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PubMedDate not supplied

[Susceptibility of Biomphalaria tenagophila and Biomphalaria glabrata from a same region to 2 Schistosoma mansoni strains].

B. tenagophila snails from Ouro Branco, MG, showed positivity for S. mansoni, with infection rates of 5%, 10%, (SJ strain), and 1% (LE strain) using a pool of miracidia. The mollusks were found to be susceptive from the 3rd generation reared in laboratory onwards. The B. tenagophila (OB, MG) when individually exposed to 10 miracidia, showed infection rate of 2% for LE strain. B. glabrata snails from Gagé, MG, showed a positivity rate of 58% for S. mansoni (LE strain), under experimental conditions. The B. tenagophila from Cabo Frio, RJ and B. glabrata from Belo Horizonte, MG used as a control for SJ strain showed infection rates of 47%-85% and 36% respectivily. For the LE strain, B. glabrata (BH, MG) used as control showed infection rate of 40%-75%.

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PubMed2004

Comparative study of the fecundity and fertility of Biomphalaria glabrata (Say, 1818) and Biomphalaria straminea (Dunker, 1848) in a laboratory through self-fertilization and cross-fertilization.

The aim of this study was to compare the fecundity and fertility of B. glabrata and B. straminea by cross- and self-fertilization. To attain this objective, laboratory-raised strains of B. glabrata and B. straminea were used. The former originated from natural breeding grounds in the municipality Paulista, state of Pernambuco, Brazil. The latter originated from irrigation ditches in the municipality of Petrolândia, in the same state. Snail populations of B. glabrata and B. straminea were maintained for 240 days in laboratory. Their fecundity was evaluated by noting the number of egg-masses, eggs and eggs per mass. Their fertility was evaluated by the number of viable eggs and the hatching rate. B. straminea was markedly more fecund than B. glabrata through cross- and self-fertilization, namely: greater egg-mass; higher egg production and more eggs per mass. Regarding fertility, there seemed to be no preferential period for occlusion to occur or a trend in the rhythm of producing viable eggs.

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PubMedDate not supplied

Competitive interactions between species of freshwater snails. I. Laboratory studies: Ib. Comparative studies of the dispersal and the vagility capabilities of Biomphalaria glabrata and Biomphalaria straminea.

Experiments reported in the current paper, carried out under semi-field conditions created in the laboratory, have shown that B. straminea has competitive superiority when compared with B. glabrata. The former species has shown higher capabilities of both dispersal and vagility. In addition, B. straminea was able to compete successfully with B. glabrata.

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PubMed1989

[Competitive behavior of Biomphalaria glabrata and Biomphalaria tenagophila--laboratory studies].

Observation about cohabitation among B. glabrata and B. tenagophila revealed a greater vulnerability of B. tenagophila population during the process of competition when its density was severely decreased in 12 trials, moderate in 2 trials. It was higher than B. glabrata in only one trial. Some snail water chemical parameters analysed such as pH, alkalinity, conductivity and oxygen dissolved, and the viability rate of batch of eggs didn't give subsidy to explain the competition mechanism. The newly-born survival, in the situation of cohabitation, was low for both species. This reveals the existence of intra and interspecific competitive interaction. The fertility rate reduction of B. tenagophila during the cohabitation was considered as a cause of its exclusion. One of the factors that seems to have influenced the fertility rate was a possible wrong crossing.

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PubMed2001

The distribution of Biomphalaria spp. in different habitats in relation to physical, biological, water contact and cognitive factors in a rural area in Minas Gerais, Brazil.

