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Avoiding Insect Bites

Biting insects e.g. ticks, mosquitos, can carry diseases such as malaria, dengue fever etc. Some insects bite during the day, others in the evening . Insects may bite indoors or outdoors. Avoiding bites is your main protection from disease, and is often your only protection e.g. Dengue fever.

Insect Behaviour

Insect	Habitat	Behaviour
Mosquitoes	Mosquitoes breed in stagnant water	Attracted by carbon dioxide, lactic acid, body heat, odours and movement.
Ticks	Long grassy areas	Attach themselves to the clothing of a human as they brush past. They crawl up the clothing until they find an area of exposed skin.
Sand flies	Worldwide	Most active between dusk and dawn but will, however, bite during daylight hours if disturbed.
Tsetse flies	Dense vegetation & savannah areas	Attracted to dark, contrasting colours, particularly the colour blue. Are less affected by repellents

 

Insect Repellent

Insect repellent, applied directly to exposed skin, should be used at all times in areas of risk. Repellents should be applied over sunscreens. Always follow the manufacturer's instructions for use to minimise the risk of adverse skin reactions.

The effectiveness of repellents varies (15 mins - 12 hours) depending on: type of repellent, local conditions (e.g. humidity), individual susceptibility, loss due to sweating, sensitivity of the insects to repellents. Insects will always choose to bite someone without repellent over someone with repellent.

Depending on where your location and the activities undertaken e.g. field work, trekking etc., you may also want to consider using:

• Barrier methods e.g. clothing, nets
• Insecticides

Barrier methods

Clothing

• Reduce the amount of exposed skin: wear long trousers and long sleeves especially in the evenings when malarial mosquitoes are most active. Wear light colours; mosquitoes are attracted to dark colours
• Tuck trousers into socks to prevent ticks, etc crawling up your legs.
• Wear loose fitting tight weave/knit clothes: mosquitoes and tsetse flies can bite through tight and/or loose weave clothing
• Clothing can be treated with insect repellant or insecticides (eg permethrin); particularly useful for avoiding tick bites.

Mosquito nets

• Sleep under a mosquito net to avoid being bitten at night, particularly if staying in basic accommodation or sleeping outdoors.
• Nets should have a mesh size of 1.2 - 1.5 mm; the smaller sizes can protect against smaller insects e.g. biting midges, but poor ventilation is a serious disadvantage. If the mesh size is more than 2 mm most mosquitos can enter!
• Improve effectiveness of the net by impregnating it with permethrin to kill landing insects; particularly useful for sandflies which fit through most nets.
• Nets should cover you completely, be spacious enough to avoid contact with the fabric, and long enough to be tucked in under the mattress or sleeping mat.

Tip: carry a small sewing kit so that minor repairs can be made if the net develops a hole.

Insecticides

Insecticides irrritate or kill insects before they manage to feed. Permethrin (a pyrethroid) is the insecticide of choice as it doesn't degrade in sunlight so is particularly suitable for ouutdoor use. Always follow the manufacturer's instructions for use to gain maximum effect.

Insecticide vaporisers have deterrent, irritant-repellent, and insecticidal effects.

• Sprays are a good way of ridding enclosed areas of insects e.g. bedrooms vehicles etc.; rapidly knocking down or killing insects
• Mosquito coils, which produce a repellent smoke, are easy to use, effective and inexpensive. Coils should only be used in well-ventilated areas and can be useful for campers. A small piece of the coil lit under the table can be a useful deterrent when dining at outdoor restaurants.
• Vaporizing mats need an electricity source and some mats lose effect towards the end of their "burn" time. Liquid vaporisers are better than mats as the amount of insecticide released remains constant over time.

Treatment of Insect Bites

Reduce swelling with by skin application of a mild anti-inflammatory cream or gel. Antihistamine tablets can be taken to relieve itching. Try to avoid scratching and keep the wound clean and dry to avoid the risk of infection.

Tick / Sting Removal

Ticks - using tweezers or specially designed tick removers grasp the tick near to the skin and pull whilst twisting it slightly. It is important that the whole tick is removed without leaving any mouth parts embedded in the skin.

Stings - Place the edge of a dull table knife firmly against your skin next to the embedded stinger. Applying constant firm pressure, scrape the knife across your skin surface and the stinger. This removes the stinger without injecting more venom, which is what happens when you remove the stinger with tweezers or your fingers.

OHS September 2005

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