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PubMed1994

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

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

Animals↗

PubMed1993

Ecology of Biomphalaria alexandrina the snail vector of Schistosoma mansoni in Egypt.

The patterns of spreading and seasonal variation of population density of Biomphalaria alexandrina, the snail vector of Schistosoma mansoni in Egypt, in correlation with some environmental parameters were studied for 1988-1990 in four irrigation canals in Giza and Qalyoubiya Governorates. Results shown that the spreading patterns of snails along canals are changeable because of water current and irrigation activities. The snail population density showed two peaks, different in height, in April-May and November-December separated by two bottoms following the Winter Closure and during the hot summer season. The height of the peaks appears to be dependent on the extent of the "Winter Closure" and the prevailing water temperature. Two snail sampling tools, the dip-net and drag scoop, were used concurrently in this study. No considerable difference in sampling efficacy was recognized between these tools in the case of Biomphalaria. However, the dip-net appears to be more efficient in sampling other pulmonates while the drag scoop is more efficient in sampling prosobranchs. It is also realized that double sampling of 50% of sampling sites the next day should be satisfactory as a quality control system in snail population studies.

Animals↗

PubMed1998

Larval trematode assemblages in the snail Lymnaea stagnalis from southeastern Wisconsin.

From May through November 1993 and 1994, Lymnaea stagnalis appressa were collected from a stream adjacent to Cedarburg Bog, Ozaukee County, Wisconsin. Observations of cercarial shedding and subsequent dissection of snails revealed a relatively depauperate digenean component community consisting primarily of 3 common species. The most frequently occurring form was the metacercaria of Cotylurus flabelliformis. Sporocysts and cercariae of this species were rarely observed. Snails also harbored sporocysts and shed cercariae of Schistosomatium douthitti and a plagiorchid. Seasonal and yearly dynamics of the component trematode community reflect the apparent inability of sporocysts to overwinter in snails at this location. They also seem to be associated closely with snail life histories in terms of the availability of large snails, most often infected by the sporocysts of S. douthitti and the plagiorchid. Analyses of double infections revealed the occurrence of a negative interspecific interaction between the tetracotyles of C. flabelliformis and sporocysts of S. douthitti. Other combinations of trematode species did not reveal negative interactions. Competition does not seem to play a major role in the structure of the component community at this location.

Animals↗

PubMed1964

ECOLOGICAL DESIGN OF IRRIGATION CANALS FOR SNAIL CONTROL.

The snail hosts of schistosomiasis have found ideal conditions for rapid colonization in many irrigation and drainage canal systems. By studying the hydrodynamic aspects of snail dislodgment it may be possible to devise a control method based on engineering the snail's microenvironment. For Australorbis glabratus, a velocity exceeding 33 cm/sec at shell height produces a hydrodynamic drag force sufficient to dislodge the snail from its position on the solid boundary of a canal.

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PubMed1958

Some aspects of snail ecology in South Africa; a preliminary report.

In this paper, the authors present the preliminary results of a recent ecological survey of some rivers in the Transvaal, Union of South Africa.Representative samples of the molluscan fauna of the rivers were collected and chemical analyses of the river waters were carried out. In addition, such characteristics as current speed, temperature, turbidity, biochemical oxygen demand, and amount of oxygen absorbed from potassium permanganate were determined.No evidence was obtained to show that the chemical composition of natural, unpolluted waters plays any part in determining vector snail habitats. Current speed was found to have some effect, bilharzia vector snails not being found in fast-flowing waters.Of the other factors, turbidity was shown to be of some importance, probably because it affects the growth of the algae on which certain snails seem to depend for their proper development, and severe pollution with sewage and industrial wastes also appeared to have an adverse affect on the snail population.

Animals↗

PubMed1961

The effect of snail control on the prevalence of Schistosoma japonicum infection in the Philippines.

