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PubMed1997

Cockroach allatostatin-like immunoreactivity in the central nervous system of the freshwater snails Bulinus globosus (Planorbidae) and Stagnicola elodes (Lymnaeidae).

Allatostatin-like immunoreactivity was demonstrated in the central nervous system (CNS) neurons of the freshwater pulmonate snails Bulinus globosus (Planorbidae) and Stagnicola elodes (Lymnaeidae). Immunopositive neurons were localized using a monoclonal antibody highly specific to allatostatin I (APSGAQRLYGFGL-amide) from the cockroach Diploptera punctata. All CNS ganglia in both snail species contained immunopositive neurons. The pedal ganglia showed large numbers (80-100) of neurons in Bulinus and Stagnicola. Large numbers of immunopositive cells were also found in the cerebral (60) and buccal ganglia (20) of Bulinus. Other ganglia contained fewer immunopositive cells, but these cells were most concentrated in the cerebral (Stagnicola) and left parietal (Bulinus) ganglia and the visceral ganglia of both species. The high concentration of immunopositive cells in the pedal ganglia and axons demonstrable in the pedal nerves suggests that one possible function for a molluscan allatostatin-like peptide would be to modulate muscular function. Extract of Stagnicola CNS effected 50% inhibition of juvenile hormone synthesis by corpora allata of D. punctata at between 15 and 30 CNS equivalents, providing further evidence that the molluscan immunoreactive material is a peptide, or peptides, with sequence similarity to the active part of the D. punctata allatostatins.

Animals↗
PubMed1977

On Schistosoma margrebowiei Le Roux, 1933: the morphology of the egg, miracidium and cercaria, the compatibility with species of Bulinus, and development in Mesocricetus auratus.

The morphology of the egg, miracidium, and cercaria of Schistosoma margrebowiei are described. The compatibility of S. margrebowiei with species of Bulinus has been examined. The parasite develops well in the diploid, tetraploid and octoploid snails of the truncatus/tropicus complex with overall infection rates of 38.1%, 30.1% and 29.1% respectively, and in reticulatus group snails (Bulinus wrighti) with an infection rate of 45.8% of those snails surviving the prepatent period. Only two species of the forskali complex (Bulinus bavayi, Aldabra; Bulinus beccarii, South Arabia) are slightly compatible, and snails of the africanus group are incompatible. The overall worm return from 24 hamsters exposed individually to 100 cercariae was 39.8%; 82.1% of the worms were paired, the remainder unpaired. The growth of the paired worms was recorded from 28-60 days. The prepatent period in hamsters in 33 days, in sheep 38 days. The mean egg production was 837 eggs/day in infections ranging from 33 to 60 days. Most eggs (80.9%) were deposited in the intestine, and only 18.2% were deposited in the liver. The parasite is pathogenic in hamsters, and peak death rate occurred in the 50-60 day group infections which coincided with the period of peak egg production.

Animals↗
PubMed2001

Bulinus species on Madagascar: molecular evolution, genetic markers and compatibility with Schistosoma haematobium.

Of the four species of Bulinus found on Madagascar, three species: B. obtusispira, B. liratus and B. bavayi are endemic while the fourth, B. forskalii, is probably a recent introduction from the African mainland. The evolutionary relationships of these species with Bulinus species from Africa were studied by phylogenetic analysis of DNA sequence variation at two mitochondrial loci: cytochrome oxidase subunit I (COI) and large ribosomal subunit (LSU) or 16S. The observed levels of nucleotide divergence within Bulinus were substantial but may underestimate the true levels as there was evidence of 'saturation' of transitional substitutions at both loci. A putative secondary structure model for the sequenced segment of the 16S was developed. Subsequent phylogenetic analysis using transversional changes only for both loci, showed that there were contrasting levels of divergence within the four species groups. B. obtusispira was consistently placed within the B. africanus group, appearing ancestral to this group and was closest to the basal node within Bulinus. Together with B. bavayi, the two species appear to have been isolated on Madagascar for a long time, contrasting with both B. liratus and B. forskalii that appear more recent colonisers; however, estimate of exact times of divergence is problematic. A PCR-RFLP assay was developed to enable identification and discrimination of B. obtusispira and B. liratus using discriminatory variation within the COI. To enable population genetic analysis within B. obtusispira, microsatellite markers were developed using an enrichment method and 8 primer pairs are reported. Laboratory infection experiments using Madasgacan S. haematobium from the Mahabo area showed that certain populations of B. obtusispira, B. liratus and B. bavayi were compatible.

