Denton Southridge Neighborhood Association

Mosquito Control

Variety of Information on Mosquitos, Control and Health Issues

Mosquito control can be divided into two areas of responsibility: individual and public. Most often it’s performed following the Integrated Mosquito Management (IMM) concept. IMM is based on ecological, economic and social criteria and integrates multidisciplinary methodologies into pest management strategies that are practical and effective to protect public health and the environment and improve the quality of life. Mosquito control includes mosquito surveillance measures, source reduction, a biological control strategy, ground and aerial application of insecticides and public education. The applications of adulticides or larvicides are made after the presence of mosquitoes has been demonstrated by surveillance procedures. Application is made by prescribed standards. All insecticides must have the name and amount of active ingredient (AI) appear on the label; examples are DEET and pyrethroids. Check the label before buying. No pesticide is 100 percent safe and care must be exercised in the use of any pesticide. Material Safety Data Sheets (MSDS) contain basic information about a product intended to help you work safely with the material (http://www.msdssearch.com/). Other IMM strategies are employed in concert with insecticide. These include source reduction, which incorporates physical control (digging ditches and ponds in the target marsh) and biological control [placing live mosquito fish (Gambusia) in the ditches and ponds to eat mosquito larvae]. Other non chemical control methods include invertebrate predators, parasites and diseases to control mosquito larvae. Adult mosquito biological control by means of birds, bats, dragonflies and frogs has been employed by various agencies. However, supportive data is anecdotal and there is no documented study to show that bats, purple martins, or other predators consume enough adult mosquitoes to be effective control agents.

Adult Mosquito Control
Repellents. Repellents are substances that make a mosquito avoid biting people. Persons working or playing in mosquito-infested areas will find repellents very helpful in preventing mosquito bites (http://www.plymouthmosquito.com/repell.htm). Repellents are formulated and sold as aerosols, creams, solids (sticks) and liquids. Use repellents containing ingredients such as diethyl phthalate, diethyl carbate, N, N-Diethyl-3-Methylbenzamide (DEET), and ethyl hexanediol. For more than 40 years, DEET has been the standard in mosquito repellents. Check the label for these active ingredients. Permethrin-containing repellents (Permanone) are recommended for use on clothing, shoes, bednets and camping gear. Permethrin is highly effective as an insecticide/acaricide and as a repellent. Permethrin-treated clothing repels and kills ticks, mosquitoes and other arthropods and retains this effect even after repeated laundering. Permethrin-treated clothing should be safe when label directions are followed. Permethrin repellents do not offer any protection from mosquitoes when applied to the skin. It is often helpful to use spray repellents on outer clothing as well as the skin. Protection generally may be expected up to 6 hours following application. Oil of citronella is another type of mosquito repellent for space repelling. Oil of citronella is the active ingredient in many of the candles, torches, or coils that may be burned to produce a smoke that repels mosquitoes. These are useful outdoors only under windless conditions. Their effectiveness is somewhat less than repellents applied to the body or clothing.

Here are some common sense rules to follow when using repellents:
a.. Wear long sleeve shirts and pants outdoors during peek mosquito activity time periods.

a.. Apply repellent sparingly only to exposed skin or clothing.

a.. Keep repellents away from eyes, nostrils and lips: do not inhale or ingest repellents or get them into the eyes.

a.. Avoid applying high-concentration (>30% DEET) products to the skin, particularly of children.

a.. Avoid applying repellents to portions of children's hands that are likely to have contact with eyes or mouth.

a.. Pregnant and nursing women should minimize use of repellents.

a.. Never use repellents on wounds or irritated skin.

a.. Use repellent sparingly; one application will last approximately 4-6 hours. Saturation does not increase efficacy.

a.. Wash repellent-treated skin after coming indoors.

a.. If a suspected reaction to insect repellents occurs, wash treated skin, and call a physician. Take the repellent container to the physician.


Mosquito Traps. Insect electocutors (bug zappers) and mosquito trapping devices are 20th century control measures. Manufacturers modernized 19th century mosquito trapping devices such as the New Jersey light trap with more “bells and whistles” to improve its appeal to the public. Insect electrocuter light traps have been extensively marketed for the past several years claiming they can provide relief from the biting mosquitoes and other pests in your back yard. Numerous devices are available for purchase that claim to attract, repel or kill outdoor infestations of mosquitoes. They should be thoroughly researched before being purchased.

