Impact of school-based malaria screening and treatment on P. falciparum infection and anemia prevalence in two transmission settings in Malawi

Background: In areas highly endemic for malaria, Plasmodium falciparum (Pf) infection prevalence peaks in school-age children, adversely affecting their health and education. School-based intermittent preventive treatment reduces this burden, however concerns about cost and widespread use of antimalarial drugs have limited enthusiasm for this approach. School-based screening-and-treatment is an attractive alternative. We conducted a school-based cohort study to evaluate the impact of screening-and-treatment on the prevalence of Pf infection and anemia in two different transmission settings. Methods: We screened 704 students in four Malawian primary schools for Pf infection using rapid diagnostic tests (RDTs). Those testing positive were treated with artemether-lumefantrine. Outcomes were Pf infections detected by microscopy or PCR and anemia after six weeks. Results: Prevalence of infection by RDT at screening was 37% (range among schools 9-64%). We detected a significant reduction after six weeks in infections by microscopy (adjusted relative reduction (aRR) 47.1%, p<0.0001) and PCR (aRR 23.1%, p<0.0001), but no reduction in anemia. In low, seasonal prevalence areas, sub-patent infections at screening led to persistent infection, but not disease, during follow-up. In high transmission settings, new infections frequently occurred within six weeks after treatment. Conclusions: School-based screening-and-treatment reduced Pf infection but not anemia. This approach could be enhanced in low transmission settings by using more sensitive screening tests and in high transmission settings by repeating the intervention or using longer acting drugs.