Effect of a novel house (Star home) and toilet design on domestic fly densities in rural Tanzania.

Abstract

Background: Diarrhoeal disease is the third leading cause of death in children under 5 years old with domestic flies acting as important mechanical vectors of diarrhoeal pathogens. To assess the effectiveness of a novel house design, "Star home", and improved toilets in reducing the abundance of domestic flies, potential carriers of diarrhoeal pathogens, a randomized controlled trial was carried out in rural Tanzania.

Methods: Domestic fly populations were monitored in 28 randomly selected Star homes and 28 traditional thatched roofs and mud-walled houses over 2 years from January 2022 to December 2023. Flies were sampled in kitchens and toilets using baited-fly traps from 07.00 h to 17.30 h every 7 weeks. To assess the production of flies from toilets, traps were placed over drop holes to collect emerging flies. Duration of external door openings to the kitchens was recorded with data loggers.

Findings: Of the 1527 flies collected, 76% were Chrysomya putoria, 16% Musca domestica and 8% Sarcophaga spp. In kitchen collections, there were 46% fewer C. putoria flies [adjusted mean rate ratio (RR) = 0.54] and 69% fewer Sarcophaga spp. (RR = 0.31) in Star homes compared to traditional houses. There was no difference in the abundance of M. domestica in the two study groups. In toilets, there was 49% fewer C. putoria (RR = 0.51), but no difference was observed for other domestic fly species. No flies emerged from Star home toilets compared with a mean of 4.2 flies/trap/day in traditional toilets. During the day, the external doors od Star homes were open for an average of 13.0 min/h less than in traditional houses.

Conclusions: Star homes reduced the abundance of domestic flies, apart from houseflies, in the kitchen and there were fewer C. putoria, a putative vector of diarrhoeal diseases, in Star home toilets compared to traditional houses. Changing the design of buildings can contribute to a decline in domestic flies and may lead to a reduction in diarrhoeal diseases.