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PubMed2003

Distribution and habitats of the snail Lymnaea truncatula, intermediate host of the liver fluke Fasciola hepatica, in South Africa.

This paper focuses on the geographical distribution and habitats of Lymnaea truncatula, the intermediate, snail host of the liver fluke, Fasciola hepatica, as reflected by the 723 samples in the database of the National Freshwater Snail Collection, Potchefstroom, South Africa. The 221 different loci (1/16-degree squares) on record reflect an extensive but discontinuous distribution, except in Lesotho and in parts of the Mpumalanga, Gauteng and North West provinces of South Africa. Although recorded from 12 different types of waterbody, it was mostly (42.0%) recovered from swamps. Most samples (45.8%) were collected in habitats with slow-flowing water. A muddy substratum was recorded for 62.5% of the samples. Most samples (86.3%) were collected in habitats with a mean annual air temperature of 10-20 degrees C, and more than 69% came from localities with a mean annual rainfall of 600-900 mm. An integrated decision tree constructed from the data indicated that temperature and types of waterbody play a decisive role in determining the presence of L. truncatula in a given area. A temperature index calculated for all mollusc species ranked L. truncatula second in a total of 53 species according to its association with low temperatures. It remains to be established whether its distribution is indeed discontinuous, and whether its preference for a particular habitat, amphibious habits and ability to aestivate could have resulted in some populations having been overlooked during surveys.

Animals↗

PubMed1995

Seasonal availability of Fasciola hepatica metacercariae in a temperate Mediterranean area (Madrid, Spain).

In this experiment, conducted over a 3-year period (1988-1990), the seasonal availability of Fasciola hepatica metacercariae in a temperate Mediterranean area (Madrid, central Spain) was analysed according to the rhythms of snail infection, the periods of cercarial emission, and the resistance of metacercariae. In this area, snails could be infected from late April to early November. Cercarial emission by spring infection started at the beginning of summer and terminated 3-4 weeks later. Mid-summer temperatures led to the extinction of shedding populations and of the metacercariae emitted by them, but were well tolerated by the snails with undeveloped infections. No aestivation was observed and summer infection led to a progressive shedding wave from August to late December, when it was interrupted. These populations became extinguished in the colder winter of 1988, but overwintered in the mild and belated winter of 1989. Only the snails infected from late summer onwards resumed activity and shed cercariae in spring, from the second half of March to late June. Risk of infection for grazing animals during winter will depend on survival of metacercariae. With a mean mortality of 23% during December and January, and of 38% during the following 2 months, no more than 30% of metacercariae reach the spring alive. Accordingly, risk of infection for grazing animals in spring will depend on overwintering infection of snails. These results indicate that temperature more than humidity could be responsible for different transmission patterns from year to year as winter thermic profiles could be the key for the transmission of fasciolosis during spring.

Animals↗

PubMed1998

CuZn superoxide dismutase activities from Fasciola hepatica.

The levels of superoxide dismutase (SOD) were determined in detergent-soluble, somatic and excretion-secretion (E-S) preparations from adult Fasciola hepatica using the xanthine oxidase system and visualized in substrate gels. Compared to detergent-soluble and somatic extracts, E-S products showed the highest SOD activity (88.5 U/mg), indicating active release to the medium in which parasites were maintained. SOD specific activity was also detected at high levels in E-S products from 3-week-old and 5-week-old immature migrating flukes (25 and 143 U/mg, respectively). In all preparations except for the somatic extract, the activity was characterized as cyanide-sensitive CuZn SOD. Differences in SOD isoenzyme profiles between the extracts were observed in native polyacrylamide gel electrophoresis: the somatic and detergent-soluble extracts exhibited 1 band of activity while the E-S products from immature and adults flukes contained 2 and 3 migrating bands, respectively. SOD was purified from the detergent-soluble extract and E-S products of adult worms by a combination of ultrafiltration, gel filtration on Sephacryl S-200 HR and ion-exchange chromatography on QAE Sephadex A-50. The SOD from detergent-soluble extract showed, by SDS-PAGE analysis, 1 band of 16 kDa apparent molecular weight. The SOD from E-S products showed 2 bands of 16 and 60 kDa apparent molecular weight. N-terminal sequence analysis of the 16 kDa band from the detergent-soluble preparation showed some similarity with Schistosoma mansoni cytoplasmic SOD. These enzymes may have a potential role in the evasion of the oxidative burst killing mechanism by immune cells.

