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WEST NILE VIRUS PREVENTION AND CONTROL

Mosquito season in Indiana runs from May 1 through October 1.  Most mosquitoes in Indiana DO NOT come from swamps, rivers, streams, farm ponds, or lakes -- they come from our own backyards.  The best protection against West Nile virus (WNV) is prevention -- prevention of mosquito breeding sites and prevention of mosquito bites.  The mosquito vectors shown here  breed in large numbers in human habitats.  Here are some things YOU can do to reduce the mosquito population and help protect yourself and your family from West Nile virus:

HABITAT CONTROL

• Make sure roof gutters drain properly.  Clean clogged gutters whenever needed. 

• Remove all discarded tires from your property.  Used tires have become the most important domestic mosquito breeding habitat in this country.

• Do not allow containers to hold water.  Dispose of tin cans, plastic containers, ceramic pots, or similar water-holding containers.  Do not overlook containers that have become overgrown by vegetation. 

• Drill holes in the bottom of recycling containers that are left out of doors.  Drainage holes that are located on the sides collect enough water for mosquitoes to breed in.  

• Tightly screen "rain barrels" to ensure that mosquitoes cannot deposit eggs on or in the water.

• Clean and chlorinate swimming pools, wading pools, and outdoor hot tubs.  If not in use, empty and cover them.

• Drain water from pool covers.

• Aerate ornamental pools or stock them with fish.  Water gardens are fashionable but become major mosquito producers if allowed to stagnate.

• Turn over wheelbarrows and change water in birdbaths at least twice a week.  

• Eliminate any and all standing water on your property.  Use landscaping as needed.  Mosquitoes will develop in any puddle that lasts for more than 4 days.

• Make sure doors and windows have tight-fitting screens.  Repair or replace all screens in your home that have tears or holes.

• Help your neighbors eliminate mosquito breeding sites on their property.

• Drain or turn unused boats or canoes upside-down to prevent water from gathering inside.

• Repair leaking or failed septic systems.  Water laden with organic material is especially attractive to Culex mosquito species.

• Check watering troughs for large animals like horses and cattle regularly for the presence of mosquito larvae or "wigglers".

• Lagoons which hold animal waste can be particularly dangerous, producing tens of thousands of disease-spreading mosquitoes.

Oftentimes, because of their location on private property, sites such as those mentioned above cannot be managed by governmental mosquito control programs.  They must be eliminated and managed by the property owner.

STIMULI THAT ATTRACT MOSQUITOES

For mosquitoes that feed during the daytime, dark-colored clothing is attractive.  Their eyesight is poor, and the dark coloring looks like the shadows where they like to hide.  Carbon dioxide is an attractant and can be detected by mosquitoes at distances up to 120 feet.  When we exhale, we are attracting mosquitoes.  At close range, skin temperature and moisture serve as attractants.  Floral fragrances from perfumes, soaps, lotions, and hair-care products may also attract mosquitoes.

REPELLENTS

You can also help prevent West Nile virus infection by not going outside when mosquitoes are biting, and by using mosquito repellents.  

• Most mosquitoes actively search for blood meals in the evening as the sun is going down, and again at dawn.  Aedes albopictus, however, bites throughout the day, and usually lives near wooded areas filled with underbrush.

• Wear light-colored clothing, long pants, socks, and long-sleeved shirts.  Apply repellent to clothing and to a few areas of exposed skin.

  • A number of repellents are available, but some are more effective than others.  In an article appearing in the Annals of Internal Medicine, Mark S. Fradlin, MD, compared several different types of mosquito repellent:

     

    DEET

     

    • N,N-diethyl-3-methylbenzamide (DEET) is the most effective and best studied mosquito repellent currently on the market.  DEET was discovered and developed by scientists at the US Department of Agriculture and was patented by the Army in 1946.  It is a broad-spectrum repellent that is effective against mosquitoes, biting flies, chiggers, ticks, and fleas.  It has a remarkable safety profile after over 40 years of worldwide use, but toxic reactions can occur, especially if the product is misused or overused on babies or young children.

    • In the US, DEET is available in 5% to 100% concentrations.  Higher concentrations provide longer-lasting protection.  Unfortunately, no guidelines are available to help consumers decide what concentration is appropriate for their specific needs.  Products with 10% to 35% DEET will provide adequate protection under most conditions.  Products with more than 50% DEET are best used in conditions where insect biting is intense, and where high temperature and humidity may result in rapid loss of repellent from the skin.

    • Repellents may be applied directly to the skin or to clothing, screens, tents, or sleeping bags.  If DEET-treated garments are stored in a plastic bag between wearings, the repellent effect can last for many weeks.

    • DEET products can damage plastics such as watch crystals and eyeglasses frames, rayon, spandex, other synthetic fabrics, leather, and painted or varnished surfaces.  It does not damage natural fibers such as cotton or wool, and has no effect on nylon.       

      • USE DEET ACCORDING TO MANUFACTURER'S DIRECTIONS.

      • Do not use mixtures with more than 10% DEET on children.  Never apply a repellent to an infant.

      • Do not use DEET on infants or pregnant women; instead, avoid outdoor activities or use netting/screens to avoid bites.

      • Do not allow children to put DEET on themselves.

      • Do not apply DEET directly to children.  Apply it to your own hands, then put it on the child.

      • Avoid putting DEET on children's hands, or near their eyes and mouth.

      • Do not spray directly on the face; spray into the hands first, then apply to the face.

      • Do not apply to cuts, wounds, or irritated skin.

      • Do not use under clothing.

