School-based screening and treatment may reduce P. falciparum transmission

Abstract

In areas where malaria remains entrenched, novel transmission-reducing interventions are essential for malaria elimination. We report the impact screening-and-treatment of asymptomatic Malawian schoolchildren (n = 364 in the rainy season and 341 in the dry season) had on gametocyte-the parasite stage responsible for human-to-mosquito transmission-carriage. We used concomitant household-based surveys to predict the potential reduction in transmission in the surrounding community. Among 253 students with P. falciparum infections at screening, 179 (71%) had infections containing gametocytes detected by Pfs25 qRT-PCR. 84% of gametocyte-containing infections were detected by malaria rapid diagnostic test. While the gametocyte prevalence remained constant in untreated children, treatment with artemether-lumefantrine reduced the gametocyte prevalence (p < 0.0001) from 51.8 to 9.7% and geometric mean gametocyte density (p = 0.008) from 0.52 to 0.05 gametocytes/microliter. In community surveys, 46% of all gametocyte-containing infections were in school-age children, who comprised only 35% of the population. Based on these estimates six weeks after the intervention, the gametocyte burden in the community could be reduced by 25-55% depending on the season and the measure used to characterize gametocyte carriage. Thus, school-based interventions to treat asymptomatic infections may be a high-yield approach to not only improve the health of schoolchildren, but also decrease malaria transmission.

Figure 1

Baseline weighted proportion of students with P. falciparum infection detected by PCR (×) and the weighted proportion of students with gametocyte-containing infections detected (black bar) and not detected (grey bar) by rapid diagnostic test in school-based cohorts.

Figure 2

Impact of treating RDT positive students on the proportion and density of gametocytes in the school-based cohort over time. Proportion of students with gametocytes in all schools combined (a) and by school in the rainy (c) and the dry (d) season. Mean gametocyte density (logarithm transformed) among students in all schools (b) and by school in the rainy (e) and the dry (f) season. Solid lines represent students who received treatment; Dashed lines represent students who did not receive treatment. Color designates season in a and b rainy (black) and dry (gray). Color designates school in c-f Bvumbwe (yellow), Ngowe (red), Maseya (blue), Makhuwira (green). Both estimates were obtained in random effects longitudinal analysis (full models in Supplemental Tables S3 and S4).

Figure 3

Predicted impact of school-based treatment of RDT positive students on the population of gametocytes in the surrounding community. Following school-based screening-and-treatment at baseline, the estimated impact on gametocyte prevalence (a in rainy and b in dry seasons), total gametocyte burden (c in rainy and d in dry seasons), and number of infections containing ≥ 10 gametocytes/µl (e in rainy and f in dry seasons) in the communities surrounding the schools are predicted at one, two, and six weeks after the intervention. Color indicates the proportion of the gametocyte measure by age group: school-age children (6-15y)—black; younger children (6 m-5y)—light grey; adults (> 15y)—dark grey. Total gametocyte burden is the sum of gametocyte densities in individuals in each age group. These calculations assume treatment is not provided to young children, adults, or school-age children who test negative by RDT when the intervention is implemented. Reduction is calculated as the proportional difference between the baseline and six-weeks post intervention.