Abstract
BackgroundAbu Hamed, the northernmost onchocerciasis focus in the world, is located along the River Nile banks in the Nubian Desert. Hydroelectric dams can alter activity of black flies and may provide breeding sites for black fly. Merowe Dam, the largest hydropower project in Africa, was built west of Abu Hamed focus in 2009. The impact of the Dam on onchocerciasis and its black fly vectors in Abu Hamed focus was measured in this study.FindingsEntomological surveys for aquatic stages and adult Simulium hamedense were conducted before and after the inception of Merowe Dam in 2007/2008 and 2010/2011. There was no black fly breeding or adult activity in the previously known breeding sites upstream of the Merowe Dam with the western most breeding site found in AlSarsaf village near the center of the focus. No adult or aquatic stages of black flies were found downstream of the Dam.ConclusionsThe artificial lake of the Dam flooded all the breeding sites in the western region of the focus and no aquatic stages and/or adult black fly activity were established in the study area upstream of the Dam. The Dam seems to have positive impact on onchocerciasis and its black fly vectors in Abu Hamed focus. These outcomes of the Merowe Dam might have contributed to the recently declared interruption of onchocerciasis transmission in Abu Hamed focus. Continuous entomological surveys are needed to monitor presence of black fly vectors and its impact on the disease.
Highlights
Abu Hamed, the northernmost onchocerciasis focus in the world, is located along the River Nile banks in the Nubian Desert
No aquatic stages of black fly were found in the same sites in Albouhira locality and the western parts of Abu Hamed locality in 2010/2011 (Table 1) due to the flooding of breeding sites by Merowe Dam artificial reservoir
Few studies have reported the impact of dams on onchocerciasis transmission in Africa and Sudan [12,13,14,15,16,17,18,19]
Summary
Construction and operation of hydroelectric dams usually leads to changes in the physical and biological environment [15,16]. Hamdab Island is currently free from black fly breeding, continuation of entomological survey is highly recommended especially during months of high density of Simulium flies (January–April) downstream Merowe Dam. The overall impact of Merowe Dam on Abu Hamed focus of onchocerciasis has been positive. The artificial reservoir of the Dam has submerged and eliminated black fly breeding sites west to Abu Hamed town, effectively shrinking the focus to a little over half of its original size. This finding supports the prediction of an overall decrease in river blindness in the area due to Merowe Dam [23]. All authors read and approved the final version of the manuscript
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