Sensitivity of Plasmodium falciparum in vivo to chloroquine and pyrimethamine-sulfadoxine in Rwandan patients in a refugee camp in Zaire

Abstract

Resistance of Plasmodium falciparum to available antimalarial drugs is now thought to be spreading progressively throughout sub-Saharan Africa. In this study we measured the susceptibility of P. falciparum to chloroquine and pyrimethamine-sulfadoxine in vivo in Rwandan patients living in Kibumba refugee camp in Goma, Zaire. Of the 39 cases treated with chloroquine, only 8 (20·5%) showed sensitive or RI (delayed) response and 31 (79.5%) demonstrated resistance at RI (30.8%), RII (33.3%) and RIII (15.4%) levels. Of the 38 individuals receiving pyrimethamine-sulfadoxine, 13 (34.2%) showed sensitive or RI (delayed) responses, and 25 (65.8%) showed resistance at RI (26.3%), RII (36.8%) and RIII (2.6%) levels. Both chloroquine and pyrimethamine-sulfadoxine reduced parasite counts by at least 75% in the majority of the patients within 2 d of treatment. A greater proportion of children with malnutrition showed a higher mean geometric parasite density and slower parasite clearance in vivo than those without malnutrition. Moreover, the frequency and degree of resistance were more pronounced in children with malnutrition. The results suggest the existence of resistance to chloroquine and pyrimethamine-sulfadoxine. However, the drugs are still effective in significantly reducing parasitaemias and they can still be used as drugs of first and second choice in the region, even in the face of some degree of resistance.