Drug-resistant malaria: mechanisms of development and inferences for malaria control

It is estimated that 110 million clinical cases of malaria, and between one and two million deaths associated with Plasmodium ,falciparum, occur each year (WHO, 1990). Antimalarial drugs constitute a fundamental component of malaria control strategies. The operational use of antimalarial drugs has unfortunately been hampered by the development of drugresistant P. fulciparum malaria. Resistance to chloroquine has been documented in most countries with P. falciparum transmission over the last two decades and resistance to alternative antimalarials has followed in many countries (BJORKMAN & PHILLIPS-HOWARD, 1990). Many mechanisms have been postulated for the development of antimalarial drug resistance; for chloroquine resistance of P. fulciparum (CRPF) the suggested mechanisms include drug pressure, extensive use of subcurative doses, migration, and increased virulence of the resistant parasites. Recommendations for drug use have been inlluenced by supposition that drug pressure, in particular, increases the spread of drug resistance. However, whilst much emphasis has been placed on the monitoring of resistance to antimalarials, the direct impact of resistance on the control of malaria remains unclear. Given the paucity of literature on this subject, we suggest some of the kinds of important information necessary for the making of rational decisions on the deployment of antimalarial drugs in control programmes.