In the News

March 20, 2006
Tulare (Calif.) Advance Register
West Nile Virus May Strike Early This Year

By Tracey La Monica
Staff writer

The threat of mosquitoes and the virus they carry is real as spring begins in Tulare County.

But this year, with standing water from winter storms hanging around and temperatures on the rise, experts are warning that mosquito season and West Nile virus could be arriving earlier this year

We had such late rains and minimal freezing temperatures, it helps amplify the virus," said Yolanda Lourenco, assistant manager with the Delta Vector Mosquito Abatement District which covers northern Tulare County.

Culex mosquitoes, the principal carriers or vectors of West Nile, are usually the most active in California from April through October, but unseasonable spring-like weather is waking them from their winter semi-hibernation, said Gregory Lanzaro, entomology professor and director of the University of California Davis, Center for Vectorborne Diseases.

"These conditions are like their wake-up call," said Lanzaro, who is also director of the University of California Mosquito Research Program in a statement. "The mosquitoes that were infected

with West Nile Virus before they went into their semi-hibernation or diapause, still have the virus. They're loaded and ready to go."

The disease, transmitted by the bite of an infected mosquito, last year killed 18 people in California, including one person in Tulare County, and infected more than 900 others throughout the state. Health officials found the virus in all 58 counties.

Last year's outbreak in California was not an isolated case, said University of California, Davis, medical entomologist Robert Washino. "It's a preview of what's to come unless we take proactive actions."

Seven D's of West Nile virus precaution and protection Dawn and dusk: Avoid spending time outside at dawn and dusk when mosquitoes are most active. Drain: Empty standing water on your property. Dress: Wear shoes, socks, long pants, and a long-sleeved shirt outdoors when mosquitoes are the most active. Wear loose clothing of a thick material. Defend: Use effective repellents such as DEET, Picaridin or oil of lemon eucalyptus, as recommended by the EPA. It is crucial to follow the label instructions. Door: Be sure your door and window screens are tight-fitting so mosquitoes can't pass through. DEET: This insect repellent, for adults, is effective on your clothing, but should be used sparingly on exposed skin. Be sure to follow the label and read the precautions on the EPA Web site, www.epa.gov /pesticides/factsheets/chemicals/deet.htm. District: Mosquito vector and control district personnel are on hand to address any mosquito problem. Source: University of California, Davis

The transmission of West Nile begins when mosquitoes feed on birds that are infected, and humans and animals become infected when bitten by an infected mosquito.

Although most infections are mild, with flulike symptoms, the virus can cause severe infections that may include neck stiffness, disorientation, coma, tremors, convulsions, muscle weakness, paralysis, and rarely, death, Lanzaro said. The most serious symptom is encephalitis (inflammation of the brain). The mosquito-borne disease also infects and kills horses and birds.

This would be the third year for the virus to strike in Tulare County, said Lourenco.

At this point, there's an expectation that there could be a larger mosquito population and the possibility of more people infected, said Lourenco.

That isn't always the case with the third year, she said.

Normally, the second year peaks, leaving the third year being relatively quiet, but she said the district is expecting the worst and hoping for the best.

Last year in Tulare County, 56 human cases and one reported death were reported, according to the Tulare County Health and Human Services Agency.

So now is the time to stress prevention.

"This is the beginning, when people should take precautions and refresh their memory as to what they need to do to not contribute to the mosquito population," she said.

Lourenco said its extremely important to remove standing water from buckets in the back yard and to clean out places where people might not normally look for water such as rain gutters.

"Standing water provides a living environment for immature mosquitoes to reach a mature stage," she said.

It typically only takes four days for the mosquito to turn from an egg to an adult.

Removing the standing water can eliminate the adult population from breeding, especially this early in the year, she said.

People should also wear long sleeves, long pants and use insect repellent, especially during the early morning and evening hours, when the mosquito who transmits the virus is active.

West Nile virus was first discovered in the United States in 1999. The virus first appeared in California in 2002 with the identification of one human case.

For more information, visit www.westnile.ca.gov.

• The reporter can be reached at tlamonica@visalia.gannett.com.

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Contact:
Kathy Keatley Garvey
Communications
UC Mosquito Research Program
Department of Entomology
396 Briggs Hall
University of California, Davis
Davis, CA 95616
Phone: (530) 754-6894
E-mail: kegarvey@ucdavis.edu