Other mosquito traps are designed to mimic a mammal (horse, cattle, man and domestic pets) by emitting a plume of carbon dioxide, heat and moisture, which is often combined with an additional attractant, i.e. octenol, to create an attractant to mosquitoes, no-see-ums, biting midges and black flies. After drawing the insects to the trap, a vacuum device sucks the insects into a net or cyclinder where they dehydrate and die. No electric killing grid or pesticides are used.

Scientific data relative to the effectiveness of these devices is sparse so be sure to review all the information available before purchasing one of these. In addition, some of the mosquito traps are expensive. The AMCA has a position paper on mosquito traps ( http://www.mosquito.org/MosqInfo/Traps.htm) .

Space sprays. Mosquitoes can be killed inside the house by using a flit gun (seldom used any longer) or a household aerosol space spray containing synergized pyrethrum or synthetic pyrethroids (allethrin, resmethrin, etc.). The major advantage of space treatment is immediate knockdown, quick application, and relatively small amounts of materials required for treatment. Space sprays are most effective indoors. Outdoors, the insecticide particles disperse rapidly and may not kill many mosquitoes. The major disadvantage of space spraying is that it will not manage insects for long periods of time.

Only insecticides labeled for flying insect management should be sprayed into the air. Best results are obtained if doors and windows are kept closed during spraying and for 5-10 minutes after spraying. Always follow directions on the label.

Outdoor Control. Homeowners, ranchers or businesses may use hand-held ULV foggers, portable or fogging attachments for tractors or lawn mowers for temporary relief from flying mosquitoes. Pyrethrins or 5% malathion can be fogged outdoors. Follow instructions on both the insecticide label and fogging attachments for application procedure.

Mechanical Barriers. Mosquitoes can be kept out of the home by keeping windows, doors and porches tightly screened (16-18 mesh). Those insects that do get into structures can be eliminated with a fly swatter or an aerosol space spray containing synergized pyrethrum.

Vegetation Management. Adult mosquitoes prefer to rest on weeds and other vegetation. Homeowners can reduce the number of areas where adult mosquitoes can find shelter by cutting down weeds adjacent to the house foundation and in their yards, and mowing the lawn regularly. To further reduce adult mosquitoes harboring in vegetation, insecticides may be applied to the lower limbs of shade trees, shrubs and other vegetation. Products containing allethrin, malathion or carbaryl have proven effective. Paying particular attention to shaded areas, apply the insecticides as coarse sprays onto vegetation, walls and other potential mosquito resting areas using a compressed air sprayer. Always read and follow label directions before using any pesticide.

Many of the mosquito problems that trouble homeowners and the general population cannot be eliminated through individual efforts, but instead, must be managed through an organized effort. Many states have some sort of organized mosquito control, either at the State, County or city level. Florida has over 50 organized mosquito control organizations that specialize in area mosquito control. Some residential communities organize to control their mosquito problems. There has been an increase in the number of these organizations in the United States since the encephalitis outbreak in 1999. These organized management programs incorporate the IMM strategies mentioned above which include permanent and temporary measures. Permanent measures include impounding water and ditching, and draining swampy mosquito breeding areas. Temporary measures include treating breeding areas to kill larvae and aerosol spraying (ULV) by ground or aerial equipment to kill adult and larval mosquitoes. If you live within an organized mosquito management district, support it in its control efforts. Organized mosquito management can accomplish much more than individual efforts. If you are not sure about whether your community has a mosquito control district, contact the local division of health officials.

Larval Control
The most effective way to control mosquitoes is to find and eliminate their breeding sites. Eliminating large breeding areas such as swamps or sluggishly moving streams or ditches may require community-wide effort. This is usually a task for your organized mosquito control program. Homeowners, however, can take the following steps to prevent mosquito breeding on their own property:

1. Destroy or dispose of tin cans, old tires, buckets, unused plastic swimming pools or other containers that collect and hold water. Do not allow water to accumulate in the saucers of flowerpots, cemetery urns or in pet dishes for more than 2 days.

2. Clean debris from rain gutters and remove any standing water under or around structures, or on flat roofs. Check around faucets and air conditioner units and repair leaks or eliminate puddles that remain for several days.

