Mosquito-Borne Illnesses

The design of tires makes them ideal breeding sites for several species of mosquitoes, some of which are vectors of disease. Improperly managed used tires provide a prime breeding habitat for disease-carrying mosquitoes. Used tires that contain water and organic matter (leaves, grass, etc.) are ideal for mosquito eggs and larvae.

Until the mid-1980s, waste tires were considered more of a nuisance and environmental threat than the possible focus of mosquito-borne disease epidemics. This changed in 1985 when a substantial breeding population of the Asian tiger mosquito (Aedes albopictus) was discovered in Houston, Texas. It is probable that this population arrived from Japan as eggs deposited inside used tires.

If we can eliminate scrap tire dumps and ensure processors comply with used tire management standards (statutes/regulations), we will eliminate a prolific mosquito habitat and the associated disease risks.

Mosquitoes proliferate by laying eggs on the surface of stagnant water. The eggs hatch to form larvae, which develop into pupae, and then develop into adult mosquitoes. The life cycle from laying of eggs to the formation of adult mosquitoes is approximately 10-14 days. Over the course of one breeding season, tens of thousands of potential disease-carrying mosquitoes can be generated from a single improperly managed used tire. Adult mosquitoes can travel up to one mile from their original breeding habitat.

Encephalitis is an inflammation of the brain that can be caused by viruses, including viruses carried by mosquitoes. Only appropriate serological testing can determine if a mosquito-borne virus is the cause of a case of encephalitis. The symptoms of encephalitis can range from mild to severe. Severe symptoms include rapid onset of severe headaches, vomiting, high fever, and mental disturbances such as confusion, irritability, tremors, stupor and coma. Severe cases sometimes end in death or with survivors suffering permanent loss of limb function, reduction of intelligence and/or emotional instability.

Saint Louis Encephalitis (SLE) is primarily spread by the common house mosquito and is the most common mosquito-transmitted human pathogen in the U.S. Overall, there have been 4,437 confirmed cases of SLE with an average of 193 cases per year. The fatality rate is 5-15%.

La Crosse Encephalitis (LAC) is primarily spread by the Ochlerotatus triseriatus with most cases occurring in children under the age of 16. An average of 75 cases occur per year with 1% death rate. In Illinois, there are 5-15 cases of LAC per year.

West Nile Virus (WNV) is a viral disease primarily spread to people by the bite of an infected mosquito. WNV can cause encephaliti. Mosquitoes first become infected when they feed on birds that carry the virus. Once the mosquito is infected, it can spread the virus to people or other animals when it bites them. The common house mosquito, the primary carrier of WNV, breeds in water-filled tires, roadside ditches, and street catch basins.

In Illinois, WNV was first identified in September 2001 when laboratory tests confirmed its presence in two dead crows found in the Chicago area. The following year, the state's first human cases and deaths from WNV were recorded and all but two of the state's 102 counties eventually reported a positive human, bird, mosquito or horse. By the end of 2002, Illinois had counted more human cases (884) and deaths (64) than any other state in the U.S.

WNV symptoms generally occur 3 to 15 days following the bite from an infected mosquito and range from a slight fever, headache, rash, swollen nodes and conjunctivitis (irritation of the eye), to the rapid onset of a severe headache, high fever, stiff neck, disorientation, muscle weakness, coma, or death. The case fatality rate ranges from 3 percent to 15 percent. American Crows and Blue Jays are particularly susceptible to the WNV.

• More information regarding WNV can be found on the Illinois Department of Public Health (IDPH) West Nile Virus (WNV) webpage. 

Dengue viruses are spread to people through infected mosquitoes, and dengue outbreaks are occurring in many countries of the world (almost half of the world's population live in areas with a risk of dengue). About one in four people infected with dengue will get sick. For people who get sick, symptoms can be mild (fever, aches, pains, rash) or severe (life-threatening)

The common house mosquito (Culex pipiens), which bites from dusk to dawn, is a vector of SLE and WNV. It becomes infected by feeding on birds that carry these viruses. Although these viruses affect mostly older adults and the immune-deficient, the risk is present to the entire human population. The tree-hole mosquito (Aedes triseriatus)¹, which bites during the day, is the main vector of LAC in Illinois. The virus infects chipmunks, squirrels and other small woodland animals; in humans, it affects mainly children. The Asian tiger mosquito (Aedes albopictus) was brought into the U.S. and other countries through the worldwide transport of used tires. The Asian tiger mosquito transmits dengue fever in other parts of the world & WNV - and could become involved in the LAC cycle in Illinois according to IDPH.