Animals↗
PubMed1994

[Experimental study of a Malagasy strain of Schistosoma haematobium: compatibility with different Bulinus snails, potential intermediate hosts].

Experimental investigation on a malagasy strain of S. haematobium: compatibility with different Bulinus snails, potential intermediate hosts. A comparative experimental study of the infectivity of different Bulinus snails by a reference S. haematobium strain was made under laboratory conditions. The results support the role of Bulinus obtusispira as an intermediate host in Madagascar but some other Bulinus species could exist and play a role in the fields far away from the experimental criteria here described.

Adolescent↗
PubMed1996

[Survival of Bulinus truncatus and Biomphalaria pfeifferi in sewer water purified in stabilization ponds in a sudanese-saharan zone].

In subsaharan Africa wastewater purification to protect the health of the population could create stagnate water reservoirs for parasitic vectors such as snails which are intermediate hosts of bilharzia. Laboratory studies of the survival of Bulinus truncatus, an intermediate host of Schistosoma haematobium, and Biomphalaria pfeifferi, an intermediate host of Schistosoma mansoni, in waste water purified in stabilization ponds showed that Biomphalaria pfeifferi thrives to dirty water (60 mg/l < or = COD < or = 1060 mg/l) while Bulinus truncatus survived only in slightly cleaner water (60 mg/l < or = COD < or = 200 mg/l). Field studies showed that Biomphalaria pfeifferi disappeared after 48 hours as compared to 25 days in the laboratory. In both laboratory and field studies Bulinus truncatus survived only 24 hours in raw waste water. The duration of survival grew longer as quality of the water improved. Temperature variations, high amounts of organic material in water, high oxygen content in water, and absence of plant-life are factors which could limit the development of the intermediate snail hosts (i.e. Bulinus truncatus and Biomphalaria pfeifferi) in the waste stabilization ponds of the Interstate School of Rural Equipment Engineers in Ouagadougou, Burkina Faso.

Animals↗
PubMed1993

Detection of genetic diversity within snail intermediate hosts of the genus Bulinus by using random amplified polymorphic DNA markers (RAPDs).

A polymerase chain reaction-based polymorphic assay procedure (RAPD) was used to study the genetic diversity of intermediate host snails within the genus Bulinus. Genetic differentiation was detected between two closely related species: Bulinus globosus and Bulinus umbilicatus. Evidence is presented demonstrating the potential of RAPD markers for differentiating populations of B. forskalii from different countries (Cameroon, Equatorial Guinea and Ivory Coast) or from the same country (Cameroon). RAPDs may be also used to identify offspring from cross- and self-fertilized hermaphrodite bulinid snails. RAPDs provide a cost-effective and routine method for genetic studies of snails transmitting schistosomiasis and for the evaluation of diversity between snail populations.

Animals↗
PubMed2001

Interactions between intermediate snail hosts of the genus Bulinus and schistosomes of the Schistosoma haematobium group.

Within each of the four species groups of Bulinus there are species that act as intermediate hosts for one or more of the seven species of schistosomes in the Schistosoma haematobium group, which includes the important human pathogens S. haematobium and S. intercalatum. Bulinus species have an extensive distribution throughout much of Africa and some surrounding islands including Madagascar, parts of the Middle East and the Mediterranean region. Considerable variation in intermediate host specificity can be found and differences in compatibility between snail and parasite can be observed over small geographical areas. Molecular studies for detection of genetic variation and the discrimination of Bulinus species are reviewed and two novel assays, allele-specific amplification (ASA) and SNaPshot, are introduced and shown to be of value for detecting nucleotide changes in characterized genes such as cytochrome oxidase 1. The value and complexity of compatibility studies is illustrated by case studies of S. haematobium transmission. In Senegal, where B. globosus, B. umbilicatus, B. truncatus and B. senegalensis may act as intermediate hosts, distinct differences have been observed in the infectivity of different isolates of S. haematobium. In Zanzibar, molecular characterization studies to discriminate between B. globosus and B. nasutus have been essential to elucidate the roles of snails in transmission. B. globosus is an intermediate host on Unguja and Pemba. Further studies are required to establish the intermediate hosts in the coastal areas of East Africa. Biological factors central to the transmission of schistosomes, including cercarial emergence rhythms and interactions with other parasites and abiotic factors including temperature, rainfall, water velocity, desiccation and salinity are shown to impact on the intermediate host-parasite relationship.

