Figure 4

Peak of parasite prevalence shifts to adolescence. Parasite prevalence assessed by A) PCR or B) slide microscopy is shown, stratified by age group, showing a significant linear increase from 0-15 years (p < 0.0001 [PCR]; p = 0.003 [slide]). In B) geometric mean parasite densities are added for each age group, showing a significant decline from 0-15 years p < 0.0001), remaining stable thereafter (p = 0.3). Plot C) shows age-stratified parasite prevalence as determined in October 1988 [38] from a village in the Farafenni area. D) Corresponding data from the Farafenni area (villages "D" "L" "S" and "W") from the survey in January 2008 (described in this paper) are shown. Bars show percentages with 95% CI.