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West Nile mosquitoes discovered

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POSTED May 30, 2014 12:53 a.m.

When a bird that tested positive for the West Nile Virus was discovered on a dairy outside of Tracy back in March, it was the earliest annual detection of the disease in San Joaquin County since it arrived in California more than a decade ago.

That was the host.

And this week when the San Joaquin Mosquito and Vector Control District announced that it had discovered two positive samples taken from adult mosquito populations in an area east of Stockton, they had isolated the first cases of infected carriers detected in what experts believe will be a long, hot, dry summer that may catch people off guard.

“West Nile Virus is here to stay so it is imperative that people take necessary precautions to avoid mosquito bites as well as removing standing water on their properties where mosquitoes can develop,” said Aaron Devencenzi, the Public Information Officer for the district.

While as many as 80 percent of the cases of West Nile Virus are asymptomatic – meaning those that are infected with it most often not have no idea that they’re even infected – the disease can be deadly for children and the elderly.

Last August an 83-year-old died after contracting the virus – the first person to succumb to the effects since 2007. The first reported human case in the county came only a month earlier in a 63-year-old man.

Because of the health implications involved with the recent discovery, the district will be stepping up its efforts in both surveillance and control of adult mosquito populations on both public and private lands in the coming weeks. Educating the public remains one of the best sources of stopping the spread of the disease, and distributing mosquito fish for placement in ornamental ponds or abandoned swimming pools will likely be part of the coming effort.

Spraying of areas where WNV – both aerial and ground spraying – has been detected is typically posted on the district’s website several days prior.

According to California Department of Public Health, the general public can protect themselves by following basic guidelines:

u Wearing long-sleeved shirts and pants when outdoors during active mosquito biting times – typically at dawn and at dusk.

u Making sure doors and windows have tight-fitting screens – replacing those that may be torn or frayed.

u Applying an insect repellant with EPA-registered ingredients such as DEET, Picaridin, IR3535 and oil of lemony eucalyptus (PMD).

Homeowners are also urged to make sure that they remove all sources of standing water that serve as breeding grounds when temperatures heat up.

Birds serve as a reservoir for the disease – it is transmitted by mosquitoes that bite an infected bird and then carry it to a human. The CDPH has opened its hotline for reporting dead birds – 1.877.WNV.BIRD (968.2473) and anybody that finds one is urged to call the number so it can be picked up and tested. They can also be reported by visiting

The San Joaquin Mosquito and Vector Control District sprays for mosquito populations when the season begins. A schedule of those spraying sessions – with maps outlining the areas that will be targeted – as well as other local mosquito and West Nile Virus information can be found at

To contact reporter Jason Campbell email or call 209.249.3544

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