Browsing by Author "Kaindoa, Emmanuel W."

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Habitat characteristics and insecticide susceptibility of Aedes aegypti in the Ifakara area, south-eastern Tanzania
(Springer Nature Switzerland AG., 2020-02-07) Kahamba, Najat F.; Limwagu, Alex J.; Mapua, Salum A.; Msugupakulya, Betwel J.; Msaky, Dickson S.; Kaindoa, Emmanuel W.; Ngowo, Halfan S.; Okumu, Fredros O.
Background: Aedes-borne diseases such as dengue and chikungunya constitute constant threats globally. In Tanzania, these diseases are transmitted by Aedes aegypti, which is widely distributed in urban areas, but whose ecology remains poorly understood in small towns and rural settings. Methods: A survey of Ae. aegypti aquatic habitats was conducted in and around Ifakara, a fast-growing town in south-eastern Tanzania. The study area was divided into 200×200 m search grids, and habitats containing immature Aedes were characterized. Field-collected Ae. aegypti were tested for susceptibility to common public health insecticides (deltamethrin, permethrin, bendiocarb and pirimiphos-methyl) in the dry and rainy seasons. Results: Of 1515 and 1933 aquatic habitats examined in the dry and rainy seasons, 286 and 283 contained Aedes immatures, respectively (container index, CI: 18.9–14.6%). In the 2315 and 2832 houses visited in the dry and rainy seasons, 114 and 186 houses had at least one Aedes-positive habitat, respectively (house index, HI: 4.9–6.6%). The main habitat types included: (i) used vehicle tires and discarded containers; (ii) fowerpots and clay pots; and (iii) holes made by residents on trunks of coconut trees when harvesting the coconuts. Used tires had highest overall abundance of Ae. aegypti immatures, while coconut tree-holes had highest densities per habitat. Aedes aegypti adults were susceptible to all tested insecticides in both seasons, except bendiocarb, against which resistance was observed in the rainy season. Conclusions: To our knowledge, this is the frst study on ecology and insecticide susceptibility of Ae. aegypti in Ifakara area, and will provide a basis for future studies on its pathogen transmission activities and control. The high infestation levels observed indicate signifcant risk of Aedes-borne diseases, requiring immediate action to prevent potential outbreaks in the area. While used tires, discarded containers and fowerpots are key habitats for Ae. aegypti, this study also identifed coconut harvesting as an important risk factor, and the associated tree-holes as potential targets for Aedes control. Since Ae. aegypti mosquitoes in the area are still susceptible to most insecticides, efective control could be achieved by combining environmental management, preferably involving communities, habitat removal and insecticide spraying
Preferred resting surfaces of dominant malaria vectors inside different house types in rural south-eastern Tanzania
(Springer Nature, 2020-01-15) Msugupakulya, Betwel J.; Kaindoa, Emmanuel W.; Ngowo, Halfan; Kihonda, Japhet M.; Kahamba, Najat F.; Msaky, Dickson S.; Matoke-Muhia, Damaris; Tungu, Patrick K.; Okumu, Fredros O.
Background: Malaria control in Africa relies extensively on indoor residual spraying (IRS) and insecticide-treated nets (ITNs). IRS typically targets mosquitoes resting on walls, and in few cases, roofs and ceilings, using contact insecticides. Unfortunately, little attention is paid to where malaria vectors actually rest indoors, and how such knowledge could be used to improve IRS. This study investigated preferred resting surfaces of two major malaria vectors, Anopheles funestus and Anopheles arabiensis, inside four common house types in rural south-eastern Tanzania. Methods: The assessment was done inside 80 houses including: 20 with thatched roofs and mud walls, 20 with thatched roofs and un-plastered brick walls, 20 with metal roofs and un-plastered brick walls, and 20 with metal roofs and plastered brick walls, across four villages. In each house, resting mosquitoes were sampled in mornings (6 a.m.–8 a.m.), evenings (6 p.m.–8 p.m.) and at night (11 p.m.–12.00 a.m.) using Prokopack aspirators from multiple surfaces (walls, undersides of roofs, foors, furniture, utensils, clothing, curtains and bed nets). Results: Overall, only 26% of An. funestus and 18% of An. arabiensis were found on walls. In grass-thatched houses, 33–55% of An. funestus and 43–50% of An. arabiensis rested under roofs, while in metal-roofed houses, only 16–20% of An. funestus and 8–30% of An. arabiensis rested under roofs. Considering all data together, approximately 40% of mosquitoes rested on surfaces not typically targeted by IRS, i.e. foors, furniture, utensils, clothing and bed nets. These proportions were particularly high in metal-roofed houses (47–53% of An. funestus; 60–66% of An. arabiensis). Conclusion: While IRS typically uses contact insecticides to target adult mosquitoes on walls, and occasionally roofs and ceilings, signifcant proportions of vectors rest on surfaces not usually sprayed. This gap exceeds one-third of malaria mosquitoes in grass-thatched houses, and can reach two-thirds in metal-roofed houses. Where feld opera‑ tions exclude roofs during IRS, the gaps can be much greater. In conclusion, there is need for locally-obtained data on mosquito resting behaviours and how these infuence the overall impact and costs of IRS. This study also emphasizes the need for alternative approaches, e.g. house screening, which broadly tackle mosquitoes beyond areas reachable by IRS and ITNs.