Mosquitoborne infectious diseases in the United States are caused by arboviruses (eg, West Nile, La Crosse, St. Louis encephalitis, eastern equine encephalitis, and western equine encephalitis viruses [see Arboviruses]). International travelers may encounter arboviral or other mosquitoborne infections (eg, malaria, Yellow fever, dengue, Japanese encephalitis) during travel (also see disease-specific chapters in Section 3). Physicians should be aware of the Epidemiology of arbovirus infections in their local areas. Prevention involves protection from the bite of an infected mosquito. In areas with arbovirus transmission, protection of children is recommended during outdoor activities, including activities related to school, child care, or camping. Education of families and other caregivers is an important component of prevention. Specific measures include:
- Eliminate local mosquito sources. Mosquitoes develop in standing water. Often, large numbers of mosquitoes are produced from sources at or very near the home. Measures to limit mosquito sources around the home include drainage or removal of receptacles for standing water (old tires, toys, flower pots, cans, buckets, barrels, other containers that collect rain water); keeping swimming pools, decorative pools, children's wading pools, and bird-baths clean; and cleaning clogged rain gutters. Under certain circumstances, large-scale mosquito Control Measures may be conducted by community mosquito-control programs or public health officials. These efforts include drainage of standing water, use of larvicides in waters that are sources of mosquitoes, and use of pesticides to control biting adult mosquitoes.
- Reduce exposure to mosquitoes. Avoiding mosquito bites by limiting outdoor activities at times of high mosquito activity, which primarily occur at dusk and dawn, and screening of windows and doors can help reduce exposure to mosquitoes. Many parts of the United States also have mosquitoes that bite during the day, and some of these have been found to transmit West Nile virus. Mosquito traps, ultrasonic repellers, and other devices marketed to prevent mosquitoes from biting people are not effective and should not be relied on to reduce mosquito biting.
- Use barriers to protect skin. Barriers include mosquito nets and screens for baby strollers or other areas where immobile children are placed. Additional protection can be gained, when practical, by using clothing to cover exposed skin (ie, long sleeves, long pants, shoes, and hats).
- Discourage mosquitoes from biting. Mosquitoes are attracted to people by odors on the skin and by carbon dioxide from the breath. The active ingredients in repellents make the user unattractive for feeding, but they do not kill the mosquitoes. Repellents should be used during outdoor activities when mosquitoes are present, especially in regions with arbovirus transmission, and should always be used according to the label instructions. Repellents are synthetic compounds or derivatives of plant oils. The most effective repellents for use on skin are products that contain diethyltoluamide (DEET). Picaridin (KBR 3023), available in 7%, 15%, and 20% formulations in the United States, has been shown to be as effective as lower concentrations of DEET, with higher concentrations offering longer protection. Finally, the plant-based oil of lemon eucalyptus (OLE) and its synthetic equivalent p-menthane-3,8-diol also have been shown to have repellent activity. Products with a higher concentration of active ingredients protect longer and are appropriate for people who will be exposed to mosquitoes during outdoor activities lasting many hours. Products with lower concentrations of active ingredients may be used where more transient protection is required, but they may require repeated applications. Studies in human volunteers document the association of active ingredient concentration with duration of repellent activity. For example, results of one study demonstrated an average duration of protection of 5 hours, 4 hours, 2 hours, and 1.5 hours for products with DEET concentrations of 23.8%, 20%, 6.7%, and 4.5%, respectively. Products containing picaridin may be as effective in repelling mosquitos as products with low concentrations of DEET but also require frequent reapplication for lasting protection. OLE appears to have similar duration of action as products containing lower concentrations of DEET, with a product containing 30% OLE providing protection roughly equivalent to a product containing 15% DEET. All other plant products studied, including those based on citronella, protected for less than 20 minutes. Ingestion of garlic or vitamin B1 or wearing devices that emit sounds or impregnated wristbands all are ineffective measures.
DEET has been used worldwide since 1957, has been studied more extensively than any other repellent, and has a good safety profile. Concerns about potential toxicity, especially in children, are unfounded. Adverse effects are rare, are most often associated with ingestions; chronic use, or excessive use; and do not appear to be related to DEET concentration used. Urticaria and contact dermatitis have been reported in a small number of people. Reports of encephalopathy have been rare, with 13 cases reported after skin application in children. Encephalopathy also has been reported after unintentional ingestion. DEET is irritating to eyes and mucous membranes. Concentrated formulations can damage plastic and certain fabrics. If used appropriately, DEET does not present a health problem.
Although concentrations of 10% to 15% DEET or lower have been recommended for children, there is no evidence that these concentrations are safer than 30% DEET. Products with DEET concentrations of 10% or less should not be used for exposures lasting more than 1 to 2 hours. There is no evidence that repellents that do not contain DEET are safer, and there are no safety data for other products in children. One approach is to select the lowest concentration that is effective for the amount of time spent outdoors. In 2001, the US Environmental Protection Agency (EPA) concluded that appropriate use of DEET at concentrations of up to 30% posed no significant risk to children or adults but that DEET should not be used in children younger than 2 months of age because of increased skin permeability. The American Academy of Pediatrics has supported this recommendation.1
The Centers for Disease Control and Prevention currently recommends DEET at concentrations up to 30% for both adults and children older than 2 months of age.
Picaridin-containing compounds have been used as an insect repellent for years in Europe and Australia as a 20% formulation with no serious toxicity reported. Except for eye irritation, products containing oil of eucalyptus appear safe, although the EPA specifies that they should not be used on children younger than 3 years of age.
The EPA recommends the following precautions when using insect repellents. Recommendations for use of any of these insect repellents should be followed for children:
- Do not apply over cuts, wounds, or irritated or sunburned skin. Avoid areas around eyes and mouth.
- Do not spray onto the face; apply with hands.
- Use just enough to cover exposed skin.
- Do not apply to young children's hands, because they may rub it into their eyes or mouth.
- Do not allow young children to apply a product themselves.
- Do not apply under clothing.
- Do not use sprays in enclosed areas or near food.
- Repellents containing DEET, applied according to label instructions, can be used along with a separate sunscreen. No data are available regarding the use of other active repellent ingredients in combination with a sunscreen.
- Reapply if washed off by sweating or by getting wet.
- After returning indoors, wash treated skin with soap and water or bathe. Also, wash treated clothing before wearing again.
- If a child develops a rash or other reaction from any insect repellent, wash the repellent off with soap and water and contact the child's physician or the poison control center (800-222-1222) for guidance.
Permethrin-containing repellents are registered by the EPA for use on clothing, shoes, bed nets, and camping gear. Permethrin is a synthetic pyrethroid that is highly effective both as an insecticide and as a repellent for ticks, mosquitoes, and other arthropods. Permethrin can be sprayed onto clothes but should not be sprayed onto skin. Some manufacturers now offer permethrin-treated clothing, but because of lack of adequate safety and efficacy data, their use is not recommended for children at this time. Repellents should not be used on clothing or mosquito nets that young children may chew or suck.
Prevention of Mosquitoborne Infections has been found in Red Book 28e
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