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PubMed1991

Influence of the nontarget mollusc Marisa cornuarietis on the hourly cercarial production of Schistosoma mansoni from Biomphalaria glabrata.

A comparative study of hourly cercarial productivities of Schistosoma mansoni from infected Biomphalaria glabrata was carried out in the presence of either healthy B. glabrata (control) or healthy Marisa cornuarietis (experimental). The results showed that, with M. cornuarietis, almost all the hourly cercarial productivities increased by a factor varying from 1.3 to 2.5 without modification of the shedding period.

Animals↗
PubMed1991

Variation of transaminases and lactate dehydrogenase in irradiated Biomphalaria alexandrina snails.

Effect of ultraviolet and gamma radiations on the activities of aspartate aminotransferase (AST), alanine aminotransferase (ALT) and lactate dehydrogenase (LD) in Biomphalaria alexandrina snails, the specific intermediate host of schistosomiasis, was investigated. Changes in the electrophoretic pattern of LD in the species under study were also taken as a measured parameter and the effect of gamma-irradiation on the glutathione content in the haemolymph of the snails have been included.

Alanine Transaminase↗
PubMed1991

Ecdysteroids as regulators of host and parasite interactions: a study of interrelationships between Schistosoma mansoni and the host snail, Biomphalaria glabrata.

Ecdysteroids have been detected in trematode parasites and in several species of gastropod snails. The potential role of these and other hormones as regulators of host/parasite interactions is discussed. This study considers the role of ecdysteroids in the host parasite interactions between Schistosoma mansoni and Biomphalaria glabrata interactions. beta-Ecdysterone was found to be effective in stimulating host location activities in S. mansoni miracidia and in enhancing growth and egg production in B. glabrata. However, plant extracts rich in phytoecdysteroids were not attractive to miracidia and did not affect growth and egg production in snails. The potential role of ecysteroids in the process of parasitism and snail physiological processes is discussed. Plants rich in phytoecdysteroids do not appear to be of value in process which may interfere with the host parasite interactions in schistosomes.

Animals↗
PubMed1990

Measurement of some selected enzymatic activities in infected Biomphalaria alexandrina snails.

The activities of aspartate (AST) and alanine (ALT) aminotransferases and that of lactate dehydrogenase (LD) were measured in the homogenate of infected Biomphalaria alexandrina snails, the specific intermediate hosts for the parasite Schistosoma mansoni which is the cause of the disease schistosomiasis. The isoenzymatic pattern of LD was also studied in the infected snails tissue.

Alanine Transaminase↗
PubMed1990

Effect of temperature on the reproduction of the snail Biomphalaria glabrata.

1. The reproduction of the snail Biomphalaria glabrata, one of the intermediate hosts of Schistosoma mansoni, was evaluated under laboratory conditions by measuring egg production, number of ovipositions, number of eggs per oviposition, and hatching rate using a Latin square design with five different temperature treatments. This permitted the elimination of occasional variation in oviposition due to manipulation or a priori group. 2. Egg production and spawning rates were higher at temperatures between 20.0 and 27.5 degrees C than at 17.5 degrees C. Number of eggs per spawning and hatching rate did not vary with temperature. 3. During a 3-day adaptation phase, a short-term thermal effect appeared in which some indices of reproductive rates differed significantly from those of the experimental phase.

Adaptation, Physiological↗
PubMed1990

Susceptibility of Biomphalaria pfeifferi from Amibara irrigation scheme to Schistosoma mansoni parasites from Adua and Gursume, Ethiopia.

A laboratory based susceptibility study was carried out on the snail Biomphalaria pfeifferi from canal habitats of the Amibara Irrigation Scheme (Awash Valley) to Schistosoma mansoni parasites from Adua (northern) and Gursume (eastern) Ethiopia. The objective of the study was to investigate the potential role of the snail in the transmission of S. mansoni in the irrigation network of Amibara. Thirty seven (74%) of the 50 snails and 55 (73.3%) of the 75 snails exposed to Adua and Gursume parasites respectively survived the prepatent period. Among the survivors, 94.6% and 96.4% infection rates were observed in those exposed to Auda and Gursume parasites respectively. Cercariae obtained from the snails were used to infect laboratory mice and the characteristic human Schistosoma mansoni eggs and adult worms were recovered. The implications of this study are discussed and future areas of research indicated.