Africa↗
PubMed1997

Observations on compatibility between Bulinus truncatus and Schistosoma haematobium in the Senegal River Basin.

In experiments to determine the compatibility between isolates of Schistosoma haematobium and Bulinus truncatus from Mali and Senegal, the parasite isolates were shown to differ in their intermediate host specificity. Bulinus truncatus from the Lower and Middle Valleys (Senegal) and the Upper Valley (Mali) of the Senegal River Basin (SRB) were all susceptible to S. haematobium isolated from the urines of children living in Tenegue, Office du Niger, Mali. However, none of the B. truncatus tested was susceptible to a parasite isolated from children living in Mbodiene, a village in the Lower Valley of the SRB, where natural transmission is normally associated with B. globosus. As B. truncatus is widely distributed in the SRB, the possible appearance of a Bulinus-truncatus-borne parasite in the Middle and Lower Valleys should be carefully monitored.

Animals↗
PubMed2002

Susceptibility of freshwater snails to the amphistome Calicophoron microbothrium and the influence of the species on susceptibility of Bulinus tropicus to Schistosoma haematobium and Schistosoma mattheei infections.

The susceptibility of Bulinus tropicus, B. globosus, Biomphalana pfeifferi, Lymnaea natalensis, and Melanoides tuberculata to Calicophoron microbothrium was examined. Bulinus tropicus had the highest prevalence (65.0%), followed by B. pfeifferi (37.5%), B. globosus (6.8%), and M. tuberculata (5.9%). Lymnaea natalensis was refractory to infection. Bulinus tropicus snails infected with C. microbothrium alone or coinfected with either Schistosoma haematobium or S. mattheei 0, 7, 14, and 21 days after exposure to C. microbothrium produced C. microbothrium cercariae only.

Animals↗
PubMed2004

Distribution patterns and cercarial shedding of Bulinus nasutus and other snails in the Msambweni area, Coast Province, Kenya.

In the Msambweni area of the Kwale District in Kenya, an area endemic for Schistosoma haematobium, potential intermediate-host snails were systematically surveyed in water bodies associated with human contact that were previously surveyed in the 1980s. Bulinus (africanus) nasutus, which accounted for 67% of the snails collected, was the only snail shedding S. haematobium cercariae. Lanistes purpureus was the second most common snail (25%); lower numbers of Bulinus forskalii and Melanoides tuberculata were also recovered. Infection with non-S. haematobium trematodes was found among all snail species. Rainfall was significantly associated with the temporal distribution of all snail species: high numbers of Bulinus nasutus developed after extensive rainfall, followed, in turn, by increased S. haematobium shedding. Spatial distribution of snails was significantly clustered over a range of up to 1 km, with peak clustering observed at a distance of 400 meters. Water lily (Nymphaea spp.) and several aquatic grass species appeared necessary for local colonization by B. nasutus or L. purpureus.

Animals↗
PubMed1988

Schistosomiasis in Kano State, Nigeria. II. Field studies on aestivation in Bulinus rohlfsi (Clessin) and B. globosus (Morelet) and their susceptibility to local strains of Schistosoma haematobium (Bilharz).

Aestivation patterns in Bulinus rohlfsi and B. globosus were studied by digging transects across the floor of their dried habitats and by monitoring changes in snail population structure during the period when the habitats were flooded. Bulinus rohlfsi, which inhabited a small man-made lake, was found to aestivate towards the bottom of its habitat, aestivation occurring during the last six weeks before the lake dried. The data on B. globosus from a temporary pool are less complete, but they show that this species also aestivates at the bottom of its habitat and can be found buried at depths up to 3 cm. A wide size range of both species of snail were found to aestivate, but there was differential mortality of young B. rohlfsi soon after the lake re-filled, and the optimally surviving size group of B. globosus was 9 mm. The beginning of aestivation in B. rohlfsi did not correlate with any of the physical parameters measured, but it coincided with the dying off of a bloom of unicellular algae. The importance of stimuli other than desiccation in the aestivation process of bulinids is stressed. Laboratory infections with isolates of Schistosoma haematobium showed that both Bulinus species were capable of transmitting local strains of the parasite and indicated the presence of snail host-specific strains.

