Widespread in vitro resistance to chloroquine of Plasmodium falciparum in the Congo, 1987.

The drug sensitivity of 184 Plasmodium falciparum isolates was studied in vitro in three areas of the Congo in January 1987. Results show that parasites resistant to chloroquine but not to quinine or mefloquine were prevalent in the three investigated regions, but the drug response pattern varied widely. In Brazzaville, after the outburst of chloroquine resistance in 1985, prevalence of chloroquine resistant isolates seemed to have stabilized around 60%. The phenomenon more recently reached the North where about 30% isolates could be considered as drug resistant. As in Cameroon, wide variations in the prevalence and the level of resistance were observed within a very limited area emphasizing the role of drug pressure in market places where chloroquine is easily available.