Animals↗
PubMed1990

In vitro effect of larval Schistosoma mansoni excretory-secretory products on phagocytosis-stimulated superoxide production in hemocytes from Biomphalaria glabrata.

The in vitro production of the reactive oxygen metabolite superoxide (O2-) was confirmed in hemocytes from the schistosome intermediate host Biomphalaria glabrata. Active forms of the enzyme superoxide dismutase (SOD) inhibited reduction of nitroblue tetrazolium (NBT) to formazan in cells that had phagocytozed zymosan particles, whereas an inactivated form of SOD did not. Moreover, based on the prevalence of O2(-)-positive hemocytes and the relative intensity of NBT staining reactions, hemocytes from the Schistosoma mansoni-resistant 10-R2 strain of B. glabrata possessed an overall greater capacity for generating superoxide than did those from S. mansoni-susceptible M-line snails. Schistosoma mansoni excretory-secretory (E-S) products, released during in vitro transformation of miracidia to sporocysts, inhibited phagocytosis of zymosan particles and superoxide activity in hemocytes from both snail strains, but 10-R2 hemocytes maintained higher levels of phagocytosis and superoxide production than did M-line hemocytes. The dose-dependent decreases in phagocytosis observed in both snail strains in the presence of E-S products could not account fully for the concomitant decrease in superoxide levels detected, indicating that either a single E-S factor differentially affects phagocytosis and superoxide production, or that different E-S factors are involved in the specific interference of each of these hemocyte functions.

Analysis of Variance↗
PubMed1990

Kinetic properties of two transaminases and lactate dehydrogenase of Biomphalaria alexandrina snails, intermediate hosts of Schistosoma mansoni.

Aspartate (AST) and alanine (ALT) aminotransferase together with lactate dehydrogenase (LD) from the tissue homogenate of the Biomphalaria alexandrina snails, were partially characterized by measuring the Michaelis constant (km) and the maximum velocity (Vmax). The isoenzymatic pattern of lactate dehydrogenase was investigated through polyacrylamide gel electrophoresis.

Alanine Transaminase↗
PubMed1990

Schistosoma mansoni modulation of phagocytosis in Biomphalaria glabrata.

Both short-term (3 hr) exposure of Biomphalaria glabrata snails (M-line and 13-16-R1) to Schistosoma mansoni (PR1) miracidia and in vitro incubation of parasite sporocysts with host hemolymph components altered host phagocytic ability. Hemocytes obtained from susceptible (M-line) snails that had been exposed to parasite miracidia for 3 hr showed reduced levels of phagocytosis of yeast cells in vitro compared to hemocytes from unexposed individuals. Incubation of whole hemolymph with sporocysts in vitro also reduced yeast phagocytosis in this susceptible strain. In contrast, resistant (13-16-R1) hemocytes showed increased levels of yeast phagocytosis after in vitro incubation with the parasite, and the opsonic properties of 13-16-R1 plasma were greater after exposure of snails to miracidia. These strain-specific effects of S. mansoni on host hemocyte phagocytosis and plasma opsonization were seen only when both plasma and hemocytes were present at the time of exposure to the parasite.

Animals↗
PubMed1990

Differential binding of hemolymph proteins from schistosome-resistant and -susceptible Biomphalaria glabrata to Schistosoma mansoni sporocysts.

