Mâncio Lima malaria cohort study 2018–2021: Prevalence surveys

Malaria is increasingly diagnosed in urban centers across the
Amazon Basin. In this study, we combined repeated prevalence
surveys over a 4-year period of a household-based random sample of 2,774
persons with parasite genotyping to investigate the epidemiology
of malaria in Mâncio Lima, the main urban transmission hotspot
in Amazonian Brazil. We found that most malarial
infections were asymptomatic and undetected by point-of-care
microscopy. Our findings indicate that as malaria transmission decreases,
the detection threshold of microscopy rises, resulting in more
missed infections despite similar parasite densities estimated by
molecular methods. We identified genetically highly diverse
populations of Plasmodium vivax and P. falciparum in the region;
occasional shared lineages between urban and rural residents suggest
cross-boundary propagation. The prevalence of low-density and asymptomatic
infections poses a significant challenge to routine surveillance and the
effectiveness of malaria control and elimination strategies in urbanized
areas with readily accessible laboratory facilities.