Malaria asymptomatic carriage in the Sahelian region: The challenge associated to young adults

Abstract Background Mali and Senegal have made important efforts to control malaria. After a period of decline, the number of cases has remained stable for several years. Asymptomatic carriage acting as a reservoir could explain malaria persistence despite malaria control. Mass drug administration (MDA) is a candidate intervention that could help to accelerate the decreasing of malaria transmission if favourable epidemiologic context and good adherence are met. We aimed to update asymptomatic reservoir description along a Sahelian ecological gradient and study MDA acceptability. Methods We conducted an open cohort in 8 villages in Mali and Senegal including all household members sampled aged >6 months. We measured P. falciparum infections prevalence by qPCR in 4 surveys: 2 in dry season 2021, 1 in rainy season 2021 and 1 in dry season 2022. We measured prospective acceptability of MDA in cohort aged ≥15 years in Senegal by questionnaire. We explored risk factors associated to asymptomatic infections and acceptability score with multilevel logistic and linear models. Results We included 168 households and 1428 participants in at least 1 survey. In preliminary results, prevalence of P. falciparum infections was 11% in dry season 2021 in Senegal, 20% in central Mali and 60% in Northern Mali. Young adults between 15 to 24 years old were more likely to carry asymptomatic infections in dry season compared to children <5 years old (OR = 5.74 [2.99;11.04]). MDA presented a good acceptability with a mean score of 3.5 (score between -7 and 7). Young adults had lower acceptability compared to older participants (β=−1.07 [-1.82,-0.32]). Conclusions Young adults were important asymptomatic carriers in Senegal and Mali but were less likely to accept to participate in MDA. Key messages • Young adults represent a public health challenge that need to be address to reach malaria elimination. • Specific sensibilization could be implement to improve adherence to malaria control interventions.