PROTECTION AGAINST MOSQUITOES AND OTHER ARTHROPOD VECTORS 
Although vaccines or chemoprophylactic drugs are available against important
vector-borne diseases such as yellow fever and malaria, there are none for most other
mosquito-borne diseases such as dengue, and travelers still should avail themselves of
repellents and other general protective measures against arthropods. The effectiveness of
malaria chemoprophylaxis is variable, depending on patterns of resistance and compliance
with medication, and for many vector-borne diseases, no specific preventatives are
available.
General preventative measures
The principal approach to prevention of vector-borne diseases is avoidance. Tick- and
mite-borne infections characteristically are diseases of “place”; whenever
possible, known foci of disease transmission should be avoided. Although many vector-borne
infections can be prevented by avoiding rural locations, certain mosquito- and midge-borne
arbo-viral and parasitic infections are transmitted around human residences and in urban
locations. Most vector-borne infections are transmitted seasonally and simple changes in
itinerary may greatly reduce risk for acquiring certain infections.
Exposure to arthropod bites can be minimized by modifying patterns of activity or
behavior. Some vector mosquitoes are most active in twilight periods at dawn and dusk or
in the evening. Avoidance of outdoor activity during these periods may reduce risk of
exposure. Wearing long-sleeved shirts, long pants and hats will minimize areas of exposed
skin. Shirts should be tucked in. Repellents applied to clothing, shoes, tents, mosquito
nets and other gear will enhance protection.
When exposure to ticks or mites are a possibility, pants should be tucked into socks
and boots should be worn; sandals should be avoided. Permethrin-based repellents applied
as directed (see below) will enhance protection. During outdoor activity and at the end of
the day, travelers should inspect themselves and their clothing for ticks. Ticks are
detected more easily on light colored or white clothing. Prompt removal of attached ticks
may prevent infection.
When accommodations are not adequately screened or air-conditioned, bednets are
essential to provide protection and comfort. Bednets should be tucked under mattresses and
can be sprayed with repellent. Aerosol insecticides and mosquito coils may help to clear
rooms of mosquitoes; however, some coils contain DDT and should be used with caution.
Repellents
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, mosqui-toes and other
arthropods and retains this effect after repeated laundering. There appears to be little
potential for toxicity from permethrin-treated clothing.
Permethrin-containing shampoo (Nix)* and cream (Elimite)*, marketed for use against
head lice and scabies infestations, potentially could be extremely effective as repellents
when applied on the hair and skin. However, they are approved only to treat existing
conditions. Most authorities recommend repellents containing deet
(N,N-diethylmeta-toluamide) as an active ingredient. Deet repels mosquitoes, ticks, and
other arthropods when applied to skin or clothing. Formulations containing <30% deet are recommended because the additional gain in repellent effect with higher concentrations is not signifi-cant when weighed against the potential for toxicity. A microencapsulated formulation (Skeedadle)* may have a longer period of activity than liquid formulations.
Deet is toxic when ingested. High concentrations applied to skin may cause blistering.
Rare cases of encephalopathy in children, some fatal, have been reported after cutaneous
exposure. Other neurologic side effects also have been reported. Toxicity did not appear
to be dose-related in many cases and these may have been idiosyncratic reactions in
predisposed individuals. However, a dose-related effect leading to irritability and
im-paired concentration and memory has been reported. Recommendations and precautions on
the use of repellents are given in Table 24.