3. Change the water in birdbaths and wading pools at least once a week and stock ornamental pools with top feeding predacious minnows. Known as mosquito fish, these minnows are about 1 - 1-1/2 inches in length and can be purchased or native fish can be seined from streams and creeks locally. Ornamental pools may be treated with biorational larvicides (Bacillus thuringiensis subsp. israelensis (Bti) or methoprene (IGR) containing products) under certain circumstances. Commercial products "Mosquito Dunks" and "Mosquito Bits" http://www.summitchemical.com/default.htm , http://www.marchbiological.com/ containing Bti can be purchased at many hardware/garden stores for homeowner use. Recently, Zodiac, a division of Wellmark International, developed "Preventative Mosquito Control" (PMC) product that kills developing mosquitoes using insect growth regulator (IGR) technology. Like "Mosquito Dunks" Zodiac's "Preventative Mosquito Control" can be found at many home/garden and pet specialty stores.

4. Fill or drain puddles, ditches and swampy areas, and either remove, drain or fill tree holes and stumps with mortar. These areas may be treated with the above Bti or methoprene products also.

5. Eliminate seepage from cisterns, cesspools, and septic tanks.

6. Eliminate standing water around animal watering troughs. Flush livestock water troughs twice a week.

7. Check for trapped water in plastic or canvas tarps used to cover boats, pools, etc. Arrange the tarp to drain the water.

8. Check around construction sites or do-it-yourself improvements to ensure that proper backfilling and grading prevent drainage problems.

9. Irrigate lawns and gardens carefully to prevent water from standing for several days.

10. If ditches do not flow and contain stagnant water for one week or longer, they can produce large numbers of mosquitoes. Report such conditions to a Mosquito Control or Public Health Office. Do not attempt to clear these ditches because they may be protected by wetland regulations.



Mosquito-borne Diseases
Mosquitoes cause more human suffering than any other organism with over one million people dying from mosquito-borne diseases every year. Not only can mosquitoes carry diseases that afflict humans, but they also transmit several diseases and parasites that dogs and horses are very susceptible to. These include dog heartworm, West Nile virus (WN) and Eastern equine encephalitis (EEE). In addition, mosquito bites can cause severe skin irritation through an allergic reaction to the mosquito's saliva - this is what causes the red bump and itching. Mosquito vectored diseases include protozoan diseases, i.e., malaria, filarial diseases such as dog heartworm, and viruses such as dengue, encephalitis and yellow fever.

The malaria parasite (plasmodium) transmission by female Anopheles mosquitoes is an ancient disease originating in Africa probably (http://www.rph.wa.gov.au/labs/haem/malaria/history.html). The term malaria is derived from the Italian, (mal-aria) or "bad air" because it was thought to come on the wind from swamps and rivers. Scientists conducted much research on the disease during the late1880s and early 1900s. Approximately 40% of the world’s population is susceptible to malaria, mostly in the tropical and sub-tropical areas of the world. It was by and large eradicated in the temperate area of the world during the 20th century with the advent of DDT and other organochlorine and organophosphate mosquito control insecticides. However, more than one million deaths and over 300 million cases are still reported annually in the world. It is reported that malaria kills one child every 40 seconds lhttp://mosquito.who.int/newdesign2/index.html). In the United States malaria affected colonization along the eastern shore and wasn’t effectively controlled until the 1940s when the Anopheles mosquitoes were controlled. A resurgence occurred during the 1960s and early 70s in the United States due to returning military personnel from Vietnam. Anopheles quadrimaculatus was the primary vector of the Plasmodium vivax (protozoa) in the United States (Foote and Cook 1959). Antimalarial drugs have been available for more than 50 years and recently scientists in Britain and the United States has cracked the code of the malaria parasite genome, a step that may help boost the campaign against the disease (http://www.nlm.nih.gov/mimcom/news/malaria_genome.html).