Age Factors↗

PubMed2006

Variation of snail's abundance in two water bodies harboring strains of Pseudosuccinea columella resistant and susceptible to Fasciola hepatica miracidial infection, in Pinar del Río Province, Cuba.

The abundance of freshwater snails in two rural sites of Pinar del Río, Cuba, which harbor Pseudosuccinea columella susceptible and resistant to miracidia of Fasciola hepatica was followed for one year. Susceptible snails were found in the most anthropic site (IPA) whereas the resistant population inhabited the most preserved one (El Azufre). Only two snail species coexisted with P. columella at IPA site (Physa cubensis and Tarebia granifera) while five species were found at El Azufre, including an endemic from that province (Hemisinus cubanianus). Populations of both resistant and susceptible snails showed stable densities throughout the year, although the susceptible strain attained higher abundance. The highest densities were observed in April-May 2004 for the susceptible population whereas the resistant strain attained its highest abundance in January 2004. No record of Fossaria cubensis was made and the thiarid T. granifera occurred only at low densities. One of the sampled sites (IPA) meets all the conditions for the first report of P. columella naturally infected with larvae of F. hepatica.

Animals↗

PubMed1982

Fasciola hepatica: attempts to immunise rats and mice with metabolic and somatic antigens derived from juvenile flukes.

Attempts were made to vaccinate rats and mice against Fasciola hepatica using either somatic or metabolic antigens derived from juvenile flukes between 10 and 16 days old. None of the regimes tried induced a good resistance to subsequent infection, though metabolic antigens derived from 13-14-day-old flukes when injected subcutaneously into rats with adjuvant did produce some protection to challenge.

Animals↗

PubMed1975

Specific and non-specific phosphatases in the miracidium of Fasciola hepatica L.

Localization and activities of alkaline phosphatase, ATPase, 5-nucleotidase, glucose-6-phosphatase, thiamine pyrophosphatase and nucleoside diphosphatase were studied in the miracidium of Fasciola hepatica L. Except for nucleoside diphosphatase whose activity in the miracidium was not observed, all the enzymes were most active in the archenteron, protonephridia and nerve ganglion. This localization of the reaction intensity allows the inference that the three organs mentioned are sites of both intense carbohydrate metabolism and lively active transport. The role of phosphatases in carbohydrate metabolism is discussed.

Adenosine Triphosphatases↗

PubMed2001

Isolation and immunological characterization of fatty acid binding protein isoforms from Fasciola hepatica.

A combination of molecular sieving chromatography and 2-step preparative isoelectric focusing showed that native Fh12, a fatty acid-binding protein isolated from Fasciola hepatica adult worms, is a protein complex of at least 8 isoforms with identical molecular mass but different isoelectric points. Using enzyme-linked immunosorbent assay (ELISA) and inhibition ELISA assays, immunological differences were observed between native (nFh12) and a recombinant molecule denoted rFh15 that was obtained after screening a cDNA library from F. hepatica adult worms with an anti-Fh12 monospecific polyclonal antibody. It was confirmed that in infected rabbits, antibodies to nFh12 appear by the second week postinfection, whereas antibodies to rFh15 appear much later, by 6 wk postinfection. Four acidic forms (Fh12(1-4)) showed more immunological identity with rFh15 than with nFh12, based on the observation that they inhibited ELISA activity by nearly 50% when they were added to the anti-rFh15 polyclonal antibody at 20 microg/ml of protein concentration. Moreover, the Fh12(1-4) isoforms were poorly reactive with sera from rabbits 2-4 wk postinfection. However, the 2 acidic forms, denoted Fh12(5) and Fh12(6), and the neutral/basic forms, denoted Fh12(7) and Fh12(8), showed more immunological identity with the native nFh12 molecule than with the recombinant rFh15 because they were highly reactive with sera of rabbits with early 2-wk F. hepatica infection and inhibited ELISA activity nearly 50% when they were quantitatively added to the anti-nFh12 polyclonal antibody. These results suggest that rFh15 could be one of the acidic forms of nFh12, and that it, in fact, may be one of the less immunogenic or immunoprotective members, or both, of the nFh12 protein complex.

