Objectives: We investigated the diversity and dynamics of Plasmodium infection in serially collected samples from asymptomatic participants of a clinical trial assessing the efficacy and safety of ivermectin in Gabon. We checked whether the baseline sample reflected the P. falciparum genotype and Plasmodium species diversity seen over 7 days of follow-up.
Methods: Blood samples were collected at inclusion, every 8 hours until hour 72, daily until day 7, and on day 14. Plasmodium species was determined by qPCR and pfmsp1 length polymorphism was assessed for P. falciparum genotyping.
Results: In 17/48 (35%) individuals, all pfmsp1 genotypes identified during the assessed period were detected at baseline; in 31/48 (65%), new genotypes were found during follow-up. Additional sampling at hour 24 allowed the identification of all genotypes seen over 7 days in 50% of the individuals. Ivermectin did not impact the genotype dynamics. Mixed Plasmodium spp. infections were detected in 28/49 (57%) individuals at baseline, and detection of non-falciparum infections during follow-up varied.
Conclusions: Our results reveal complex intra-host dynamics of P. falciparum genotypes and Plasmodium species and underscore the importance of serial sampling in clinical trials for antimalarial drugs with asymptomatically P. falciparum-infected individuals. This might allow a more accurate identification of genotypes in multiple infections, impacting the assessment of drug efficacy.
Keywords: Asymptomatic infection; Clinical trial; Parasite population dynamics; Plasmodium falciparum; msp1.
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