Adaptation, Physiological↗
PubMed1977

[Cercaria ogunis n. sp. (echinostomatidae) from Bulinus globosus in West Africa (author's transl)].

Cercaria ogunis n. sp. (Echinostomatidae) is described. The cercaria has 47 collar spines, 2 X 15 flame cells, a small dorsal and a small ventral finfold near the tip of the tail. A peculiar organ located dorsally next to the brain is explained, hypothetically, as a statocyst. In the behaviour of the cercaria there are some conspicuous features, i.e. a rapid swimming-velocity, a striking positive geotaxis and a positive phototaxis. Second intermediate hosts are gastropods and amphibians. The metacercarial cysts exist in two distinct modifications: Cysts from Bulinus are globular, cysts from amphibians are elongated-ellipsoid. The Bulinus population of the habitat shows at the same time a high prevalence of Schistosoma haematobium. C. ogunis has never been observed as being involved in double infections. This seems to suggest that the rediae of this species are incompatible with other trematodes in the snail.

Africa, Western↗
PubMed1983

Studies on the relationship between Schistosoma and their intermediate hosts. V. The genus Bulinus and Schistosoma bovis from Iringa, Tanzania.

The relationship between an isolate of Schistosoma bovis from Iringa, Tanzania, and various species of the host snail genus Bulinus from East Africa was studied using the total cercarial production per 100 exposed snails over a period of 4 weeks following patency as an index of the compatibility. All populations of Bulinus forskalii and B. africanus tested exhibited a high level of susceptibility while the populations of B. truncatus and B. globosus tested were either refractory or of low to moderately low susceptibility. All populations of B. abyssinicus, B. canescens, B. nasutus and B. tropicus tested were refractory. It is suggested that B. africanus is the most important host snail for S. bovis in East Africa, that B. forskalii at least locally may contribute significantly to the transmission and that B. truncatus and B. globosus only play a limited role in the transmission.

Animals↗
PubMed1990

Development of cloned DNA probes for the identification of snail intermediate hosts within the genus Bulinus.

DNA fragments have been isolated from Bulinus cernicus and cloned in Escherichia coli strain JM109 using pUC18 as the vector. Four recombinant plasmids designated pBC123, pBC126, pBC127 and pBC134 were selected for further analysis and were shown by both dot and Southern blot hybridisations to have different specificities to species representing the four species groups of Bulinus. Non-specific hybridisation occurred with pBC126 whereas pBC123 and pBC134 hybridised only to B. cernicus. Partial restriction maps of the inserts revealed sequence differences between pBC123 and pBC134. Intermediate specificity was shown by pBC127 as this probe hybridised only to DNA from snails of the B. forskalii group and B. truncatus of the B. truncatus/tropicus complex. The results demonstrate the potential of DNA probes for the identification and characterisation of intermediate hosts of schistosomes.

Animals↗
PubMed2001

Molecular evolution of freshwater snail intermediate hosts within the Bulinus forskalii group.

Freshwater snails of the Bulinus forskalii group are one of four Bulinus species complexes responsible for the transmission of schistosomes in Africa and adjacent regions. The species status of these conchologically variable and widely distributed planorbids remains unclear, and parasite compatibility varies considerably amongst the eleven taxa defined, making unambiguous identification and differentiation important prerequisites for determining their distributions and evolutionary relationships. Random Amplified Polymorphic DNA (RAPD) analyses were used to investigate relationships between taxa, with particular emphasis on Central and West African representatives. RAPD-derived phylogenies were compared with those from other independent molecular markers, including partial sequences of mitochondrial cytochrome oxidase subunit I (COI) gene, and the nuclear ribosomal RNA internal transcribed spacer 1 region (ITS1). The phylogenetic reconstructions from the three approaches were essentially congruent, in that all methods of analysis gave unstable tree topologies or largely unresolved branches. There were large sequence divergence estimates between species, with few characters useful for determining relationships between species and limited within species differentiation. Nuclear and mtDNA sequence data from Central and East African representatives of the pan-African B. forskalii showed little evidence of geographical structuring. Despite the unresolved structure within the phylogenies, specimens from the same species clustered together indicating that all methods were capable of differentiating taxa but could not establish the inter-specific relationships with confidence. The limited genetic variation displayed by B. forskalii, and the evolution and speciose nature of the group, are discussed in the context of the increasingly arid climate of the late Miocene and early Pliocene of Africa.

