Evolution of chloroquine resistance in central and west Africa.

The evolution of in vitro chloroquine susceptibility of clinical isolates of Plasmodium falciparum obtained from travellers returning to France was studied between 1986 and 1991 using the isotopic semi-microtest. Based on the analysis of 1,147 interpretable tests on isolates originating from Central and West Africa, the study showed that the proportion of chloroquine-resistant falciparum malaria remained stable between 1986 and 1988 and has diminished between 1989 and 1991. The diminution of chloroquine-resistant imported malaria may be associated, at least in part, with a better compliance of French travellers with the recommendation to use either mefloquine or a combination of chloroquine and proguanil since 1989 and an increasing proportion of African immigrants who tend to neglect regular chemoprophylaxis during the visit to their countries. The reason for the stabilisation of chloroquine resistance is unknown, and this phenomenon may be temporary, necessitating a continuous surveillance of drug susceptibility.