Abstract
BackgroundDuring the last decades two dams were constructed along the Senegal River. These intensified the practice of agriculture along the river valley basin. We conducted a study to assess malaria vector diversity, dynamics and malaria transmission in the area.MethodsA cross-sectional entomological study was performed in September 2008 in 20 villages of the middle Senegal River valley to evaluate the variations of Anopheles density according to local environment. A longitudinal study was performed, from October 2008 to January 2010, in 5 selected villages, to study seasonal variations of malaria transmission.ResultsAmong malaria vectors, 72.34% of specimens collected were An. arabiensis, 5.28% An. gambiae of the S molecular form, 3.26% M form, 12.90% An. pharoensis, 4.70% An. ziemanni, 1.48% An. funestus and 0.04% An. wellcomei. Anopheles density varied according to village location. It ranged from 0 to 21.4 Anopheles/room/day and was significantly correlated with the distance to the nearest ditch water but not to the river.Seasonal variations of Anopheles density and variety were observed with higher human biting rates during the rainy season (8.28 and 7.55 Anopheles bite/man/night in October 2008 and 2009 respectively). Transmission was low and limited to the rainy season (0.05 and 0.06 infected bite/man/night in October 2008 and 2009 respectively). During the rainy season, the endophagous rate was lower, the anthropophagic rate higher and L1014F kdr frequency higher.ConclusionsMalaria vectors are present at low-moderate density in the middle Senegal River basin with An. arabiensis as the predominant species. Other potential vectors are An. gambiae M and S form and An. funestus. Nonetheless, malaria transmission was extremely low and seasonal.
Highlights
During the last decades two dams were constructed along the Senegal River
All species were captured by HLC and all but An. wellcomei and An. ziemanni by Pyrethrum spray catches (PSC)
An. gambiae is known to be present and sympatric with An. arabiensis in relatively dry regions like the Niger River in Mali or Mauritania [19], especially in rice culture areas [20]. Both M and S molecular forms of An. gambiae s.s. were identified in this study
Summary
During the last decades two dams were constructed along the Senegal River. These intensified the practice of agriculture along the river valley basin. In many African countries, food self-sufficiency is a goal that favors the development of irrigated areas. This strategy requires the management of water resources and the implementation of new hydro-agricultural arrangements. During the 1980s’, important development programs have been implemented including the construction of two dams on the Senegal River [1] Following these developments, irrigated areas have been enlarged and rice culture expanded. These ecological changes have largely promoted an increase in water-related diseases such as malaria, Rift Valley fever and schistosomiasis, [2,3]. The environmental changes associated with water development projects were suspected to be responsible for having created favourable conditions for the reestablishment of An. funestus
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