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.