الفهرس 
Control of snails by chemical molluscicidesOnly 14 pages are availabe for public view
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Abstract
The aim of the present investigation is to study the effect of certain molluscicide, Bayluscide, on the resistance of the pulmonate freshwater snails Biomphalaria alexandrina and Bulinus truncatus the intermediate hosts of the two species of Schistosoma in Egypt. The original wild stock snails were collected from Mansouriya and Nazlet, El-Seman areas in Giza Governorate. The snails were kept under well defined conditions of temperature, humidity, air supply, light etc. The mortality rate curves for the effect of Bayluscide on different phenotypes of the snails collected from treated and untreated areas were done. The mortality rate of wild field snails as well as the laboratory-bred generations (F1) and (F2) were recorded for 24 hours. The result obtained indicated that both the two phenotypes of -B. alexandrina and -B. truncatus snails collected from untreated area gave higher mortality rate than those collected from treated area. The results also revealed that the light morph of the former species displayed higher mortality rate for the snails collected from both treated and untreated areas. While the pigmented morph of the latter species gave higher mortality rate of snails collected from both areas. from the data concerning the resistance of the second generation (F2) which their parents had been collected from both treated and untreated areas showed that g. alexandrina has a higher resistance than those of -B. truncatus. Agarose gel electrophoretic studies of the effect of the molluscicide on esterase isoenzyme of different phenotypes of the two species under investigation indicated that the dark and light morphs of normal -B. alexandrina have a highly significant differences between different groups of esterases, while in -B. truncatus there was no significant difference between different groups of esterases. The. results also indicated that the relative heterozygosity of the dark morph of -B. alexandrina displayed higher heterozygosity than the light morph of the normal snails. While in snails treated with Bayluscide, the ligh morph displayed high heterozygosity than the dark morph. In -B. truncatus the pigmented and unpigmented morphs of normal snails showed higher heterozygosity than treated snails. Investigation of effect of different concentrations of some carboxylic acids as attractant or arrestant on the response of different morphs of g. alexandrina and g. truncatus snails collected from treated area displayed a highly significant attractant effect towards acetic, proionic and butyric acids. The dark morph of -B. alexandrina showed more highly significant response than the light morph, while the pigmented morph of -B. truncatus showed more highly significant response than the unpigmented morph. Histological and histochemical investigation of the effect of Bayluscide and acetic acids on the development of different stages of ova and sperms in the hermaphrodite gland of -B. alexandrina and B. truncatus snails, showed that either Bayluscide or acetic acid obviously had great effect on the spermatogenic and oogenic cells, in the hermaphrodite gland of the two species under investigation. In conclusion, the present study provides the bases for a theoretical conception that may has practical application for selectively controlling the snail hosts of schistosomiasis; -B. alexandrina and -B. truncatus through the use of palatable matrices containing a bound molluscicide at the transmission foci, by incorporating water soluble chemical which serve as specific attractants, arrestants into these matrices thereby it would theoretically be possible to remove the snail hosts without harming other species.