Rationale:

• Because no chemoprophylactic regimen is available for dengue, it is essential that measures be taken to reduce mosquito vector exposure.
• Clothing that covers the extremities can prevent mosquito bites.
• DEET and permethrin repel mosquitoes.

Evidence:

• Reviews and commentaries indicate that mosquitoes in the home, mosquito bites, and standing water are associated with dengue infection; the A. aegypti vector typically breeds in clean, stagnant water, such as that in vases, tins, and gutters. A. aegypti is highly susceptible to the dengue virus, is a daytime feeder, feeds preferentially on human blood, and is able to bite several people in a short period of one blood meal (23; 24; 25).
• A clinical review article emphasizes that covering the extremities should decrease the risk of mosquito bites (26).
• An article describing the British Army's strategy for controlling arthropod vectors of disease during overseas deployments concluded that practical insect avoidance measures combined with pyrethroid-treated nets and clothing and DEET-based topical repellents can achieve almost 100% protection against biting arthropods (27).
• A systematic review found DEET to be the most effective and well-studied insect repellent on the market and that it had a remarkable safety profile after 40 years of worldwide use. Nearly 100% protection against bites could be achieved when DEET-based repellents were applied in combination with permethrin-treated clothing. Plant-based repellents were generally less effective than DEET-based products (28).
• A study on the relative efficacy of insect repellents tested four products containing N,N-diethyl-m-toluamide (now called N,N-diethyl-3-methylbenzamide or DEET), a repellent containing ethyl butylacetylaminopropionate, three repellent-impregnated wristbands, and a moisturizer that is commonly claimed to have repellent effects in 15 volunteers. DEET-based products provided complete protection for the longest duration. Higher concentrations of DEET provided longer-lasting protection. A formulation containing 23.8% DEET had a mean complete-protection time of 301.5 minutes. A soybean oil-based repellent protected against mosquito bites for an average of 94.6 minutes. The ethyl butylacetylaminopropionate-based repellent protected for an average of 22.9 minutes. All other repellents tested provided protection for a mean duration of less than 20 minutes. Repellent-impregnated wristbands offered no protection (29).
• A randomized, double-blind, therapeutic trial of insect repellents for the prevention of malaria in pregnancy (n=897) assessed the safety of daily application of DEET, 1.7 g/d, in the second and third trimesters of pregnancy. No adverse neurologic, gastrointestinal, or dermatologic effects were seen in women who applied a median total dose of 214.2 g of DEET per pregnancy. Among a randomly selected subgroup of DEET users (n=50), DEET was found to cross the placenta and was detected in 8% of cord blood samples. No adverse effects on survival, growth, or development at birth or at 1 year were found. The investigators concluded that the risk of DEET accumulating in the fetus is low and that DEET is safe to use late in pregnancy (30).
• A review of available data on the effectiveness and safety of DEET-based products concluded that the evidence does not support an increased risk in young children (31).

Comments:

• Currently no vaccine is available for dengue in humans.
• The principal dengue mosquito vector, A. aegypti, is most often found in or near human habitations and prefers to feed on humans during the day. It has two peak periods of biting activity: in the morning for several hours after daybreak and in the late afternoon for several hours before dark. However, the mosquito may feed at any time during the day, especially in shady areas, indoors, or when it is overcast.
• Mosquito breeding sites include artificial water containers, such as discarded tires, uncovered barrels, buckets, flower vases or pots, cans, and cisterns.
• Products containing 30% DEET are considered safe and effective for up to 4 to 6 hours in adults and children older than 2 months if used according to the manufacturer's directions.
• No definitive studies have been published regarding the concentration of DEET that is safe for use in children. No serious illness has been reported from use of DEET according to the manufacturer's recommendations.
• Although the use of DEET has not been shown to be injurious in pregnancy (30; 31), the minimal effective concentration for the estimated time of mosquito exposure should be used in this setting (28; 29).
• DEET can be applied to clothing as an effective alternative to skin application.
• Instructions on the appropriate application of DEET products are provided by the Environmental Protection Agency.
• Products containing niacin, citronella, and other plant and animal oils provide little, if any, protection. Some perfumed products may attract mosquitoes.
• Insecticide-treated mosquito nets have limited usefulness in controlling dengue because the vector species bites during the day.