Abstract
Abstract. Entomological studies to determine the effect of the physical characteristics of mosquito larval breeding water bodies and reservoir water level changes on the occurrence of Anopheles mosquito larvae were conducted in two villages at Koka reservoir in central Ethiopia between August and December 2007. Of the two study villages, Ejersa is located close to the reservoir, and Kuma is 5 km away from it. Data on the type, number and physical characteristics of Anopheles larval breeding habitat, species composition and densities of anopheles mosquitoes in and around the study villages were investigated and recorded. Meteorological and reservoir water level data were compared with availability of Anopheles larval breeding sites and densities. Entomological data, derived from weekly larval collections, showed that Anopheles pharoensis Theobald, Anopheles gambiae s.l. Giles, Anopheles coustani Laveran and Anopheles squamosus Theobald were breeding in the study area. The mean larval density of An. gambiae s.l. in this study was higher in slightly turbid and shallow aquatic habitat than in turbid and relatively deep aquatic habitat. The density of An. pharoensis in habitat with floating vegetation and with relatively shady conditions was significantly higher than that of less shaded aquatic habitat and greater emergent vegetation. There was also a positive correlation between the occurrence of Anopheles larvae with the water and daily minimum atmospheric temperature. Similarly at Ejersa, over the sampling period, there was a positive correlation between falling reservoir water levels and the number of positive breeding habitats. These results confirm that physical characteristics of the water bodies play an important role in the species composition, total Anopheles larval count, and the density of Anopheles mosquitoes. Suitable breeding habitat in the vicinity of the reservoir village was strongly associated with the reservoir. This is particularly important for An. pharoensis and An. gambiae s.l. which are important vectors of malaria in the area.
Highlights
In Africa, water resource development activities largely focus on dams and irrigation schemes which contribute substantially to food security, renewable energy production, and sustainable economic development
Ethiopia is engaged in extensive water resource development activities such as construction of dams and reservoirs for irrigation and hydroelectricity (McCartney et al, 2007)
The number of positive sites encountered throughout the sampling period was 97 for the reservoir village and 22 for the non-reservoir village
Summary
In Africa, water resource development activities largely focus on dams and irrigation schemes which contribute substantially to food security, renewable energy production, and sustainable economic development. Ethiopia is engaged in extensive water resource development activities such as construction of dams and reservoirs for irrigation and hydroelectricity (McCartney et al, 2007). The ecologic changes associated with these development activities often entail negative health impacts due to the creation of new mosquito breeding sites and altered human-vectorparasite contact patterns. There is an association between malaria incidence and proximity to dams in Ethiopia. Malaria case rates among people living within 1 km of the Koka reservoir are about 2.9 times greater than for those living between 1 and 2 km from the reservoir and 19.9 times greater than for those living 5–9 km from the reservoir (Kibret et al, 2009)
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