Humoral factors have been associated with resistance of Biomphalaria glabrata to infection by Schistosoma mansoni. The goal of this study was to determine which serum (cell-free hemolymph) proteins bind to the surface of S. mansoni sporocysts. For this, 125I-labeled serum from schistosome-resistant (10-R2) and -susceptible (M-line) B. glabrata was incubated with sporocysts, washed, and then subjected to SDS-PAGE and autoradiography. Other samples examined included radiolabeled 10-R2 and M-line serum, sporocysts incubated with unlabeled serum followed by incubation with radiolabeled serum, and radiolabeled sporocysts. Results indicated that many polypeptides in the serum from both strains of B. glabrata were radiolabeled. Dominating both profiles were bands in the 90-210-kDa range. However, some differences between the serum of the 2 snail strains were observed with M-line serum having several radiolabeled polypeptides in the 31-40- and 66-85-kDa range that were absent in serum from 10-R2 B. glabrata. When sporocysts were incubated with radiolabeled serum, 3 polypeptides (116, 180, 210 kDa) from both snail strains bound to the surface of the parasite. Further, a 55-kDa polypeptide bound to sporocysts incubated with 10-R2 serum but did not bind to those parasites incubated with M-line serum. Preincubation of sporocysts with unlabeled serum prior to incubation with radiolabeled serum significantly inhibited the uptake of radiolabeled proteins. This differential binding of serum polypeptides from different strains of B. glabrata may be important in determining resistance or susceptibility of the snail to larval schistosome infection.

Animals↗
PubMed1990

Biological control of Biomphalaria glabrata by Thiara granifera under laboratory conditions.

The effect of the snail Thiara granifera on the snail Biomphalaria glabrata, intermediate host of Schistosoma mansoni in the Dominican Republic, was evaluated. Plastic aquaria, 3 and 1.5 gallons in capacity, were used. The aquaria were either unpartitioned or partitioned by a fine screen into two equal compartments, and the two snail species were introduced in different proportions. The results over a 1-year period showed that T. granifera effectively reduced the fecundity of B. glabrata, especially when the initial densitites of the two species were equal or where T. granifera was more abundant. There was still competition, although starting at a later date, when the density of T. granifera was half that of B. glabrata. The competitive interaction does not seem to be due to competition for food but to a chemical factor(s), possibly water-soluble pheromones.

Analysis of Variance↗
PubMed1985

Isolation and partial characterization of an antigen shared between Schistosoma mansoni, Fasciola hepatica, and Biomphalaria glabrata.

An antigen was isolated and partially characterized from adult Schistosoma mansoni which immunologically cross-reacted with Fasciola hepatica and Biomphalaria glabrata, a schistosome intermediate snail host. The antigen was isolated from a solubilized freeze-thaw preparation containing 0.5% Triton X-100 by passage through a CNBr-activated Sepharose 4B column coupled with rabbit IgG prepared against a homogenate of B. glabrata hepatopancreas. The eluted antigen (designated as SMw-53P) stained with Coomassie Brilliant Blue R250, but not with Nile Blue A or periodic acid-Schiff's stains. The antigen did not bind to a Concanavalin A affinity column. SMw-53P was determined to have a molecular weight of 53,000 daltons by SDS-polyacrylamide gel electrophoresis. Western blotting, using sera from mice infected with S. mansoni, revealed the presence of the antigen in whole worm preparations of both S. mansoni and F. hepatica. The serodiagnostic potential of the antigen was evaluated by ELISA utilizing sera from S. mansoni-infected mice, or rabbits injected with homogenates of F. hepatica or S. mansoni whole worm, or B. glabrata hepatopancreas. SMw-53P was shown to strongly react with all antisera, but not normal mouse or rabbit sera. These data suggest a limited value for the antigen for the specific immunodiagnosis of schistosomiasis mansoni, but do suggest a possible potential as a general screening tool for detecting trematode infections. Further studies regarding the antigen's potential as a vaccine are indicated.

Animals↗
PubMed1989

The molluscicidal properties of Ambrosia maritima L. (Compositae). 4. Temporal and spatial distribution of Biomphalaria alexandrina in Egyptian village irrigation systems with reference to schistosomiasis transmission control.

Data on the temporal and spatial distribution of Biomphalaria alexandrina were collected throughout one year in two village irrigation systems near Alexandria, Egypt. Snails bearing Schistosoma mansoni cercariae were found from May to December but about 80% of annual transmission potential was confined from June to August. Although snail infection rates were generally 0-2%, higher rates were recorded and tended to be associated with smaller number snail collections. Infected snails were found in most canal and drain types and were judged to be present across most of the irrigated area of each village. In view of the dispersed nature of both infected snails and human-water contact in the area, it is suggested that schistosomiasis transmission is more widespread than focal. Effective transmission control using molluscicides should therefore require application to all village irrigation water-courses. The difficulties these various findings might impose on the use of commercial molluscicides are discussed and some possible advantages of the alternative plant molluscicide, Ambrosia maritima are noted.