A total of 256 sites in 11 habitats were surveyed for Biomphalaria in Melquiades rural area (State of Minas Gerais) in August and November 1999 and in March 2000. Of the 1,780 Biomphalaria collected, 1,721 (96.7%) were B. glabrata and 59 (3.3%) B. straminea. Snails were found in all habitats except in wells, with the largest mean numbers in tanks, seepage ponds and canals, and the smallest numbers in springs, rice fields and fishponds. People's knowledge of the occurrence of Biomphalaria at the collection sites and the presence of Biomphalaria ova were strongly correlated with the occurrence of snails, and distance between houses and collection sites, as well as water velocity were inversely correlated with Biomphalaria occurrence (p < 0.001). The strongest predictor o f Biomphalaria occurrence was the presence of tilapia fish in fishponds. Fourteen Biomphalaria (0.8% of all snails) found at 6 sites were infected with Schistosoma mansoni. Suggestions are made for the utilization of local people's knowledge in snail surveys and further studies are recommended on the possible use of tilapia for biological control of Biomphalaria in fishponds, as well as modeling of S. mansoni transmission and reinfection.

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PubMed2005

A molecular survey of biomphalaria in Egypt: is B. glabrata present?

Two species of Biomphalaria are reported from Egypt, the indigenous Biomphalaria alexandrina and Biomphalaria glabrata, the latter believed to be introduced during the past few decades. Both are known to be excellent hosts of Schistosoma mansoni, the human-infecting blood fluke common in Egypt. Given the concerns regarding the spread of the exotic B. glabrata, this study was carried out to get a more current picture of the status of Biomphalaria in Egypt. Snail collections were undertaken during 2002-2003 from regions between Alexandria and Ismailia in the north of the Nile Delta, to as far south as Abu Simbel at Lake Nasser. Biomphalaria snails were found in 37 out of 76 sampled localities and were widely distributed in the Nile Delta and along the Nile as far south as Aswan. According to the results of species-specific polymerase chain reaction assays that sampled both nuclear and mitochondrial genomes, and according to DNA sequence data, all Biomphalaria collected during this survey were B. alexandrina. There was no evidence of the presence of B. glabrata or of hybridization of B. alexandrina with B. glabrata in the examined sites. The results were surprising given that some field-collected snails strongly resembled B. glabrata in both size and conchology and that previous survey work suggested B. glabrata had established in Egypt. Continued scrutiny to ascertain the possible presence of B. glabrata in Egypt is warranted. Also, the planorbid Helisoma duryi was detected in the Delta and as far south as Aswan, so it is important for Egyptian schistosomiasis workers to accurately distinguish this non-schistosome-transmitting snail from Biomphalaria.

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PubMed1998

Genetic evidence of two species in the Biomphalaria havanensis complex (Gastropoda. Planorbidae) from Cuba.

In Cuba, several species of freshwater gastropods belonging to the genus Biomphalaria have been described according to morphological characters. However, the taxonomy of this group remains unclear and a number of synonyms are often cited in the literature. This is the case for B. havanensis whose taxonomical status is not well established. Multilocus enzyme electrophoresis at 18 loci was carried out on adult snails of B. havanensis from the type locality in Havana and from several other sites harbouring a morphologically slightly different form, referred to here as Biomphalaria sp. Another local distinct species B. helophila was used as an outgroup. Allelic distribution showed the presence of nine and 12 diagnostic loci between B. havanensis and Biomphalaria sp. and B. helophila, respectively. We detected eight fixed alleles between Biomphalaria sp. and B. helophila. The genetic divergence estimated by absolute genetic distances strongly supports the assumption that Biomphalaria sp. is quite different from the sympatric B. havanensis, morphologically the closest species.

Alleles↗
PubMed2001

Schistosoma mansoni and Biomphalaria: past history and future trends.

