PostDoc Ifakara Health Institute Dar es salaam, Dar es Salaam, Tanzania
Abstract: The objective of this study was to compare the bio efficacy of a new mosquito adulticide ReMoa Tri applied by ULV spray against pyrethroid susceptible and resistant An. gambiae ss and An. arabiensis, two of the main vectors of malaria in Africa.
Fully pyrethroid susceptible Anopheles gambiae s.s. (Ifakara), knockdown resistant An. gambiae (Kisumu) and metabolic resistant An. arabiensis (Kingani) were used in this study. The mechanism of resistance is both 1014F kdr West and 1014S kdr East for An. gambiae (Kisumu KDR) and upregulation of CYP450 for An. arabiensis (Kingani). The semi-field bioassays were performed at the Vector Control Product Testing Unit (VCPTU) testing facility located at the Bagamoyo branch of Ifakara Health Institute (IHI), Tanzania (6.446ºS and 38.901ºE). Following WHO guidelines, cages were set at 25, 50, 75 and 100m in a block randomized design and three replicates were conducted per distance for each mosquito strain. The ULV backpack sprayer fontan® Portastar S was used to apply a droplet size of (Dv0.5) 12 to 24-micron volume median diameter (VMD). The trial was conducted at dusk when the wind speed was 3-10 kilometers per hour (kph) with 5kph optimal wind speed. The ULV machine was walked across the test plot at 3.5 kph. All 3 replicates of the spraying were conducted on the same night.
After exposure, outcomes of knockdown at 60 minutes, mortality at 24 and 48 hours were recorded. The mosquitoes were held under controlled conditions at 27 ± 2 ℃ temperature and relative humidity of 80 ± 10%. A test was valid when control mortality was less than 20% at 24-hours.
Results show 99-100% mortality across the board – in both susceptible and resistant strains of both species. These results and their implications will be discussed.
