Impact of artemether-lumefantrine treatment, circadian rhythm and serum replacement on the infectiousness of wild P. falciparum gametocytes to An. gambiae sensu stricto mosquitoes

Dorin Joachim Mmasi^1,2*Prisca Kweyamba^1,3,4Fatuma Matwewe¹Masudi Suleiman Maasayi¹Nolvin J Mvungi¹Ummi Abdul Kibondo¹Tibebu Habtewold^1,5Jennifer C Stevenson^1,3,4Lorenz Martin Hofer^1,3,4Sarah Jane Moore^1,2,3,4Mgeni M Tambwe^1,2

• ¹Ifakara Health Institute, Ifakara, Tanzania
• ²Nelson Mandela African Institution of Science and Technology, Arusha, Arusha, Tanzania
• ³Swiss Tropical and Public Health Institute (Swiss TPH), Basel, Basel-Landschaft, Switzerland
• ⁴University of Basel, Basel, Switzerland
• ⁵Department of Life Sciences, Faculty of Natural Sciences, Imperial College London, London, England, United Kingdom

Background: In the era of asymptomatic gametocytaemia, participants are scarce but serve as key reservoirs for Plasmodium falciparum gametocytes. Transmission-blocking interventions (TBIs) are gaining attention, taking into account factors such as artemether-lumefantrine (AL) treatment, mosquito feeding time (day vs. night), and serum replacement, recognised for their potential in influencing Direct Membrane Feeding Assay (DMFA) outcomes and reduce assay precision. This study aimed to assess the effect of optimising DMFA towards re using gametocytemic participants (1) prior artemether-lumefantrine treatment, (2) mosquito feeding time, and (3) serum replacement on gametocyte infectiousness to mosquitoes in a low malaria transmission setting.Methods: Six gametocytemic participants found to be eligible and donated 4 mL of venous blood. This blood was offered to female Anopheles gambiae sensu stricto (ss) mosquitoes via DMFA under controlled conditions. Oocyst prevalence and intensity was determined on fed mosquitoes: 1) 9 days post AL treatment 2) for day feeds versus night feeds and 3) with and without serum replacement. Results: Mosquito infection rates declined post-AL treatment, with significantly fewer mosquitoes infected (odds ratio (OR) = 0.20, 95% confidence interval (CI) = 0.13-0.31, p=0.001) compared to day 0. Feeding during the mosquito dark cycle time did not significantly affect mosquito infection rates (OR=0.77, 95% CI: 0.53-1.12, p=0.175). Lastly, serum replacement increased infection rates (OR = 1.73, 95% CI: 1.33-2.25, p = 0.001) compared to whole blood. Conclusion: To obtain robust results we confirm that DMFA should be conducted using blood from gametocytemic participants without a recent history of AL treatment, using serum replacement to enhance infection success. In this setting, assays could be conducted outside of the mosquito dark cycle without affecting results.