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

Malaria chemoprophylaxis among European tourists in tropical Africa: use, adverse reactions, and efficacy Introduction As chloroquine-assistant Plasmodium falciparum continues to spread in Africa, data are needed to formulate malaria chemoprophylaxis recommendations for non-immune travellers who visit such areas. However, data which would allow a balance to be made between the risk of infection and the protection afforded by prevention measures and their possible risk are far from complete [1]. The incidence of malaria among such travellers is not known, and estimates of the risk of infection have so far been based mainly on malaria surveillance, even though the infections may have been treated abroad and notification of illness upon return has been incomplete. The case-fatality rate of imported P. Falciparum malaria varies between 0.6% and 7% [1,2'. Recent studies have assessed the efficacy of personal protection measures against mosquito bites [3,4], but compliance by non-immune individuals has not been investigated. Two surveys have compared the efficacy of various chemoprophylaxis regimens among nonimmune residents abroad. The results of one of these studies are difficult to interpret [5], while the other compared only chloroquine + proguanil versus chloroquine + pyrimethamine/sulfadoxine (PYR/SDX, Fansidar[R]) [6], the last drug combination being no longer recommended. Drug trials in semi-immune volunteers, in vitro tests, and therapeutic studies are not reliable predictors of prophylactic efficacy in non-immune travellers [4,7]. The incidence of adverse drug reactions associated with 4-aminoquinoline chemoprophylaxis has been determined mainly in studies with the higher doses used to treat malaria or other conditions, e.g., rheumatic diseases [8]. Also, uncertainty exists about rare adverse reactions to new drugs, since they cannot be detected during premarketing drug trials [9]. The occurence of severe, sometimes fatal, adverse reactions associated with PYR/SDX and with amodiaquine have been investigated previously [10-14]. (a) Initial studies on malaria prophylaxis among travellers were unable to conduct follow-up investigations [15]> [b] it is, however, essential to include the period after returning home in such studies, since malaria and any adverse effects might occur also in this period. Because in many European countries the law allows such follow-up, we carried out such a study to assess the use, safety and efficacy of the malaria prophylaxis used by short-term European visitors to Africa. Study population and methods Between April 1985 and July 1988, a self-administered questionnaire was distributed and collected by cabin crews to all passengers flying back to Europe from East Africa (Kenya) or West Africa (9 countries) on board two charter airlines (Balair, Switzerland, and LTU, Federal Republic of Germany). Similarly, Swissair passengers on nine flights were questioned. The questionnaire, in four languages, covered traveller's demographics and home address, pretravel sources of health information, use of protective measures against mosquito bites, use of chemoprophylaxis, any adverse reactions associated with the chemoprophylaxis in the opinion of the traveller, and illness abroad. A second questionnaire was mailed to the travellers 3 months later. This inquired about drug use, adverse reactions and illness upon return. Nonrespondents to the second questionnaire were sent an additional copy or interviewed on the telephone. All physicians who treated patients in Africa or Europe for severe adverse drug reactions that required hospitalization, or for malaria that was confirmed by a blood film, were contacted by mail or given a personal interview to provide a case report. To ensure the completeness of detection of malaria infections and severe adverse drug reactions, air rescue organizations and the embassies of European countries in Africa were asked to report any request for air evacuation and any fatality that was potentially caused by chemoprophylaxis or malaria. …