Updated October 2010

Insect and Tick Bite Avoidance

• Introduction
• Personal protection measures during travel

• Measures that cannot be recommended for repelling insects

• Treatment of insect/tick bites

• Links

• Reading list

Introduction 

Many tropical diseases are transmitted by biting arthropods (e.g. mosquitoes, flies, lice and ticks) such as dengue, Japanese encephalitis, leishmaniasis, malaria, yellow fever, rickettsia, Lyme disease, and Crimean Congo Haemorrhagic Fever. In many instances (e.g. dengue, onchocerciasis, leishmaniasis and rickettsia), bite avoidance is the only means of prevention.

Mosquitoes

Mosquitoes are attracted by several factors, including the presence of carbon dioxide, heat, odours and movement. It is the female mosquito that feeds on humans, as she requires a blood meal for her larvae to develop. There are many mosquito species; some species bite during daylight hours (e.g. Aedes spp.), and some are more active from dusk to dawn (e.g. Anopheles spp.).

Flies

Black flies, the vectors of onchocerciasis, bite during daylight hours and live close to fast-flowing water.

Sand flies, the vectors of leishmaniasis, are found in many areas of the world and are most active between dusk and dawn. They will bite during daylight hours if disturbed. They usually feed close to the ground.

Tsetse flies transmit African trypanosomiasis and inhabit the dense vegetation and savannah areas in sub-Saharan Africa. They are attracted to dark, contrasting colours, particularly the colour blue, and to moving objects such as cars, canoes, animals and people.

Ticks

Ticks typically live in long grassy areas. Their usual hosts are small mammals. On humans, ticks crawl on skin or clothing until they find a suitable place to attach, often at a skin fold in the groin, under the arm, at the scalp line, or at the edge of underclothes. Tick-borne diseases, such as tick-borne encephalitis, are transmitted during the feeding process.

Personal protection measures during travel

Behaviour

•  Be aware of the risk.

•  Try to avoid highly infested areas.

Clothing

•  When travelling in areas with malaria it is advisable to wear loose-fitting garments, and long trousers and long sleeves in the evenings.

•  When in tick-infested areas, trousers should be tucked into socks to prevent ticks from crawling up the legs.

•  Clothing can be treated with an insecticide, often permethrin, which kills insects on contact, including ticks. Permethrin is available in formulations designed to be sprayed on to clothing.

•  Avoid dark blue clothing when travelling in Africa in areas where tsetse flies exist.

Insect repellent: General information

•  N, N-diethylmetatoluamide (DEET) based repellents are the most effective [1]; they have been widely tested under field conditions, and have more than 50 years of use. DEET is available in several concentrations. Concentrations of 20% have been shown to offer protection for 1-3 hours, and higher concentrations provide longer-lasting protection [2]. As the duration of protection plateaus at concentrations higher than 50% [3], there is no need to use repellents with concentrations greater than 50%.

•  DEET-containing preparations should not be used in babies younger than 2 months of age. They may be used in concentrations up to 50% in pregnant or breast-feeding women, and in infants and children older than 2 months. Manufacturers in the UK have applied their own age restrictions, however, there is no evidence that using DEET on infants and children older than 2 months causes harm. Care should be taken to ensure that repellents are not ingested, and that they do not come into contact with the eyes or mouth.

•  Repellents should be reapplied at regular intervals, after swimming and in hot, humid conditions when they may be removed by perspiration. When both sunscreens and repellents are used, the repellent should be applied over sunscreen [4].

•  Research and extensive clinical experience indicate that DEET is very safe when used according to the manufacturer’s instructions.

Insect repellent: Advice for travellers

•  Use only on exposed areas of skin.

•  Remove with soap and water when the repellent is no longer needed.

•  Do not spray directly on the face, and wash hands after application to avoid contact with lips and eyes.

•  Do not apply to cuts, abrasions or irritated skin.

•  Sunscreen that is combined with repellent should usually be avoided.

•  Picaridin (Autan®) and lemon eucalyptus extract (Mosiguard®) are available for those who prefer not to use DEET-based products [5, 6]. These repellents have compared favourably with DEET [1]. Icaridin should be used in concentrations of approximately 20%.

•  Follow manufacturer’s instructions when applying repellents to babies and infants.

•  Many travel clinics, pharmacies, camping and outdoor shops stock a range of insect repellents and insecticides for purchase. 

Screening and mosquito nets 

Travellers staying in accommodation without screening should sleep under a net to avoid being bitten at night.