• ¹The scientific name for Aedes triseriatus was recently changed to Ochlerotatus triseriatus.

The National Pesticide Information Center (NPIC), a cooperative effort of the United States Environmental Protection Agency (U.S. EPA) and Oregon State University has developed a West Nile Virus Resource Guide.

The Asian tiger mosquito (Aedes albopictus) is a very aggressive daytime biter with peaks generally occurring during the early morning and late afternoon. Adult males and females are covered with shiny black scales with distinct silver white bands on the palpus and tarsi. Its most striking characteristic is the band of silver scales forming a distinct stripe on the dorsal surface of the thorax and head. The flight range of adults is limited, and they have not been observed to fly in strong winds. Its major means of dispersal is through the transport of used and waste tires. Depending on temperature and the availability of food, Aedes albopictus can complete larval development between 5 and 10 days. The eggs of Aedes albopictus are similar to Aedes aegypti. Discarded automobile and truck tires are an important habitat of Aedes albopictus.

The tree-hole mosquito (Ochlerotatus triseriatus) or "tris" has become an important urban mosquito because of its association with scrap tires. This Eastern tree-hole mosquito also uses tires as a major breeding ground. It can be found in a single water-filled tire behind the garage or in a tire dump with thousands of tires. In scrap tire yards, adults reach incredibly high numbers, as many as 60,000 females per acre in mid-summer. The major food source for Ochlerotatus triseriatus larvae is decomposing leaves collected in used tires. The most diagnostic characteristic of this mosquito is the silvery scales covering the sides of the thorax. The abdominal segments are dark and un-banded. The flight range of adults is rather short and often ranges only a few hundred yards from the tree-hole or tire pile where they are produced. Ochlerotatus triseriatus females can pass the Lacrosse virus on through the eggs to the next generation thus providing an overwintering mechanism for the virus.

The common house mosquito (Culex pipiens) is the most common species of mosquito found in urban areas. Adults are light brown mosquitoes identified by the presence of distinctive, basal, pale abdominal bands. Abdominal bands are broadly rounded medially and distinctly constricted sub-laterally before joining large, lateral scale patches. Members of the Culex pipiens complex are the principal vectors of the SLE virus in the central and eastern United States. Eggs hatch in 1-2 days. Development from egg to adult is temperature dependent, requiring 8 to 12 days in summer. Females may travel considerable distances from resting sites to search for blood hosts. Maximum flight range is about 1-2 miles.                                  

Mosquitoes use visual, thermal, and olfactory stimuli to locate a host. Avoid mosquito bites to avoid infection.

1. Wear appropriate clothing: light colored clothes (dark colors attract mosquitoes); long pants/shirts; and/or tightly woven material. 
2. Wear a bug spray with N, N-diethyl-3-toluamide (DEET) as the major ingredient. Concentrations of 5% to 100% are available. Products with 25-35% DEET will provide adequate protection for general circumstances (24% concentration will provide protection for about 5 hours according to a study by the New England Journal of Medicine).
3. Avoid spraying plastics, rayon, or synthetic fabrics.
4. For extra protection in severe circumstances, a combination of permethrin and 35% DEET can be used to provide 99.9% protection. Permethrin should be applied directly to clothing. To apply to clothing, spray each side of the fabric outdoors for 30 to 45 seconds (just enough to moisten fabric). Allow the garment to dry for 2 to 4 hours before wearing it. 
5. Don't wear cologne or perfume.

By controlling the mosquitoes at the tire facilities, we can greatly reduce the risk of encephalitis to workers and nearby residents. For example, in Ohio over 60% of LAC cases are associated with used tires.

