Return of widespread chloroquine-sensitive Plasmodium falciparum to Malawi.

BACKGROUND The return of chloroquine-sensitive Plasmodium falciparum to the limited area of Blantyre, Malawi, has been well demonstrated in several studies. METHODS To characterize chloroquine susceptibility over a wide geographic area, infants and children aged 6-59 months were selected using 2-stage cluster sampling in 8 Malawian districts. Pyrosequencing of the pfcrt gene codon 76 region was performed for children with asexual parasitemia. RESULTS Of 7145 children, 1150 had microscopic asexual parasitemia, and sequencing was performed in 685, of whom 1 had a chloroquine-resistant genotype. CONCLUSIONS Systematic countrywide sampling demonstrates that the chloroquine pfcrt genotype has reached near-fixation, raising the possibility of reintroducing chloroquine for malaria prevention and treatment.