Impact of irrigation development projects on disease vectors in West Timor, Indonesia

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Impact of environmental changes caused by dam construction on disease vectors, especially fauna, density and seasonal dynamics of mosquitoes, were investigated in the suburbs of Kupang, West Timor, Indonesia. Observation was started just before the start of the project and continued until the completion of construction of the dam and associated irrigation systems and the start of construction of new irrigated rice filed.The river above the dam site changed into the dam lake. As a consequence, mosquito larval habitats along river edges disappeared. In the new lake, the guppy and other released fished reproduced rapidly and suppressed mosquito breeding. Below the dam site, the amount of water flow decreased and slowly running parts increased. However, water level fluctuations due to artificial water discharge increased instability of mosquito habitats. Concrete-lined water channels connecting the dam and the rice fields were not mosquito habitats insofar as water flows but they became mo … More squito habitats if water was stagnant. The side ditches constructed along water channels in hill sides were often filled with the soil and kept stagnant water suitable for mosquito breeding. In the newly constructed irrigated rice fields, mosquitoes can breed throughout the year, and mosquito densities were high. Irrigation water is taken from the bottom of the dam through filters, so there was no fish in newly constructed channels and rice fields. Artificial introduction of larvivorous fishes into those habitats could effectively suppress mosquito breeding. Buildings destroyed and machines and other equipments discarded after the project afforded breeding sites for mosquito larvae. As basic information useful to prevention of vector-borne diseases in irrigation development projects in West Timor, distribution of larvivorous fishes and the parasites of rats were investigated.Dam construction produces new mosquito habitats, but risks of mosquito breeding can be reduced by appropriate and constant improvement and maintenance. A widely accepted idea that dam construction increase the aquatic habitats and risks of epidemics of vector-borne diseases such a malaria is not necessarily correct. It is necessary to recognize also that the irrigation development can contribute to disease vector mosquito control by the increased water manageability. Less