Bulinus Truncatus Research Articles

Bidirectional Introgressive Hybridization between a Cattle and Human Schistosome Species

Schistosomiasis is a disease of great medical and veterinary importance in tropical and subtropical regions, caused by parasitic flatworms of the genus Schistosoma (subclass Digenea). Following major water development schemes in the 1980s, schistosomiasis has become an important parasitic disease of children living in the Senegal River Basin (SRB). During molecular parasitological surveys, nuclear and mitochondrial markers revealed unexpected natural interactions between a bovine and human Schistosoma species: S. bovis and S. haematobium, respectively. Hybrid schistosomes recovered from the urine and faeces of children and the intermediate snail hosts of both parental species, Bulinus truncatus and B. globosus, presented a nuclear ITS rRNA sequence identical to S. haematobium, while the partial mitochondrial cox1 sequence was identified as S. bovis. Molecular data suggest that the hybrids are not 1st generation and are a result of parental and/or hybrid backcrosses, indicating a stable hybrid zone. Larval stages with the reverse genetic profile were also found and are suggested to be F1 progeny. The data provide indisputable evidence for the occurrence of bidirectional introgressive hybridization between a bovine and a human Schistosoma species. Hybrid species have been found infecting B. truncatus, a snail species that is now very abundant throughout the SRB. The recent increase in urinary schistosomiasis in the villages along the SRB could therefore be a direct effect of the increased transmission through B. truncatus. Hybridization between schistosomes under laboratory conditions has been shown to result in heterosis (higher fecundity, faster maturation time, wider intermediate host spectrum), having important implications on disease prevalence, pathology and treatment. If this new hybrid exhibits the same hybrid vigour, it could develop into an emerging pathogen, necessitating further control strategies in zones where both parental species overlap.

Micro-distribution of freshwater snails before and after water flow events in hydraulic structures in Tessaout Amont irrigation system, Morocco

Bulinus truncatus, the intermediate host of Schistosoma haematobium, is widely distributed in modern irrigation schemes in Morocco. These schemes have intermittent irrigation and canals dry out in between irrigation periods. The snail species is therefore associated with the 'siphon boxes' connecting canal segments, as these contain water that stagnates between irrigation cycles. The micro-distribution of snails in siphon boxes, was studied before and after one irrigation period, to identify factors that could be manipulated in order to control this snail species. Density of B. truncatus, Ancylus fluviatilis, Lymnaea peregra and Melanopsis praemorsa varied significantly with water depth before and after irrigation. The pulmonate snail species had the highest densities at depths ranging between 20 and 80 cm. After an irrigation period of 10 to 12 hours B. truncatus, A. fluviatilis and L. peregra were relatively more abundant at the bottom of the siphon boxes than in the upper sections. Aggregation at the corners of the boxes could be among the factors that enable snail species to avoid the detrimental effect of turbulent water flow during irrigation. The relevance of changes in density and micro-distribution following an irrigation cycle in the control of B. truncatus is discussed.

Miracidial infectivity of snail host (<i>Bulinus truncatus</i>) in the laboratory

Miracidial infectivity rate of snail Bulinus truncatus collected from Agulu Lake was studied in the laboratory. The snails were maintained in the laboratory and eggs deposited were allowed to hatch and dates noted until snails of different ages were produced. These snails were consequently exposed to miracidia hatched from eggs collected from urine of patients known to have active S. haematobium infections. Infection of snails in the laboratory showed that the miracidia can penetrate snail of any age. For the snails of ages 2, 4, 6, and 8 weeks, 15 (60%), 13 (52%), 12 (48%) and 14 (56%) miracidia respectively penetrated. The study showed that 54 out of 100 (54%) of miracidia penetrated the snail Bulinus truncatus while 46 out of 100 (46%) miracidia did not penetrate the snail species. Penetration was found to be independent of the age of snail (÷² = 7.8, df=3). The implication of the findings to the effort of the disease control is discussed. Keywords : Bulinus truncatus , miracidia, age of snail, S. haematobium, laboratory. Nigerian Journal of Parasitology Vol. 29 (2) 2008: pp. 77-79

Can the freshwater crayfish (Procambarus clarkii) help control schistosomiasis and fascioliasis in Egypt?