Schistosoma mansoni is one of the most abundant infectious agents of humankind. Its widespread distribution is permitted by the broad geographic range of susceptible species of the freshwater snail genus Biomphalaria that serve as obligatory hosts for its larval stages. Molecular phylogenetic studies suggest that Schistosoma originated in Asia, and that a pulmonate-transmitted progenitor colonized Africa and gave rise to both terminal-spined and lateral-spined egg species groups, the latter containing S. mansoni. Schistosoma mansoni likely appeared only after the trans-Atlantic dispersal of Biomphalaria from the Neotropics to Africa, an event that, based on the present African fossil record, occurred only 2-5 million years ago. This parasite became abundant in tropical Africa and then entered the New World with the slave trade. It prospered in the Neotropics because a remarkably susceptible and productive host, B. glabrata, was widely distributed there. Indeed, a snail similar to B. glabrata may have given rise to the African species of Biomphalaria. Schistosoma mansoni has since spread into other Neotropical Biomphalaria species and mammalian hosts. The distribution of S. mansoni is in a state of flux. In Egypt, S. mansoni has nearly completely replaced S. haematobium in the Nile Delta, and has spread to other regions of the country. A susceptible host snail, B. straminea, has been introduced into Asia and there is evidence of S. mansoni transmission in Nepal. Dam and barrage construction has lead to an epidemic of S. mansoni in Senegal, and the parasite continues its spread in Brazil. Because of competition with introduced aquatic species and environmental changes, B. glabrata and consequently S. mansoni have become less abundant on the Caribbean islands. Control of S. mansoni using praziquantel and oxamniquine has reduced global prevalence but control is difficult to sustain, and S. mansoni can develop tolerance/resistance to praziquantel, raising concerns about its future efficacy. Because of legitimate environmental concerns, snail control is unlikely to be an option in future control efforts. Global warming will impact the distribution of Biomphalaria and S. mansoni, but the magnitude and nature of the effects are poorly understood.

Africa↗
PubMed2001

Evolutionary relationships and biogeography of Biomphalaria (Gastropoda: Planorbidae) with implications regarding its role as host of the human bloodfluke, Schistosoma mansoni.

The wide geographic distribution of Schistosoma mansoni, a digenetic trematode and parasite of humans, is determined by the occurrence of its intermediate hosts, freshwater snails of the genus Biomphalaria (Preston 1910). We present phylogenetic analyses of 23 species of Biomphalaria, 16 Neotropical and seven African, including the most important schistosome hosts, using partial mitochondrial ribosomal 16S and complete nuclear ribosomal ITS1 and ITS2 nucleotide sequences. A dramatically better resolution was obtained by combining the data sets as opposed to analyzing each separately, indicating that there is additive congruent signal in each data set. Neotropical species are basal, and all African species are derived, suggesting an American origin for the genus. We confirm that a proto-Biomphalaria glabrata gave rise to all African species through a trans-Atlantic colonization of Africa. In addition, genetic distances among African species are smaller compared with those among Neotropical species, indicating a more recent origin. There are two species-rich clades, one African with B. glabrata as its base, and the other Neotropical. Within the African clade, a wide-ranging tropical savannah species, B. pfeifferi, and a Nilotic species complex, have both colonized Rift Valley lakes and produced endemic lacustrine forms. Within the Neotropical clade, two newly acquired natural hosts for S. mansoni (B. straminea and B. tenagophila) are not the closest relatives of each other, suggesting two separate acquisition events. Basal to these two species-rich clades are several Neotropical lineages with large genetic distances between them, indicating multiple lineages within the genus. Interesting patterns occur regarding schistosome susceptibility: (1) the most susceptible hosts belong to a single clade, comprising B. glabrata and the African species, (2) several susceptible Neotropical species are sister groups to apparently refractory species, and (3) some basal lineages are susceptible. These patterns suggest the existence of both inherent susceptibility and resistance, but also underscore the ability of S. mansoni to adapt to and acquire previously unsusceptible species as hosts. Biomphalaria schrammi appears to be distantly related to other Biomphalaria as well as to Helisoma, and may represent a separate or intermediate lineage.

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PubMedDate not supplied

Immunoelectrophoretic study on common antigens of São Lourenço da Mata and Belo Horizonte strains of Schistosoma mansoni adult worms and Biomphalaria snails.

