenth (16th) case of West Nile Virus in California in 2023 was confirmed in San Luis Obispo County. On August 30, 2023, a vaccinated 4-year-old Arabian gelding in San Luis Obispo County displaying neurologic signs was confirmed positive for West Nile Virus. The gelding is alive and recovering.
The fifteenth (15th) case of West Nile Virus in California in 2023 was confirmed in Riverside County. On August 16, 2023, an 8-year-old Quarter Horse gelding in Riverside County was confirmed positive for West Nile Virus. Current status of the gelding is unknown.
The fourteenth (14th) case of West Nile Virus in California in 2023 was confirmed in San Luis Obispo County. On August 24, 2023, an undervaccinated 5-year-old Quarter Horse mare in San Luis Obispo County displaying neurologic signs was confirmed positive for West Nile Virus. The mare is alive and recovering.
The thirteenth (13th) case of West Nile Virus in California in 2023 was confirmed in Orange County. On August 23, 2023, a 1-year-old Mustang colt in Orange County with no known vaccine history displaying neurologic signs was confirmed positive for West Nile Virus. The colt is affected and alive.
The twelth (12th) case of West Nile Virus in California in 2023 was confirmed in Stanislaus County. On August 24, 2023, a 5-year-old Andalusian stallion in Stanislaus County with no known vaccine history displaying neurologic signs was confirmed positive for West Nile Virus. The stallion is alive and recovering.
The eleventh (11th) case of West Nile Virus in California in 2023 was confirmed in Merced County. On August 22, 2023, a vaccinated 2-year-old Quarter Horse gelding in Merced County displaying neurologic signs was confirmed positive for West Nile Virus. The gelding was euthanized due to comorbidities though neurological signs were improving.
The tenth (10th) case of West Nile Virus in California in 2023 was confirmed in Yuba County. On August 17, 2023, an unvaccinated 2-year-old Paint Horse filly in Yuba County displaying neurologic signs was confirmed positive for West Nile Virus. The filly is alive and recovering.
The ninth (9th) case of West Nile Virus in California in 2023 was confirmed in Napa County. On August 17, 2023, an undervaccinated 4-year-old Quarter Horse mare gelding with no known vaccine history in Butte County displaying neurologic signs was confirmed positive for West Nile Virus. The mare was euthanized due to severity of clinical signs.
The eighth (8th) case of West Nile Virus in California in 2023 was confirmed in Butte County. On August 17, 2023, a 2-vaccinated year-old Haflinger gelding with no known vaccine history in Butte County displaying neurologic signs was confirmed positive for West Nile Virus. The gelding is alive and recovering.
The seventh (7th) case of West Nile Virus in California in 2023 was confirmed in Santa Clara County. On August 17, 2023, an unvaccinated 5-year-old Lusitano mare in Santa Clara County displaying neurologic signs was confirmed positive for West Nile Virus. The mare is alive and recovering.
The sixth (6th) case of West Nile Virus in California in 2023 was confirmed in Sacramento County. On August 11, 2023, an unvaccinated 3-year-old Quarter Horse mare in Sacramento County displaying neurologic signs was confirmed positive for West Nile Virus. The mare was euthanized due to severity of clinical signs.
The fifth (5th) case of West Nile Virus in California in 2023 was confirmed in Kern County. On August 15, 2023, an undervaccinated 3-year-old Quarter Horse mare with no known vaccine history in Kern County displaying neurologic signs was confirmed positive for West Nile Virus. The mare was euthanized due to severity of clinical signs.
The fourth (4th) case of West Nile Virus in California in 2023 was confirmed in Stanislaus County. On August 15, 2023, a 10-year-old Quarter Horse gelding with no known vaccine history in Stanislaus County displaying neurologic signs was confirmed positive for West Nile Virus. The gelding was euthanized due to severity of clinical signs.
The third (3rd) case of West Nile Virus in California in 2023 has been confirmed in Fresno County. On August 8, 2023, a 7-year-old Quarter Horse gelding with unknown vaccine history in Fresno County displaying neurologic signs was confirmed positive for West Nile Virus. The gelding is alive and recovering.
The second (2nd) case of West Nile Virus in California in 2023 was confirmed in Kings County. On July 31, 2023, a 4-year-old vaccinated Quarter Horse mare in Kings County displaying neurologic signs was confirmed positive for West Nile Virus. The mare is alive and recovering.
The first (1st) case of West Nile Virus in California in 2023 was confirmed in Kern County. On July 10, 2023, a 6-year-old vaccinated Warlander mare in Kern County displaying neurologic signs was confirmed positive for West Nile Virus. The mare is alive and recovering.
To date for 2023, a total of thirty-one (31) horses have been confirmed positive for WNV in California. The positive horses were located in Butte (1), Fresno (2), Kern (2), Kings (1), Madera (1), Merced (2), Napa (1), Orange (1), Placer (1), Riverside (4), Sacramento (3), San Bernardino (1), San Joaquin (2), San Luis Obispo (2), San Mateo (1), Santa Clara (1), Siskiyou (1), Stanislaus (2), Tulare (1) and Yuba (1) Counties. Fifteen (15) horses were unvaccinated, four (4) horses were undervaccinated, nine (9) horses were vaccinated, and three (3) horses had unknown vaccine history. Twenty-two (22) horses are alive and recovering, eight (8) horses were euthanized or died, and one (1) horse has unknown status.
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.
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.