Insect Bite Avoidance
Apart from acting as carriers of disease, insect bites can result in unpleasant and occasionally serious skin reactions.
Avoidance of Bites
There are several practical measures that individuals can take to avoid insect bites. A combination of these measures is usually most effective.
Mosquitoes spread Malaria, Yellow fever, Dengue fever, Japanese Encephalitis, Chikungunya, Zika Virus, Eastern Equine Encephalitis, Filariasis, Rift Valley Fever (occasionally) Ross River Virus and Murray Valley Encephalitis, St Louis Encephalitis and West Nile Fever. The bite can be sore but is often painless.
- To avoid bites wear clothing that covers as much of the body as possible such as long sleeved clothing and long trousers.
- Mosquitoes may bite through thin clothing, so spray an insecticide or repellent on them. Insect repellents should also be used on exposed skin.
- Burning pyrethroid coils and heating insecticide impregnated tablets all help to control mosquitoes.
- If sleeping in an unscreened room, or out of doors, a mosquito net (which should be impregnated with insecticide) is a sensible precaution. Nets that have pyrethroid incorporated into the material or bound to the material with resin have an expected life of 3-5 years and are superior to nets that require re-impregnation.
- Portable, lightweight nets are available and any outdoor shops now stock nets and it can be helpful to practice erecting nets before departure.
- Garlic, Vitamin B and ultrasound devices do not prevent bites.
Blackflies, Tsetseflies and Sandflies
Blackflies are the carrier of Onchocerciasis (river blindness) and Mansonellosis. The bite itself can cause a very red and itchy rash.
Tsetse flies are the carrier of African trypanosomiasis. The bite itself is usually painful.
Sandflies are the carrier of Leishmaniasis and Bartonellosis. The bite itself is often very itchy.
- Avoid unnecessary exposure (including while at work and when sleeping) in infested areas.
- To avoid bites wear clothing that covers as much of the body as possible such as long-sleeved clothing and long trousers.
- Insects may bite through thin clothing, so spray an insecticide or repellent on them. Insect repellents should also be used on exposed skin.
- Local advice should be sought by those staying in rural infested areas for long periods.
- Since blackflies are very small they can pass through most nets (holes need to be of a certain size to allow ventilation) but impregnation of the net with an insecticide helps to kill them before they find their way through.
A bug is the carrier of South American trypanosomiasis - Chagas Disease.
- Bugs live in the walls of mud houses and only come out at night.
- Ideally avoid sleeping in these houses and sleep well away from walls.
- Mosquito nets can provide protection (see mosquitoes above).
Ticks are the carrier of African tick-bite fever, Crimean-Congo haemorrhagic fever, Lyme disease, Rocky Mountain Spotted Fever and Tick-borne encephalitis. The bite itself can cause an itchy and very red, inflamed local reaction especially if the mouth parts are left in-situ. An adrenaline pen should be carried by those with a history of anaphylaxis. Prompt removal of the offending tick is important.
- Bites from ticks are unusual in package tourists staying in urban or developed tourist resorts - ticks prefer long grassy areas.
- Ticks normally become attached to skin or clothing after brushing against bracken or long grass and then migrate to warm moist areas of the body such as groins or axillae to feed.
- Avoid unnecessary exposure in infested areas and where possible, keep to paths.
- Clothing should cover the legs with socks outside trousers to prevent the ticks reaching the skin.
- Insect repellents can be used to impregnate exposed clothing such as trousers and socks.
- Ticks should always be removed as soon as possible, ideally with tweezers hooked around the mouthparts under the tick's body. A long fingernail can also act as a lever to prize the tick off. Do not squeeze the body of the tick.
- Ticks do not normally feed for about 12-24 hours after attaching themselves during which time infection risk is small.
Rat fleas are the carriers of Plague in humans.
- As the name suggests, rat fleas live mainly on rats but can also live on other small animals and rodents.
- They can be found in tropical areas where sanitation is poor.
- Rat fleas hide in beds and bed clothing.
- Repellents and insecticides should be used if entering a plague-endemic area.
Choosing Insect Repellents
Insect repellents are available in various forms and concentrations. Many skin preparations are available, mostly containing di-ethyltoluamide (DEET).
DEET has been proven to be the most effective in preventing mosquito bites so it is the repellent of choice in areas with diseases such as malaria and dengue.
For those allergic to DEET, alternatives include Icardin, Dimethyl Pthalate or Eucalyptus oil.
Aerosol and pump-spray products are available which are suitable for treating clothing e.g. permethrin - if aerosols and pump sprays are used on skin it is best to spray liquid onto your hand and then rub onto exposed areas.
Liquid, creams, lotions and sticks are designed for skin application.
Products with a lower concentration are usually used on skin (30 – 50%) and higher concentrations (100%) on clothes.
Using Insect Repellents Safely
- Clothes are the best protection - normally only use repellents on the remaining exposed areas of skin and shirt collars and cuffs and the ankle bottoms of trousers or slacks.
- Never use repellents over cuts, wounds, or irritated skin.
- Don't apply to eyes and mouth, and apply sparingly around ears. When using sprays do not spray directly onto face; spray on hands first and then apply to face.
- When sunscreen and DEET are used together, DEET should be applied after sunscreen. The effectiveness of repellent reduces more rapidly than sunscreen, therefore, repellent may have to be reapplied on top of sunscreen.
- If using sunscreen and repellent together, use SPF 30-50 sunscreen to allow for the reduction in SPF caused by DEET repellent.
- Do not allow young children to handle repellents - they may get them into their eyes. Apply to your own hands and to the child's skin. For children, use clothing as the main barrier and repellent only where necessary.
- Use just enough repellent to cover exposed skin. Heavy application is unnecessary.
- After use, wash treated skin. This is particularly important when repellents are used repeatedly.
- If you suspect that you or your children are reacting to an insect repellent, discontinue use, wash treated skin and then contact your doctor.
- Always follow the manufacturer's instructions.
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