2022 Equine West Nile Virus (WNV) Update:

SIXTEENTH Confirmed Equine WNV Case

On October 26, 2022, a 15-year-old Paint gelding with an unknown vaccination history in Los Angeles County, displaying neurological signs, was confirmed positive for West Nile Virus. The gelding was euthanized. This is the sixteenth case of equine WNV confirmed in California in 2022.

On October 21, 2022, a 6-month-old unvaccinated Quarter Horse colt in Kings County, displaying acute neurological signs, was confirmed positive for West Nile Virus. The colt died. This is the fifteenth case of equine WNV confirmed in California in 2022.

On October 6, 2022, a 6-year-old Quarter Horse mare with an unknown vaccination history in Sacramento County, displaying acute neurological signs, was confirmed positive for West Nile Virus. The mare is alive and recovering. This is the fourteenth case of equine WNV confirmed in California in 2022.

On October 5, 2022, a 3-year-old Quarter Horse mare with an unknown vaccination history in Tehama County, displaying acute neurological signs, was confirmed positive for West Nile Virus. The mare is alive and recovering. This is the thirteenth case of equine WNV confirmed in California in 2022.

On October 3, 2022, a 1-year-old unvaccinated Quarter Horse filly in Stanislaus County, displaying acute neurological signs, was confirmed positive for West Nile Virus. The filly is alive and recovering. This is the twelfth case of equine WNV confirmed in California in 2022.

On September 28, 2022, a 4-year-old Quarter Horse gelding with an unknown vaccination history in San Joaquin County, displaying acute neurological signs, was confirmed positive for West Nile Virus. The gelding is alive and recovering. This is the eleventh case of equine WNV confirmed in California in 2022.

On September 26, 2022, a 10-year-old unvaccinated Quarter Horse gelding in Nevada County, displaying transient fever and neurological signs, was confirmed positive for West Nile Virus. The gelding is currently alive and recovering. This is the tenth case of equine WNV confirmed in California in 2022.

On September 19, 2022, an 8-year-old vaccinated Thoroughbred gelding in Tulare County, displaying acute neurological signs, was confirmed positive for West Nile Virus. He was euthanized due to the severity of clinical signs. 

On September 14, 2022, a 15-year-old unvaccinated Warmblood stallion attending an event in San Luis Obispo County, displaying acute neurological signs, was confirmed positive for West Nile Virus. He was imported from Mexico within one week of onset of clinical signs so exposure was likely in Mexico. The stallion is alive and recovering. 

On September 12, 2022, a 1-year-old unvaccinated Quarter Horse filly in Tulare County, displaying acute neurological signs, was confirmed positive for West Nile Virus. She is alive and recovering. 

On September 2, 2022, a 2-year-old unvaccinated Paint filly in Kern County, displaying acute neurological signs, was confirmed positive for West Nile Virus. She is alive and recovering.

On August 31, 2022, a 5-year-old unvaccinated Friesian stallion in Tulare County, displaying acute neurological signs, was confirmed positive for West Nile Virus. He was euthanized due to poor prognosis. 

On August 24, 2022, a 5-year-old Spanish Mustang stallion in Tehama County, displaying acute neurologic signs, was confirmed positive for West Nile Virus. The stallion's vaccination status is unknown, and he is currently alive. 

On August 19, 2022, a 4-year-old Thoroughbred mare in Sacramento County, displaying acute neurologic signs, was confirmed positive for West Nile Virus. The mare's vaccination status is unknown, and she is currently alive and recovering. 

On July 11, 2022, an unvaccinated 4-year-old Quarter Horse gelding in Kern County, displaying acute neurologic signs, was confirmed positive for West Nile Virus. The gelding was euthanized due to severiity of clinical signs.

On July 13, 2022, an unvaccinated 6-year-old Arabian/Quarter Horse gelding in Kern County, displaying acute neurologic signs, was confirmed positive for West Nile Virus. The gelding is currently alive and recovering.

For 2022, a total of sixteen (16) horses have been confirmed positive for WNV in California. 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).

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.