Showing papers on "Biomphalaria alexandrina published in 1998"

Compatibility of Biomphalaria alexandrina, Biomphalaria glabrata and a hybrid of both to seven strains of Schistosoma mansoni from Egypt.

Abstract: The susceptibility of Biomphalaria alexandrina, Biomphalaria glabrata and a hybrid snail of both, all obtained from natural habitats in Egypt, to infection with six human local strains of Schistosoma mansoni and a laboratory strain of human origin was determined. The infection rate, prepatent period, periodic cercarial production and duration of cercarial shedding were compared in all cases. The results showed that each of the three studied Biomphalaria snails had different rates of infection and different values of total periodic cercarial production with various strains of S. mansoni. However, the mean infection rate of all local S. mansoni strains was significantly much higher in B. alexandrina than each of B. glabrata and the hybrid snail, being 66%, 7.2% and 8.5%, respectively. Considering the mean of results of all local S. mansoni strains used, the longevity of cercariae-shedding B. glabrata and the hybrid snails was much longer than that of B. alexandrina, with high significant difference between them (P < 0.01), being 94.5, 103.3 & 69.1 days, respectively. The mean prepatent period of various S. mansoni strains showed no significant difference in the three Biomphalaria snails studied. The hybrid snail produced periodically (1 h stimulant twice weekly) more schistosome cercariae/snail (4,784.2) than B. glabrata (2,913.4 cercariae/snail) and the least production was in the case of B. alexandrina (1,397.2 cercariae/snail) (P < 0.05). The diurnal pattern of S. mansoni cercarial shedding was found to be similar for B. glabrata, B. alexandrina and the hybrid snail showing a peak of cercariae at the same time (9-10 a.m.).

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

Abstract: 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.

Invasion of the Nile Valley in Egypt by a hybrid of Biomphalaria glabrata and Biomphalaria alexandrina, snail vectors of Schistosoma mansoni.

Abstract: Two years (1996-1997) of systematic survey showed that a hybrid of Biomphalaria glabrata and Biomphalaria alexandrina has invaded the irrigation and drainage systems in the Nile Delta and the Valley nor the of El-Menya. However, the infestation of water courses by and the population density of this snail were variable in various localities. The infestation rate ranged between 7.1% in El-Fayoum Governorate and 52.6% in El-Dakahliya Governorate and the snail density from 2 snails/site to 69.7 snails/site in the same governorates, respectively. Comparing the survey results of the two study years in the sampling sites indicated that the hybrid snail has relatively increased in population density than B. alexandrina. The hybrid snail of B. glabrata and B. alexandrina was found alone in some sites, but was mostly associated with B. alexandrina. The results showed also that both Biomphalaria have almost the same major physicochemical requirements. However, the hybrid snails and B. alexandrina were found differently associated with aquatic snails and plants. The hybrid snail was found naturally infected with S. mansoni thus giving indication that it is presently participating in schistosomiasis mansoni transmission in Egypt.

Effect of six non-target snails on Schistosoma mansoni miracidial host finding and infection of Biomphalaria alexandrina under laboratory conditions.

Abstract: Six snail species naturally associated with Biomphalaria alexandrina, the snail host of Schistosoma mansoni in Egypt, were tested under standard laboratory conditions, for impact on miracidial host findings and infection of the snail host. These snails are the prosobranchs Melanoides tuberculata, Cleopatra bulimoides, Bellamys unicolor and Lanistes carinatus, the pulmonates Planorbis planorbis and Physa acuta. The tested snail ssp. reduced considerably the infection rate of Biomphalaria with S. mansoni especially at a ratio of 10 decoy snails to one Biomphalaria snail. The prosobranchs Melanoides, Cleopatra and Lanistes exhibited more reducing effect on Biomphalaria infection than Bellamya and the pulmonates Physa and Planorbis being 65.2%, 78.8%, 62.9%, 33.3%, 30.3% and 46.9%, respectively.

Studies on the molluscicidal action of some isatin derivatives against Biomphalaria alexandrina in Egypt.

Abstract: Some compounds selected from the isatin derivatives and their metalleted products were used to study their molluscicidal effect on Biomphalaria alexandrina. The results indicated that some of these compounds showed good results and seem to be promising molluscicides.

Seasonal variation in molluscicidal activity of Solanum nigrum L.

