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Showing papers on "Biomphalaria alexandrina published in 1993"


Journal ArticleDOI
TL;DR: A shift in relative abundance of the snail vectors Biomphalaria alexandrina and Bulinus truncatus is increasing while the latter has disappeared from a village in the Fayoum where formerly only schistosomiasis haematobia was endemic.
Abstract: Schistosoma mansoni is progressively replacing S. haematobium along the Nile River in Egypt. This change has occurred in the past 15–20 years following construction of the Aswan High Dam in the 1960s. The cause is a shift in relative abundance of the snail vectors Biomphalaria alexandrina and Bulinus truncatus. Biomphalaria is increasing while the latter has disappeared from a village in the Fayoum where formerly only schistosomiasis haematobia was endemic. A cross-sectional household survey in this village in 1991 showed the following prevalence values: S. mansoni, 22.3%; S. haematobium, 3.4%; and mixed infections, 2.8%. Only two children less than 10 years of age had S. haematobium infections. A review of the local Ministry of Health records showed that 1) both species were parasitologically diagnosed during the past 7.5 years, 2) Biomphalaria had been abundantly present in the local waterways for the past 10 years and has been found infected with S. mansoni since 1985, 3) Bulinus has not been detected in the local canals and drains since 1986 and the few found between 1981 and 1985 were not infected, and 4) Biomphalaria in this village and in two others in the Fayoum were believed infected by laborers from the Delta who helped build schools in 1984. This change in the distribution of schistosomiasis will impact upon public health and medical practice in Middle and Upper Egypt as it already has in Lower Egypt.

28 citations


Journal Article
TL;DR: Results shown that the spreading patterns of snails along canals are changeable because of water current and irrigation activities, and double sampling of 50% of sampling sites the next day should be satisfactory as a quality control system in snail population studies.
Abstract: The patterns of spreading and seasonal variation of population density of Biomphalaria alexandrina, the snail vector of Schistosoma mansoni in Egypt, in correlation with some environmental parameters were studied for 1988-1990 in four irrigation canals in Giza and Qalyoubiya Governorates. Results shown that the spreading patterns of snails along canals are changeable because of water current and irrigation activities. The snail population density showed two peaks, different in height, in April-May and November-December separated by two bottoms following the Winter Closure and during the hot summer season. The height of the peaks appears to be dependent on the extent of the "Winter Closure" and the prevailing water temperature. Two snail sampling tools, the dip-net and drag scoop, were used concurrently in this study. No considerable difference in sampling efficacy was recognized between these tools in the case of Biomphalaria. However, the dip-net appears to be more efficient in sampling other pulmonates while the drag scoop is more efficient in sampling prosobranchs. It is also realized that double sampling of 50% of sampling sites the next day should be satisfactory as a quality control system in snail population studies.

10 citations


Journal Article
TL;DR: The natural growth, reproductivity, mortality and schistosomal infection of Biomphalaria alexandrina, the snail vector of Schistosoma mansoni in Egypt, were studied for one year in four irrigation canals.
Abstract: The natural growth, reproductivity, mortality and schistosomal infection of Biomphalaria alexandrina, the snail vector of Schistosoma mansoni in Egypt, were studied for one year in four irrigation canals, namely El-Khassa and Radwan (Giza Governorate) and Sendebis and Sanafeer (Qalyoubiya Governorate). Radwan canal contains a considerably dense Biomphalaria population and three generations of snails (parents generation and autumn and spring generations) were recognized. Two phases of growth were distinguished in both autumn and spring generations, a faster phase followed by a slower one. The faster phase extends from January to May and from March to August in the autumn and spring generations, respectively. The daily mortality rate of snails was highest in the hot season (June--September) and lowest in the cold months (December--April). Continuous reproductivity of Biomphalaria snails was observed allover the year with highest values of reproduction index from November to March. Biomphalaria snails collected from El Khassa and Radwan canals were free of S. mansoni infection, while snails of Sanafeer canal carried patent infection in September and October. Prepatent infection was also found in Sanafeer canal in July and September and in Sendebis canal in September.

7 citations


Journal Article
TL;DR: Helisoma population showed a major peak in the warmest months of the year (July-August), thus showing recovery in population after "Winter Closure" later than Bulinus, Biomphalaria and Physa.
Abstract: The range of distribution of Helisoma duryi, a potential competitor to schistosomiasis snail vectors in Egypt, was determined in the south of Nile Delta. Results show that H. duryi was found in the River Nile, Geziret El Kerateyeen banks, Damietta and Rosetta Branches, Tawfiky and Menoufy Canals and their branches and Bassoussiya, Bahadiya and Sheshaa canals and their branches. Helisoma was found in all categories of canals and drains co-existing in various degrees with other snail species including schistosomiasis vectors (Bulinus truncatus and Biomphalaria alexandrina). The population density of H. duryi and associated B. truncatus, B. alexandrina and Physa acuta were studied for one year in three channels. Statistical analysis of results show that Helisoma has a significantly negative correlation with schistosomiasis vectors in these channels. Helisoma population showed a major peak in the warmest months of the year (July-August) thus showing recovery in population after "Winter Closure" later than Bulinus, Biomphalaria and Physa. Helisoma proved to be free of any natural trematode infection.

7 citations


Journal Article
TL;DR: Both susceptible species have higher affinity to hydrogen peroxide (H2O2) and oxidized glutathione (GSSG) than the non-susceptible one.
Abstract: The activities of catalase (H2O2-oxidoreductase EC 1.11.1.6)- and glutathione reductase (EC 1.6.4.2) as two important scavenger enzymes, were measured in tissue homogenates of Biomphalaria alexandrina and Bulinus truncatus, the snail vectors of Schistosomiasis. A parallel study was done on Lymnea truncatula snails which are not susceptible to Schistosoma infection. The apparent Michaelis constant (Km) for both anzymes were determined in tissue homogenates of the three studied species. The results obtained showed that both susceptible species have higher affinity to hydrogen peroxide (H2O2) and oxidized glutathione (GSSG) than the non-susceptible one.

3 citations