Falciparum malaria, imported into The Netherlands, 1979-1988. I. Epidemiological aspects.

From 1979-1988, 427 patients with falciparum malaria were prospectively investigated for chloroquine resistance. About 90% were infected in sub-Saharan Africa. Of the 361 non-immune patients 235 were evaluable; in 158 (67%) chloroquine resistance of Plasmodium falciparum could be confirmed. Chloroquine sensitivity was found in 77 (32%) patients. Sulfadoxine-pyrimethamine resistance was found in 33 patients. The history of use of chemoprophylaxis was recorded in 357 patients: 168 (49%) took adequate, 103 inadequate and 86 no chemoprophylaxis. In 65 of the 168 patients with a history of good compliance, prophylactic serum concentrations could be measured; in 56 (86%) patients the history was confirmed by the chloroquine level. All but one of them were infected with a resistant P. falciparum strain. Of the 66 semi-immune patients, 60 were infected in their homeland; in 5 (8%) chloroquine resistance was found. Only 1 of the 60 patients had used adequate chemoprophylaxis and proved to be infected with a resistant P. falciparum strain. During the study the spread of drug resistance from East Africa to other parts of Africa could be observed. Monitoring for drug-resistant falciparum malaria in travellers returning from malaria-endemic areas is a helpful tool in predicting the evolution of drug resistance in that area. In the non-endemic area such monitoring is essential for optimal advice on treatment of patients and of chemoprophylaxis in travellers.