Malaria parasites were detected and counted by microscopy following Giemsa staining of thick and thin blood films [15] . Malaria Parasite (MP) densities were calculated as follows MP/ Table 1) . The microscopic criterion for declaring a participant to be free of malaria was the absence of parasites in 100 high-power (1000X) fields. One in 10 thick blood films were randomly selected and independently reviewed by local experienced microscopists not part of the research team.