Carriage of chloroquine-resistant parasites and delay of effective treatment increase the risk of severe malaria in Gambian children.

Two hundred thirty-four Gambian children with severe falciparum malaria who were admitted to the pediatric ward of a rural district hospital each were matched for age with a same-sex control subject presenting as an outpatient with uncomplicated falciparum malaria. Severe malarial anemia (SMA) was the most common presentation (152 cases), followed by cerebral malaria (38 cases) and hyperparasitemia (26 cases). Children presenting with SMA were significantly younger and more likely to carry gametocytes than were children with other severe presentations. Alleles of the genes pfcrt and pfmdr1 associated with chloroquine-resistant parasites occurred together among cases presenting with SMA alone more often than among their matched controls (odds ratio, 2.08 [95% confidence interval, 1.04-4.38]; P=.039). Costs of travel to the hospital of more than US $0.20, use of mosquito repellents, and carriage of resistant parasites were identified as independent risk factors for severe malaria in the case-control analysis. We conclude that, in this setting, poor access to the hospital and a high prevalence of chloroquine-resistant parasites lead to a delay of adequate treatment for young children with malaria, who may then develop SMA.