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PubMed2003

A comparative parasitologic study on Biomphalaria glabrata snail and C3H/He mice infected with human and murine isolates of Schistosoma mansoni derived from Sumidouro, Rio de Janeiro, Brazil.

Experiments were carried out to analyze the biological characteristics of two sympatric isolates of Schistosoma mansoni derived from humans and murines in a low endemic transmission area (Sumidouro county, state of Rio de Janeiro, Brazil). Sympatric reared-laboratory Biomphalaria glabrata and C3H/He mice were used as experimental hosts. Parameters assessed comprised: precercarial period, infectivity and mortality (snails), prepatent period, infectivity (percentage of cercariae maturation into adult worm) and intestinal egg count (mice). The murine isolate showed a shorter precercarial period and higher infectivity than human isolate (p<0.05). This biological heterogenicity did not correspond to the vertebrate data because any biological parameter presented significant difference (p>0.05). These data suggest that both isolates are local sub-populations, providing support for the hypotheses that in a same biotope mixed populations or sub-populations circulate among their main host (human beings) and/or rodent as an anfixenous infection.

Animals↗
PubMed2004

Ultrastructural study of the in vitro interaction between Biomphalaria glabrata hemocytes and Schistosoma mansoni miracidia.

Biomphalaria glabrata and Schistosoma mansoni relationship was studied by light microscopy (LM) and freeze-fracture replica technique (FFR). We observed very thin cytoplasmic extensions of hemocytes in the LM, which then surround immobilize the miracidia. FFR images showed that the contact site between hemocytes cytoplasmic extensions and the external tegumentary coat involved only superficial layers of miracidia. Numerous vacuoles and filopodia were observed in the hemocyte cytoplasm, the latter binding with those from neighboring cells. In spite of the close interfilopodia contact, no cellular junctions were seen at these sites nor between filopodia-miracidia contact areas. The observed migration of hemocytes and their disposition in layers surrounding the miracidia in vitro correspond to previous studies.

Animals↗
PubMed2004

Dominant character of the molecular marker of a Biomphalaria tenagophila strain (Mollusca: Planorbidae) resistant to Schistosoma mansoni.

Biomphalaria tenagophila population from Taim (state of Rio Grande do Sul, Brazil) is totally resistant to Schistosoma mansoni, and presents a molecular marker of 350 bp by polymerase chain reaction and restriction fragment length polymorphism of the entire rDNA internal transcriber spacer. The scope of this work was to determine the heritage pattern of this marker. A series of cross-breedings between B. tenagophila from Taim (resistant) and B. tenagophila from Joinville, state of Santa Catarina (susceptible) was carried out, and their descendants F1 and F2 were submitted to this technique. It was possible to demonstrate that the specific fragment from Taim is endowed with dominant character, since the obtained segregation was typically mendelian.

Animals↗
PubMed2004

Diagnostic of Biomphalaria snails and Schistosoma mansoni: DNA obtained from traces of shell organic materials.

Freshwater snails belonging to the genus Biomphalaria act as intermediate hosts for the parasite trematode Schistosoma mansoni in Africa and in the neotropical region. Identification of such molluscs is carried out based on morphological characters and the presence of cercariae is verified through squeezing snails between two glass slides or by exposing them to artificial light. However, sometimes, the material collected includes molluscs with decomposed bodies or, yet, only empty shells, which precludes their identification and S. mansoni detection. Due to these difficulties, we have developed a methodology in which DNA may be extracted from traces of organic material from inside shells in order to identify molluscs through polymerase chain reaction and restriction fragment length polymorphism and to detect S. mansoni into these snails, by using low stringency polymerase chain reaction. Species-specific profiles obtained from B. glabrata, B. straminea, and B. tenagophila snails and their shells, maintained in laboratory for ten years, showed the same profiles. S. mansoni profiles showed to be present in shell specimens as far as the eighth week after being removed from aquarium.

Animals↗
PubMed2005

Distribution and Schistosoma mansoni infection of Biomphalaria glabrata in different habitats in a rural area in the Jequitinhonha Valley, Minas Gerais, Brazil: environmental and epidemiological aspects.

This paper examines the distribution and infection of Biomphalaria glabrata with Schistosoma mansoni in all aquatic snail habitats in a rural area in the state of Minas Gerais, Brazil, in relation to physico/biotic and behavioral factors. Snail and environmental surveys were carried out semi-annually between July 2001 and November 2002 at 106 sites. Collected snails were examined in the laboratory for infection. B. glabrata densities were highest in overflow ponds, irrigation ponds, springs, canals and wells, and lowest in fishponds and water tanks. Snail densities were higher during the hot, rainy season except for streams and canals and were statistically associated with the presence of fish, pollution, and vegetation density. Tilapia fish and an unidentified Diptera larva were found to be predators of B. glabrata but ducks were not. Twenty-four of the 25 infected snails were collected in 2001(1.4% infection rate) and only one in 2002, after mass chemotherapy. The occurrence of B. glabrata in all 11 snail habitats both at and away from water contact sites studied indicates widespread risk of human infection in the study area. In spite of the strong association between B. glabrata and tilapia in fishponds we do not recommend its use in schistosomiasis control for ecological reasons and its relative inefficiency in streams and dams.