ab experiments and field survey have been carried out to investigate the impact and the relationship between the exotic crayfish; Procambarus clarkii and Schistosoma and Fasciola vector snails in Egypt. In the Lab, several species of freshwater snails, fish and aquatic plants were reported to serve as food for the freshwater crayfish. In the field, a survey for the crayfish and freshwater snails has been conducted at several irrigation channels in Qalyobiya, Ismailia and Behera governorates, which had been previously surveyed during 1990s. The results of the experimental Lab indicated that the vector snails; Biomphalaria alexandrina, Bulinus truncatus and limnaea natalensis were the preys of first choice for the crayfish. The field surveys showed high reduction and sometimes complete disappearance of vector snails in irrigation channels, which have been invaded by Procambarus clarkii, while in water courses which do not harbor the crayfish, such as El Manayef drain and Fayed canal (West of Suez Canal), high densities of these vector snails were recorded. The present study is providing encouraging indication of the possible overcoming schistosomiasis and fascioliasis in Egypt by the freshwater crayfish Procombarus clarkii.

Ecological Studies Of The Gastropod Fauna Of Some Minor Tributaries Of River Benue In Makurdi, Nigeria

Some tributaries of Benue river in Makurdi were surveyed for gastropod fauna between May and October 2004. The scoop net method was employed and complimented with hand picking technique. Four species of snails were encountered; Lanistes libycus (44.78 %), Melanoides tuberculata (21.86 %), Bulinus truncatus (22.03 %) and Potandoma species (11.33 %). ANOVA revealed no significant difference (P < 0.05) in distribution of snail species and physio-chemical parameters showed no striking disparity in the water bodies sampled. The predominant aquatic flora encountered were Ipomoea aquatica, Nymphaea lotus and Graminae species. The nutritional and medical implications of snail species encountered and observed human water contact pattern were discussed.

Comparative sensitivity of two freshwater snail Melanopsis nodosa and Bulinus truncatus to 2, 4-D pesticide

The molluscicidal effects of herbicide 2, 4-D were studied against tow species of freshwater snail Bulinus truncatus and Melanopsis nodosa by short term experiments. Calculated values of lethal concentrations (LC50 and LC100) were maid to two spices for different period of time 24hr, 48hr, 72hr and 96hr. The study had showed that the herbicide 2, 4-D was toxic against the tow species. The toxicity of the herbicide was low or unknown in low concentrations in the first period of exposure 24and 48hr to two spices but it increase gradually with increase period of exposure. The spice of B.truncatus was more tolerant than the M.nodosa. All the individual of M nodosa was death while in B.truncatus the complete death was not appear until finish the period of exposure 96hr.

Comparative sensitivity of two freshwater snail Melanopsis nodosa and Bulinus truncatus to 2, 4-D pesticide

The molluscicidal effects of herbicide 2, 4-D were studied against tow species of freshwater snail Bulinus truncatus and Melanopsis nodosa by short term experiments. Calculated values of lethal concentrations (LC50 and LC100) were maid to two spices for different period of time 24hr, 48hr, 72hr and 96hr. The study had showed that the herbicide 2, 4-D was toxic against the tow species. The toxicity of the herbicide was low or unknown in low concentrations in the first period of exposure 24and 48hr to two spices but it increase gradually with increase period of exposure. The spice of B.truncatus was more tolerant than the M.nodosa. All the individual of M nodosa was death while in B.truncatus the complete death was not appear until finish the period of exposure 96hr.

Focalisation de la transmission de Schistosoma haematobium au sein des périmètres irrigués de la vallée du Niger (Niger) : importance des facteurs malacologiques

Background Currently, the control of urinary schistosomiasis is mostly based on mass treatment. Characterization of Schistosoma haematobium transmission could lead to adding new methods to the control strategy. Methods We carried out malacological and cercariometrical surveys in irrigated perimeters of the Niger River valley. A semi-monthly follow-up was performed in three main sites of human-water contact in a village located at the border of the irrigated perimeter. Bulinids were collected during 20 min; after identification based on the shell morphology, their parasites were characterized by isoelectrofocalisation. The cercariometrical technique by differential filtration was used to evaluate the density of cercariae in every site with two 20 litres samples of water collected at various periods of the day (9, 12, 15 and 18 h). Results In the arm of the river, the cercariometry never showed cercariae whereas only some Bulinus truncatus, all negative, were collected. In the channels, B. truncatus and B. globosus were observed and highest density was found during the dry season. Only B. truncatus was naturally infested. Homozygote BB phenotype (characteristic of S. haematobium) was observed in all positive molluscs. Using cercariometry, more than two third of cercariae were collected at 3:00 PM. Conclusion Transmission of S. haematobium was primarily focused in the irrigating channels during the dry hot season at the beginning of afternoon. These results should lead to improve the output of S. haematobium control methods within irrigated areas.

