Many tropical diseases, such as malaria, yellow fever, and Japanese encephalitis, West Nile virus, Lyme disease, are transmitted by insect bites, usually through the insect’s saliva.
No antimalarial drug is 100% effective and in the case of some diseases (for example, dengue fever) there is no protection at all, so it is best to avoid getting bitten in the first place.
Luckily, insects aren’t a problem in most countries around the world, just annoying, and in those places where they are, only some of them carry diseases.
For example, there are more than 3,000 species of mosquitoes worldwide, and 420 species of the Anopheles mosquito, of which only about 70 are capable of transmitting malaria. Of those 70 species, only about 30 to 40 species are considered “good transmitters”. For each of these 30 to 40, only 5 to 10 percent of the insect population is capable of transmitting malaria.
These may seem like good odds, but the sheer numbers of the Anopheles mosquito around the world can make them appear less favourable. In parts of Africa, research has shown that some (unprotected) people suffer around 300 to 1,000 infectious bites per person per year, i.e. one to three malarious infections per day.
To get infected, you have to be bitten by a disease-carrying insect, and although it may take more than one bite from that insect to transmit the disease, you can still get infected from just one bite from one insect.
You can greatly reduce the chance of any infection by taking precautions to limit the number of times you get bitten. Even in low-risk or non-malarious areas it pays to do so, as insect bites can be irritating and sometimes painful.
When reading about and comparing repellents, insecticides and netting, remember that a lot are sold for domestic use (in the backyard at home), some just for backcountry use (in the USA), and some for use abroad.
Be careful to choose the right combination for your situation. For example, a close mesh net is ideal for keeping out tiny insects in the forests of the US but would be too hot in the tropics where a more open mesh mosquito net (treated with an insecticide) which lets in the breeze would be fine.
Clothing
One of the best ways to stop getting bitten is to reduce the amount of exposed skin by wearing long-sleeved shirts and long trousers, as well as enclosed shoes and long socks (not open sandals or flip flops).
Covering up in this way also (partially) protects against exposure to the sun.
Fabrics must be either thick or closely woven (not knit) as well as loose-fitting, as insects can bite though thin fabric or can reach your skin through tight clothing.
Luckily, loose clothing is also more comfortable in hot climates.
Also, light colors (khaki, for example) appear to be less attractive to mosquitoes.
The best shirt I have found that meets all of the above criteria is the 
Craghoppers Nosquito Long Sleeved Shirt. I personally have two of these (in Stone and Khaki) and they are worth every penny. Part of the ‘Bear Grylls’ range of clothing they are practical as well as very stylish. You can read more about them in the Clothing section of this website.
Craghoppers also make the best travel trousers too in the Craghoppers Kiwi Trousers. They are similar in performance to the shirt and are (justifiably) a best seller.
To deter ticks, tuck trousers into socks, and remember to inspect yourself for ticks after outdoor activities.
Spraying or soaking your clothes with an insect repellent or insecticide is also recommended (see below). The Nosquito shirt above is treated like this.
You can find anti-mosquito clothing treatments here
here
Repellents
The next method for keeping the insects away is to use an insect repellent on your skin.
Humans and animals give off various chemicals that attract insects. Insect repellents are thought to work by blocking the stimulation of the receptors that detect these chemicals.
The most popular (and also the most effective) repellents are those which contain DEET (diethyl-meta-toluamide). Others contain oil of lemon eucalyptus, botanicals, and other chemicals (picardin) but despite their claims, these may not be as protective.
Read more about the alternatives here. There is an update to this information here. Both give recommendations for domestic (USA) use. To find information about overseas travel, read the information here.
When evaluating claims make sure they are comparing like with like (some tests use lower concentrations of DEET, for example, when they claim their product is more effective), and check which insects they protect against (some are only more effective against ticks and certain (non-malarial) mosquitoes).
The U.S. Environmental Protection Agency considers DEET-based products safe when used as directed. This means they should not be used under clothing or on open cuts, wounds, or irritated skin, and shouldn’t be used with sunscreen.
Combination repellents and sunscreens are still being evaluated by the EPA, but because sunscreens are meant to be applied liberally and frequently and DEET products are used sparingly, you will inevitably end up putting on too much of one or too little of the other. Better to use separate products at the same time, applying sunscreen first, then the insect repellent.
DEET-based repellent should be applied following the manufacturer’s instructions to all exposed skin. It should also be kept away from your eyes, mouth and nasal membranes, and definitely should not be swallowed. Spray the repellent onto hands and then apply to face. You should use just enough to cover exposed skin and it should be washed off whenever safe to do so.
Even though you should not use it on your skin under clothing, many people apply it to the outside of their clothes on sleeves, collars, socks, and cuffs as additional protection.
