Modeling Insecticide Susceptibility and Resistance in Anopheles spp. Populations in Tanzania, 2022.

Insecticide resistance in anopheline malaria vectors poses a major threat to malaria control and elimination efforts. We conducted spatial analyses using publicly available and published data to document and model the geospatial distribution of Anopheles spp. insecticide resistance in Tanzania at the national, regional, district, and subdistrict levels for the 2012-2021 period. An insecticide resistance map modeled for 2022 predicted that anopheline insecticide susceptibility remained above the 90% susceptibility threshold for all major insecticide classes, except for pyrethroids. We calculate that although resistance to pyrethroids occurs in 99.8% of Tanzania's territory, resistance to carbamates, organophosphates, and organochlorines is present in only 7.4%, 0.2%, and 1.3% of the territory, respectively. These modeled findings indicate that despite widespread pyrethroid resistance in Tanzania, significant opportunities for insecticide-based vector control remain, as major vectors are still broadly susceptible to other insecticide classes. The regular use of this predictive methodology can help malaria program management staff adjust their vector control strategies.