Insect Bite Avoidance
Many serious tropical diseases are spread by insects. Some examples are malaria,
yellow fever, Japanese encephalitis, dengue fever, West Nile virus, and leishmaniasis.
For some of the diseases such as dengue fever, avoiding bites is the only way to
prevent them.
Mosquitoes are attracted by carbon dioxide, heat, smells and movement. Day-biting
mosquitoes can carry yellow fever and dengue fever, night-biting mosquitoes may
carry malaria and Japanese encephalitis. Sand flies, the carriers of leishmaniasis
are most active between dusk and dawn. They will, however, bite during the day if
they are disturbed.
Insect Repellents
There are many types of repellent, but evidence shows that products containing the
chemical DEET are the most effective. DEET is available in several strengths suitable
for use on skin. Research shows 20% DEET repellents offer protection for up to 3
hours. Higher concentrations give longer-lasting protection, with some 30% DEET
repellents providing protection for up to 6 hours.
There is no need to use a repellent stronger than 50% DEET. The length of protection
is affected by conditions such as heat, humidity and amount of sweating.
DEET repellents should not be used on babies younger than 2 months old. 50% strength
DEET repellents can be used by pregnant or breast-feeding women, and on babies and
children older than 2 months. Manufacturers in the UK have applied age restrictions
on use of DEET, and these must be followed. Particular care should be taken with
children to ensure they are not able to swallow repellent, and that it does not
come into contact with their eyes or mouth
Repellents need to be reapplied at regular intervals, especially after swimming
and in hot, humid countries, when they can be removed by sweating. When both sunscreens
and repellents are used, sunscreen should be applied first and then repellent.
There have been concerns about the safety of DEET, but research and extensive clinical
experience suggest that it is very safe when used according to the manufacturer’s
instructions.
- Don’t spray directly onto your face.
- Use only on exposed skin.
- Avoid contact with lips and eyes.
- Wash hands after application.
- Don’t apply to cuts, abrasions, broken or irritated skin.
- Wash off the repellent
with soap and water when it is no longer needed.
- Sunscreen containing repellent
should be avoided as it may encourage excessive use of DEET.
Clothing
When travelling in areas with malaria, wear loose-fitting long trousers and long
sleeves in the evenings, as the mosquitoes that carry malaria are most active at
this time.
When in tick infested areas avoid shorts and tuck your trousers into your socks
to prevent ticks from crawling up your legs
Mosquitoes can bite through tight clothing, so wear loose fitting clothing. Clothing
can be treated with permethrin, a contact insecticide which will kill insects. Permethrin
is available in formulations designed to be sprayed on to clothes.
Screening and Mosquito Nets
Travellers who will be staying in basic accommodation without screening or air conditioning
should sleep under a mosquito net to avoid being bitten at night. Nets should be
impregnated with permethrin; most nets are bought already treated prior to purchase.
Generally nets will need to be impregnated with permethrin again after six months
of use.
Permethrin is a contact insecticide, which will kill insects landing on the net
and therefore increase effectiveness.
Carry a small sewing kit so that repairs can be made if the net develops a hole.
Knock-down Sprays and Electric Plug-ins
These can be used before you go to bed, to rid bedrooms of insects. Plug-in devices
which release an insecticide vapour are also available.
Insecticide coils should only be burnt in well-ventilated areas and can be useful
for campers. A small piece of coil lit under the table can be a deterrent when eating
at outdoor restaurants in the evenings.
Vitamin B and Garlic
There is no scientific evidence that taking vitamin B tablets or eating marmite
or garlic makes humans less attractive to mosquitoes.
Buzzers
Devices that emit a sonic tone inaudible to humans are not effective.