Be aware that DEET can also melt some plastics, such as eyeglass frames, rayon, spandex, and other synthetic fabrics, and can damage leather and painted or varnished surfaces.
DEET products come in different concentrations which can be confusing. In concentrations over approximately 25%, DEET does not work better, it just lasts longer. If you are hiking or sweating a lot it will dissipate much faster and last a lot less.
Products containing 25% to 35% DEET are recommended by the CDC for adults. These will usually repel mosquitos for several hours (read the instructions), and there should be no need to reapply it more often that this. Ultrathon
Some DEET products consist of a 100% formulation
There may be circumstances where constant reapplication may be impractical, however, such as where there is a rapid loss of repellent due to rain or heavy sweating. Some people also use higher concentrations when traveling to an area where there is a very high density of biting insects.
As well as being a lower concentration, Ultrathon is also absorbed less through the skin, thus making it safer than 100% DEET. In addition, it is recommended by many health care professionals. If you have sensitive skin you can get it in a spray can at a 23% concentration which lasts up to eight hours.
Insecticides
Whereas insect repellents are designed to keep insects away, insecticides stun or kill insects that come into contact with it. In this way the two methods compliment each other and should both be used (one does not replace the other). Ideally, use a combination of a DEET product on exposed skin, and wear insecticide-treated clothing.
Permethrin is a common synthetic chemical, widely used as an insecticide and as an insect repellent. It is usually applied to mosquito netting (see below) and clothes. Permanone Coulston’s Duranon
When applied to clothing by aerosol or trigger spray, Permethrin provides protection lasting up to two weeks or two washings. Clothing soaked in a Permethrin solution is effective as am insecticide for months if it is stored out of the sun.
There should be no problems using it as long as it is used according to the instructions, as it has a low toxicity, is poorly absorbed by skin, and is generally environmentally safe except that it is toxic to honey bees and other beneficial insects, fish, aquatic insects, crayfish, and shrimp.
More recently, Deltamethrin has become more popular and widely used. It is a member of one of the safest classes of pesticides. However, it is still a neurotoxin and should be treated with care. It is used by companies (e.g. Tana Netting and Travel Health Help) to manufacture long-lasting insecticidal mosquito nets.
Mosquito nets
Mosquito nets are a very useful and practical way to prevent insect bites, especially when sleeping at night. There are a number of things to look out for when buying a net.
There are basically two types, circular or rectangular. The circular type hangs from the ceiling by a string, with the net fanning out from a ring at the top and tucked tightly under the mattress on all sides. The rectangular type ties to the ceiling with four strings and hangs straight down on all sides of the bed, with the fringes again tucked under the mattress. Whichever type you choose it should be wide enough not to touch the body while sleeping.
The mesh size should be large enough for air circulation but as small as possible to keep out the mosquitos. For effective malaria protection, the mesh size that is recommended is 120-200 holes per square per inch. This will not keep out some types of sand flies, however, which can also transmit diseases to humans.
‘Noseeum’ netting is a lot finer at 500-600 holes per square inch, but the airflow is greatly restricted which can be stifling. Spraying or soaking mosquito netting in Permethrin or Deltamethrin dramatically increases effectiveness (see above). Store the net in a plastic bag to keep the permethrin effective longer.
Finally, make sure there are no gaps or holes in the netting around you and that there are no mosquitoes already inside the netting before you get inside or got to sleep.
Mosquito head nets may also be useful. Head nets alone are not enough in malarial areas, though.
Other preventative measures
Mosquitoes can bite any time. However, the peak hours of mosquito biting activity are usually at dawn and dusk, so try to reduce the amount of time you spend outdoors at these times.
You can use insecticides in the form of aerosols, vaporizers, candles, smoke spirals or others in living and, most of all, in sleeping areas. Close all doors and windows and spray the walls.
Mosquito coils are spiral-shaped candles that repel mosquitoes and other bugs with the natural chemical pyrethrum. They burn for several hours, and are useful when cooking dinner while camping, or in hotel rooms without screening.
Citronella (in the form of candles, soaps, sprays, etc.), is a natural repellent, useful in backyards in the USA but is not effective in serious biting insect areas.
Avoid wearing perfumes and aftershaves, which attract some mosquitoes. Also, for the same reason, don’t use scented soaps, shampoos, or deodorants. Unscented deodorants are available.
Mosquitoes do not attack as long as you walk quickly or if there is a breeze as they need to land on you to bite. While many hotels in the tropics lack screens, they often have fans which produce enough breeze to prevent mosquitoes from landing as long as the power holds out.
Stay in mosquito-protected rooms after twilight and at night, that is in rooms with air-conditioning or mosquito nets attached to windows and doors and those with fans.
For tours in the country, or if camping out, carefully select sites for sleep. Try to keep away from stale waters, ditches and water barrels. Also try to avoid traveling in high-risk areas during the rainy season.