Animals↗

PubMed1979

[The effectiveness of the drugs Dovenix and Bilevon(R)-Injection against liver fascioliasis (Fasciola hepatica, Linné 1758) in cattle].

Dovenix and Bilevon-injection (manufactured by SPECIA, France and BAYER, West Germany, respectively) were tested for their anthelmintic efficacy against Fasciola hepatica in cattle. The drugs proved highly effective against both adult and immature flukes. The faeces of the treated animals were negative for F. hepatica eggs when examined 91 days after the treatment. In experiments with rats Dovenix and Bilevon-injection were tolerated up to eight times and ten times higher doses than the normal therapeutic dose, respectively.

Animals↗

PubMed2005

Peptide synthesis by recombinant Fasciola hepatica cathepsin L1.

Synthesis of the tripeptide Z-Phe-Arg-SerNH2 has been accomplished by a recombinant cysteine protease, cathepsin L1 from liver fluke (Fasciola hepatica), using Z-Phe-Arg-OMe as acyl acceptor and SerNH2 as nucleophile in 0.1 M ammonium acetate pH 9.0-12.5% v/v acetonitrile at 37 degrees C. LC-MS detection indicated tripeptide formation after 10 min, continuing up to 5.5 h. The ester Z-Phe-Arg-OMe was detected throughout the experiment but the hydrolysis product Z-Phe-Arg-OH appeared early and in quite large amounts. We believe that this is the first application of a parasite protease in enzymatic peptide synthesis.

Animals↗

PubMed1981

Precipitating antibodies against excretory/secretory antigens of Fasciola hepatica in sheep serum.

Gel diffusion techniques were used to study antigen-antibody reactions in precipitates forming around juvenile, semi-mature and adult Fasciola hepatica cultured in serum from infected sheep. The number of reactions was analysed in both primary and challenge infections. The number of antigens shared by the various developmental stages of the fluke was also examined. At least 2 antigens were involved in precipitate formation around juvenile flukes. These antigens were also produced by the later stages of development. Two additional antigens were produced by semi-mature flukes and these, together with two others, produced by adult flukes. Challenge infections had little effect on the number of antigens or antibodies in the precipitate.

Animals↗

PubMed1986

Identification of functional Fasciola hepatica antigens in experimental infections in rabbits.

Studies done comparing the reactivity of serum from an infected rabbit at different intervals of infection with a Fasciola hepatica crude tegument extract, F. hepatica excretory-secretory (ES) products and Fh arc 2 by ELISA show that the first 2 antigen preparations offer a better sensitivity for detecting acute infection, especially in its early stages (3 weeks). The ES proteins from F. hepatica adult worms were identified by the enzyme-linked immunotransfer blot (EITB) in order to define the antigens recognized by the sera from rabbits with experimental fascioliasis. A group of 7 polypeptides with molecular weights of 23-28 Kd were the major antigens recognized. Reactivity to these antigens is maximum at 8-10 weeks of infection by EITB. As the infection progresses, reactivity to the 23-28 Kd antigens decreases but does persist through 52 weeks of infection. At least 5 other polypeptides of 120, 84, 58, 52, 39 and 33 Kd were recognized by the sera of infected rabbits from 6 to 52 weeks of infection. A different pattern was observed in parallel studies done with these same sera by immunoprecipitation of ES antigens. In addition to a 33 Kd antigen, which was detected by both techniques, a 62 Kd antigen was detected early in infection (5 weeks) and 3 major antigens of 38, 40 and 44 Kd were prominent by immunoprecipitation from 9 weeks onward. This implies the presence of multiple Fasciola antigens with serodiagnostic potential. The expression of these antigens during development and their possible role in immunity is discussed.