Snail control measures undertaken in Palo, Leyte, Philippines, in the course of a bilharziasis control project reduced the vector population by 95% in two years. Stool examinations performed before and after the snail control operations indicate that the human prevalence of bilharziasis has shown a significant concomitant decrease in both the urban and coastal areas of Palo, that decrease being most pronounced in children under 10 years of age. No measurable reduction in prevalence occurred in the inland area of Palo, but snail control there appeared to protect the urban area downstream.The authors discuss the manner in which data on the decline in the snail population can be used to predict the change in prevalence in each age-group examined.

Animals↗

PubMed2001

Effects of the serotonin receptor ligand methiothepin on reproductive behavior of the freshwater snail Biomphalaria glabrata: reduction of egg laying and induction of penile erection.

The biogenic monoamine serotonin (5-HT) has been reported to enhance egg laying in the freshwater gastropod Biomphalaria glabrata, an intermediate host for human blood flukes. Methiothepin, a vertebrate 5-HT(1/2) receptor ligand which binds with high affinity to a 5-HT receptor (5-HTlym) in Lymnaea stagnalis was tested for its ability to block egg laying in B. glabrata as a possible target for snail control. A single 30-min application of methiothepin (1 microM) was sufficient to prevent egg laying for over 1 week and did so in a dose-dependent fashion. Furthermore, single applications of methiothepin (1 microM and 10 microM) induced penile erection in a high percentage of snails tested. Latency to erection was long (at least 8 hr), but the duration of erection was long-lasting (up to 48 hr). Despite the erections, methiothepin-treated snails failed to achieve copulations. The pharmacological effect of methiothepin on both male and female reproductive processes is similar to that produced in other molluscs, and points to the gene for the 5-HT receptor mediating or modulating both or either processes as a potential target of snail control strategies. J. Exp. Zool. 289:202-207, 2001.

Animals↗

PubMed2004

Expression of chicken slug and snail in mesenchymal components of the developing central nervous system.

Slug and Snail are members of the Snail family of zinc-finger transcription factors. They are involved in triggering epithelial-mesenchymal transitions during the development of the neural crest and the mesoderm. We have analyzed by in situ hybridization their expression in the nervous system of chicken embryos at mid-gestation stages, from 4 to 15 days of incubation. We show that Slug and Snail show specific and nonoverlapping expression patterns in mesenchymal structures associated to the developing central nervous system. While Slug is expressed in the meninges and in the pericytes/vascular smooth muscle cells (vSMCs) of the brain, the spinal cord and other embryonic tissues, Snail is expressed in the stroma of the choroid plexus of both the hindbrain and the forebrain.

Animals↗

PubMed2005

Regulation of Twist, Snail, and Id1 is conserved between the developing murine palate and tooth.

The development of both the tooth and palate requires coordinated bone morphogenetic protein (BMP) and fibroblast growth factor (FGF) signalling between epithelial and mesenchymal tissues. Here, we demonstrate that transcription factors Twist and Snail are downstream targets of FGF signalling, that Id1 and Msx2 are downstream targets of BMP signalling, and that Msx1 is regulated by both signalling pathways during tooth and palate development. We show that Twist and Snail expression in the mesenchyme is regulated by the overlying epithelium and that exogenous FGF4 in tooth and FGF2 in palate can mimic this regulation in isolated mesenchymal explants. Ids act in a dominant-negative manner to inhibit the function of other transcription factors such as Twist and Snail. FGF and BMP signalling can regulate development antagonistically, and we suggest that FGF-regulated Twist and Snail and BMP-regulated Id1 may mediate these antagonistic effects during both tooth and palate development.

Animals↗

PubMed1981

Reproductive anomalies in stenoglossan snails related to pollution from marinas.