Dog heartworm (Dirofilaria immitis) can be a life-threatening disease for canines. The disease is caused by a roundworm. Dogs and sometimes other animals such as cats, foxes and raccoons are infected with the worm through the bite of a mosquito carrying the larvae of the worm. It is dependent on both the mammal and the mosquito to fulfill its lifecycle. The young worms called microfilaria circulate in the blood stream of the dog. These worms must infect a mosquito in order to complete their lifecycle. Mosquitoes become infected when they blood feed on the sick dog. Once inside the mosquito the microfilaria leave the gut of the mosquito and live in the body of the insect, where they develop for 2-3 weeks. After transforming twice in one mosquito the third stage infective larvae move to the mosquito's mouthparts, where they will be able to infect an animal. When the mosquito blood feeds, the infective larvae are deposited on the surface of the skin. The larvae enter the skin through the wound caused by the mosquito bite. The worms burrow into the skin where they remain for 3-4 months. If the worms have infected an unsuitable host such as a human the worms usually die at this point (http://www.plymouthmosquito.com/dog.htm). The disease in dogs and cats cannot be eliminated but it can be controlled or prevented with pills and/or injections. Some risk is present when treating dogs infected with heartworms but death is rare – prevention is best. Of course good residual mosquito control practices reduce the treat of mosquito transmission. Until the late sixties, the disease was restricted to southern and eastern coastal regions of the United States. Now, however, cases have been reported in all 50 states and in several provinces of Canada (http://edis.ifas.ufl.edu/scripts/htmlgen.exe?DOCUMENT_MG100).

Arthropod-borne viruses (arboviruses) are the most diverse, numerous and serious diseases transmitted to susceptible vertebrate hosts by mosquitoes and other blood-feeding arthropods. All arboviral encephalitides are zoonotic, being maintained in complex life cycles involving a nonhuman primary vertebrate host and a primary arthropod vector. These cycles usually remain undetected until humans encroach on a natural focus, or the virus escapes this focus via a secondary vector or vertebrate host as the result of some ecologic change. Humans and domestic animals can develop clinical illness but usually are "dead-end" hosts because they do not produce significant viremia, and do not contribute to the transmission cycle There are several virus agents of encephalitis in the United States: West Nile virus (WN), eastern equine encephalitis (EEE), western equine encephalitis (WEE), St. Louis encephalitis (SLE), La Crosse (LAC) encephalitis, dengue and yellow fever all of which are transmitted by mosquitoes. Another virus, Powassan, is a minor cause of encephalitis in the northern United States, and is transmitted by ticks. A new Powassan-like virus has recently been isolated from deer ticks (http://www.cdc.gov/ncidod/dvbid/arbor/arbdet.htm). Encephalitis is global, for example; in Asia about 50,000 cases of Japanese encephalitis (JE) are reported annually (http://www.cdc.gov/mmwr/preview/mmwrhtml/00020599.htm).

Dengue is a serious disease of Asia and Africa (http://www.who.int/inf-fs/en/fact117.html). It has a low mortality with very uncomfortable symptoms and has become more serious, both in frequency and mortality, in recent years. Aedes aegypti and Ae. albopictus are the vectors of dengue. The spread of dengue throughout the world can be directly attributed to the proliferation and adaptation of these mosquitoes. Over the last 16 years dengue has become more common, for example; in south Texas 55 cases were reported in 1999 causing one death. More recently, Hawaii recorded 85 cases of dengue during 2001.

Yellow fever, which has a 400-year history, occurs only in tropical areas of Africa and the Americas. It is a rare illness of travelers anymore because most countries have regulations and requirements for yellow fever vaccination that must be met prior to entering the country (http://www.cdc.gov/ncidod/dvbid/yellowfever/index.htm). However, over the past decade it has become more prevalent. In 2002 one fatal yellow fever death occurred in the United States in an unvaccinated traveler returning from a fishing trip to the Amazon.

EEE (http://www.astdhpphe.org/infect/equine.html) is spread to horses and humans by infected mosquitoes. It is among the most serious of a group of mosquito-borne arboviruses that can affect the central nervous system and cause severe complications and even death. EEE is found in North America, Central and South America, and the Caribbean. It has a complex life cycle involving birds and a specific type of mosquitoes including several Culex species and Culiseta melanura. These mosquitoes feed on infected birds and become carriers of the disease and then feed on humans, horses and other mammals. Symptoms may range from no symptoms to a mild flu-like illness with fever, headache, and sore throat. Infections of the central nervous system lead to a sudden fever and severe headache followed quickly by seizures and coma. About half of these patients die from the disease. Of those who survive, many suffer permanent brain damage and require lifetime institutional care. There is no specific treatment. A vaccine is available for horses, but not humans.