Animals↗

PubMed2004

Tegumental surface changes in adult Fasciola hepatica following treatment in vitro and in vivo with an experimental fasciolicide.

Our objective was to determine by scanning electron microscopy the structural changes in the tegument of adult Fasciola hepatica after treatment with 5-chloro-2-methylthio-6-(1-naphtyloxy)-1 H-benzimidazole, called compound alpha, and its active metabolite sulphoxide, under in vitro and in vivo conditions. For the in vitro studies, flukes from sheep were exposed to 40 mg/l of compound alpha-sulphoxide over different incubation times. Flukes for the in vivo studies were raised in sheep treated orally with compound alpha and killed at different times post-treatment. Non-treated controls were included for each time of incubation. The results showed lesions after 6 h of treatment, such as swelling and furrows. At 12 h, the spines appeared to be surrounded by the tegument. At 24 h the tegument in some areas showed an exposed basal lamina. These changes became more severe as the incubation periods of the treated flukes increased. Compound alpha exerts a significant effect on the tegument of F. hepatica.

Animals↗

PubMed1990

Comparative efficacy of closantel and triclabendazole against Fasciola hepatica in experimentally infected sheep.

The effect of closantel (10 mg/kg orally) and triclabendazole (10 mg/kg orally) on the reappearance of a patent infection of Fasciola hepatica was studied in experimentally infected sheep. The treatments resulted in the interruption of faecal egg output for 11 weeks with triclabendazole and 13 weeks with closantel. Necropsy of untreated control animals revealed a mean burden of 360 flukes with a mean (+/- se) surface area of 171 +/- 64.3 mm2, whereas the fluke burdens in the closantel and triclabendazole-treated animals 14 weeks after treatment were 61 (83 per cent reduction) and 21 (94 per cent reduction), respectively. The surface areas of the flukes in the triclabendazole-group were comparable with the untreated controls (141 +/- 51.8 mm2), but the flukes in the closantel group were markedly smaller (43.1 +/- 26.9 mm2). It is concluded that closantel has, in epidemiological terms, a potency comparable with that of triclabendazole, despite its slightly lower efficacy against the very immature stages.

Animals↗

PubMed1987

[Fasciola hepatica L.: the productivity of a sporocyst as a function of the size of Lymnaea truncatula Müller].

Experimental studies were undertaken on the rediae of Fasciola hepatica and on their content in two populations of Lymnaea truncatula snails, individually exposed to a single miracidium and fixed for histologic observations just after their death between days 74 and 81 postexposure at 20 degrees C. The numbers of free rediae and of larval stages per snail increased with the shell height. A constant number of free rediae was observed in snails measuring 11 mm and more in size. There was no limit of increase in number for the different types of larval stages, but these increases were lower for the youngest larval types. The number of larval stages per redia also increased with snail size; it was always higher in the first redial generation than in the following generations. Cercariae were produced by 40%-43% of the rediae contained in a snail: 65%-80% of these mature rediae belonged to the first generation and to the first cohort of the second generation.

Animals↗

PubMed1993

Cathepsin L proteinase secreted by Fasciola hepatica in vitro prevents antibody-mediated eosinophil attachment to newly excysted juveniles.

Cathepsin L-like activity was demonstrated in the excretory/secretory (E/S) products of Fasciola hepatica newly excysted juveniles (NEJ), 3-week-old, 5-week-old and mature flukes using the fluorogenic substituted 7-amino-4-methylcoumarin substrates Z-phe-arg-AMC, Z-arg-arg-AMC and Z-arg-AMC. Gelatin-substrate polyacrylamide gel analysis revealed that the E/S from each of these stages contained multiple proteolytic enzymes; however, the pattern of proteinases obtained for NEJ E/S differed markedly from that of all other stages examined. The four NEJ proteinases identified were inhibited by leupeptin and Z-phe-ala-diazomethyl ketone indicating that each had cathepsin L-like activity. The E/S products of all four developmental stages contain an enzyme capable of cleaving immunoglobulin at the hinge region, the activity of which is also inhibited by Z-phe-ala-diazomethyl ketone. Using in vitro cell attachment assays we show that the cathepsin L-like proteinase purified from the E/S products of adult F. hepatica can prevent the antibody-mediated attachment of eosinophil to NEJ. These experiments indicate that this proteinase has an important biological function in immune evasion.

