against Mosquitoes and Other Arthropods
March 3, 2003)
Although vaccines or
chemoprophylactic drugs are available against important
vector-borne diseases such as yellow fever and malaria,
travelers still should be advised to use repellents and
other general protective measures against biting arthropods.
The effectiveness of
malaria chemoprophylaxis is variable, depending on patterns
of resistance and compliance with medication, and no similar
preventive measures exist for other mosquito-borne diseases
such as dengue. For many vector-borne diseases, no specific
preventives are available.
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 arboviral and parasitic infections are
transmitted seasonally, and simple changes in itinerary can
greatly reduce risk for acquiring them.
Travelers should be advised
that 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 can reduce risk of exposure. Wearing
long-sleeved shirts, long pants, and hats minimizes 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
biting insects is a possibility, travelers should be advised
to tuck their pants into their socks and to wear boots, not
sandals. Permethrin-based repellents applied as directed
(see the following section, Repellents) will enhance
protection. Travelers should be advised to inspect
themselves and their clothing for ticks, both during outdoor
activity and at the end of the day. Ticks are detected more
easily on light-colored or white clothing. Prompt removal of
attached ticks can prevent some infections.
When accommodations are not
adequately screened or air conditioned, bed nets are
essential to provide protection and comfort. Bed nets should
be tucked under mattresses and can be sprayed with a
repellent, such as permethrin. The permethrin will be
effective for several months if the bed net is not washed.
Aerosol insecticides and mosquito coils can help to clear
rooms of mosquitoes; however, some coils contain
dichlorodiphenyl- trichloroethane (DDT) and should be used
should be advised that permethrin-containing repellents
(e.g., Permanone or deltamethrin) are recommended for use on
clothing, shoes, bed nets, and camping gear. Permethrin is
highly effective as an insecticide and as a repellent.
Permethrin-treated clothing repels and kills ticks,
mosquitoes, and other arthropods and retains this effect
after repeated laundering. There appears to be little
potential for toxicity from permethrin-treated clothing. The
insecticide should be reapplied after every five washings.
Most authorities recommend
repellents containing N,N-diethylmetatoluamide (DEET) as an
active ingredient. DEET repels mosquitoes, ticks, and other
arthropods when applied to the skin or clothing. In general,
the more DEET a repellent contains, the longer time it can
protect against mosquito bites. However, there appears to be
no added benefit of concentrations greater than 50%. A
microencapsulated, sustained-release formulation can have a
longer period of activity than liquid formulations at the
same concentrations. Length of protection also varies with
ambient temperature, amount of perspiration, any water
exposure, abrasive removal, and other factors.
No definitive studies have
been published about what concentration of DEET is safe for
children. No serious illness has arisen from use of DEET
according the manufacturers recommendations. DEET
formulations as high as 50% are recommended for both adults
and children >2 months of age. Lower concentrations are
not as long lasting, offering short-term protection only and
necessitating more frequent reapplication. Repellent
products that do not contain DEET are not likely to offer
the same degree of protection from mosquito bites as
products containing DEET. Non-DEET repellents have not
necessarily been as thoroughly studied as DEET and may not
be safer for use on children. Parents should choose the type
and concentration of repellent to be used by taking into
account the amount of time that a child will be outdoors,
exposure to mosquitoes, and the risk of mosquito-transmitted
disease in the area. The recommendations for DEET use in
pregnant women do not differ from those for nonpregnant
DEET is toxic when ingested
and may cause skin irritation in sensitive persons. High
concentrations applied to skin can cause blistering.
However, because DEET is so widely used, a great deal of
testing has been done, and over the long history of DEET
use, very few confirmed incidents of toxic reactions to DEET
have occurred when the product is used properly.
Travelers should be advised
that the possibility of adverse reactions to DEET will be
minimized if they take the following precautions:
- Use enough repellent to
cover exposed skin or clothing. Do not apply repellent
to skin that is under clothing. Heavy application is not
necessary to achieve protection. If repellent is applied
to clothing, wash treated clothing before wearing again.
- Do not apply repellent
to cuts, wounds, or irritated skin.
- After returning indoors,
wash treated skin with soap and water.
- Do not spray aerosol or
pump products in enclosed areas; do not breathe in.
- Do not apply aerosol or
pump products directly to the face. Spray your hands and
then rub them carefully over the face, avoiding eyes and
- When using repellent on
a child, apply it to your own hands and then rub them on
your child. Avoid the childs eyes and mouth and apply
sparingly around the ears.
- Do not apply repellent
to childrens hands. (Children tend to put their hands
in their mouths.)
- Do not allow children
under ten years old to apply insect repellent to
themselves; have an adult do it for them. Keep
repellents out of reach of children.
- Protect infants two
months of age and under by using a carrier draped with
mosquito netting with an elastic edge for a tight fit.
- Bed nets, repellents
containing DEET, and permethrin should be purchased
before traveling and can be found in hardware, camping,
sporting goods, and military surplus stores. Overseas,
permethrin or another insecticide, deltamethrin, may be
purchased to treat bed nets and clothes.