Mesh size in mosquito bed nets should be no larger than 1.5 mm.

Nets should be impregnated with permethrin (or other contact insecticide); most nets have been treated prior to purchase. Nets may need to be impregnated with permethrin again after six months of use; long-lasting insecticide nets will generally not need treating throughout their lifetime, e.g. Olyset® Net [7].

Contact insecticides will kill insects landing on the net and therefore increase the effectiveness.

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

Many travel clinics, pharmacies, camping and outdoor shops stock a range of mosquito nets.

Other preventative measures

Knock down sprays that are designed to kill flying insects are not likely to provide sufficient protection from either nuisance biting or malaria to be recommended [1].

A systemic review demonstrated that mosquito coils can decrease bites by repelling and killing mosquitoes [8]. Coils, which contain synthetic insecticide, should only be used in well-ventilated areas and may be useful for campers. A small piece of the coil lit under the table can be a deterrent when dining at outdoor restaurants.

Measures that cannot be recommended for repelling insects 

These measures are either less effective or ineffective, and not recommended:

•  Bath oil

•  Citronella oil-based repellents (these have very short durations of action)

•  Citrosa plant (geranium)

•  Garlic: fresh or capsules

•  Vitamin B12 complex

•  Yeast extract spread

•  Electronic (ultrasonic) buzzer devices

•  Vitamin B1 tablets

•  Tea tree oil

Treatment of insect/tick bites

Arthropod bites usually appear as small, red, raised papules that itch. Local swelling can be reduced by the topical application of a mild steroid cream. Antihistamine tablets can be taken to relieve itching. Mosquito bites should not be scratched and should be kept clean and dry to avoid infection.

Ticks need to be removed from the skin very carefully. This can be done with tweezers or specially designed tick removers. Grasp the tick near to the skin and steadily pull out the tick being careful not to crush the tick’s body or squeeze the stomach contents into the site of the bite. Illustrated instructions on this can be found on the Centers for Disease Control and Prevention Division of Vector-Borne Infectious Diseases website.

References

1. Goodyer LI, Croft AM, Frances SP, et al. Expert review of the evidence base for arthropod bite avoidance. J Trav Med. 17:182-92, 2010.

2. Medical Letter. Prevention of malaria. Med Lett Drug Ther 2005;1223:100, 2005. Available at: http://secure.medicalletter.org/w1223c

3. Koren G, Matsui D, Bailey B. DEET-based insect repellents: safety implications for children and pregnant and lactating women. Can Med Assoc J 169:209-12, 2003. Available at: www.cmaj.ca/cgi/content/full/169/3/209

4. Murphy ME, Montemarano AD, Debboun M, Gupta R. The effect of sunscreen on the efficacy of insect repellent: a clinical trial. J Am Acad Dermatol 43:219-22, 2000.

5. Costantini C, Badolo A, Ilboudo-Sanogo E. Field evaluation of the efficacy and persistence of insect repellents DEET, IR3535, and KBR 3023 against Anopheles gambiae complex and other Afrotropical vector mosquitoes. Trans R Soc Trop Med Hyg 98:644-52, 2004.

6. Medical Letter. Picaridin - A new insect repellent. Med Lett Drugs Ther 47:46-7, 2005.

7.  World Health Organization Pesticide Evaluation Scheme. Report of the thirteenth WHOPES working group meeting. 28-30 July 2009. [Accessed 22 October 2010]. Available at: http://whqlibdoc.who.int/publications/2009/9789241

598712_eng.pdf

8. Lawrence CE & Croft AM. Do mosquito coils prevent malaria? A systemic review of trials. J Travel Med. 11:92-6, 2004.

 Reading list

•  Chen LH, Wilson ME, Schlagenhauf P. Prevention of malaria in long-term travelers. JAMA 296:2234-44, 2006.

•  Chiodini P, Hill D, Lalloo D, et al.  Guidelines for malaria prevention in travellers from the United Kingdom.  2007, London: Health Protection Agency.

•  Fradin MS. Day JF. Comparative efficacy of insect repellents against mosquito bites. N Engl J Med. 347:13-8, 2002.

•  Goodyer L. Travel Medicine (6) Bite Avoidance. Pharmaceu J 265:298-304, 2000.

•  Health Canada Information: Safety Tips on Using Personal Insect Repellents. Available at: www.pmra-arla.gc.ca/english/consum/insectrepellents-e.html