Africa↗
PubMed2001

Bulinus nyassanus is an intermediate host for Schistosoma haematobium in Lake Malawi.

At Cape Maclear on the Nankumba Peninsula, close to the southern end of Lake Malawi, Schistosoma haematobium is highly prevalent in the local people and many tourists become infected with this parasite each year. A 'Bilharzia Control Programme' was initiated in this area in August 1998, as a development collaboration between the Government of Malawi, the Danish Agency for Development Assistance (Danida), and the Danish Bilharziasis Laboratory. Although Bulinus globosus is a known host for S. haematobium, B. nyassanus has not previously been incriminated as an intermediate host. However, schistosome-infected B. nyassanus were discovered in surveys to identify transmission sites on the peninsula. Experimental infections of wild-caught B. nyassanus with S. haematobium proved successful and S. haematobium eggs were found in hamsters experimentally exposed to cercariae retrieved from schistosome-infected, field-collected B. nyassanus. These are remarkable observations since, although there are very few reports of diploid members of this species group being experimentally infected with S. haematobium, B. nyassanus is a diploid member (2n = 36) of the truncatus/tropicus group. Bulinus nyassanus is probably responsible for transmission in Lake Malawi, along rather exposed shorelines, devoid of aquatic macrophytes, with a substrate of sand or gravel.

Animals↗
PubMed2002

Implication of Bulinus truncatus in the transmission of urinary schistosomiasis in Senegal, West Africa.

Studies on the compatibility between Bulinus truncatus and Schistosoma haematobium from various areas in the Senegal River basin (SRB) were carried out, to investigate the role of B. truncatus in the epidemiology of urinary schistosomiasis in Senegal. The results show that B. truncatus from the Lower Valley is not compatible with S. haematobium from the Middle Valley. Interestingly, the study reveals that B. truncatus from the Upper Valley is compatible with S. haematobium from the same area, and that S. haematobium from the Middle Valley is compatible with B. truncatus from the Lower Valley. Bulinus truncatus naturally infected with S. haematobium have been collected from the Upper Valley of the SRB. These results indicate that B. truncatus is involved in the urinary schistosomiasis in Senegal.

Animals↗
PubMed2006

Molluscicidal activity of some Cameroonian plants on Bulinus species.

OBJECTIVE: To evaluate some locally available plants for their molluscicidal activity on Bulinus camerunensis and B. truncatus (slender form). DESIGN: Experimental studies. SETTING: Ndongo stream near the University of Buea and the University of Buea Life Sciences Laboratory. SUBJECTS: Evaluation of molluscicidal activity on snails of Bulinus camerunensis and B. truncatus (slender form). MAIN OUTCOME MEASURES: Plant extracts with molluscicidal activity determined. Determination of LC50, LC90 and LC100 of the potent plant extracts. Application of the extracts on aquaria-reared snails. Semi-field application of extracts. RESULTS: A preliminary screening test using 10,000 ppm solution of the water extracts of thirteen plants revealed that 61.5% (8/13) of the plants investigated had molluscicidal properties, with snail mortality rates above 90%. Extracts of Nicotiana tabacum, Aframomum citratum, A. melegueta, Curcuma domestica and Solanum scabrum killed 100% of the snails after twenty four hours exposure. B. camerunensis was more susceptible to the water extracts than B. truncatus. The LC50, LC90 and LC100 of the different plant extracts against B. camerunensis were generally lower than those against B. truncatus. The concentrations that produced 50%, 90% and 100% snail mortalities were lower with the methanol extracts than with water extracts, indicating that the methanol extracts were more toxic. to the snails than the water extracts. Generally, the eggs were more susceptible to the extracts than the young and adult snails. Application of the water extracts at LC 100 on snails reared in aquaria and under semi-field conditions revealed that N. tabacum could kill up to 100% of the snails in aquaria and 61.25% under semi-field conditions. CONCLUSION: Eight plant species with molluscicidal activity were identified, among which Nicotiana tabacum, Aframomum citratum, A. melegueta, Solanum scabrum and Curcuma domestica presented the highest activity. B. camerunensis was more susceptible to all the plant extracts tested than B. truncatus, and the methanol extracts proved more toxic than the water extracts. Semi-field testing of potent extracts showed promise, with N. tabacum having the highest effects on the snails.

Animals↗