Mosquito season never ends

Photo courtesy of Theresa Shelton County Vector Ecologist Jim O'Brien inspects and treats a potential mosquito trouble spot in Hillsborough to prevent the spread of West Nile virus, a serious, life-altering and even fatal disease.

It’s always mosquito season for San Mateo County Vector Ecologist Dr. Chindi Peavey. There are, after all, 20 species of mosquitoes that inhabit the county, each with its own season.

For her and the rest of the 20 employees at the San Mateo County Mosquito and Vector Control District, battling the bugs is serious business.

And the battle could not be won without help from the public, especially with increasing numbers of foreclosed and abandoned properties in the county.

"We rely on neighbors and real estate agents a lot to inform us about troubled spots,” Peavey said.

Mosquitoes love standing water and neglected homes can be a prime breeding ground for its larvae.

"People are getting used to hearing about West Nile virus and might not take it as seriously as before. We do have West Nile in this county. It’s throughout the state,” Peavey said.

West Nile virus is spread by infected mosquitoes, and can cause serious, life-altering and even fatal disease.

And although only two dead birds tested positive for West Nile virus in the county last year — one in Atherton and the other in South San Francisco — there may have been many more birds infected, Peavey said.

"If someone finds a newly dead bird they should call us immediately so it can be tested,” she said.

Some birds, such as crows, are highly susceptible to West Nile virus. Reports of dead birds are an early indication that the virus is circulating in the environment and being transmitted by mosquitoes, according to the district.

The district works year round to control mosquitoes by targeting its larvae in catch basins, backyard fishponds and other breeding sites.

As summer approaches, the salt marsh mosquito season is about to start. Last year, the district got hundreds of calls from people who were bitten by the bug.

Adult salt marsh mosquitoes virtually hatch all at once by the thousands and can survive through the summer. They can lay eggs up to six times that won’t hatch for several months. The females are especially vicious biters.

Peavey says it is important to contact the district if someone has been bitten by a mosquito.

"We are very responsive to the public. If we get a call, we will be there within 24 hours,” she said.

The district will even stock a backyard pond with mosquito fish.

Most of the district’s job is to battle the bugs in its beginning stages but rarely the district is forced to use fogging to kill off the adults.

The district needed to fog near Bair Island in Redwood City about three years ago, she said.

A recent court case, however, may prevent the district from doing any fogging this summer.

Pollution discharge permits will now be required to have for any fogging by any vector control agency, Peavey said. The trouble is, the pollution discharge permits do not currently exist.

"Fogging is an important tool although we don’t want to use it,” she said.

One of the most important ways to keep mosquitoes under control is by keeping creeks clean. Creeks often collect garbage which can keep the water still. Keeping storm drains clear is also important in keeping the problem under control. The district works with all the cities in the county, primarily with public works departments in helping to keep the mosquito problem under control.

The district also fights rats in residential areas.

The San Mateo County Mosquito and Vector Control District was formed in 1916 and is funded by property taxes. Although revenue is down a bit, Peavey says the district is financially stable.

If someone finds a dead bird, still fresh, they should call (877) WNVBIRD. If someone is bitten by a mosquito they should call 344-8592.

Bill Silverfarb can be reached by e-mail: or by phone: (650) 344-5200 ext. 106.

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