Animals↗

PubMed2006

Associations between anti-Fasciola hepatica antibody levels in bulk-tank milk samples and production parameters in dairy herds.

Our primary objective was to determine the relationships between Fasciola-specific antibody levels in bulk-tank milk and measures of productivity to estimate economic losses that are associated with Fasciola infections. A bulk-tank milk sample was collected in March 2004 from 1105 dairy herds in Flanders and the antibody levels against Fasciola hepatica (ODRf) and Ostertagia ostertagi (ODRo) were determined. The association of ODRf with four production parameters (milk yield, milk-protein %, milk-fat % and inter-calving interval) was assessed by multivariable linear-regression models. Production data were available for 463 out of the 1105 herds sampled. An increase in ODRf from the 25% quantile (0.428) to the 75% quantile (1.064) was associated with a decrease in the annual average milk yield of 0.7kg/(cowday) (P=0.002), with a decrease in the average milk-fat % of 0.06% (P<0.001) and with an increase of the mean inter-calving interval of 4.7 days (P=0.03). No significant relationship was found with the average milk-protein %. When the relationships of ODRf and ODRo with milk yield were tested simultaneously, we saw an additive rather than synergistic effect of concurrent infections.

Animals↗

PubMed1996

[Cloning of a protease gene family in Fasciola hepatica using the polymerase chain reaction (PCR)].

RT-PCR and degenerative Oligonucleotide primers derived from conserved cysteine protease sequences were used to amplify seven different Fasciola hepatica cysteine protease cDNA clones (Fcp1-7). Five of the clones showed homology to proteases of the cathepsin L type, whereas two appeared to represent the cathepsin B family. The 5' and the 3' regions of Fcp1 were amplified using the rapid amplification of cDNA Ends PCR (RACE-PCR) protocol. The Fcp1 cDNA fragment was also subcloned in the expression vector pGEX and expressed as a glutathione-S-transferase (GST) fusion protein. Antibodies, raised in rabbits against the GST:Fcp1 fusion protein, were used in Western blot analysis to examine expression in different life-cycle stages of F. hepatica. In extracts from immature and adult parasites proteins of 30 and 38 kDa were detected. In other stages, proteins of different molecular weight were recognized by anti-GST:Fcp1 antiserum, indicating stage-specific gene expression.

Amino Acid Sequence↗

PubMed2002

Larval development of Fasciola hepatica in experimental infections: variations with populations of Lymnaea truncatula.

A retrospective study was undertaken on 70 French populations of Lymnaea truncatula experimentally infected with Fasciola hepatica to determine whether or not susceptibility of snails to infection influenced redial and cercarial production. Results were compared with those obtained from two control populations, known for prevalences higher than 60% when experimentally infected with F. hepatica. In the 70 other populations examined, the prevalences ranged from 2 to 75%. In 55 of these populations, where the prevalence was more than 20%, a high proportion (50.1-56.8%) of snails died after cercarial shedding, whereas in the other groups (non-shedding snails with the most differentiated larvae being free cercariae, rediae containing cercariae, immature rediae, or sporocysts, respectively), snail death was significantly less. In 11 populations, where the prevalence values were 5-19%, only 14% of snails died after cercarial shedding, whereas snails with free cercariae, rediae with cercariae, or immature rediae showed significant increases in snail mortality. In the remaining four snail populations, with prevalences of less than 5%, the most differentiated larval forms were only immature rediae and/or sporocysts. Overall, the number of rediae containing cercariae significantly decreased with decreasing prevalence values. The low prevalence of experimental infection in several populations of snails might be explained by the occurrence of natural infections with miracidia originating from a mammalian host other than cattle, and/or by genetic variability in the susceptibility of snails to infection.

Animals↗