Patterns of patent and sub-patent Plasmodium falciparum infections in household members of children under seasonal malaria chemoprevention coverage in the health district of Nanoro, Burkina Faso.

Background: Seasonal Malaria Chemoprevention (SMC) has been adopted since 2014 in Burkina Faso to reduce malaria burden in children under 5 years. However, the intervention's expected potential has not yet been achieved in real-life conditions, suggesting other factors may influence its effectiveness. Asymptomatic carriers, including patent and sub-patent Plasmodium falciparum infections in household members seems to be a potential factor maintaining the high malaria burden in children under SMC coverage. This study assessed the patterns of these infections in household members living around children under SMC coverage in Nanoro, Burkina Faso.

Methods: A cross-sectional survey nested to a large SMC study named "SMC_RST" was conducted during the 2022 SMC campaign in Nanoro, including 745 participants. Sub-patent infections were defined as varATS qPCR-positive/RDT-negative, and patent infections as positive by both methods. Prevalence of patent and sub-patent malaria infections were presented with 95% confidence intervals (CI), accounting for clustering of individuals within households. Multinomial regression with robust standard errors assessed the effect of age, sex, and locations on risk of malaria infection.

Results: Out of 745 participants, diagnostic results regarding malaria status were available for 650 (87.2%). Plasmodium falciparum infections in household members were detected in 68.6% (446/650, 95% CI: 64.7-72.5), including 27.4% (178/650, 95% CI: 23.9-30.8) patent and 41.2% (268/650, 95% CI: 37.3-45.2) sub-patent infections. Patent infections declined with age: 37.7%, (95% CI: 31.9-43.5) among 5-14 years, 25% (95% CI: 17.0-33.0) among 15-24 years, and 17.1% (95% CI: 12.6-21.5) among ≥ 25 years. Prevalence of sub-patent infection was 38.0% (95% CI: 32.4-43.7) among 5-14 years, 49.2% (95% CI:40.3-58.1) among 15-24 years and 40.7% (95% CI: 34.5-46.8) among ≥ 25 years. No significant difference across villages was observed in terms of prevalence of household members with patent (χ² = 4.16, P-value = 0.38) or sub-patent infections (χ² = 3.92, P-value = 0.41).

Conclusion: Over two-thirds of the household members living with children under SMC coverage area in Nanoro, Burkina Faso, harboured patent and sub-patent P. falciparum infection. Among those aged 15 years and older, asymptomatic carriage was largely sub-patent. This study supports the extension of the SMC intervention to school-aged children and the implementation of interventions such as testing and treatment of household members of children under SMC coverage.