Wednesday, September 22, 2010

West Nile Virus Detected in Solano County for First Time in 2010


Solano Public Health officials confirmed today that there is current evidence of local West Nile virus activity and urged residents to avoid exposure to mosquitoes and horse owners to vaccinate their horses.

Solano Public Health received lab confirmation late last week that a horse within the city limits of Dixon, had contracted West Nile virus (WNV) which resulted in its death. The horse had not been vaccinated.

In addition, a chicken within one of the county’s (Cordelia) sentinel surveillance flocks, which are screened routinely to test for mosquito-borne diseases, tested positive for WNV Friday.

“These two test results are the first confirmed equine and poultry WNV cases of 2010 in Solano County, and are the first confirmed indication of local WNV activity for this year,” said Michael W. Stacey, MD, Interim Solano Public Health Officer.

WNV is a virus transmitted to humans and animals from mosquitoes who feed on the blood of infected birds.

“I urge residents to avoid exposure to mosquitoes, and urge horse owners to vaccinate their horses,” Dr. Stacey said. Horses need to be vaccinated against WNV at least annually and horse owners are advised to consult with their local veterinarian for advice on frequency of vaccinations for their specific area.

Solano County Mosquito Abatement District (SCMAD) regularly traps and tests groups of mosquitoes for various diseases, as one of many steps they take to control the mosquito population.

“Three samples of mosquitoes collected in the vicinity of the deceased horse in Dixon were tested, and all three were negative for WNV,” said Jon Blegen, Solano County Mosquito Abatement District Manager.

“We are vigilantly working to control the mosquito population in our county. Our mosquito counts have been very low so far for this season. However, unmaintained swimming pools due to home foreclosures have become a problem statewide and can potentially produce the types of mosquitoes that spread WNV. If you have seen a green pool, please report it to us at (707) 437-1116,” said Jon Blegen, Solano County Mosquito Abatement District Manager.

Symptoms of West Nile fever in humans include headache, fatigue, fever, skin rash on the trunk of the body, swollen lymph glands and eye pain.

“It’s important to remember that 80 percent of people who contract WNV will have no symptoms. Approximately 19 percent of people infected with WNV will develop West Nile fever and notice mild, flu-like symptoms. Less than one percent of those infected will develop severe neurological disease,” Dr. Stacey explained.

“West Nile virus is rarely life threatening, but the most severe forms of the virus may
affect the central nervous system causing meningitis and encephalitis,” Dr. Stacey said.

Although people of all ages can become ill, people at most risk for developing severe neurological diseases as a result of WNV infection include those over age 50, those with immune systems compromised by illnesses such as HIV/AIDS, or people who are undergoing cancer treatments.

“Anyone who experiences flu-like symptoms with a stiff neck should seek medical care,” Dr. Stacey emphasized. There is presently no vaccine or antiviral treatment available to combat WNV in humans.

As of September 20 this year, the California Department of Public Health reports that there have been forty-five human cases of WNV from eleven counties across the state. The first human fatality in California was announced last week from Fresno County.

“The best strategy to avoid contracting WNV is to prevent mosquito bites. I strongly urge the public to practice the five D’s of prevention,” Dr. Stacey added.

  • Dawn and dusk - wear pants and long-sleeve shirts when you are going to be out at these times.
  • DEET – use insect repellent that contains DEET according to packaging directions (non-DEET alternatives, picaridin and oil of lemon eucalyptus are also approved by the EPA).
  • Doors and windows – make sure screens are tight fitting and doors close completely.
  • Drain standing water around your house and use mosquito fish in areas, such as ornamental ponds and horse troughs [call SCMAD at (707) 437-1116 for free mosquito fish].
  • Dead birds – report dead birds and tree squirrels online at or by calling 1-877-WNV-BIRD (1-877-968-2473).
“As we approach duck hunting season, with hunters out in the marsh at dawn and dusk, we remind them to take precautions to protect themselves from mosquitoes and to use DEET,” Blegen said.

From 2002 through 2009, there have been fifteen symptomatic cases of WNV in humans in Solano County, eight of which had neuroinvasive disease. There have been no fatalities in Solano County attributed to WNV to date. In 2009, Solano County had no confirmed human cases of WNV and there have been no human cases year to date in 2010.

Additional information about WNV can be found on the Internet at or

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