SLE (http://fmel.ifas.ufl.edu/online/sle.htm) transmitted from birds to man and other mammals by infected mosquitoes (mainly some Culex species) SLE is found throughout the United States, but most often along the Gulf of Mexico, especially Florida. Major SLE epidemics occurred in Florida in 1959, 1961, 1962, 1977, and 1990. The elderly and very young are more susceptible than those between 20 and 50. Symptoms are similar to those seen in EEE and like EEE, there is no vaccine.

LAC (http://www.astdhpphe.org/infect/lacenceph.html) is much less common than EEE or SLE, but occurs in all 13 states east of the Mississippi, particularly in the Appalachian region. It was reported first in 1963 in LaCrosse, Wisconsin and the vector is thought to be a specific type of woodland mosquito (Aedes triseriatus) called the tree-hole mosquito with small mammals the usual warm-blooded host. It occurs in children younger than 16 and once again there is no vaccine for LaCrosse encephalitis.

WEE (http://www.astdhpphe.org/infect/wee.html) was first recognized in 1930 in a horse in California. It is found west of the Mississippi including parts of Canada and Mexico. The primary vector is Culex tarsalis and birds are the most important vertebrate hosts with small mammals playing a minor role. Unlike LAC it is nonspecific in humans and since 1964 fewer than 1000 cases have been reported As with EEE a vaccine is available for horses against WEE but not for humans.

West Nile virus (WN) emerged from its origins in 1937 in Africa into Europe, the Middle East, west and central Asia and associated islands. Similar to the other encephalitis it is cycled between birds and mosquitoes and transmitted to mammals (including horses) and man by infected mosquitoes. While over 25 species of mosquitoes have tested positive for WN transmission, the Cules pipiens group seem the most common species associated with infecting people and horses. It first appeared in North America in 1999 in New York (http://www.cfe.cornell.edu/erap/wnv/) with 62 confirmed cases and 7 human deaths. Nine horses died in New York in 1999. In 2001 66 cases (10 deaths) were reported in 10 states. It occurred in birds or horses in 27 states and Washington D.C., Canada and the Caribbean. There were 733 horse cases in 2001 in 19 states with Florida reporting 66% of the cases and approximately 33% were fatal. In 2001 more than 1.4 million mosquitoes were tested for WN. As of June 2002, 14 states and Canada have reported positive bird or horse cases in 2002, but no human cases have thus far been reported. It is a central nervous system infection similar to EEE. There is a vaccine for horses. Up to date information from a variety of resources from county, state, federal and international sources may be found at http://www.mosquito.org/WNVteaser/WNVteaser.htm.



The use of brand names and any mention or listing of commercial products or services in this article does not imply endorsements by the AMCA or Florida A & M University or discrimination against similar products or services not mentioned. Individuals who use chemicals are responsible for ensuring that the intended use complies with current regulations. Please check with your local county agent or regulatory official before using any pesticide mentioned in this publication.



ALWAYS READ AND FOLLOW LABEL DIRECTIONS
FOR SAFE USE OF ANY PESTICIDE!

Other Resources:

Maryland Department of Agriculture Mosquito Control contact Cyrus Lesser

Alameda County Mosquito Abatement District

Kentucky Mosquitoes and their control

Public Health Pest Control

Darsie,RF,Jr, JJVlach and EM Fussell. 2002. New addition to the mosquito fauna of the United States, Anopheles grabhanii ( Diptera: Culicidae). J. Med. Entomol. 39:430-431.

Reinert, JF. 2000. New classification for the composite genus Aedes (Diptera: Culicidae: Aedini), elevation of subgenus Ochleratatus to generic rank, reclassification of the other subgenera, and notes on certain subgenera and species. J Am Mosq Control Assoc 16: 175-188.

Spielman, A and M D'Antonio. 2001. Mosquito: a natural history of our most persistent and deadly foe. Hyperion.

Foote, RH and DR Cook. 1959. Mosquitoes of medical importance. Agriculture Handbook No. 152. Superintendent of Documents, US Gov Printing Office.



Inquires may be sent to: Joe Conlon, AMCA Technical Adviser,
Updated 6.22.02

--------------------------------------------------------------------------------

American Mosquito Control Association
P. O. Box 234
Eatontown, NJ 07724-0234
Telephone: 732.932.0667
FAX: 732.542.3267
E-mail: amca@mosquito.org

Copyright©2000
American Mosquito Control Association

Mosquito Control

American Mosquito Control Association
Center for Disease Control