The use of cercariae infection of the Bulinus truncatus snail for evaluation of schistosomiasis control in Iran

The use of cercariae infection of the <i>Bulinus truncatus</i> snail for evaluation of schistosomiasis control in Iran

Studies on the ecology and distribution of some medically important freshwater snail species in Bauchi State, Nigeria.

Two Local Government Areas in Bauchi State, Nigeria, harboring many snail infested water bodies were surveyed for the presence of intermediate host snail vector species for a period of 13 months. This study revealed five medically important snail species which were comprised of Bulinus (Physopsis) globosus, Bulinus (Bulinus) truncatus, Bulinus (Bulinus) forskalii, Biomphalaria pfeifferi, and Lymnaea natalensis. A significant fluctuation in relative abundance of these snails was observed with a peak at the beginning of the dry season. This peak was then followed by a decline during the rainy season resulting in almost the elimination of the snails in some sites and low numbers in others. It was equally observed that the snails had a water velocity, rainfall and temperature-dependent seasonal cycle with rapid increases in abundance during periods of favorable conditions. Snail-plant relationships and preferred substratum were also evaluated. Results obtained from this study are very vital for the planning of snail control in Bauchi State. International Journal of Biological & Chemical Sciences Vol. 1 (2) 2007: pp. 121-127

Studies on seasonal variations in the gut contents of snail intermediate hosts of schistosomes in Kano State of Nigeria

Samples of two species of freshwater gastropod, namely, Bulinus rohlfsi (Clessin) and Bulinus globosus (Morelet), intermediate hosts of Schistosoma haematobium were collected from two freshwater habitats in Kano State of Nigeria for a period of one year. Their gut contents were analyzed. Among the items found to have been ingested by these snails were rotifers, protozoa, diatoms, and various forms of algae, macrophyte tissue and spore-like materials. For the two species, the quality as well as quantity was seen to vary probably with seasonal changes in their habitat flora and fauna. Keywords : Bulinus rohlfsi, Bulinus globosus , schistosomiasis, gastropod snails. Nigerian Journal of Parasitology Vol. 27 2006: pp. 49-53

Effects of Schistosoma mansoni and Schistosoma haematobium infections on calcium content in their intermediate hosts

Flame atomic absorption spectrometry was performed to determine the alteration of calcium concentration in the soft parts and shells of Biomphalaria alexandrina and Bulinus truncatus due to the infection with Schistosoma mansoni and S. haematobium, respectively. The results showed significant lowering in the calcium content of the shells of cercariae shedding B. alexandrina and B. truncatus relative to the calcium content in the shells of uninfected ones. In contrast, the calcium content in the soft parts of cercariae shedding snails was higher than in the soft parts of uninfected snails; the differences were statistically significant. Generally, calcium content was significantly higher in the shells than in the soft parts of the snails, regardless infected or uninfected. The results obtained and the hypothesis of hypercalcification in shells of infected snails were discussed.

Habitats of Bulinus truncatus and Planorbarius metidjensis, the intermediate hosts of urinary schistosomosis, under a semiarid or an arid climate

Since Bulinus truncatus and Planorbarius metidjensis are the intermediate hosts of Schistosoma haematobium in southwestern Morocco, five rivers were investigated to identify sites colonized by either of both species and determine the characteristics of their habitats via the study of 12 physicochemical parameters in running water. P. metidjensis was observed in the upper valleys of three rivers, whereas B. truncatus was found in sites of lower altitude. A component analysis demonstrated that altitude (from 4 to 1,380 m), water pH (from 5.9 to 9.2), and electric conductivity (from 120 to 6,020 microS/cm) were the main descriptors of environment. A multiple correspondence analysis showed that P. metidjensis was associated to Ancylus fluviatilis, high altitude, and possibly low electric conductivity. B. truncatus was associated to Melanoides tuberculata and was found in lower altitude sites with medium electric conductivity in water. Using logistic regressions, the main characteristics were altitude and dissolved oxygen for B. truncatus, and chlorides and CaCO3 for P. metidjensis. As the habitats of both S. haematobium intermediate hosts differed from each other by altitude and the frequency of snails, which cohabited with them, these findings may be used to detect the presence of either of both intermediate hosts in numerous spring heads which are present on the western slope of the Anti Atlas mountains and the corresponding valleys.

