SEARCH · PubMed Health

Results for “FASCIOLA HEPATICA”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 289 records · Page 16Linked to original sources

PubMed1989

Identification, expression and in situ hybridization of an eggshell protein gene from Fasciola hepatica.

The molecular basis of egg formation in the parasitic liver fluke, Fasciola hepatica, was investigated by isolating and characterizing an abundant cDNA from a female genital complex cDNA library. It was expressed in Escherichia coli as a beta-galactosidase fusion protein, which was purified and used to produce polyclonal antibodies. Using immunoblots, the antiserum recognized two soluble constituents of isolated egg shells, both significantly larger than predicted from cDNA sequencing. Using in situ hybridization, the message was detected in cells in the adult vitelline follicles. Eggshell protein mRNA expressed in E. coli will provide a source of precursor protein for further studies of parasite eggshell formation.

Animals↗

PubMed1982

An analysis of variations in the age structure of Fasciola hepatica populations in sheep.

The processes which govern the age structure of Fasciola hepatica populations in sheep were investigated by means of a simple mathematical model. The mortality of the metacercariae on the pasture was shown to be a factor of major importance. The mortality rate depends on the micro-climate that prevails at the pasture surface, and thus the age distribution curve of a population of flukes is also determined in part by the weather. This has important implications for the chemotherapy of fascioliasis: flukicides are not equally effective over the whole range of age-classes of parasite and so the factors which govern the age distribution curve of the parasite population within individual hosts ultimately determine the efficiency of chemotherapy.

Aging↗

PubMed1993

Fasciola hepatica: a secreted cathepsin L-like proteinase cleaves host immunoglobulin.

Adult Fasciola hepatica secrete a cysteine proteinase capable of cleaving host IgG close to the papain cleaving site. The proteinase was separated by size permeation chromatography. Gelatin-substrate polyacrylamide gel electrophoresis analysis revealed that the proteinase migrates as 6 proteolytic bands in the apparent molecular size range 60-90 kDa. Based on pH profiles of activity, inhibition studies using diethylpyrocarbonate and the diazomethylketone Z-phe-ala-CHN2, and characterising the substrate specificity of the enzymes using fluorogenic peptide substrates we have shown that the 60-90-kDa proteinases are cathepsin L-like proteinases.

Animals↗

PubMed2001

Imported Fasciola hepatica infection in the United States and treatment with triclabendazole.

Infection with Fasciola hepatica, a liver trematode, is not frequently reported in the United States. We describe 2 patients, both originally from Cape Verde, who illustrate the spectrum of clinical presentations of F. hepatica as well as the means of treating infection with this parasite. Patient 1 had extensive disease and underwent multiple diagnostic procedures before the correct diagnosis was reached. Patient 2, who had few symptoms, had fascioliasis diagnosed by a noninvasive evaluation. Both patients were treated with triclabendazole without experiencing significant side effects. Fascioliasis that has been imported to the United States may elude prompt or accurate diagnosis. Obtaining a detailed travel history and recognizing the clinical presentation early in the course of infection may permit timely and noninvasive identification of infection. Triclabendazole is now the recommended drug for treating for fascioliasis because of its efficacy, safety, and ease of use.

Adult↗

PubMed1981

Hypersensitivity in rats infected with Fasciola hepatica: possible role in protection against a challenge infection.

Rats infected with Fasciola hepatica showed an increase in intestinal mast cells which reached a peak between four and six weeks and fell to control levels by week 14. Following a challenge infection sensitised rats showed evidence of a transitory mild intestinal anaphylactic response. The numbers of intestinal eosinophils, already increased as a result of the primary infection, were rapidly supplemented. In previously uninfected rats the majority of flukes penetrated the mid gut region, but in sensitised rats there was a shift towards the caecal end. Resistance to challenge and a pronounced intestinal eosinophil response were evident in previously infected rats irrespective of the presence or absence of detectable serum reaginic antibody. Systemic anaphylaxis, induced by intravenous fluke antigen administration, occurred whether serum reagins could be detected or not.

Anaphylaxis↗

PubMed1986

Immunoprecipitation of in vitro translation products of Fasciola hepatica RNA.

Incubation of in vitro translation products of RNA isolated from Fasciola hepatica with immune rat serum and sera from infected sheep resulted in the immunoprecipitation of a number of polypeptides, most of which had similar electrophoretic mobilities. Although only one of these (a 30 kDa species) correlated precisely in mobility with that of biosynthetically labelled excretory-secretory (ES) antigens, this polypeptide (along with several others) was also immunoprecipitated by sheep sera raised against authentic ES antigens. This verified that the isolated RNA contained mRNA species encoding ES antigens of the parasite. In addition, immune rat serum immunoprecipitated a 64 kDa polypeptide which was not immunoprecipitated by infected sheep serum or anti-ES antigen sheep serum. The possible significance of this finding in terms of the ability of rats to develop resistance to fascioliasis in contrast to sheep which apparently cannot is discussed.

Animals↗

PubMed1978

Acquired immunity to the trematode Fasciola hepatica in rats.