Immunoelectrophoretic studies on common antigens were carried out by using rabbits sera immunized against São Lourenço da Mata and Belo Horizonte strains of Schistosoma mansoni adult worms and antigens of Biomphalaria glabrata pigmented (Jaboatão--PE); B. glabrata albino (Belo Horizonte--MG) and B. straminea (São Lourenço da Mata, PE). Furthermore, the reverse approach was proceeded, namely, sera anti Biomphalaria snails produced in rabbits were tested against both strains of Schistosoma adult worm antigens. The analysis of the common antigens between the SLM strains of S. mansoni adult worm and B. glabrata pigmented showed 8 to 9 precipitin bands, 3 bands with B. glabrata albino and only 1 band with B. straminea crude extracts. On the other hand, the BH strain of S. mansoni adult worm antisera produced 6 to 7 bands with B. glabrata pigmented, 5 bands with B. glabrata albino and 1 band with B. straminea antigenic extract. Biomphalaria snails crude extracts were fractionated by Sephadex G-100 column and three fractions were collected from each snail strain. The fractions were tested with anti SLM and BH strains of S. mansoni adult worm sera by immunoelectrophoresis. The common antigens fractionated from Biomphalaria snails crude extracts and those found for both strains of S. mansoni adult worm mostly existed in the first fraction and they were estimated to have molecular weight over 158,000 daltons. In our laboratory, it was found a relationship between the antigenic similarities and experimental infection rates of S. mansoni towards Biomphalaria snails so that more bands were seen with increasing infection rates of S. mansoni.

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PubMed1992

Studies on common antigenicities between the Belo Horizonte strain, Brazil of Schistosoma mansoni eggs and Biomphalaria snails by immunoelectrophoresis.

Immunoelectrophoretic studies of common antigenicities were carried out by using rabbit sera immunized against the Belo Horizonte strain of Schistosoma mansoni eggs and crude antigens of Biomphalaria snails and vice versa. With regard to common antigenicities between S. mansoni eggs and Biomphalaria snails, S. mansoni eggs produced 4 to 5 bands with Biomphalaria glabrata pigmentado, 3 to 4 bands with B. glabrata albino and only 1 band with B. straminea. In our laboratory, the infection rate of S. mansoni miracidia to B. glabrata pigmentado was 64.3% and 55.0% for B. glabrata albino, but B. straminea was not found to be susceptible to S. mansoni miracidia. It was observe that more bands were seen between S. mansoni egg and suitable hosts. Biomphalaria snail crude antigens were fractionated by Sephadex G-100 column, and each fraction antigen was tested with anti-S. mansoni egg sera by immunoelectrophoresis. As results, three fractions were collected form each snail strains. The common antigenicities between fractionated antigens from Biomphalaria snails crude antigens and anti-S. mansoni egg sera mostly existed in the first fraction and they were estimated to have molecular weights over 45,000.

Animals↗
PubMed1994

Studies on host-parasite relationship between the Puerto Rican strain of Schistosoma mansoni and Biomphalaria snails.

Immunoelectrophoretic studies on common antigenicities were carried out by using rabbits sera immunized with the Puerto Rican strain of Schistosoma mansoni adult worms or eggs and antigens of several adult Biomphalaria snails and vice versa. As the result, S. mansoni adult worm extracts produced 8 bands both with extracts of Biomphalaria glabrata pigmentation and B. glabrata pigmentado, 3 to 4 bands with those of B. glabrata albino and 1 to 2 bands with those of B. straminea. On the other hand, S. mansoni egg extracts produced 5 bands with extracts of B. glabrata pigmentation, 4 bands with those of B. glabrata pigmentado, 2 bands with those of B. glabrata albino and 1 band with those of B. straminea. In the experimental infection of adult Biomphalaria snails with five S. mansoni miracidia, the infection rate in B. glabrata pigmentation was 78.8%, and 71.2% in B. glabrata pigmentado, whereas the infection rate in B. glabrata albino was 10.3%, and B. straminea was not susceptible to S. mansoni. The infectivity of each snail corresponded with the number of bands representing common antigenicities between host and parasite. Crude antigens of Biomphalaria snails were fractionated by Sephadex G-100 column, and each antigen fraction was tested with anti-S. mansoni adult worm and egg sera by immunoelectrophoresis. The common antigenicities between fractionated antigens of Biomphalaria snails and of ani-S. mansoni adult worm or egg sera mostly existed in the first fraction 1 with Mr > 45 kDa.

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