Bites from mosquitoes, ticks, and other insects

Mosquitoes: To prevent mosquito bites, wear long sleeves, long pants, hats and shoes (rather than sandals). Apply insect repellents judiciously to exposed skin and clothing. Repellents containing DEET (N,N-diethyl-3-methylbenzamide) are recommended for areas where travelers may encounter potentially life-threatening mosquito-borne diseases, such as malaria and yellow fever.

Products containing lower concentrations of DEET are as effective as those with higher concentrations, but for shorter periods of time. On average, products containing 100% DEET will be effective for 9.5 hours, 30% DEET for 6.5 hours, 15% DEET for 5 hours, 10% DEET for 3 hours and 5% DEET for 2 hours. Controlled release preparations containing 20-35% DEET, such as Ultrathon, may be effective for 8-12 hours or more. Factors such as high temperature, humidity, sweating, and water exposure may reduce the duration of a repellent's effectiveness.

In general, adults and children greater than 12 years of age should use preparations containing 25-50% DEET. Preparations containing higher concentrations of DEET carry greater toxicity with little additional benefit. Children between 2 and 12 years of age should use preparations containing no more than 10% DEET, applied sparingly. If children require prolonged protection, it is safer to use low-concentration DEET, reapplied when needed, than to use high-concentration products. Neurologic toxicity has been reported from DEET, especially in children, but appears to be extremely uncommon and generally related to overuse. DEET-containing compounds should not be used on children under age two.

The Centers for Disease Control states that the recommendations for DEET use in pregnant women do not differ from those in nonpregnant adults.

Insect repellents should not be applied to eyes, mouth, cuts, wounds, or irritated skin. If this accidentally occurs, the affected area should be rinsed promptly with water. Do not apply to skin under clothing. Do not use repellents in enclosed, poorly ventilated areas or near food. Children should not be allowed to apply their own repellents. Do not apply to children's hands, since they may put these in their mouths. Insect repellents should be washed off with soap and water when no longer needed.

DEET-containing products may also be applied to garments, window screens, mosquito nets, tents, and sleeping bags, though care must be exercised, because DEET may damage certain plastics and synthetic fabrics. If DEET is applied to clothing, the garments should be washed before worn again.

A newly developed repellent called picaridin (Bayrepel) appears to be about as effective as DEET when used in comparable concentrations. Unlike DEET, picaridin does not have any odor or stickiness and does not have the potential to damage synthetic fibres. However, the only product currently marketed in the United States (Cutter Advanced) contains only 7% picaridin, which requires reapplication every 3-4 hours, comparable to 10% DEET. Higher concentration products are available in Europe and Australia.

Though less effective, insect repellents containing certain botanical products may be an option when the duration of insect exposure is short or when the risk of contracting a serious infection from mosquito bites is small. A preliminary study in the New England Journal of Medicine found that those containing oil of eucalyptus (Fite Bite Plant-Based Insect Repellent, Travel Medicine; and Repel Lemon Eucalyptus Insect Repellent, WPC Brands) provided protection against mosquito bites for an average of two hours, and a product containing soybean oil (Bite Blocker for Kids, HOMS) was effective for an average of 90 minutes. By contrast, repellents based on citronella prevented bites for less than 20 minutes and are not recommended. Oil of lemon eucalyptus should not be used on children less than three years of age.

For additional protection against mosquito bites, products containing permethrin, a contact insecticide, may be applied to clothing, shoes, tents, and bed nets. Studies have shown that permethrin-impregnated bednets are more effective than untreated ones. When bed nets are not washed, the insecticide remains effective for several months. Even when items such as clothing are laundered, permethrin treatments remain effective for at least two weeks. Permethrin should be reapplied after every five washings. There is no signifcant toxicity when applied to clothing, but permethrin should not be applied directly to skin.

Sleeping quarters should be protected from mosquitoes. Windows should be closed or screened. If sleeping outdoors or in an accommodation that allows entry of mosquitoes, a bed net should be used, preferably impregnated with insect repellent, with edges tucked in under the mattress. The mesh size should be less than 1.5 mm. Mosquito nets can be purchased online from Long Road Travel Supplies. If sleeping in an area not otherwise protected, mosquito coils, which fill the room with a vapor of insecticide, may be useful. Coils which contain dichlorodiphenyltrichloroethane (DDT) should be used with caution.

Repellent-impregnated wristbands are not effective.

Ticks: Follow the same precautions as for mosquito bites, except that boots are preferable to shoes, with pants tucked in. In rural or forested areas, where most tick bites occur, perform a thorough tick check at the end of each day with the assistance of a friend or full-length mirror. Ticks should be removed with tweezers, grasping the tick by the head. Many tick-borne illnesses can be prevented by prompt tick removal. Insect repellents based on botanical products, described above, have not been adequately studied for insects other than mosquitoes and cannot be recommended at present to prevent tick bites.

Sandflies: Follow the same precautions as for mosquito bites, except that netting must be finer-mesh (at least 18 holes to the linear inch) since sandflies are smaller.

Tsetse flies: Insect repellents are ineffective. The best means of prevention is to avoid areas infested with tsetse flies, which are usually known to local inhabitants. Travelers at risk should wear long sleeves and long pants of medium weight fabric in neutral colors that blend with the environment. Also, travelers should avoid riding in the back of open vehicles, since dust may attract tsetse flies, and should take care not to disturb bushes (where tsetse flies rest) during the warmer parts of the day. For further information on personal protection measures, go to Health Canada.

If allergic to bites or stings, be sure to bring along a self-administered epinephrine injection, such as EpiPen.

From the World Health Organization (WHO)

Vectors of diseases (Part 1) (PDF) Weekly Epidemiological Record , Vol. 76, 189, 2001.

Vectors of diseases (Part 2) (PDF) Weekly Epidemiological Record , Vol. 76, 201, 2001.

From the Centers for Disease Control (CDC)

Protection against Mosquitoes, Ticks, Fleas and Other Insects and Arthropods

Updated Information regarding Insect Repellents

Insect Repellent Use and Safety

From the New England Journal of Medicine

"Comparative Efficacy of Insect Repellents against Mosquito Bites" (Mark S. Fradin, M.D., and John F. Day, Ph.D.; NEJM, July 4, 2002; 347:13-18)

From the United States Environmental Protection Agency (EPA)

Reregistration of the Insect Repellent DEET