الفهرس 
Epidemiology of schistosomiasisOnly 14 pages are availabe for public view
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Abstract
The present study was performed in order to compare the conventional methods of diagnosis of snail infection with S. haematobium including cercarial shedding and sporocysts examination with real time PCR. Also to determine the effect of tested molluscicides on those different procedures of diagnosis as well as to calculate the detection limit for PCR. The study included: I) comparison between sporocysts formation and cercarial shedding with real time PCR and determination of the effect of copper sulfate and bayluscide on sporocysts formation, cercarial shedding and real time PCR, this included: I.A. Infection of the snails with S. haematobium miracidia. I.B. Calculation of the sublethal concentration (LC10) of both copper sulfate and bayluscide from 140 non-infected B. truncatus snails. I.C. Exposure of infected snails to copper sulfate and bayluscide. I.D. Examination of the snails for sporocyst formation. I.E. Examination of the snails for cercarial shedding. I.F. DNA extraction from B. truncatus snails. I.G. Real time PCR. This was carried out on 380 laboratory bred B. truncatus snails (> two mm in diameter). These snails were divided into four groups: Group I: non-infected control group. Group II: infected control group. Group III: infected snails exposed to copper sulfate. Group IV: infected snails exposed to bayluscide. II) Calculation of the detection limit of S. haematobium-infected B. truncatus snails for real time PCR by Pooled real time PCR technique. The present study revealed that real time PCR could detect snail’s infection 48 hours after exposure of the snail to four miracidia with 100% sensitivity. On the other hand, sporocysts formation and cercarial shedding showed 70% and 30% sensitivity after about 30 days and 45 days respectively. So it could be concluded that real time PCR was superior, sensitive and more specific than the conventional methods for early detection of snail’s infection. In the present study, in order to calculate the sublethal concentration (LC10) of both bayluscide and copper sulfate, the snails’ mortality in different concentrations was examined. It revealed that the number of dead snails raised gradually by increasing the concentration of the molluscicide and it indicated that bayluscide was more effective than copper sulfate. As regards to the result of sporocysts formation in all examined groups, there was a significant difference (P-value <0.05) between them. There was a reduction in the number of sporocysts in the snails by increasing the exposure time to the molluscicides. However, there was no statistically significant difference (P-value >0.05) between the exposed groups. As regards to the result of sporocysts count in all examined groups, it revealed that there was a reduction in the sporocysts mean in the snails by increasing the exposure time to the molluscicides. There was a highly significant difference (P-value <0.001) between all examined groups as cercarial shedding was found only in the infected group that had not been exposed to any molluscicides. However, other groups exposed to either bayluscide or copper sulfate did not show any cercarial shedding. As regards to the result of real time PCR, there was a highly significant difference (P-value <0.001) between all examined groups. There was a reduction in the number of the snails positive for real time PCR by increasing the exposure time to the molluscicides. However, there was no statistically significant difference (P-value >0.05) between the exposed groups. Regarding the infection rate, it was highly detected by real time PCR, less detected by the sporocysts formation and not detected at all (except in GP II which was infected and not exposed to any molluscicide) by cercarial shedding. It could be concluded that the snails after exposure to the sublethal concentration (LC 10) of the molluscicides (copper sulfate or bayluscide) were not infective at all as sporocysts might be formed but stopped and couldn’t progress to the cercarial stage. The present study revealed that the snails’ mortality rate was increased by its exposure to infection and molluscicides. The mortality rate was raised by increasing the exposure time to the molluscicides. However, there was no statistically significant difference (P-value >0.05) between the exposed groups. Regarding the survival rate, it was decreased by prolonged duration of exposure to the molluscicides. In this study, infected snails with S. haematobium and maintained for a prolonged duration after exposure to the molluscicides had a proportional relationship with the mortality rate. As regards to pooled PCR results, it could detect a single infected snail in pooled material from 100 uninfected snails.