Figure 2. IgG antibody frequencies and levels according to age groups.

IgG antibody frequencies in the total study population (n = 195) (a), and in the blood smear positive (PP; n = 80) and blood smear negative (PN; n = 115) populations (b). The number of individuals within each age group is shown in Table 1. # indicates significant differences between the PP and PN as assessed using the χ² test (#P<0.05, and ##P<0.01). Total IgG antibody responses (ROU) to the four antigens grouped according to age for the total population (n = 195) (c), blood smear positive (PP; n = 80) and negative (PN; n = 115) individuals (d). x indicates significant differences in antibody levels (ROU) between blood smear positive and negative groups using multiple comparison analysis in conjunction with ANOVA (x, P<0.05). * indicates a significant correlation between increases in antibody frequencies, levels and age (r = 0.322, P = 0.0001 and r = 0.413, P = 0.001 in (a, c) and (b, d) respectively).