الفهرس 
AcknowledgementOnly 14 pages are availabe for public view
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Abstract
This study was carried out at El-Rubumaiya village (Beheira Governorate). Map of the area was drawn and fifty permenant stations were shosen according to the density of the spail vectors and the type of water cha nnel. A complete survey for snail vectors, accompB.Dying sMils, aquatic vegetations, water temperature, water e. depth, water velocity and hydrogen ion ooncentration was performed. The collected snails were identified, counted, then the size and oercarial infection among both Biom phalaria alexandrina and Bulinus truncatus was reoorded. The pe riod of study extended for one Call1nder year from November (1982) till October (1983). Data obtained were recorded and statistical analysis was done. from this study it is clear that: 1. Biomphalaria alexandrina and Bu1inus trunoatus snails were collected from different types of water courses during the study period at El-Rubumaiya village (Beheira Governorate). The number of the collected Biompha1aria alexandrina snails was muoh higher than those of Bu1inus truncatus snails. 2. Biomphalaria alexandrina snails were present allover the year with high density during the Summer and late Autumn months and in drains more than oanals. 3. .The infeoted Biomphalaria alexandrina snails with Sohistosoma mansoni oeroariae were observed in med iurn and old size snails. The maximUm infeotion rate was reoorded during June and November mainly in tertiary oanals and tertiary drains. Also, the infeoted Biomphalaria alexandrina snails with other trematode oeroariae showed the highest peroentage during May and Deoember. 4. Bulinus trunoatus snails were p:resent allover the year except in October. The high density was recor ded in late Winter and Spring months in canals more than drains. 5. No infected Bulinus truncatus snails with Schisto ~ haematobium cercariae were oollected during the study period. But higher percentage of infec tion with other trematode ceroariae was deteoted more than in the oase of Biomphalaria alexandrina snails especially during the Winter and Spring months. 6. The most common accompanying snails during the study period were Physa acuta and Lymnea caillaudi (from nonoperculated snails) and Cleopatra bulimoides, Vivipara unicolor and Melania tuberculata (from operculated snails). 7. Aquatic vegetations were present allover the year in different types of water oourses. The high density of aquatic vegetations was reoorded in seoondary drains during Summer months. The most oommon speoies were Eichhornia cressipus and Lemna gibba (from floating vegetations), Ceratophyllum demersum and Potamogeton orispus (from submerged vegetations) and Panicum repens and Polygonum serrulatum (from emergent vegetations). 8. The mean water temperature all over the year ranged from 26.72°C (July) to l3.46°c (January). 9. The mean water depth was low in Winter months , (January = 48.33 Cm. and February = 37.73 oOm.) due to the Winter closure and it was nearly ~ in: the other months. 10. The highest water velocity was observed during the Summer months. The mean water velocity was higher in the primary canal and drain than in secondary and tertiary canals and drains. 11. The mean PH values was high during the Winter and Spring months and no variation between the canals and drains values was observed.