Over 3090 snails of the dioecious intertidal species Nassarius obsoletus Say were collected from a total of 71 localities. Their reproductive anatomy was examined for a superimposition of male characteristics on to the normal female anatomy, an abnormality called 'imposex'. Imposex was rated numerically in terms of the fraction of the population affected and the intensity of expression in bearer snails. An initial survey of 22 localities in Fairfield and Westport, Connecticut, led to the hypothesis that imposex was related to a substance arising from marinas. This was tested at nine pairs of marina and control localities in Long Island Sound, as well as six pairs along a transect ranging from Rhode Island to Georgia. Imposex scores were significantly higher at the marina locality in every pair. Further confirmation was found in a detailed survey of the estuarine harbor at Southport, Connecticut, which showed that adjacent populations could differ in the amount of imposex to the extent that both the snails and the waters they lived in remained separated by natural or man-made barriers. Imposex has been found in populations of N. obsoletus ranging from Damariscotta, Maine, to Savannah, Georgia, and it has been reported from San Francisco Bay, California. Similar anatomical abnormalities have been reported in at least 27 other species of taenioglossan and stenoglossan snails, extending the range to the Atlantic and Mediterranean coast of Europe and the British Isles. Concern is raised regarding the possible existence of another global pollutant with novel effects on marina biota.

Animals↗

PubMed2001

Mannan-degrading enzymes purified from the crop of the brown garden snail Helix aspersa Müller (Gastropoda Pulmonata).

Two mannan-degrading enzymes were purified from the crop of the terrestrial snail Helix aspersa Müller. The crude extracts were taken from dormant (for 4 months) snails. The enzymes were a betaD-mannanase of 37.4 +/- 0.3 kDa (EC 3.2.1.78) and a betaD-mannosidase of 77.8 +/- 1.9 kDa (EC 3.2.1.25). Both enzymes degraded insoluble mannan, releasing either mannose only (beta-mannosidase) or oligosaccharides, possibly mannotriose and mannopentaose (beta-mannanase). The beta-mannanase had a typical endo-activity pattern, while the beta-mannosidase was an exoenzyme. The incubation of both enzymes with mannan increased the catalysis by 83%. The best synergy was found with 75% mannosidase combined with 25% mannanase. The beta-mannanase also hydrolysed beta-linked heteromannans and its affinity for different galactomannans was studied. The Km values, varying from 2.89 +/- 0.47 mg x ml(-1) to 0.26 +/- 0.01 mg x ml(-1), revealed the inhibitory effect of the alphaD-galactosyl residues released. The beta-mannosidase was acidic (optimum pH = 3.3) and heat-sensitive (50% residual activity at 42 degrees C after 5 min of pre-incubation), while the beta-mannanase remained stable until 48.5 degrees C (50% residual activity) and over a pH range of 4.3-7.5. The properties of these mannanolytic enzymes are discussed in this paper compared with those purified in other gastropods and in a bacterium, Enterococcus casseliflavus, a quite similar strain previously isolated from this snail intestine. The occurrence of thermostable enzymes in H. aspersa digestive tract could be a zootechnic parameter of great importance for snail farming. J. Exp. Zool. 290:125-135, 2001.

Animals↗

PubMed1994

Metabolic depression in land snails: in vitro analysis of protein kinase involvement in pyruvate kinase control in isolated Otala lactea tissues.

Isolated tissues from the land snail Otala lactea were used to examine the relationship between protein kinase activity and phosphorylation-induced changes associated with metabolic depression. Hepatopancreas and foot muscle were removed from active and estivating land snails and incubated in vitro under aerobic and anoxic conditions. Pyruvate kinase (PK), cAMP-dependent protein kinase (PKA), and protein kinase second messenger compounds (cyclic AMP and inositol 1,4,5-triphosphate) were measured after incubating the tissues for 4 hours. Pyruvate kinase from the hepatopancreas of active snails was phosphorylated during anoxic incubations as indicated by changes in the I50 value for L-alanine. However, measurements of PKA activity and of cellular cAMP concentrations suggested that PKA activity was lower in these incubated tissues. When foot muscle was used as the tissue source, incubation under anoxic conditions produced no changes in PK activity even though PKA activity was drastically reduced. Analysis of changes in inositol 1,4,5-triphosphate concentrations after tissue incubation showed that they were not consistent with changes in PK activity in either organ. These results suggest that PKA and Ca2+/phospholipid-dependent protein kinase C do not phosphorylate PK during anoxia in land snails. The differences between values measured in incubated tissues and those measured in vivo suggest that isolated O. lactea tissues are not a good in vitro model system for studying metabolic changes associated with depressed metabolism.

