Pyrethroid resistance is quietly eroding the effectiveness of the bed nets and indoor spraying programs that protect hundreds of millions of people from malaria. Finding compounds that can block parasite transmission inside the mosquito itself—rather than just killing the insect—represents a fundamentally different strategic layer that could complement existing tools even as resistance spreads.
This laboratory study tested whether female Anopheles darlingi mosquitoes, the primary malaria vector in the Amazon basin, could absorb antimalarial compounds through their tarsi—the leg segments that contact treated surfaces—at a sufficient dose to eliminate Plasmodium vivax before or after the mosquito takes an infectious blood meal. Six compounds were evaluated at 1 mmol/m² on impregnated Petri dish surfaces. Atovaquone (ATQ), a mitochondrial electron transport inhibitor already used clinically, produced complete elimination of P. vivax oocyst development when mosquitoes had 60 minutes of tarsal contact before feeding. Even a brief 6-minute pre- or post-feed exposure meaningfully reduced infection prevalence. Mefloquine reduced oocyst intensity without affecting prevalence, while other compounds showed limited or no significant activity under these conditions.
The transmission-blocking potential of surface-absorbed atovaquone is conceptually important because it targets the sporogonic cycle within the vector rather than the human host—an approach sometimes called a "transmission-blocking" strategy. Atovaquone's high potency against Plasmodium mitochondria, and its likely low mobility through the mosquito cuticle when impregnated on a surface, may explain why sustained contact time mattered. The critical caveat is that this is an in-vitro assay using membrane feeders rather than natural biting behavior; field efficacy will depend on whether wild mosquitoes maintain sufficient contact duration with treated surfaces, and whether resistance mechanisms relevant to atovaquone (mutations in cytochrome b) could emerge under selective pressure. This is a proof-of-concept finding, incremental in scope but mechanistically meaningful—particularly for Amazonian settings where An. darlingi is the dominant vector and where P. vivax, often neglected relative to P. falciparum, causes the majority of regional cases.