Population dynamics of Chaetogaster limnaei (Oligochaeta: Naididae) in the field populations of freshwater snails and its implications as a potential regulator of trematode larvae community

The objectives of this work were to study (1) the population dynamics of Chaetogaster limnaei in the field populations of freshwater snails and the implications for the species as a potential regulator of the trematode larvae community and (2) prevalence and intensity of C. limnaei in relation to host species, host size, and season. This study was conducted at Al-Salam Canal and Al-Abtal village (new cultivated area in north Sinai). The samples were collected from March 2004 to February 2005. The natural infection rate by trematodes and C. limnaei was assessed monthly. Thirteen species of snails were examined for C. limnaei infection, five species were found infected. There were positive correlations between host size and both combined prevalence and mean intensity in all hosts. The data demonstrated that prevalence in Bulinus truncatus was higher when compared with other hosts. Bellamya unicolor has higher mean intensity when compared with other host species. A significant difference was found between host species and both prevalence and intensity. There were spatial and temporal variations in prevalence and mean intensity in most hosts, and the data suggest some seasonality. A negative correlation was found between prevalence of C. limnaei and trematode infection. C. limnaei did not co-occur with trematode larvae in infected hosts indicating that the oligochaete may protect the hosts from trematode infection. B. unicolor was recorded for the first time as a host for C. limnaei. C. limnaei may be a potential regulator of the trematode community in freshwater snails. In conclusion, this study demonstrated that C. limnaei, symbiotically associated with snail vector of parasitic diseases, may have important implications with respect to biological control and/or changes in the epizootiology of native parasites in the study area.

Gut content studies of aquatic snail intermediate hosts of schistosomes in Kano State, Nigeria

Natural diets of Bulinus (P) globosus, Bulinus rohlfsi and Biomphalaria pfeifferi, gastropod intermediate hosts of the Schistosoma parasite were investigated by examining their gut content. It was found that the diet of B. globosus consisted of rotifers, various forms of algae, diatoms, macrophytic tissue and spore-like materials. The diet of B. pfeifferi was also similar but some of the food varied in species types suggesting omnivorous habit. Algae frequently predominated other items in the gut content of the all snail species, while macrophytic tissues were least frequently encountered. For each of the examined snail species, the quantity of material ingested varied slightly with the nature of habitat. International Journal of Natural and Applied Sciences Vol. 2(1) 2006: 47-54

Identification of the Boudicca and Sinbad retrotransposons in the genome of the human blood fluke Schistosoma haematobium

Schistosomes have a comparatively large genome, estimated for Schistosoma mansoni to be about 270 megabase pairs (haploid genome). Recent findings have shown that mobile genetic elements constitute significant proportions of the genomes of S. mansoni and S. japonicum. Much less information is available on the genome of the third major human schistosome, S. haematobium. In order to investigate the possible evolutionary origins of the S. mansoni long terminal repeat retrotransposons Boudicca and Sinbad, several genomes were searched by Southern blot for the presence of these retrotransposons. These included three species of schistosomes, S. mansoni, S. japonicum, and S. haematobium, and three related platyhelminth genomes, the liver flukes Fasciola hepatica and Fascioloides magna and the planarian, Dugesia dorotocephala. In addition, Homo sapiens and three snail host genomes, Biomphalaria glabrata, Oncomelania hupensis, and Bulinus truncatus, were examined for possible indications of a horizontal origin for these retrotransposons. Southern hybridization analysis indicated that both Boudicca and Sinbad were present in the genome of S. haematobium. Furthermore, low stringency Southern hybridization analyses suggested that a Boudicca-like retrotransposon was present in the genome of B. truncatus, the snail host of S. haematobium.

Molecular phylogeny of diploid Bulinus sp. (Gastropoda: Planorbidae) populations in Cameroon crater lakes

Bulinus sp. (2 n = 36) is a diploid freshwater snail found in Cameroon crater lakes; it belongs to a group of medically important freshwater snails. Some members ( Bulinus truncatus, Bulinus tropicus) of this group had been reported to be involved in the transmission of parasites ( Schistosoma sp. and Calicophoron microbothrium) to human and livestock in tropical Africa. Yet, understanding of the evolutionary identity of the diploid snail such as its phylogenetic position and the genetic divergence among populations, remains limited. In this study, we constructed the molecular phylogeny of Bulinus sp. using sequences of mitochondrial cytochrome oxydase subunit 1 (CO-1, 365 nucleotides). Partial sequences of CO-1 were obtained and genetic divergences between populations estimated after the alignment of 365 nucleotides from each studied population. The lack of deep molecular divergences between populations of Bulinus sp. from western Cameroon crater lakes may indicate that they belong to the same lineage; therefore, it implies that diploid B. truncatus/ tropicus complex snail-like in Cameroon share a common ancestor. The CO-1 of the three studied populations of Bulinus sp., clustered together with other diploid pan-African representatives of the B. truncatus/ tropicus complex, showed little evidence of genetic similarities.

