Mosquito-borne Disease Information

Mosquito Management

Because some areas of the state do not have an organized mosquito management/control program, the individual must take proper protective measures. Individuals can reduce mosquito populations in many ways in and around their homes to protect themselves and their family from mosquito bites. These activities can be grouped into three primary management areas: personal protection, mosquito larval control, and adult mosquito control.

Personal Protection

The aim of personal protection is the prevention of mosquito bites. All individuals are encouraged to use personal protective measures. Personal protection is particularly important in areas of known or suspected occurrence of mosquito-borne diseases like encephalitis.

Window/Door Screens: Mosquitoes can be kept out of the home by keeping windows, doors, and porches tightly screened (16-18 meshes to the inch). Frequently, mosquitoes follow people into buildings or enter on humans or pets. For this reason, screen doors should open outward and have automatic closing devices. Screens should be kept in good repair.

Avoiding Mosquitoes: Most mosquito species bite at night, especially during twilight hours, but some species bite during the day in wooded or other shaded areas. If possible, avoid exposure during these times and in these areas. Children usually do not notice mosquito bites while engaged in play. Be especially watchful and see that they are protected. Avoid wearing perfume or scented products.

Protective Clothing: Wear light-colored clothing rather than dark when spending time outdoors. Considerable protection from mosquito bites is offered by clothing made of tightly woven materials that cover the arms and legs. Button the collars and keep trouser legs tucked into socks or boots.

Vegetation Management: Homeowners can reduce the number of areas where adult mosquitoes can find shelter by cutting down weeds and overgrown vines adjacent to the house foundation and in their yards and mowing the lawn regularly.

Repellents: Repellents are an important tool to assist people in protecting themselves from mosquito-borne diseases. A wide variety of insect repellent products are available. CDC recommends the use of products containing active ingredients that have been registered with the U.S. Environmental Protection Agency (EPA) for use as repellents applied to skin and clothing. EPA registration of repellent active ingredients indicates the materials have been reviewed and approved for efficacy and human safety when applied according to the instructions on the label.

CDC evaluation of information contained in peer-reviewed scientific literature and data available from EPA has identified several EPA-registered products that provide repellent activity sufficient to help people avoid the bites of disease-carrying mosquitoes. Products containing these active ingredients typically provide reasonably long-lasting protection:

DEET (Chemical Name: N,N-diethyl-m-toluamide or N,N-diethly-3-methyl-benzamide)
Picaridin (KBR 3023, Chemical Name: 2-(2-hydroxyethyl)-1-piperidinecarboxylic acid 1-methylpropyl ester )
Oil of Lemon Eucalyptus* or PMD (Chemical Name: para-Menthane-3,8-diol), the synthesized version of oil of lemon eucalyptus
IR3535 (Chemical Name: 3-[N-Butyl-N-acetyl]-aminopropionic acid, ethyl ester)

* Note: This recommendation refers to EPA-registered repellent products containing the active ingredient oil of lemon eucalyptus (or PMD). “Pure” oil of lemon eucalyptus (for example, essential oil) has not received similar, validated testing for safety and efficacy, is not registered with EPA as an insect repellent, and is not covered by this CDC recommendation.

EPA characterizes the active ingredients DEET and Picaridin as “conventional repellents” and Oil of Lemon Eucalyptus, PMD, and IR3535 as “biopesticide repellents”, which are derived from natural materials. For more information on repellent active ingredients, see EPA Active Ingredients in Insect Repellents.

Published data indicate that repellent efficacy and duration of protection vary considerably among products and among mosquito species and are markedly affected by ambient temperature, amount of perspiration, exposure to water, abrasive removal, and other factors.

In general, higher concentrations of active ingredient provide longer duration of protection, regardless of the active ingredient, although concentrations above ~50% do not offer a marked increase in protection time. Products with <10% active ingredient may offer only limited protection, often from 1-2 hours. Products that offer sustained release or controlled release (micro-encapsulated) formulations, even with lower active ingredient concentrations, may provide longer protection times. Regardless of what product you use, if you start to get mosquito bites, reapply the repellent according to the label instructions or remove yourself from the area with biting insects if possible.

These recommendations are for domestic use in the United States where EPA-registered products are readily available. See CDC Travelers’ Health website for additional recommendations concerning protection from insects when traveling outside the United States.

In addition, certain products that contain permethrin are recommended for use on clothing, shoes, bed nets, and camping gear, and are 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 to clothing following the label instructions. Some commercial products are available pretreated with permethrin.

EPA recommends the following precautions when using insect repellents:

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.
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 you or your child get a rash or other bad reaction 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.
Note that the label for products containing oil of lemon eucalyptus specifies that they should not to be used on children under the age of three years.

Other than those listed above, EPA does not recommend any additional precautions for using registered repellents on pregnant or lactating women, or on children. For additional information regarding the use of repellent on children, please see the CDC’s Frequently Asked Questions about Repellent Use.

DEET-based repellents applied according to label instructions may be used along with a separate sunscreen. No data are available at this time regarding the use of other active repellent ingredients in combination with a sunscreen. For additional information on using repellents, see EPA-registered repellents.

DEET (N, N-diethyl-m-toluamide):

DEET remains the most effective insect repellent currently available.
DEET has been used safely for over 40 years by millions of people worldwide.
DEET always should be used in accordance with the manufacturer's product label.
Formulations containing 30 percent DEET provide long lasting protection and are recommended for use in adults and children over 2 months of age. Higher concentrations do not provide significantly increased or longer repellent effect. Lower concentrations of DEET provide a shorter duration of protection and have not been shown to be safer for adults or for children.

