Malaria chemoprophylaxis among European tourists in tropical Africa: use, adverse reactions, and efficacy.

In order to determine knowledge, attitudes and practices towards malaria prophylaxis, as well as its side-effects and efficacy, a self-administered questionnaire was distributed to European travellers on return flights from tropical Africa to Europe. Between 1985 and 1988 the questionnaire was completed by 44,472 passengers (80.1% of those on board) on 242 flights. A follow-up questionnaire was completed by 42,202 (94.9%) of the same travellers 3 months later. Almost all knew about the risk of malaria, but 10% relied solely on advice from nonmedical sources. While 55.6% had taken at least one measure against mosquito bites, only 4.5% adopted three such measures (used repellents and insecticides and wore long clothing after dusk). Compliance with chemoprophylaxis use was reported by 57.0% of travellers who spent less than 3 months in Africa, compared with 29.2% who stayed 3-12 months. Depending on the antimalaria regimen taken, 11-44% of the travellers experienced adverse effects, while four deaths were attributed to the chemoprophylaxis. The incidence of malaria per month of exposure for travellers who took no chemoprophylaxis was 15.2 per 1000 in East Africa and 24.2 per 1000 in West Africa. In East Africa, the prophylactic efficacy of the currently recommended antimalaria regimens (relative to that of no chemoprophylaxis) was zero for a chloroquine dosage of 300 mg base per week (4 malaria fatalities), 64.1% for a chloroquine dosage of 600 mg base per week (P = 0.03), and 94.0% for mefloquine (P = 0.003).