Molluscicidal activity against Bulinus truncatus of Croton campestris

The bark of Croton campestris provided three furano-clerodane named, respectively, velamone, velamolone acetate and velamolone. Fractions containing these diterpenoids were investigated for their molluscicidal activity against Bulinus truncatus, one of the aquatic snail vectors of schistosomiasis. A dichloromethanic extract of root barks, rich in furano-clerodane and molluscicidal at 20 ppm was promising as natural molluscicide. Enriched fraction with velamone gave 80% mortality from 25 ppm, while its LD 100 was at 50 ppm. The LD 80 was ca. at 45 ppm, while LD 100 was at 60 ppm for the enriched fraction containing velamolone acetate. The velamolone-enriched fraction was less efficient and gave a mortality of 90% at 90 ppm. The pure compounds, velamone and velamolone acetate were active at 100% at 3 and 6 ppm, respectively. Velamolone showed a molluscicidal activity at 20 ppm.

Structure – activity relationships and determinants of selectivity for congeners of the selective α7 partial agonist 3‐(2,4‐dimethoxybenzylidene)‐anabaseine (DMXBA or GTS‐21) with the ACh binding proteins (AChBPs)

Nicotinic ACh receptors (nAChRs) are prototypic members of the ligand-gated ion channel family of receptors. AChBPs identified in the fresh and saltwater snails, Lymnaea stagnalis (L), Bulinus truncatus (B) and Aplysia californica (A), have been used as soluble surrogates for the extracellular domain of nAChRs. By combining equilibrium binding measurements, absorption and fluorescence spectroscopy, molecular modeling and X-ray crystallography, we have elucidated further the molecular determinants of structure, function and selectivity. DMXBA selectively stimulates α7 nAChRs and enhances cognition and sensory gating. The O-demethylated primary metabolites of DMXBA retain the same activity profile on α7 receptors, but are more efficacious in stimulating the human α7 nAChR (Kem et al., 2004). In our current study we examine a series of 24 structurally related benzylidene-anabaseines (BAs), including DMXBA, and contrast the results with those obtained for epibatidine and nicotine. Using [3H]-epibatidine as the competitor the rank order of Kd values were determined (400 pM - 250 nM, 30 nM - 5 μM and 2 nM - 1 mM for L, B and A). Further, the unusual conjugation of BAs enables one to examine electronic configuration and ionization equilibria in the bound state. Our findings on ligand binding are correlated with those obtained by molecular modeling, spectroscopic and docking experiments. NIH R37-GM18360, F32 NS043063 and RO1-MH6142

Spatio-Temporal Distribution of Freshwater Snail Species in Relation to Migration and Environmental Factors in an Irrigated Area from Morocco

Nine sites were sampled 19 times over 2 years in an irrigation system in Morocco in order to study species abundance in a snail community in relation to environmental parameters (including human activities) and migration (geographic distance) among sites. Each site was made of a sink and the first meters of the downstream canal. The snail community included four species (Bulinus truncatus, Lymnaea truncatula, Mercuria similis and Physa acuta). Strong spatial variation in species occurrence and abundance was detected which might be partly due to variation in water availability. However abundance in sinks and canals in which water availability differs were correlated. There was, as predicted, limited evidence in favor of isolation by distance which might be due to fast water current. Dispersal might therefore be an important factor structuring this community. On the other hand, the temporal variation was much more limited. This is consistent with the analysis of individual size distributions in B. truncatus, since no clear-cut cohorts were detected. The environmental parameters recorded (e.g. temperature, occurrence of macrophytes or cleaning of sinks) were extremely variable in time and space, except temperature. Analyzing their association with species through multidimensional methods indicated that P. acuta is ubiquitous and B. truncatus positively associated with macrophytes. These two species were associated in sinks. Less clear trends were detected for the two other species. Annual cleaning of sinks affected all species, but population recovery was fast in B. truncatus and P. acuta.