Animals↗
PubMed2004

Biomphalaria tenagophila/Schistosoma mansoni interaction: premises for a new approach to biological control of schistosomiasis.

Biomphalaria tenagophila is very important for schistosomiasis transmission in Brazil. However its mechanisms of interaction with Schistosoma mansoni are still scantly studied. Since this snail displays strains highly susceptible or completely resistant to the parasite infection, the knowledge of that would be a useful tool to understand the mechanism of snail resistance. Particularly, the Taim strain consistently shows absolute resistance against the trematode, and this resistance is a dominant character. A multidisciplinary research group was created aiming at studying B. tenagophila/S. mansoni interaction. The possibility for applying the knowledge acquired to obtain a biological model for the control of S. mansoni transmission in endemic areas is discussed.

Animals↗
PubMed2005

Biomphalaria tenagophila: dominant character of the resistance to Schistosoma mansoni in descendants of crossbreedings between resistant (Taim, RS) and susceptible (Joinville, SC) strains.

The aim of the present work was to study parasitological, molecular, and genetic aspects in descendants of crossbreedings between a totally resistant Biomphalaria tenagophila strain (Taim, RS) and another one highly susceptible (Joinville, SC) to Schistosoma mansoni. Descendants F1 and F2 were submitted to S. mansoni infection (LE strain). The susceptibility rates for individuals from Group F1 were 0 to 0.6%, and from Group F2 was 7.2%. The susceptible individuals from Group F2 discharged a lower number of cercariae, when compared with the susceptible parental group, and in 2 out of 9 positive snails the cercarial elimination was discontinued. In order to identify genetic markers associated with resistance the genotype of parental snails and their offspring F1 and F2 were analyzed by means of the randomly amplified polymorphic DNA method. Nevertheless, it was not possible to detect any marker associated to resistance, but the results showed that in the mentioned species the resistance character is determined by two dominant genes.

Animals↗
PubMed2005

Isolation and characterization of the full-length cDNA encoding a member of a novel cytochrome p450 family (CYP320A1) from the tropical freshwater snail, Biomphalaria glabrata, intermediate host for Schistosoma mansoni.

Cytochrome p450s (cyp450s) are a family of structurally related proteins, with diverse functions, including steroid synthesis and breakdown of toxins. This paper reports the full-length sequence of a novel cyp450 gene, the first to be isolated from the tropical freshwater snail Biomphalaria glabrata, an important intermediate host of Schistosoma mansoni. The nucleotide sequence is 2291 bp with a predicted amino acid sequence of 584aa. The sequence demonstrates conserved cyp450 structural motifs, but is sufficiently different from previously reported cyp450 sequences to be given a new classification, CYP320A1. Initially identified as down-regulated in partially resistant snails in response to S. mansoni infection, amplification of this gene using RT-PCR in both totally resistant or susceptible snail lines when exposed to infection, and all tissues examined, suggests ubiquitous expression. Characterization of the first cyp450 from B. glabrata is significant in understanding the evolution of these metabolically important proteins.

Amino Acid Sequence↗
PubMed2006

Physiological changes in Biomphalaria glabrata Say, 1818 (Pulmonata: Planorbidae) caused by sub-lethal concentrations of the latex of Euphorbia splendens var. hislopii N.E.B (Euphorbiaceae).

Molluscides have been used as one of the strategies to control schistosomiasis. Many plant extracts with molluscidal effects have been tested, but the action of the latex of Euphorbia splendens var. hislopii is considered the most promising because it meets the recommendations of the World Health Organization (WHO). The objective of this study was to determine the lethal dose and identify the effects of the different doses of latex of E. splendens var. hislopii on the physiology of Biomphalaria glabrata submitted to treatment for 24 h. The concentrations of glucose, uric acid and total proteins in the hemolymph and of glycogen in the digestive gland and cephalopodal mass were determined. The LD50 value was 1 mg/l. The highest escape index was found to be at a concentration of 0.6 mg/l. The results showed that the latex of E. splendens var. hislopii caused a sharp reduction in the reserves of glycogen in the digestive gland and elevation of the protein content in the hemolymph of B. glabrata.

Animals↗
PubMed2006

Compatibility of Biomphalaria tenagophila with Schistosoma mansoni: a study of homologous plasma transference.