      • Do not spray DEET-containing products in enclosed areas.

      • DEET is effective for about 4 hours.  Avoid prolonged or excessive use of DEET.  Use sparingly to cover exposed skin and clothing.

      • Wash all treated skin after returning indoors.

      • Store DEET out of the reach of children.

     

    PICARDIN and LEMON EUCALYPTUS OIL 

     

    • (April 28, 2005)  After years of promoting the chemical DEET as the best defense against West Nile-bearing mosquitoes, the government for the first time is recommending the use of two other insect repellents.  Repellents containing the chemical picaridin or the oil of lemon eucalyptus offer "long-lasting protection against mosquito bites," the Centers for Disease Control and Prevention said, adding that repellents with DEET remain on the agency's recommendation list.  Both products have been available elsewhere in the world, including Europe and Australia, since the 1980s.  Consumers tend to like picaridin repellents because they are more pleasant to the skin and don't have the odor that DEET repellents have. And oil of lemon eucalyptus is a natural ingredient, which appeals to those who don't like the thought of putting chemicals on their skin, said Angela Proctor, a product manager for the Cutter line of insect repellents by Spectrum Brands.  Spectrum Brands introduced a picaridin-based repellent in January (2005) -- Cutter Advanced (www.cutterinsectrepellent.com) -- and it has been marketing a repellent with oil of lemon eucalyptus since 2002. The products provide four and six hours of protection, respectively, Proctor said.

     

    SKIN-SO-SOFT

     

    • Consumers have reported Avon's Skin-So-Soft to be an effective mosquito repellent.  When tested under laboratory conditions against Aedes albopictus, Skin-So-Soft oil provided 40 minutes of protection from bites, a duration of 10 times less than that of 12.5% DEET.  The repellent effect of Skin-So-Soft could be caused by its fragrance, or by the presence of diisopropyl adipate and benzophenone, both which have some repellent activity.

     

     

    CITRONELLA

     

    • Citronella is the active ingredient found in most "natural" or "herbal" insect repellents.  Studies show that citronella can be an effective repellent, but it provides shorter complete protection time than most DEET-based repellents.  Frequent reapplication of the oil can partially compensate for this.  Buzz Away (Quantum, Inc. Eugene, Oregon) with 5% citronella oil provided an average protection time of 1.9 hours against Aedes species.  Repellency was greatest within the first 40 minutes of application and decreased over the remainder of the test period.  

    • Citronella candles have been promoted as an effective way to repel mosquitoes in the backyard.  In one study, people near the candles had 42% fewer bites than did the controls, who had no protection.  However, burning ordinary candles reduced the number of bites by 23%.  

     

    BITE BLOCKER

     

    • Bite Blocker (Consep, Inc., Bend, Oregon) is a plant-based repellent that was released in the US in 1997.  It combines soybean oil, geranium oil, and coconut oil.  Studies showed that this product gave more than 97% protection against Aedes mosquitoes under field conditions, even 3.5 hours after application.

     

     

     

     

    PERMETHRIN

     

    • Pyrethrum is a powerful, fast-acting insecticide, originally derived from the dried flowers of the Chrysanthemum cinerariifolium (shown at left).  Permethrin is a man-made synthetic pyrethoid.  It is a contact insecticide, causing death of the insect.  The chemical is effective against mosquitoes, flies, ticks, and chiggers.  Permethrin should be applied directly to clothing or other fabrics, not to skin.

    • The combination of permethrin-treated clothing and skin application of a DEET-based repellent creates a formidable barrier against mosquito bites.  In a field trial under intense biting conditions, persons wearing permethrin-treated clothing and a 35% DEET product had more than 99.9% protection over 8 hours.  Protected persons received an average of 1 bite per hour, whereas unprotected persons suffered an average of 1,188 bites per hour.

LARVACIDING AND ADULTICIDING

Homeowners can do a lot to reduce mosquitoes around their homes.  Many times, though, they have no control over sources such as catch basins, agricultural waste, or wetlands. 

• LARVACIDING is the most efficient type of mosquito control, second only to the elimination of breeding sites.  A limited number of chemicals are legally available for the control of mosquito larvae in Indiana.  The following are available and should be used by trained professionals:

  • Bacillus thuringiensis variety israelensis (Bti) is a bacterial spore that kills mosquitoes, black flies, and fungus gnats.  After the spores are ingested by the larvae, they grow and reproduce, producing a crystalline toxin that paralyzes the larvae's digestive tract, causing it to stop eating.

    • Hazards to humans are negligible thought inhalation or contact with eyes or open wounds should be avoided.

    • The different strains of Bt are class-specific, meaning beneficial or non-targets insects are not harmed.

    •  The insects that ingest Bt and later die from it are not considered dangerous to birds or other insects that may feed on the dead insect.

    • Bt is not known to injure plants on which it has been applied and it is not considered harmful to the environment

INEFFECTIVE MEANS OF REDUCING MOSQUITO BITES

• Consumers may find ads for small ultrasonic electronic devices meant to be carried on the body.  These purportedly emit sounds that repel mosquitoes.  Many field and lab studies show that these devices do not work.

• Encouraging natural predation by setting up bird and/or bat houses has also been unsuccessful in reducing local mosquito populations.  Birds and bats eat many types of insects, not only mosquitoes.

• Backyard "bug zappers", which lure and electrocute insects, are also ineffective.  Mosquitoes continue to be more attracted to humans than to the devices.  One study showed that of all the insects killed by these devices, only 0.13% were female (biting) mosquitoes.