Effect of a novel house design (star home) on indoor malaria mosquito abundance in rural Tanzania: secondary outcomes of an open-label, household, randomised controlled trial

Background: Screening houses can reduce malaria transmission in sub-Saharan Africa. Our study evaluated whether a novel screened house design (star home) with bedrooms on the second storey reduced indoor mosquito abundance compared with traditional houses in Mtwara, Tanzania.

Methods: In this open-label, household, randomised controlled trial, indoor mosquito abundance was assessed in 110 star homes and 110 neighbouring traditional houses in 59 villages from Jan 5, 2022, to Dec 20, 2023. Mosquitoes were collected using US Centers for Disease Control light traps every 7 weeks. Anopheles gambiae and Anopheles funestus species were identified using PCR and Plasmodium falciparum sporozoites detected using ELISA. Nightly temperature, CO₂ concentrations, and duration of door opening was recorded. Differences between study groups were analysed using generalised linear mixed-effects models. The trial is registered with ClinicalTrials.gov (NCT04529434).

Findings: Of 9290 mosquitoes collected, 1899 were A gambiae, 69 were A funestus, and 7322 Culex species, mainly Culex quinquefasciatus. Star homes had 51% less A gambiae (adjusted risk ratio [RR] 0·49, 95% CI 0·35 to 0·69; p<0·0001) and 61% less Culex species (RR 0·39, 0·32 to 0·48; p<0·0001) than traditional houses. At night, star homes were 0·5°C cooler (95% CI 0·2 to 0·9; p=0·010), with similar concentrations of CO₂ (-7 ppm, 95% CI -19 to 6; p=0·285) and had external doors open 53% less time than traditional houses (7·5 min/h vs 16·2 min/h; p<0·0001).

Interpretation: Star homes reduced indoor mosquito abundance and malaria transmission risk compared with traditional houses, demonstrating the protective efficacy of houses that are well screened and air permeable in rural Africa.

Funding: Hanako Foundation, Singapore.