The effect of urban and rural water pollutants on the life history of the major malaria vector Anopheles arabiensis (Diptera: Culicidae)

Abstract

Malaria is the most significant vector-borne disease globally, and its transmission in Africa has historically been concentrated in rural regions. .In South Africa, Anopheles arabiensis, a member of the An. gambiae complex, is the primary malaria vector and is also predominately associated with rural areas, where it breeds in agricultural landscapes. However, throughout Africa, theAn. gambiae complex is increasingly adapting to breeding in urban areas and contributing to urban malaria transmission Understanding the capacity of An. arabiensis to withstand water pollutants characteristic of either urban or rural areas could provide insight into its suitability to each region. In this study, two laboratory strains of An. arabiensis were used. SENN is an insecticide susceptible strain and SENN-DDT is selected for DDT resistance from SENN. These strains were exposed to pollutants associated with either rural areas (nitrates, nitrites) or urban areas (sulphates, sulphides). The effect of larval exposure to these pollutants in these strains were examined on larval development, adult longevity and deltamethrin tolerance. The pollutants had variable effects on the strains. A total of 5 life parameter advantages were observed for SENN after being exposed to sulphurous treatments, including reduction in larval developmental time, increase in pupation success and increase in insecticide tolerance. By contrast, nitrogenous treatments improved only two life-cycle traits in SENN. The opposite trend was observed for SENN-DDT. Nitrogenous treatments resulted in 6 advantages across all life history parameters compared to 4 advantages of improved pupation success and increased insecticide tolerance caused by exposure to sulphurous treatments.. These findings demonstrate the capacity of An. arabiensis to adapt to polluted environments, underscoring its potential to persist in urban areas, and withstand rising pollution in rural areas. This adaptability underscores the risk of An. arabiensis as an urban malaria vector.