The larvicides available to control mosquito larvae include Abate ^R, VectoBac ^R, VectoLex ^R, and Altosid. The Abate pellets have been effective since 1965 and are the most cost effective larvicide on the market today. VectoBac ^R is a biological larvicide that has no adverse effects on humans, and has had no cases of resistance in the field. VectoLex ^R is particularly effective against Culex pipiens mosquito larvae, which is known to carry WNV and SLE. Altosid ^R provides long-term protection by using an insect growth regulator called methoprene, which interferes with the metamorphoses of mosquitoes. This product is available in several different forms including granules, bricquets, liquid and pellets.

There are several different adulticides available for adult mosquito control, including Biomist ^R, Anvil ^R, and Scourge ^R. Biomist ^R, which contains permethrin, has a fast knockdown time, low mammal toxicity, and is 80% biodegradable on plant surfaces within 24 hours. Anvil ^R uses Sumithrin and is best used around creeks, swamps, and residential areas with high numbers of mosquitoes. This product has a high knockdown rate and is effective against organophosphate-resistant species. Scourge ^R combines Resmethrin and Piperonyl Butoxide and is available in two different concentrations 18%+54% or the 4%+12% ready-to-use formula.

Initial screening tests in a New Orleans laboratory have shown that the Asian tiger mosquito may be as much as 5 to 6 times as difficult to kill as some of the native mosquitoes. Because of this, different combinations may be needed to control different mosquito populations. In this study, the control measures included using a combination of adulticides applied by Ultra-Low Volume spray. Malathion and Resmethrin (Scourge) were used to control adults. Chlorpyrifos (Dursban) and Bacillus thuringiensis Berliner var. israelensis were used to control larvae in tires (Ohio State University Extension).

Proper management of used tires will help reduce the proliferation of disease-carrying mosquitoes. The following steps should be taken to help eliminate breeding habitats for known disease-carrying mosquitoes:

• Don’t leave tires outside. Keep them inside a building or fully enclosed container so they can’t accumulate water.
• If tires must be kept outdoors, alter the tires so they can’t accumulate water.
  
• Dispose of used tires at an Illinois EPA-permitted commercial used tire processing facility.
  
• Report improperly managed used tires or waste tire dumps to the Illinois EPA.
  
• If your business accepts or stores used tires, store the tires inside a building or fully enclosed container to reduce the risk of exposure to mosquito-related diseases.

Visit the Illinois EPA Used Tires webpage for more information. The Illinois EPA has removed and properly disposed of more than 20 million used and waste tires that were improperly discarded in Illinois.

To report improperly managed or discarded tires, please refer to the Illinois EPA Bureau of Land Regional Offices.

The most effective mosquito control is to keep tires dry. Chemical treatment of tire piles to control either larval or adult stages is much more difficult than most routine applications and may not be fully effective. Shredding tires, or otherwise rendering them incapable of holding water and supporting mosquito production, substantially decreases mosquito populations and is usually more preferable than attempting control through the application of larvicides and adulticides. However, studies show that a small percentage of mosquito larvae survive shredding allowing the dispersal of larvae at a lower rate. Because of this, a combination of shredding, draining, and the use of larvicides/adulticides may be needed to control the mosquito infestation in some areas.

Although tires are the major haven for mosquitoes, they can be found in almost any place capable of holding water. Soda cans, birdbaths, rain gutters, toys, pool covers, tree stumps, and garbage cans are all capable of harboring mosquitoes. Therefore, it is important to drain anything capable of retaining water at least once a week to prevent the larvae from hatching.

According to IDPH, if a dead crow or blue jay is found between May 1 and the end of October and appears to have died of natural causes, you should report it to your local health department. If it appears that birds, especially crows, are dying at an unusual rate, some dead birds will be collected for testing for WNV and other possible causes of bird deaths.

If you have any specific questions about the mosquito populations or the diseases spread by these mosquitoes, please contact:

Linn Haramis, Ph.D.,                                    
Entomologist / Vector Control Program Manager                                    
IDPH Division of Environmental Health                        
525 W. Jefferson St. Springfield, IL 62761                                    
217-782-5830
Fax: 217-785-0253

IDPH WNV hotline: 866/369-9710

For questions concerning the removal of used tires in your area, please contact the Illinois EPA at 217-785-8604.

Mosquitoes
Centers for Disease Control and Prevention

Mosquitoes and Disease
IDPH

Mosquitoes and Mosquito Repellents: A Clinician's Guide
Annals of Internal Medicine