Animals↗
PubMed1989

Biological control of Biomphalaria glabrata and B. straminea by the competitor snail Thiara tuberculata in a transmission site of schistosomiasis in Martinique, French West Indies.

In Martinique, intestinal schistosomiasis was discovered at the beginning of this century. The intermediate host snail, Biomphalaria glabrata, was considered in the past as a common species in the different habitats of the island, but during the last decade it has been found only in water-cress beds. Several of these water-cress cultures contained mixed populations of B. glabrata and B. straminea. Moreover, these habitats also constituted transmission sites for Schistosoma mansoni infection. In 1979 the thiarid snail Thiara ( = Melanoides) tuberculata was discovered in Madame river, Fort-de-France, and in the following years at other sites. In 1983 a programme of biological control using this snail was started in two groups of water-cress beds. In 1981-1982 the study site, Roxelane valley, sheltered important populations of B. glabrata (45-256 individuals/m2) and of B. straminea (2-30 ind./m2). In January 1983 the competitor T. tuberculata was introduced into the two groups of water-cress beds (1.3 and 1.7 ind./m2 respectively) and during subsequent years snail population sampling was carried out. The results showed rapid colonization by the competitor snail, whose densities reached 178 and 325 ind./m2 in November 1983 and a maximum of 9941 and 13,388 ind./m2 in October 1984. During that time, B. glabrata populations declined: 153 and 41 ind./m2 in November 1983, 4 and 0 ind./m2 in October 1984, and 0 ind./m2 in the two groups of water-cress beds in October 1985. A similar phenomenon was observed for B. straminea. Since October 1985 neither planorbid species has been found by exhaustive sampling of the habitats.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Effect of infection with Trichobilharzia ocellata and Schistosoma mansoni on the ultrastructure of the albumen gland of their respective hosts, Lymnaea stagnalis and Biomphalaria glabrata.

The albumen gland, a female accessory sex gland of pulmonate snails, produces the perivitelline fluid. The ultrastructure of the albumen glands of control and infected specimens of Lymnaea stagnalis and Biomphalaria glabrata was studied. The albumen gland of L. stagnalis contains two types of secretory cells--light (active) and dark (inactive)--and two types of supporting cells--centroacinar and myoepithelial. The secretory cells apparently represent two activity stages of one type of cell. The gland B. glabrata possesses only one secretory cell type, which alternates with one type of supporting cell. The albumen glands of L. stagnalis and B. glabrata infected at a juvenile stage were studied 4 and 14 weeks (L. stagnalis) and 4 and 9 weeks (B. glabrata) after exposure. After four weeks' infection, B. glabrata produced some egg masses, but in subsequent stages egg mass production completely coased. Infected L. stagnalis never produced eggs. B. glabrata was apparently infected at a "physiologically" more mature stage than L. stagnalis. The morphology of the albumen glands four weeks after exposure (the daughter sporocyst stage) is in agreement with this hypothesis. At this interval the secretory cells of L. stagnalis appeared to be much more severely affected (inactive Golgi bodies and rough endoplasmic reticulum, crinophagy of the secretory granules) than the cells of B. glabrata. In the later stages studied (shedding of the cercariae), the glands of both species appeared to be completely inactive (reduced height of the epithelium, inactive organelles, crinophagy, absence of secretory granules). At this stage of infection, daughter sporocysts containing cercaria embryos were seen in the connective tissue of the albumen gland of B. glabrata, but not of L. stagnalis. The results thus indicate that the development and synthetic activity of the albumen gland are seriously affected by infection. These processes are known to be under the endocrine control of the female gonadotrophic hormones. Since it has been established that these hormones are normally present in the haemolymph of infected snails, the findings can be explained by assuming that the parasite interferes in some way or other with the snail's endocrine system.

