Insects, Repellents and Bed Nets

Insects are a nuisance and may transmit several diseases like malaria, yellow fever and dengue fever.

Mosquito nets

An impregnated bed net around the bed or sleeping place at night is the most efficient way of preventing malaria after taking regular prophylaxis as tablets.

The effects are greatly enhanced by impregnating the net with a synthetic pyrethrum like permetrhine, deltamethrine or lambda-cyhalothrine.

The impregnation lasts from 6 to 12 months. If not used, the shelf life may be prolonged by packing the net in an air- tight plastic bag.

The net must be so large that it can be tugged under the mattress and so big that it is not touched during sleep.

Correct use of an impregnated bed net at night reduces the risk of getting malaria by at least 50%.

Insect bites

Insect bites are a nuisance and may transmit diseases like malaria, yellow fever, dengue fever, Japanese encephalitis. Ticks transmit scrub typhus, central European encephalitis and borreliosis.

How to reduce insect bites?

• wear clothes with long sleeves and long trousers, and avoid clothes in dark colours
• sleep in a room with screens covering the windows or with air-conditioning
• If the sleeping room is not air-conditioned or has no screens, use an impregnated bed net
• An electric ceiling, wall or desk fan disturbs the flight path of the insect
• Smoke-coils. Coils, which burn during the night and are assumed to evaporate insecticide into the room can be bought in most tropical countries. The effect is doubtful and the method is not recommended
• Electric evaporator. The device contains a ceramic plate, which is heated by electricity. A tablet containing insecticide is placed on the plate and insecticide is released throughout the night if the tablet is fresh. The device is better than the burning spiral, but not as efficient as the bed net
• A night light with an electric grill behind a protective screen can be very effective if kept clean. The insect is drawn to the light by a small suction fan.
• Wristbands. Several companies’ market wristbands im-pregnated with DEET and citronella oils. They have absolutely no effect no matter what level of impregnation

Repellents: There are several insect repellents on the market. The best known is based on DEET (Di-Ethyl-Toluamide) usually in a 20% solution.

The Eucalyptus extract p-menthane-3,8-diol, PMD, (marketed under the name of Quwenling or Mosi-guard) in a 50% preparation is equally effective as DEET.

There any many natural products, for instance citronella and coco oils, but these are generally much less effective.

DEET 20% protects against mosquitoes for at least 4 hours and PMD 50% for the same time period.

Citronella and related natural products can only be relied upon for several minutes.

All repellents may cause adverse reaction like allergic contact dermatitis and should not be used on the face nor should they be used on children less than 3 years old.