This study aims to investigate the importance of the serum factors present in the plasma of resistant Biomphalaria tenagophila snails, when transferred to susceptible conspecific. Susceptible B. tenagophila (CF) received plasma from resistant B. tenagophila (Taim), and both were later infected with Schistosoma mansoni. We noticed that the plasma transfer showed an increase on the resistance of susceptible snails of about 86% when compared to the non-immunized group (p < 0.001).

Adoptive Transfer↗
PubMed2006

The effects of temperature change on the infection rate of Biomphalaria glabrata with Schistosoma mansoni.

The aim of this study was to investigate the influence of temperature on the development of Schistosoma mansoni infections in Biomphalaria glabrata. The snails were infected at 15, 20, and 30 degrees C, and the cercarial release was analyzed after 30 and 60 days post-infection. Our results showed that a decrease in the temperature has a substantial influence on the development of S. mansoni infection in B. glabrata, with significant differences (p < 0.05) between 15 and 30 degrees C. These data could provide a better understanding of the epidemiological aspects of schistosomiasis.

Analysis of Variance↗
PubMed1999

Changes in the behavioral and immunological parameters of the mollusk Biomphalaria tenagophila induced by disruption of the circadian cycle as a consequence of continuous illumination.

In the present investigation we studied some behavioral and immunological parameters of adult gastropod mollusk, Biomphalaria tenagophila, which have been reproducing for several generations under laboratory conditions. One group of gastropods was kept on a 14-h light/10-h dark cycle, corresponding to a regular circadian cycle, and another group was exposed to continuous light for 48 h. Animals were studied along (behavioral groups) or immediately after (immunological groups) 48 h of regular circadian cycle or continuous light conditions. Stopping/floating, dragging and sliding were the behavioral aspects considered (N = 20 for regular cycle; N = 20 for continuous illumination) and number of hemocytes/microl hemolymph was the immunological parameter studied (N = 15 for regular cycle, N = 14 for continuous illumination). Animals under continuous illumination were more active (sliding = 33 episodes, dragging = 48 episodes) and displayed a lower number of hemocytes (78.0 +/- 24. 27/microl) when compared with mollusks kept on a regular circadian cycle (sliding = 18 episodes, dragging = 27 episodes; hemocytes = 157.6 +/- 53.27/microl). The data are discussed in terms of neural circuits and neuroimmunological relations with the possible stressful effect of continuous illumination.

Animals↗
PubMedDate not supplied

[History of the discovery of Biomphalaria occidentalis Paraense, 1981].

The article addresses the discovery of Biomphalaria occidentalis Paraense, a mollusk whose shell is indistinguishable from that of B. tenagophila, natural vector of Schistosoma mansoni. This reconstruction of the history of its discovery necessarily entails reference to the professional life of malacologist Wladimir Lobato Paraense. In addition to demonstrating how essential basic biology and taxonomy are in the epidemiology of mansoni schistosomiasis, the study also focuses on the discovery process itself and the socioeconomic factors which influenced it.

Animals↗
PubMed2005

Malacological assessment and natural infestation of Biomphalaria straminea (Dunker, 1848) by Schistosoma mansoni (Sambon, 1907) And Chaetogaster limnaei (K. Von Baer, 1827) in an urban eutrophic watershed.

The objective of this study was to perform a malacological assessment at the Ibirité reservoir watershed in the metropolitan region of Belo Horizonte (Minas Gerais) and to evaluate the natural infestation rate of Biomphalaria straminea (Gastropoda: Planorbidae) by Schistosoma mansoni (Platyhelminthes: Trematoda) and Chaetogaster limnaei (Oligochaeta: Naididae). The samples were collected from July to August 2002. The B. straminea individuals collected were kept in the laboratory; the natural infestation rate by S. mansoni and C. limnaei was assessed weekly. The malacological assessment identified five mollusk species present in the Ibirité reservoir watershed: B. straminea, Physa marmorata, Lymnea sp., Melanoides tuberculatus, and Pomacea austrum. Laboratory observations showed that the B. straminea individuals were infected by C. limnaei rather than S. mansoni. Although there was no infection of B. straminea by S. mansoni, presence of B. straminea in itself merits close attention due to possible risk of human schistosomiasis by the local population.

Animals↗
PubMed2001

Effects of diet on the development of Schistosoma mansoni in Biomphalaria glabrata and on the neutral lipid content of the digestive gland-gonad complex of the snail.