Animals↗
PubMed1989

Ultrastructural evidence for the destruction of Schistosoma mansoni sporocysts associated with elevated lysosomal enzyme levels in Biomphalaria glabrata.

The activity levels of serum acid phosphtase, aminopeptidase, and lysozyme in a Brazilian strain of Biomphalaria glabrata were ascertained at 1, 2, and 3 hr after mechanical wounding or injection with albumin on the 30th day postexposure to a compatible strain of Schistosoma mansoni miracidia and found to be elevated. Parallel transmission electron microscope studies on daughter sporocysts and developing cercariae at these time intervals revealed progressive disintegration of the parasites that was associated with increased numbers of host granulocytes abutting the sporocyst surfaces. Furthermore, host granulocytes were observed to have passed through eroded sporocyst walls and attacked developing cercarial embryos. It is proposed that the elevated levels of lysosomal hydrolases released from activated host granulocytes as a result of challenge altered the parasite's surfaces so that these were recognized as nonself. Consequently, additional host granulocytic response, which included additional release of lysosomal enzymes into serum as well as phagocytosis of remnants of both sporocysts and developing cercariae, was elicited.

Acid Phosphatase↗
PubMed1989

Molluscicidal activity of Solanum aculeatum (family: Solanaceae) berries against Biomphalaria pfeifferi, Bulinus globosus and Lymnaea natalensis.

Aqueous suspensions of powder of sun- or freeze-dried berries of the plant Solanum aculeatum (Family Solanaceae), indigenous in Kenya, were tested for molluscicidal activity against Biomphalaria pfeifferi, Bulinus globosus and Lymnaea natalensis under laboratory conditions. One hundred or 50 mg powder L-1 of sun- or freeze-dried berries killed over 60% of the test B. pfeifferi, Bul. globosus and L. natalensis. Whereas 25 mg L-1 of the sun dried material killed less than 60% of the test snails, similar concentrations of the freeze dried molluscicide produced 60-80% mortality in the snails, under similar conditions. Using L. natalensis as the target snail, it was shown that the freeze dried material was more potent than the freeze-dried berries of S. incanum, S. nigrum or leaves of Polygonum senegalensis (Family Polygonaceae), all present in Kenya, and known to possess molluscicidal properties. The powdered material retained molluscicidal activity even after several months storage at room temperature. These findings suggest that S. aculeatum is a potent plant molluscicide, and has the potential for the control of vectors of schistosomiasis and fascioliasis in Kenya.

Animals↗
PubMed1989

Phagocytic activity of hemocytes of M-line Biomphalaria glabrata snails: effect of exposure to the trematode Echinostoma paraensei.

The phagocytic activity of hemocytes from 6-8-mm M-line Biomphalaria glabrata snails was studied in an in vitro assay using glutaraldehyde-fixed sheep erythrocytes (SRBC) as target cells. For individual snails, the percentage of hemocytes ingesting SRBC during a 1-hr interval, termed the phagocytic activity index (PAI), was determined. Hemocytes from snails infected for 1 day with Echinostoma paraensei had a slightly elevated PAI, but at both 8 and 30 days postexposure (DPE), hemocytes from infected snails had a significantly lower PAI than controls. Hemocytes taken from snails at 8 DPE also had a low PAI using rabbit erythrocytes and yeast as target cells. The low PAI at 8 DPE is attributed to the presence of large numbers of poorly spreading hemocytes with low phagocytic activity. Hemocytes from snails with 30-day infections were well spread but nonetheless had a low PAI. The presence of plasma from 8-day infected snails did not alter the PAI of hemocytes from control snails, nor was the PAI of hemocytes from infected snails changed by plasma from control snails. SRBC preincubated for 60 min in plasma from various groups of M-line snails did not elicit an increase in PAI when presented to hemocytes from control snails; in some cases, as with plasma from 6-8-mm control snails, such preincubation significantly reduced the PAI below levels obtained using SRBC preincubated in culture medium. As compared to hemocytes from snails with normally developing, 8-day-old intraventricular sporocysts (IS), hemocytes from snails exposed to infection but subsequently lacking IS had a significantly higher PAI.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