Background P. falciparum parasite genotyping in longitudinal studies was described as a suitable manner for measuring outcomes of interventions and to estimate the force of the infection.

Methods This study was designed to compare the force and multiplicity of infection (FOI and MOI) in children on SMC (<5 years) or not (5 to 12 years) in Banfora, an area of intense malaria transmission in Burkina Faso. Both groups received supervised curative doses of artesunate (AS) or dihydroartemisinin-piperaquine (DHA-PQ) to eliminate existing parasites. Parasite DNA was extracted and then analyzed by nested PCR to detect and genotype P. falciparum parasites. Both active (biweekly sampling at home) and passive (sampling at health center visits) case detection were used to ensure that a high proportion of infections were captured.

Results A total of 458 PCR-detected P. falciparum positive samples were collected and 87.99% were positive for msp2 gene. There were no differences in MOI (p=0.80) and FOI (p=0.09) between the two DHA-PQ and AS treatment cohorts. The mean values of FOI and MOI were 2.00 [1.82–2.18] and 2.98 [2.83–3.14] respectively. In comparison, there was no statistically significant difference (p=0.92) between the mean values of the FOI of subjects on SMC (1.98 [1.57–2.39]) and those who were not (2.00 [1.82–2.21]). The same was true (p=0.75) between the MOI of subjects on SMC (3.03 [2.69–3.38]) and the other group (2.97 [2.79–3.15]). With a fever and parasitemia >5000 trophozoites/µL, the value of the polyclonality in passive detection was 57.69% [43.26–70.99] and the difference with that in active detection (2.28% [1.06–4.62]) was statistically significant (p<0.01).

Conclusion Both FOI and MOI were not age-dependent, despite current malaria control methods that target children under five years. This would suggest that the SMC did not provide specific protection on these children living in an area of very high transmission.