The mosquito fighters are out in force again in Clovis.
The first evidence of West Nile virus mosquito activity in Fresno County was reported Thursday. An infection has yet to be reported, but infections from the the night-biting Culex mosquito send county residents to hospitals every year.
West Nile virus causes mild flu-like symptoms in most people, but some can have complications and the virus can be fatal.
Fresno County health officials are asking people to eliminate water sources where mosquitoes breed and to wear bug spray to protect against mosquito bites.
Aedes aegypti, the mosquito species that can spread Zika, chikungunya virus and dengue fever, has plagued Clovis neighborhoods for the past four years, defying efforts to eliminate it. So far, no local mosquito has spread the Zika virus, which can cause severe birth defects and neurological problems in adults, but the rapid spread of the virus in Latin America and the Caribbean has increased the urgency to reduce mosquito numbers here.
Maybe this proves to be an effective strategy, and hopefully it might become a standard control method.
And for a second summer, the Consolidated Mosquito Abatement District has taken a multipronged approach to curtail Aedes aegypti, including sending workers into backyards in search of sources of standing water and deploying bacterium-laced male mosquitoes to mate with females, whose eggs then don’t hatch.
In Braden Court, a subdivision in southeast Clovis, the district has asked residents for permission to enter yards to find and destroy mosquito breeding spots. The goal is to empty containers that hold water and install covers over yard drains to prevent egg-laying mosquitoes from entering.
In one neighborhood in southeast Clovis, district workers are trying a novel assault: releasing thousands of male mosquitoes that are infected with Wolbachia, a bacterium-like organism. It’s the first time in California that Wolbachia-altered Aedes aegypti males have been released to mate with females.
Residents may notice a flurry of mosquitoes, but the males don’t bite. The district will be releasing batches of them twice a week through Sept. 23 in the neighborhood west of DeWolf Avenue between Barstow and Shaw avenues.
This is the second time the district has commandeered male mosquitoes to interrupt the proliferation of the Aedes aegypti mosquito. Last summer it released males that had been dusted with an insecticide. Offspring of the dusted males withered and never developed into mature, biting pests.
Consolidated District Manager Steve Mulligan said it’s too soon to know the degree of success of last summer’s release of dusted mosquitoes. Researchers, though, are encouraged by the results they are seeing from the data, he said.
640,000Number of male mosquitoes with Wolbachia that are being released in Clovis
Last summer’s study was smaller than the one being conducted this year. In 2015, the district released about 50,000 dusted males. This summer 640,000 male mosquitoes with Wolbachia will be released.
“Both of these strategies are worth investigating to see how effective they are,” Mulligan said.
The district will need to continue to ask the public’s help to eliminate sources of standing water, and it will use mosquito fish and spraying to knock down the mosquitoes, Mulligan said.
They will need to wage an attack on several fronts, said Anthony Cornel, an associate professor in the Department of Entomology at the University of California, Davis. Cornel, who works at the university’s Mosquito Control Research Laboratory in Parlier, has teamed with Consolidated on its mosquito-control projects associated with conventional methods, such as eliminating sources of standing water.
“There is no silver bullet,” Cornel said.
But he hopes for success from the latest sterile mosquito technique. “Maybe this proves to be an effective strategy, and hopefully it might become a standard control method.”