Abstract: Solanum nigrum L. leaves and fruits were shown to have molluscicidal activities against snails transmitting schistosomiasis and fascioliasis. In the present study, their molluscicidal activity against adult Biomphalaria alexandrina snails was assessed to determine whether plants collected at various seasons would have different degrees of toxicity. Leaves and fruits of three S. nigrum varieties were collected from Faiyoum and/or Giza during the four seasons. Leaves collected in autumn had the highest effect (LC50-35.4) followed by spring (LC50 = 44.36), summer (LC50 = 46.7) and winter (LC50 = 100.4). Toxicity of plant extracts was also affected by other seasonal dependent factors. These are the duration of plant exposure to direct sunlight and the size of the fruits. S. nigrum (black fruits) was more toxic (LC50 = 18.1) than the other two types, S. nigrum v. vellosum (yellow fruits) (LC50 = 38.9) and S. nigrum v. juidaicum (red fruits) (LC50 = 34.7).

Study of the saponin content of atriplex stylosa viv. and its molluscicidal effect

Abstract: From the aerial parts of Atriplex stylosa Viv, four triterpenoidal saponins have been isolated. Their structures were established as 3-O-a-L-rhamnopyranosyl-(1®3)-b-D-glucuronopyranosyl hederagenin; 3-O-b-D-glucopyranosyl-(1®3)-b-D-glucuronopyranosyl hederagenin; 3-O-a-L-rhamnopyranosyl-(1®3)-b-D-glucuronopyranosyl hederagenin; 28-O-b-D-glucopyranoside and 3-O-a-L-rhamnopyranosyl-(1®)-[b-D-glucopyranosyl-(1®2)]-b-D-glucuronopyranosly oleanolec acid by spectroscopic methods (IR, 1H-NMR, 13C-NMR and FAB-MS) as well as on basis of acidic and alkaline hydrolysis. The three monodesmosidic saponins exhibited various molluscicidal activities against the two aquatic snails; Biomphalaria alexandrina and Lymnaea cailliaudi, the intermediate hosts of Schistosoma mansoni and Fasciola gigantica respectively in Egypt whereas the bidesmosidic saponin was inactive against the two snail species.

Susceptibility of Biomphalaria alexandrina to the plant Azolla pinnata and some herbicides in relation to infection with Schistosoma mansoni miracidia.

Abstract: Molluscicidal activity of the herebicides 2,4-D and Graminol, as well as both extracts and dry powder of the plant Azolla pinnata were evaluated against B. alexandrina snails. It was observed that 2,4-D proved to be the most toxic compound among he tested ones, showing LC90 of 52 ppm after 24 h of exposure. Ethanol extract of Azolla showed the highest molluscicidal activity against the tested snails compared with the other extracts and dry powder (LC90 = 3300 ppm). Ethanol extract at 6600 ppm after 3 h of exposure killed 100% and 19.4% of S. mansoni miracidia and cercariae, respectively. The molluscicidal activity of 2,4-D was not influenced by the presence of Azolla (900 plants/liter) for 7 days, while Graminol effect was significantly reduced. However, the infectivity of S. mansoni miracidia to B. alexandrina snails was not affected by Azolla existence.

Molluscicidal steroidal saponins from agave ferox

Abstract: Four steroidal saponins were isolated from the methanol extract of the leaves of Agave ferox. On the basis of chemical and spectroscopic evidence, the structures of these saponins were established as yamogenin 3-O-α-L-rhamnopyranosyl- (1→ 2) –[α-L- arabinopyranosyl-(1→3)-β-D-glucopyranoside; yamogenin 3-O-α-L-rhamopyranosyl –(1→ 2 ) [-B-D-glucopyranosyl-(1→4)-6-D- glucopyranoside; gentrogenin 3-O-α-L-rhamnopyranosyl- (1→2)-α-L-arabinopyranosyl- (1→3) - β-D-glucopyranosyl-(1→ 4)-β-D- galactopyranoside and gentrogenin 3-0-a-L- rhamnopyranosyl-(1→2)-B-D-glucopyranosyl(1-→3)-B-D glucopyranosyl- (1→4) -B-D- galactopyranoside. The four saponins were found to possess various molluscicidal activities against Biomphalaria alexandrina snails; the intermediate host of Schistosoma mansoni in Egypt.