In a previous study, when the snail Biomphalaria glabrata was infected with Schistosoma mansoni and maintained on a diet of hen's egg yolk, it produced fully developed cercariae in about one-half the time taken by snails fed Romaine lettuce. Increased lipids were also noted in the snails fed the yolk diet. The purpose of the present study was to further investigate nutritional effects of a high-lipid diet on larval schistosome development and to reexamine the time to cercarial patency in infected snails maintained on either the yolk or lettuce diet and to use high-performance thin-layer chromatography (HPTLC) to analyze the neutral lipids in the digestive gland-gonad complex (DGG) of snails maintained on both diets. Infected snails maintained at 26 C and fed either diet produced fully developed cercariae by 4 wk postinfection (PI). Likewise, infected snails maintained at 23 C and fed either diet produced fully developed cercariae by 6 wk PI. The contention that the yolk diet enhanced the time to cercarial patency was not confirmed. The HPTLC analysis of neutral lipids showed that the DGG of infected snails fed the yolk diet contained significantly greater amounts of free sterols and cholesteryl esters but not triacylglycerols than that of the infected snails fed the lettuce diet.

Animals↗
PubMed2001

Killing of Schistosoma mansoni sporocysts by hemocytes from resistant Biomphalaria glabrata: role of reactive oxygen species.

The fate of Schistosoma mansoni (Trematoda) sporocysts in its molluscan host Biomphalaria glabrata (Gastropoda) is determined by circulating phagocytes (hemocytes). When the parasite invades a resistant snail, it is attacked and destroyed by hemocytes, whereas in a susceptible host it remains unaffected. We used 3 inbred strains of B. glabrata: 13-16-R1 and 10-R2, which are resistant to the PR-1 strain of S. mansoni, and M-line Oregon (MO), which is susceptible to PR-1. In an in vitro killing assay using plasma-free hemocytes from these strains, the rate of parasite killing corresponded closely to the rate by which S. mansoni sporocysts are killed in vivo. Hemocytes from resistant snails killed more than 80% of S. mansoni sporocysts within 48 hr, whereas sporocyst mortality in the presence of hemocytes from susceptible snails was <10%. Using this in vitro assay, we assessed the involvement of reactive oxygen species (ROS) produced by resistant hemocytes, during killing of S. mansoni sporocysts. Inhibition of NADPH oxidase significantly reduced sporocyst killing by 13-16-R1 hemocytes, indicating that ROS play an important role in normal killing. Reduction of hydrogen peroxide (H2O2) by including catalase in the killing assay increased parasite viability. Reduction of superoxide (O2-), however, by addition of superoxide dismutase or scavenging of hydroxyl radicals (*OH) and hypochlorous acid (HOCl) by addition of hypotaurine did not alter the rate of sporocyst killing by resistant hemocytes. We conclude that H2O2 is the ROS mainly responsible for killing.

Animals↗
PubMed2001

Effect of miracidial dose on adoptively transferred resistance to Schistosoma mansoni in the snail intermediate host, Biomphalaria glabrata.

Adoptively transferred resistance to Schistosoma mansoni in the snail intermediate host Biomphalaria glabrata was measured as a function of miracidial challenge dose. Schistosome-susceptible snails implanted with the amebocyte-producing organ (APO) from resistant donors showed 29 and 39% prevalences of infection after challenge with 5 and 10 miracidia, respectively, but 68-83% prevalences when exposed to 25-200 miracidia. Prevalences in control (untampered) susceptible snails ranged from 97 to 100% at the different miracidial doses. Higher infection prevalences at elevated doses suggest that a range of transferred resistance occurs and possibly that low levels of APO-derived plasma factors or hemocytes in some recipients can be overwhelmed by larger numbers of parasites.

Adoptive Transfer↗
PubMed2001

Involvement of nitric oxide in killing of Schistosoma mansoni sporocysts by hemocytes from resistant Biomphalaria glabrata.

In strains of the snail Biomphalaria glabrata (Gastropoda) that are resistant to the parasite Schistosoma mansoni (Trematoda), hemocytes in the hemolymph are responsible for elimination of S. mansoni sporocysts. The defensive role of reactive nitrogen species was investigated in in vitro interactions between hemocytes derived from the resistant 13-16-R1 strain of B. glabrata and the parasite. The nitric oxide synthase (NOS) inhibitor N(omega)-nitro-L-arginine methylester (L-NAME) and the nitric oxide (NO) scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide reduced cell-mediated killing of S. mansoni sporocysts. To determine if peroxynitrite (ONOO-) is involved in killing, assays were run in the presence of the ONOO- scavengers uric acid and deferoxamine. These did not influence the rate of parasite killing, indicating that NO is directly responsible for mediating cytotoxicity, but ONOO- is not. The combination of the NOS inhibitor L-NAME and catalase, an enzyme that detoxifies hydrogen peroxide (H2O2), reduced average sporocyst mortality to a greater extent than L-NAME alone. Killing of the sporocysts was, however, not totally inhibited. It is suggested that NO and H2O2 are both involved in hemocyte-mediated toxicity of 13-16-R1 B. glabrata against S. mansoni sporocysts.

Animals↗