10-YEAR SURVEILLANCE OF DRUG-RESISTANT MALARIA IN BURKINA-FASO (1982-1991)

To understand the evolution of drug-resistant forms of malaria in time and in space, we carried out an analysis of the results of a series o f passive and active surveys conducted in Burkina Faso between 1982 an d 1991. A total of 607 tests for resistance to chloroquine and mefloqu ine were carried out in vitro and 3,679 tests for resistance to chloro quine, quinine, and sulfadoxine-pyrimethamine were performed in vivo. The surveys principally involved the two main cities of Burkina Faso, Ouagadougou and Bobo-Dioulasso. However, another 10 locations represen ting the three different zones of malaria transmission were also studi ed. The first cases of Plasmodium falciparum resistant to chloroquine in vitro were reported in 1983, but it was only in 1988 that in vivo r esistance appeared. The first cases of in vitro resistance to mefloqui ne were noted in 1987 while chloroquine sensitivity at a high rate (15 .8%), which decreased during the following years. The prevalence of re sistance to chloroquine increased in parallel to this decrease in sens itivity to an overall peak of 41% in vitro and 16% in vivo in 1990. Th ese rates then decreased to 3% and 6%, respectively, in 1991. This pat tern of decreasing resistance was broadly similar in all sites except for the town of Bobo-Dioulasso, where the level of resistance remained stable at approximately 14% from 1988 to 1991. Only two cases of resi stance in vivo to sulfadoxine-pyrimethamine were noted. In 1988, the y ear of the first appearance of in vivo chloroquine resistance, the hig hest prevalence was observed in towns situated along the main railway line linking the capitals of Cote d'Ivoire and Burkina Faso, suggestin g a spread of the resistance by the travels of infected persons. Resis tance to chloroquine in vivo was at RI/RII levels. Since the rate of c linical resistance to chloroquine is only about 5%, chloroquine remain s the drug of choice for uncomplicated cases of malaria in Burkina Fas o.