The drug sensitivity of 246 Plasmodium falciparum isolates was studied in vitro in five areas of Cameroon at the end of 1985. Results demonstrate that parasites resistant either to chloroquine, quinine, or mefloquine, or to two of these drugs, were prevalent in four of the areas investigated, but the drug response pattern varies widely from one area to another.
The recent explosive emergence of chloroquine resistance in the south of the country, where both prevalences and levels are very high (up to 86%), contrasts with only moderate levels of resistance in the north. This may be related to differences in transmission by mosquitoes between Sahel and forest areas.
Quinine resistance was observed in 24% of the isolates studied in vitro and was frequently associated with chloroquine resistance.
The presence of isolates responding poorly to mefloquine, observed mainly in northern Cameroon, suggests that resistance may occur in areas where the drug has never been used.