The following precautions should always be followed when using DEET:

Always follow the instructions on the product label.
Do not apply DEET to children under 2 months of age.
DEET should not be applied to hands or near eyes and mouth of young children.
Young children should not be allowed to apply DEET to themselves.
DEET should not be applied over cuts, wounds, or irritated skin.
Spray clothing with repellents containing Permethrin or DEET because mosquitoes might bite through thin clothing.
Avoid spraying DEET in enclosed areas or around food.
Treated skin should be washed with soap and water after returning indoors.

For further information about DEET and recommendations for its use on adults and children:

Larval Mosquito Control

By eliminating or treating mosquito-breeding areas, individuals can impact the number of mosquitoes in and around their homes. Some mosquitoes have limited flight ranges and might fly only a few hundred feet from their breeding areas. One such mosquito, Culex quinquefasciatus, a vector of West Nile virus, breeds extensively in water containers around houses and commonly is known as the Southern House Mosquito. Every effort should be taken to eliminate standing water that may support mosquito breeding. Some suggested activities are as follows:

Eliminate all items from your yard like tin cans, jars, bottles, old tires, drums, old appliances, or any item that will catch and hold water.
Repair any leaky pipes or outside faucets.
Change the water in birdbaths at least once each week.
Root or grow outdoor plants in sand or soil instead of only water.
Empty and clean children’s wading pools at least once each week and maintain swimming pools with proper pool chemicals.
Empty and refill pet-watering containers daily.
Cover trash containers/garbage cans to prevent accumulation of rainwater.
Keep gutters clean and free of leaves and other debris, and check frequently.
Fill in tree holes and hollow stumps with sand or concrete.
Stock ornamental garden ponds with mosquito-eating minnows, and keep vegetation, which protects mosquito larvae, trimmed from the edge of the pond.
Store boats/canoes covered or upside down so they will not collect and hold rainwater. Make sure that tarps or other covers do not hold water.
Drain or fill any low places in your yard where water collects and stands for more than five to seven days.
Ensure that roadside ditches or other drainage ditches are kept free of vegetation or other debris that would cause them to hold water and prevent proper drainage. Particular attention should be given to driveway culverts. See that water does not stand inside or near the ends of the culvert.
Be sure that all permanent water containers such as wells, septic tanks, cisterns, water tanks, and cesspools are tightly covered and insect-proof.
Inspect septic drain fields. Do not allow septic water to accumulate on the ground surface.
Screen rain barrels so adult females can not lay eggs there.
Use mosquito control products from your local lawn and garden/home improvement store to treat small areas that can not be drained.

Adult Mosquito Control

Although elimination of larval breeding areas and larval control efforts will decrease a great number of mosquitoes, some species have flight ranges from one to several miles and might present a biting problem in and around your home. Because a continuous re-infestation of adult mosquitoes from breeding areas might occur, adult control activities are usually temporary.

Most adult mosquitoes require and seek cool, dark, damp areas to rest during the day. By eliminating the availability of such areas on your property, adult mosquitoes can not find suitable places to rest and will seek resting places elsewhere. Eliminating mosquito-resting areas might help in reducing the number of biting mosquitoes on your property and can be accomplished in the following ways:

Use screens on windows and doors.
Keep your car windows rolled up and garage doors closed at night.
Use yellow light bulbs or sodium vapor orange lights for outside lighting purposes.
Wear long-sleeved shirts and long trousers while outside.
Keep your shrubs, ivy, and grass trimmed.

Under certain circumstances, such as planned outdoor parties or similar activities, temporary relief outdoors can be had by using a small hand-held fogger (not a garden sprayer) made specifically for mosquito control. A special insecticide will be sold for use with the fogger. Use it a few hours before an outdoor activity is planned. It will not be very effective on a windy day. Fogging applications are temporary and usually kill only those mosquitoes that are flying in the area at the time. Therefore, applications are most effective when applied at the time mosquitoes are most active, during twilight. Applications made earlier may kill some resting mosquitoes in the area. If the sprayed space is relatively small, mosquitoes entering from outside of the area still might cause a significant biting problem. Heat-activated repellent pads or mosquito coils may be somewhat effective in repelling mosquitoes in a small area such as a patio. Check with your local lawn and garden/home improvement store for mosquito control products to use around the home. Read and follow all label directions. Do-it-yourself mosquito spraying is not a substitute for a community-based mosquito control program or for personal protection.

References

Barnard DR, Xue RD. Laboratory evaluation of mosquito repellents against Aedes albopictus, Culex nigripalpus, and Ochlerotatus triseriatus (Diptera: Culicidae). J Med Entomol. 2004;41(4):726-30.

Barnard DR, et al. Repellency of IR3535, KBR3023, para-menthane-3,8-diol, and DEET to Black Salt March mosquitoes (Diptera: Culicidae) in the Everglades National Park. J Med Entomol. 2002; 39(6): 895-899.

Fradin MS, Day JF. Comparative efficacy of insect repellents against mosquito bites. N Engl J Med. 2002; 347(1):13-8.

Thavara U et al. Laboratory and field evaluations of the insect repellents 3535 (ethyl butyletylaminopropionate) and DEET against mosquito vectors in Thailiand. J of Am Mosq Cont Assoc. 2001, 17(3):190-195.