Sunday, 16 June 2024

Mosquitoes infected with West Nile Virus found in Lake County

LAKE COUNTY – Mosquitoes collected in Lake County earlier this week have tested positive for West Nile Virus, Lake County Vector Control District reported Friday.

“This is the first West Nile activity we've had in Lake County this year,” District Manager and Research Director Jamesina J. Scott, Ph.D., told Lake County News.

Scott said this is the time of year when officials expect to see more mosquito activity and, along with it, more West Nile activity throughout the state.

The mosquitoes, Culex stigmatosoma – the banded foul water mosquito – were collected in Lakeport on Tuesday, Scott said.

She said the mosquitoes develop in backyard sources of standing water such as birdbaths, neglected pools and ornamental ponds, as well as larger sources like ditches and wastewater ponds.

West Nile Virus is a disease most often spread by the bite of an infected mosquito, according to the California West Nile Virus Web site. The mosquitoes' main source for the virus is wild birds.

Scott said most people who get West Nile Virus from infected mosquitoes won't become ill, but about 20 percent may experience mild to moderate flu-like symptoms which may be prolonged.

About one in 150 people will become very ill, she said. People over age 50 and people with suppressed or compromised immune systems are more likely to become seriously ill. West Nile Virus infection is rare, but people with symptoms, including high fever, severe headache and stiff neck, should contact their health care provider immediately.

Scott urged residents and visitors to take common-sense precautions to protect themselves from being bitten by mosquitoes that transmit the disease. Precautions include avoiding spending time outside at dawn and dusk when the mosquitoes are active; if you must be outside, use a mosquito repellent.

She also asked community members to spend a few minutes this weekend checking out their yards and eliminating standing water where mosquitoes develop in order to protect themselves, their families and fellow community members.

Other than the mosquitoes, this year so far there have been no West Nile cases in horses, humans or chickens, and no dead wild birds, said Scott. Last year there were three dead birds, eight mosquito samples and two sentinel chickens that were positive for West Nile virus in Lake County.

According to state West Nile Virus statistics, Lake is the first North Coast county to show any West Nile activity.

In Southern California the story is different, said Scott, with numerous cases of both birds and mosquitoes found to be infected. In addition, three of the four cases of horses infected this year are in Southern California counties, with the fourth case in Fresno County, the state West Nile Virus Web site reported.

Most of the state's 29 human cases also are located in Southern California, according to state statistics.

Officials reports fewer cases this year

There have been fewer cases of humans with West Nile Virus this year as opposed to last year at this time, when 65 human cases had already been reported.

In addition to the 29 human cases and four cases of horses infected this year, there are have been 808 dead birds, 604 mosquito samples, 30 sentinel chickens and five squirrels found to have the disease statewide, the state reported.

There is no human vaccine for West Nile, although several very good vaccines exist for protecting horses, with the California Department of Food and Agriculture encouraging vaccination. That's the only way to keep horses safe, as there's no cure for the disease in horses.

Horses cases have been down over the last few years, statistics show.

Since West Nile gained a foothold in California in 2003, it has infected hundreds of horses. In its two peak years of 2004 and 2005, it infected 540 and 456 horses, respectively, according to California Department of Food and Agriculture officials. The numbers of cases in horses have since appeared to taper off dramatically due to a variety of factors, including vaccination.

Getting rid of breeding grounds

Scott said an issue of particular concern is homes with neglected swimming pools, since such pools are an ideal breeding ground for mosquitoes.

That problem has been compounded, she said, by the statewide foreclosure crisis, with pools, fountains, water features and spas being left unattended and, therefore, becoming a contributing factor to mosquito breeding.

Vector Control has a special ally in the fight against West Nile Virus, said Scott: mosquitofish.

The little gray guppies thrive on mosquitoes, she said. “They're a good employee.”

The district makes the fish available free of charge, Scott said, for use in pools or water features that don't have chlorine or chemicals.

“If someone can let us know they've got a neighbor with a bad pool we'll come out and put some fish in it,” she said.

County residents are encouraged to report dead birds and squirrels to the state’s toll-free Dead Bird Hotline 1-877-WNV-BIRD (1-877-968-2473) or online at the California Department of Public Health’s website

If you would like to report a mosquito problem, have questions about mosquitoes or mosquito control, or need mosquito fish, please call the Lake County Vector Control District at 263-4770.

E-mail Elizabeth Larson at This email address is being protected from spambots. You need JavaScript enabled to view it..


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