Prophylaxis against malaria. Preventing mosquito bites is also effective.

Editor—Berger’s list of measures for protecting travellers against malaria is extremely useful.1 The particular emphasis on compliance with drug regimens should not, however, detract from the importance of strict adherence to effective measures for preventing contact with mosquitoes and bites. No drug is totally effective, and in areas of low transmission the risk of adverse events attributed to chemoprophylaxis may well exceed the benefit of avoided infections.2 Although the World Health Organisation advocates protection against mosquito bites as the first line of defence against malaria, the basis for this recommendation has until recently been questionable.3 Evidence for a protective effect of insect repellants applied to the skin, air conditioners, fans, coils, vaporising mats, and long sleeved clothing has been largely speculative; use of these measures has been shown to result in decreased feeding by mosquito vectors, but direct evidence of a protective effect against malaria infection has not been gathered. Use of personal protection measures may have been compromised by widely publicised reports of encephalopathic reactions in children associated with the most widely used insect repellant, diethyltoluamide (DEET), and the nonchalance of many travellers. This is exemplified by the results of a postal survey of visitors to the Kruger National Park, South Africa, during the seasonal high risk period. Over 95% (7034/7387) of tourists provided responses to the section investigating use of personal protection measures. Altogether 912 (13%) of these travellers used no personal protection measures and only 1209 (17.1%) used four or more. Neglect of these measures was positively associated with non-use of chemoprophylaxis, with 17.3% of tourists who were not taking chemoprophylaxis neglecting to use personal protection measures compared with 11.9% of those who were (χ2=28.24, df=1; or Fisher’s exact P<0.001). The most commonly used personal protection measures were insect repellants applied to the skin (by 5525 people), long sleeved clothing (by 2815), socks and shoes (by 2374), coils (by 1651), and vaporising mats (by 1076). Specific effective protection measures were little used, particularly aerosolised insecticides, usually synthetic pyrethroids, administered by spraying under pressure by a handled canister, much like a large deodorant can (by 548), bed nets (by 49) and impregnation of clothing with insecticide (by 12). Some travellers relied on ineffective measures, including ultrasonic buzzers (12 people), alcohol consumption (9), and ingestion of garlic (4). Two recent papers are enlightening. A review of the toxicity of diethyltoluamide showed only two case reports of systemic toxicity after topical application in adults and 13 of encephalopathic toxicity in children despite 40 years of extensive use.4 A questionnaire survey of over 100 000 European tourists to east Africa found that air conditioned rooms (χ2=4.01, P=0.05) and clothing that covered arms and legs (χ2=5.25, P=0.02) effectively reduced the risk of malaria.5 Regular use of all or some of the four most important personal protection measures (air conditioned room and/or bed net, adequate clothing, insecticides and/or coils, repellants) reduced the risk of malaria to about half compared with that of other travellers using no such precautions (χ2=8.47, P=0.04). Geographic knowledge of the distribution, drug resistance, and prevalence of malaria should be used to determine the type and necessity of chemoprophylaxis. Travellers should also be aware of the best personal protection measures against mosquito bites.