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PubMed2000

The snail as a target organism for the evaluation of industrial waste dump contamination and the efficiency of its remediation.

The diagnosis of contamination and the efficiency of remediation of an industrial waste dump (IWD) were done before and after remediation. For this study, two species of snails were used for passive and active biomonitoring: a nonnative species, Helix pomatia and young garden snails (Helix aspersa aspersa) of standardized rearing (age, 2 months). Bioaccumulation analysis of pollutants (cadmium, nickel, iron, lead, chromium, manganese, copper, and zinc) in viscera of the snails gave data on the evolution of the biotop biodisponibility over time. Those data allowed the conclusion that the snails were useful for passive and active biomonitoring. Comparison of two contamination grids corroborated previous conclusions. Furthermore, the results obtained indicated the efficiency of the remediation technique used for the IWD.

Animals↗

PubMed1993

DNA probes for the detection of Fasciola hepatica in snails.

Fasciola hepatica, also called the large liver fluke, is a trematode which can infect most mammals. Monitoring the infection rate of snails, which function as intermediate hosts and harbour larval stages of F. hepatica, is an important component of epidemiological studies on fascioliasis. For this purpose, DNA probes were generated which can be used for the detection of F. hepatica larvae in snails. Four highly repetitive DNA fragments were cloned in a plasmid vector and tested by Southern blot hybridization to the DNA of various trematodes for specificity and sensitivity. The probes Fhr-I, Fhr-II and Fhr-III hybridized only to F. hepatica DNA. Fhr-IV contained ribosomal RNA gene sequences and cross-hybridize with the DNA from various other trematode species. Squash blot analysis showed that the different probes were able to detect the parasite larvae in trematode-infected snails even as isolated single larvae. No signals were obtained in squash blots of uninfected snails. Probes Fhr-I, Fhr-II and Fhr-III are thus useful specific tools for studying the epidemiology of fascioliasis. The probe Fhr-IV, because of its broader spectrum, can be used to detect the larvae of a wide range of trematode species of waterbirds, which are the causative agents of swimmer's itch.

Animals↗

PubMed1976

[Histological studies of the African giant snail (Achatina fulica) experimentally infected with Angiostrongylus vasorum or Angiostrongylus cantonensis (author's transl)].

African Giant Snails (Achatina fulica) about 6 weeks old were experimentally infected with each 5,000 to 20,000 first stage larvae of Angiostrongylus vasorum or A. cantonensis by exposure to a larval suspension. The snails were histologically examined after various intervals after infection: 1 hour post infectionem (p.i.) larvae were present in the foot and 2 hours p.i. in addition in the gastrointestinal tract. 12 hours p.i. larvae were seen for the first time in the lung which reached nearly half of the total number of larvae via the hemolymph system. 24 hours p.i. or later 80-90% of the total larval population were detected in the foot and the lung. In the various organs (lung, mantle, hepatopancreas, gastro-intestinal tract, foot) the larvae were found in the loose connective tissue near or within the hemolymph vessels. The cellular defense mechanism of the snail is activated 12 hours p.i. and the parasites are surrounded by large numbers of leucocytes (leucocytic encapsulation). Three days p.i. the nuclei of the cells become spindle shaped and are forming concentric layers in the outer part of the capsule (fibroblastic type of encapsulation). Later on the wall of the encapsulation becomes thinner and a karyolysis can be recognized in the centre, consequently a cavity occurs. Encapsulations in organs poor in muscle cells can histologically not be differentiated from those located in the foot, which consists mainly of muscle cells; a myofibrous type of encapsulation has to be doubted. The effects of the infection on the snail are discussed.

