Schistosomiasis in newly reclaimed areas in Egypt. 1-distribution and population seasonal fluctuation of intermediate host snails.

Two newly reclaimed areas located west & east of Suez Canal, namely El Manayef area and El Morra area, were studied for patterns of distribution and population seasonal fluctuation of Biomphalaria alexandrina and Bulinus truncatus, the intermediate host snails of Schistosoma mansoni and S. haematobium, respectively. In this study Geographic Information System (GIS) techniques were utilized for producing maps and analyzing the results. Habitats of the two vector snail species were categorized into suitability levels depending on the frequency with which snails were collected over a 12 months period. Data obtained from the most suitable habitats were only used for studying the seasonal fluctuation of snail population. The results showed that both study areas were almost similar in major physico-chemical parameters. However, oxygen content in canals was higher than in drains and conductivity was higher in drains than in canals. As regards snail distribution and density, most snails of both considered species were clustering in much fewer numbers of sites, more pronouncedly in the case of Biomphalaria than Bulinus. Population density of snails was significantly higher in El-Manayef area than in El-Morra area and in canals than in drains. Both species exhibited 2 population peaks/year, the peaks of Biomphalaria were in March-April & August in both study areas, while for Bulinus these peaks occurred in March-May and August in El-Manayef area and in May and March, respectively, in El-Morra area.