An uptick in West Nile virus in mosquitoes has prompted insecticide spraying in some Fresno and Clovis neighborhoods in the hopes it will reduce the likelihood of human infections, according to the Consolidated Mosquito Abatement District.
“There is a lot more West Nile activity than last year,” said Steve Mulligan, the district manager.
Officers in the district’s white trucks have been seen driving through neighborhoods at night spraying. The aerosol fogging machines are mounted on the trucks. Neighborhoods where trapped mosquitoes have tested positive for West Nile are targeted.
The Culex species of mosquito carries West Nile virus. It typically feeds (bites) from evening to morning.
The spray is not harmful to people or pets, Mulligan said, but it does have a distinct odor.
There are about 10 mosquito abatement districts in the Valley. Some, including the Delta Vector Control District in Tulare County, also are spraying insecticide in hopes of quelling the spread of West Nile virus.
West Nile in California
State data shows there have been 18 cases of West Nile virus confirmed throughout the state as of Aug. 9. Ten of those people showed symptoms and eight were asymptomatic. There has been one death reported statewide in 2019.
On Tuesday, Butte County announced a confirmed case, bringing the statewide total to 11.
The Fresno County Department of Public Health said on Monday it could not confirm the number of cases of West Nile because of pending test results. But in July, the health department said two people tested positive and five others were suspected of carrying the virus.
Last week, Tulare County officials said four people were thought to have contracted the virus in Visalia and Tulare.
How is the Aedes Aegypti surviving?
Another mosquito species that officials are keeping tabs on is the Aedes Aegypti, which was first found in Fresno County in 2013.
Mulligan said the Aades Aegypti is originally from tropical climates like Africa, but it has learned to adapt to the central San Joaquin Valley by living in backyards and near homes with plants, water and its favorite meal – humans.
“We didn’t think it’d be able to survive here,” Mulligan said, “but we create a spot where they can.”
For now, the Aegypti are just strange nuisances, as they bite in the daytime hours, unlike other mosquitoes. But they have the potential to spread diseases like Zika, dengue and chikungunya if those diseases were brought to the area. They cannot transmit West Nile.
Officials are asking the public to report daytime bites online or by calling 800-821-1577.
Best defense against bites
Mulligan urged people to protect themselves from all mosquitoes. “I don’t want people to become complacent,” he said. Just because a neighborhood was sprayed doesn’t mean residents shouldn’t take precautions.
Always wear repellent with either DEET, IR3535, oil of lemon eucalyptus or picaridin, Mulligan advised. Loose-fitting long sleeve shirts and pants should be worn outdoors from dusk to dawn. Also make sure window screens are tight fitting and don’t have holes where mosquitoes can get in.
Mulligan recommends residents walk around their home at least once a week and empty any standing water. If there is a spot that water needs to be in, such as a dog bowl, Mulligan says to dump the water, rinse the bowl and refill it often. When algae starts to grow, that’s when mosquitoes are attracted to lay eggs.
Pools that are well-maintained, chlorinated and filtered won’t breed mosquitoes, Mulligan said, but neglected pools are a big problem. The district conducts flyovers, but officials also ask residents to report neglected pools. Whether the home is occupied or not, district workers will ask permission to spray insecticide around the pool.