A south Sacramento County horse has become the 10th in California to die of West Nile virus this year, the Sacramento-Yolo Mosquito and Vector Control District announced Wednesday in Elk Grove.
The horse, from an unidentified location, is the first in the county to test positive as this year's pace of infections begins to quicken, said David Brown, district manager.
"We know we have infected birds all over the county. What's significant is we now know mammals are being infected," Brown said in an interview. "That raises our level of concern because humans are mammals too."
County agricultural officials urged horse owners to consult with veterinarians and vaccinate their animals against the virus.
"We strongly urge every single horse owner to vaccinate," said Sacramento County Agricultural Commissioner Frank Carl.
Regional mosquito abatement officials also urged residents to take preventive measures.
"It is now more important than ever that residents of Sacramento and Yolo counties heed this warning," Brown said in a statement. "West Nile virus is here, and we need people to start paying close attention to the warning signs."
He urged residents to reduce their risk of infection by using mosquito repellents containing ingredients such as DEET, picaridin or oil of lemon eucalyptus. People also are urged to wear long sleeves and long pants when outdoors at dawn and dusk, when mosquitoes are most active.
District officials confirmed Wednesday that the infected horse was euthanized after being diagnosed with West Nile virus July 14 by officials at the California Animal Health and Food Safety Laboratory at the University of California, Davis.
So far this year, animal health officials have confirmed at least 16 infected horses in nine counties, including Sacramento, Calaveras, Fresno, Kern, Kings, Plumas, Riverside, Sonoma and Tulare. Half the infections have been confirmed since July 8, according to the California Department of Food and Agriculture.
The disease also has been confirmed in 456 birds in 36 counties, agricultural officials reported.
At least 14 people in seven counties have contracted the disease this year, according to state statistics. Last year, 830 Californians became infected and 28 died. Another 229 horses succumbed to the disease.
West Nile virus is a group of disease-causing viruses that are spread to humans and animals by mosquitoes that have fed on infected birds. Eighty percent of infected people will not experience any symptoms, which may include fever, headaches and muscle aches.
About 1 percent of those infected face serious consequences that include encephalitis or meningitis.
Brown urged residents to drain sources of standing water, add mosquito fish to small ponds and bird baths, and report stagnant swimming pools to the mosquito abatement district. The Sacramento-Yolo district office can be reached at (800) 429-1022.
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