Animals↗

PubMed1980

Carbohydrate reserves and hemolymph sugars of the African giant snail, Achatina fulica in relation to parasitic infection and starvation.

In the snail, Achatina fulica, parasitized by the rat lungworm Angiostrongylus cantonensis, levels of carbohydrate in hemolymph and digestive glands were determined. The normal level of hemolymph glucose of 11.7 mg% dropped to 4.25 mg% in the infected snails, a significant difference after only one week of infection. The level of total reducing sugar in the hemolymph also decreased significantly (12.3 mg% to 3.6 mg%) in this period. Later on, the snails were capable of adapting themselves to the parasitic infection and the concentration of hemolymph sugars returned to the normal range. Starvation caused a decrease in the carbohydrate reserves of the digestive gland only when the starved snails had been previously infected.

Angiostrongylus↗

PubMed1991

Toxicity evaluation of ammonium sulphate and urea to three developmental stages of freshwater snails.

Studies were performed to evaluate the toxic effects of ammonium sulphate and urea (chemical fertilizers currently applied in ricelands of Cameroon) against eggs, juveniles, and adults of two species of freshwater snails (Helisoma trivolvis and Biomphalaria havanensis). Results obtained from ammonium sulphate tests indicated 24-h LC50 values of 558 mg/L and 669 mg/L for eggs; 393 mg/L and 526 mg/L for juveniles, and 701 mg/L and 657 mg/L for adults of H. trivolvis and B. havanensis, respectively. Similar analysis with urea revealed LC50 values of 14,241 mg/L and 13,532 mg/L for eggs; 18,255 mg/L and 24,504 mg/L for juveniles and 30,060 mg/L and 26,024 mg/L for adults of H. trivolvis and B. havanensis, respectively. Following 48 h exposure, the concentrations of ammonium sulphate killing 100% of snails were 1,250 mg/L and 1,000 mg/L for the adults of H. trivolvis and of B. havanensis, respectively. Those of urea were computed to be 25,000 mg/L for H. trivolvis and 35,000 mg/L for B. havanensis. In rice culture in Cameroon, these fertilizers are applied at doses of 100 kg/ha (ammonium sulphate) and of 150 kg/ha (urea); hence, the above found concentrations lethal to snails appeared to be 10 to 13 times (ammonium sulphate) and to be 165 to 235 times (urea) higher assuming an average water depth of 10 cm in these ricefields. Therefore, the use of ammonium sulphate and urea as chemical fertilizers in ricelands of the Republic of Cameroon might adversely affect the survival of freshwater snails only in the case of spills or of stressful environmental conditions. Under normal laboratory conditions, both chemicals show a low molluscicidal activity with urea being about 25 to 35 times less potent than ammonium sulphate.

Ammonium Sulfate↗

PubMed1994

Comparison of the migrations of Fasciola hepatica sporocysts in Lymnaea truncatula and other related snail families.

The migration and definitive localization of sporocysts in the snail body were studied in four species (Aplexa hypnorum, Lymnaea glabra, L. truncatula, Physa acuta), each of which was exposed to a single miracidium and killed during a period ranging from the 1st to the 5th day postexposure. When penetration occurred through the mantle, tunnels were found mainly in the mantle or kidney in Lymnaea adults and also extended to the foot in many physidid adults and in newborns of the four species. The sporocysts preferentially localized in the zone surrounding the kidney and heart beginning on the 4th day in Lymnaea spp. and disappeared in Aplexa and Physa snails on the 3rd day. When penetration occurred through the foot and extended inconstantly to the mantle according to the snail species involved. Sporocysts were encountered in the foot as well as the mantle or the zone surrounding the kidney and heart. The significance of these results is discussed in relation to the snail host and the entry site used by the Fasciola hepatica miracidium.

Animals↗