Available online 29 May 2025

Method established to feed antimalarial drugs to mosquitoes for screening activity against Plasmodium oocysts and sporozoites.

Azithromycin reduces infectivity of sporozoites in P. berghei.

Borrelidin reduces sporozoite development in P. berghei.

T111 is highly potent for stopping oocyst development into infective sporozoites in both P. berghei and P. falciparum.

T111 shown to have significant environmental stability suitable for practical applications.

A decade-long decline in malaria cases has plateaued, primarily due to parasite drug resistance and mosquito resistance to insecticides used in bed nets and indoor residual spraying. Here, we explore the innovative control strategy targeting Plasmodium with antimalarials during the mosquito stages. This strategy has the potential to reduce the risk of resistance emerging because a relatively small population of parasites within the mosquito is subject to selection. After validating mosquito feeding strategies, we screened a range of parasiticidal compounds by feeding them to mosquitoes already infected with mouse malaria (P. berghei). Three antimalarials showed activity against P. berghei in mosquitoes, apparently targeting specific stages of P. berghei development during transmission. Borrelidin, a threonyl-tRNA synthetase inhibitor, significantly reduced P. berghei sporozoite numbers. Azithromycin, an antibiotic targeting apicoplast protein synthesis, significantly lowered sporozoite infectivity in mice. T111, a next generation compound targeting the parasite electron transport chain, reduced sporozoite numbers in P. berghei at equivalent concentrations to the gold standard electron transport chain inhibitor, atovaquone. T111 also prevented sporozoite production in mosquitoes infected with human malaria, P. falciparum, even after very short exposure times. Encouragingly, T111 remained efficacious after being freeze-dried onto a substrate and later reconstituted with water, suggesting this compound would be effective in easy-to-distribute-and-deploy transmission control devices. Our findings suggest that several antimalarials can be used to target mosquito-stage parasites via sugar baits and limit malaria transmission. Importantly, mosquito feeding of antimalarials could vastly increase the range of potentially useful parasiticidal compounds to include those failing to meet the exacting standards required for human antimalarial drugs, potentially improving malaria control for minimal cost.

Plasmodium

Transmission

Electron transport chain

Anti-malarial drugs

Sugar baits

Malaria

Oocyst

Sporozoite

insecticide treated bed nets

© 2025 The Authors. Published by Elsevier Ltd on behalf of Australian Society for Parasitology.