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Mosquitoes and West Nile Virus in Placer County |
Introduction: What is West Nile Virus?
The Placer Mosquito and Vector Control District has prepared this site to inform you about West Nile Virus in an effort to reduce the number of mosquitoes in your yard, neighborhood and community, for the purpose of reducing the need for more aggressive mosquito control measures.
West Nile Virus (WNV) is a mosquito-borne virus commonly found in humans, birds, and other vertebrates in Africa, Eastern Europe, West Asia and the Middle East. The virus, which can lead to an infection of the brain called encephalitis, was first identified in the United States in New York City in the late summer of 1999
What are the symptoms of WNV?
People become infected with WNV from the bite of an infected mosquito. After 3 to 15 days, most people develop mild symptoms including fever, headache and body aches, occasionally with skin rash and swollen lymph glands. More severe infections are marked by high fever, neck stiffness, tremors, muscle weakness, disorientation, and other signs of increasing illness. Symptoms should be evaluated by your health care provider.
How likely am I to get sick?
The chances of becoming severely ill from any one mosquito bite are extremely small. Even in areas where mosquitoes carry the virus, very few mosquitoes-much less than 1%, are infected. If the mosquito is infected, less than 1% of people who get bitten and become infected will become severely ill.
Prevention and Protection
Although the chances of an individual contracting encephalitis are small, there are some simple measures that you and your family can take to reduce those chances even further. Here is what you can do and what you need to know.
Where do mosquitoes live and breed?
Mosquitoes rest in tall grass, weeds, and brush near inhabited locations such as homes and other buildings.
• Mosquitoes breed in stagnant, standing fresh water oftentimes found around the home.
• In tin cans, buckets, discarded tires and other artificial containers that hold stagnant water.
• In untended pools, birdbaths, clogged rain gutters, and plastic wading pools that hold stagnant water.
• In storm drains and catch basins in urban areas.
• In septic seepage and other foul water sources above or below ground level.
• In agricultural irrigation.
What can I do to reduce mosquitoes breeding near my house?
• Whenever water stands for four to seven days, mosquitoes can multiply. Eliminating even small amounts of standing water eliminates mosquitoes.
• Dispose of empty cans, buckets, flowerpots, old tires, trash cans, etc.
• Clear clogged roof gutters.
• Change water in bird baths and fountains at least once a week.
• Flush sump pump pits weekly.
• Empty plastic swimming pools when not in use.
• Drain swimming pool covers.
• Clean and chlorinate swimming pools, outdoor saunas and hot tubs.
• Drill holes in the bottoms of recycling containers that are kept outdoors.
• Use landscaping to eliminate stagnant water that collects on your property.
• Clip tall grass or weeds standing near the house or where people use the yard. Clean vegetation and debris from the edges of ponds.
What can I do to avoid being bitten?
• Check and repair all screens and screen doors.
• Minimize outdoor activities between sunset and sunrise when mosquitoes are most active.
• Avoid mosquito habitats such as areas with heavy underbrush or standing water.
• When outdoors, wear clothing that covers the skin, such as long-sleeved shirts and pants.
• Consider spraying clothing with repellents containing permethrin, since mosquitoes may bite through thin clothing.
• On exposed skin, consider applying a repellant that contains DEET, picaridin, or oil of lemon eucalyptus. More information on these products can be found here: CDC Mosquito Repellant Recs 2005
Mosquito Repellant Guidelines
General information: Presently there are four active ingredients that are known to be effective mosquito repellants: DEET (N,N-diethyl-m-toluamide), picaridin (KBR 3023), oil of lemon eucalyptus [p-menthane 3,8-diol (PMD)], and permethrin.
DEET is an insect repellent that can reduce the risk of mosquito bites, and has been widely used for more than 50 years, but products containing DEET have been occasionally associated with some health problems.
Picaridin is a non-greasy, nearly odorless alternative to DEET, and is registered with the EPA for use as a mosquito repellant.
Oil of lemon eucalyptus is a plant based repellent, is also registered with EPA. In two recent scientific publications, when oil of lemon eucalyptus was tested against mosquitoes found in the US it provided protection similar to repellents with low concentrations of DEET.
Permethrin is recommended for use on clothing, shoes, bed nets, and camping gear, and is registered with EPA for this use. Permethrin is highly effective as an insecticide and as a repellent. Permethrin-treated clothing repels and kills ticks, mosquitoes, and other arthropods and retains this effect after repeated laundering. The permethrin insecticide should be reapplied following the label instructions. Some commercial products are available pretreated with permethrin. Note that unlike DEET, picaridin, and oil of lemon eucalyptus, PERMETHRIN SHOULD NOT BE APPLIED DIRECTLY TO THE SKIN.
The Placer Mosquito and Vector Control District recommends the following precautions when using insect repellents:
• Read all instructions on the label before applying, and follow those instructions for the best results.
• Apply repellents only to exposed skin and/or clothing (as directed on the product label.) Do not use repellents under clothing.
• Never use repellents over cuts, wounds or irritated skin.
• Do not apply to eyes or mouth, and apply sparingly around ears. When using sprays, do not spray directly on face—spray on hands first and then apply to face.
• Store all repellants out of reach of children.
• Do not allow children to handle the product. When using on children, apply to your own hands first and then put it on the child. You may not want to apply to children’s hands.
• Use just enough repellent to cover exposed skin and/or clothing. Heavy application and saturation are generally unnecessary for effectiveness. If biting insects do not respond to a thin film of repellent, then apply a bit more.
• After returning indoors, wash treated skin with soap and water or bathe. This is particularly important when repellents are used repeatedly in a day or on consecutive days. Also, wash treated clothing before wearing it again. (This precaution may vary with different repellents— check the product label.)
• If using a product containing DEET, use products with less than 25% DEET for adults and less than 10% DEET for children.
• If using a product containing oil of lemon eucalyptus, note that the label specifies that it should not to be used on children under the age of three years.
• If you or your child gets a rash or other bad reaction that you suspect is from an insect repellent, stop using the repellent, wash the repellent off with mild soap and water, and call a local poison control center for further guidance. If you go to a doctor because of the repellent, take the repellent with you to show the doctor.
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