الفهرس 
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Abstract
Water resources development projects, in general, aim at raising the standard of human well-being. Sometimes, however, undesired negative impacts on human health accompany such projects due to landscape disturbances and man-made hydraulic interventions. Vector-borne diseases transmitted by freshwater host snails are among the most threatening of these illnesses that are water-related. In Egypt, diseases such as schistosomiasis (namely, S. mansoni transmitted by Biomphalaria alexandrina snails and S. haematobium transmitted by Bulinus truncatus snails) and fascioliasis (transmitted by Lymnaea natalensis snails) may be extended, unless integrated water resources management programs interfere for remediation. The present study hence aimed at assessing the impact of some ecological/hydrological parameters on the distribution and abundance of freshwater snail vectors both in the Old Lands represented by the traditional surface irrigation system at Kafr El-Sheikh (KES) Governorate, Qellin District, as well as in the New Lands represented by El-Salam Canal (SC) study area west and east of Suez Canal (North Sinai Development Project) with its 1:1 mixture of drainage and River Nile water. Seven sites at KES and twelve at SC study areas were selected for sampling snails and the co-existing aquatic plants, and for analyzing water quality seasonally throughout the year 2009. Statistical tools were used to study those relations using 28 ecological variables. Obtained results showed that, in both study areas, schistosome snails had highest peaks mainly in spring and sometimes in autumn when moderate temperatures prevail, and that B. alexandrina snails were prevalent in drains rather than canals tolerating highly polluted water, unlike B. truncatus snails which were more sensitive to polluted water, hence were absent from drains and survived only in canals. Cercarial infection was also detected in El-Houri drain (KES) and Bahr Hadous drain (SC) rendering those two locations high risk points for Schistosoma disease hazards. Also B. truncatus proved to have well established themselves in the east not only the west of Suez Canal, making the possible future occurrence of schistosomiasis in this newly reclaimed area not excluded. As for L. natalensis snails, they were rare in KES and totally absent in SC due to their being very fragile and sensitive to water pollution and ecological stressors. Moreover, modeling the ecological study variables using discriminant analysis (DA) in El-Salam Canal, given its importance as one of the national water resources development mega projects in Egypt, showed that the presence of schistosome vector snails could be predicted based upon five predictor variables, foremost of which are: (1) the density of aquatic plants – which constitute the main source of food and shelter for the snails – and (2) the calcium level in water which is needed by the snails for shell-formation. Results showed that the DA model was efficient enough to predict the presence of B. alexandrina snails with 87.5% and B. truncatus snails with 100%. Finally, GIS-based risk maps were developed to highlight the hotspots where snail distribution is most prevalent, hence highest potential for disease hazard is expected. Early detection, early warning and preparedness for planning thus become mandatory in order to minimize the risk of such water-related snail-borne hazards and their related health and economic impacts.
Iii
Water resources development projects, in general, aim at raising the standard of human well-being. Sometimes, however, undesired negative impacts on human health accompany such projects due to landscape disturbances and man-made hydraulic interventions. Vector-borne diseases transmitted by freshwater host snails are among the most threatening of these illnesses that are water-related. In Egypt, diseases such as schistosomiasis (namely, S. mansoni transmitted by Biomphalaria alexandrina snails and S. haematobium transmitted by Bulinus truncatus snails) and fascioliasis (transmitted by Lymnaea natalensis snails) may be extended, unless integrated water resources management programs interfere for remediation. The present study hence aimed at assessing the impact of some ecological/hydrological parameters on the distribution and abundance of freshwater snail vectors both in the Old Lands represented by the traditional surface irrigation system at Kafr El-Sheikh (KES) Governorate, Qellin District, as well as in the New Lands represented by El-Salam Canal (SC) study area west and east of Suez Canal (North Sinai Development Project) with its 1:1 mixture of drainage and River Nile water. Seven sites at KES and twelve at SC study areas were selected for sampling snails and the co-existing aquatic plants, and for analyzing water quality seasonally throughout the year 2009. Statistical tools were used to study those relations using 28 ecological variables. Obtained results showed that, in both study areas, schistosome snails had highest peaks mainly in spring and sometimes in autumn when moderate temperatures prevail, and that B. alexandrina snails were prevalent in drains rather than canals tolerating highly polluted water, unlike B. truncatus snails which were more sensitive to polluted water, hence were absent from drains and survived only in canals. Cercarial infection was also detected in El-Houri drain (KES) and Bahr Hadous drain (SC) rendering those two locations high risk points for Schistosoma disease hazards. Also B. truncatus proved to have well established themselves in the east not only the west of Suez Canal, making the possible future occurrence of schistosomiasis in this newly reclaimed area not excluded. As for L. natalensis snails, they were rare in KES and totally absent in SC due to their being very fragile and sensitive to water pollution and ecological stressors. Moreover, modeling the ecological study variables using discriminant analysis (DA) in El-Salam Canal, given its importance as one of the national water resources development mega projects in Egypt, showed that the presence of schistosome vector snails could be predicted based upon five predictor variables, foremost of which are: (1) the density of aquatic plants – which constitute the main source of food and shelter for the snails – and (2) the calcium level in water which is needed by the snails for shell-formation. Results showed that the DA model was efficient enough to predict the presence of B. alexandrina snails with 87.5% and B. truncatus snails with 100%. Finally, GIS-based risk maps were developed to highlight the hotspots where snail distribution is most prevalent, hence highest potential for disease hazard is expected. Early detection, early warning and preparedness for planning thus become mandatory in order to minimize the risk of such water-related snail-borne hazards and their related health and economic impacts.
Iii