Following a primary infection of 5 metacercariae (mc) of Fasciola hepatica, rats became immune to challenge with 30 mc. Immunity was less consistently demonstrated following challenge infection with 5 mc. The levels of precipitating and miracidial immobilizing antibodies, and antibodies detected by an indirect fluorescent antibody test, were monitored during the course of a primary infection of 5 mc and challenge infection of 30 mc. Following primary infection, peaks in the antibody response were associated with the invasion and migration of juvenile flukes in the liver parenchyma. Antibody titres fell when flukes entered the bile duct. There was a slight elevation in the titre of all antibodies following challenge, but, apart from those detected by the fluorescent antibody test, this elevation was not as marked as in control animals. It is suggested that flukes become isolated from, or have diminished contact with, the immune system once they enter the bile duct. This might explain why adult flukes survive in immune hosts whereas challenge metacercariae are destroyed.

Animals↗

PubMed1981

Proline biosynthesis by Fasciola hepatica at different developmental stages in vivo and vitro.

The ability of Fasciola hepatica to produce proline was assessed by measuring activity of the proline biosynthesis enzyme ornithine-delta-transaminase, and the arginine-dependent production of proline in vitro. This was related to the changes in bile proline of rats during the course of infection. It was found that the total production of proline and total enzyme activity per fluke increased as the fluke increased in size. However, while the specific enzyme activity remained constant throughout development, there was a preferential increase in proline production relative to protein content of the flukes just prior to their migration into the bile ducts. This early amplification of proline production could provide the stimulus to induce hyperplasia in the bile duct in preparation for fluke entry as proline production relative to protein content of fluke dropped markedly after migration into the bile ducts and never again reached the pre-migration level.

Animals↗

PubMed2006

Fasciola hepatica: effects on the antioxidative properties and lipid peroxidation of rat serum.

Fasciola hepatica infection is accompanied by increased formation of reactive oxygen species. The aim of this study was to analyze antioxidative properties of rat serum in the course of fasciolosis. Wistar rats were infected per os with 30 metacercariae of F. hepatica. Activities of antioxidant enzymes and concentrations of non-enzymatic antioxidants in serum were determined at 4, 7, and 10 weeks post-infection (wpi). Activity of superoxide dismutase (Cu, Zn-SOD) significantly decreased (by 35% during the migratory phase, by 40 and 23% at 7 and 10 wpi, respectively), while glutathione reductase activity significantly increased (by 62, 65, and 41%, at 4, 7, and 10 wpi, respectively). No significant changes were found in the activity of glutathione peroxidase. Significant decreases in concentrations of reduced glutathione, vitamins C, E, and A were observed, particularly during the migratory phase of fasciolosis (at 4 wpi). These changes were accompanied by enhancement of lipid peroxidation processes as evidenced by increased levels of malondialdehyde (MDA) and 4-hydroxynonenal (4-HNE). Concentrations of MDA and 4-HNE at 4 wpi increased by 38% and by 59%. MDA increased by 51% at 7 wpi and by 79% at 10 wpi, while 4-HNE increased by 87 and 118%, respectively. The results indicate that fasciolosis is associated with enhanced oxidative reactions and reduced antioxidant defense capability of rat serum.

Aldehydes↗

PubMed1986

Phosphofructokinase in the liver fluke Fasciola hepatica. Purification and kinetic changes by phosphorylation.

Phosphofructokinase from the liver fluke Fasciola hepatica was purified from extracts of the whole organisms. The molecular weight of the protomer as determined by sodium dodecyl sulfate-gel electrophoresis is 83,000. Phosphorylation of the liver fluke phosphofructokinase by the catalytic subunit of cAMP-dependent protein kinase occurred at a rate that was at least an order of magnitude greater than that observed with mammalian heart phosphofructokinase. The maximum level of phosphate incorporated was 0.22 mol P/mol of protomer. The kinetic properties of the enzyme were greatly altered as a result of phosphorylation. Compared to native enzyme, phosphorylated enzyme had a greater affinity for its substrate Fru-6-P and a decreased sensitivity to inhibition by ATP. These kinetic changes were similar to those of native enzyme in the presence of positive modifiers such as AMP. AMP also activated the phosphorylated enzyme. Activation of the phosphorylated enzyme by AMP was characterized by a further increase in affinity for Fru-6-P and a further decrease in sensitivity to ATP inhibition. Thus, the liver fluke phosphofructokinase can be modulated by covalent phosphorylation as well as noncovalent binding of different modifier ligands.

Adenosine Monophosphate↗

PubMed2001

An experimental study on triclabendazole resistance of Fasciola hepatica in sheep.

The efficacy of triclabendazole in sheep experimentally infected with Fasciola hepatica was studied. Two groups of 12 lambs were infected with a susceptible (S) or a resistant (R) strain of F. hepatica. Eight weeks after infection, six lambs of each group (ST and RT) were treated with triclabendazole (10mg/kg). The other lambs were used as untreated controls (SC and RC). The parameters studied were: GLDH, gamma-GT, ELISA measuring antibodies against recombinant cathepsin-L(1) and eggs per gram faeces (epg). The lambs were slaughtered 16 weeks after infection and the number of flukes counted. The GLDH, gamma-GT levels and the OD value of the ELISA decreased as a result of the treatment in group ST. Patent infections were observed in all animals of groups SC, RT and RC. In group ST, occasionally a few eggs were found in five lambs. The percentage of flukes was 31.3 in SC and 37.6 in RC. In the treated groups ST and RT, the percentage of flukes was 0.06 and 33.6, respectively. These results corresponded to efficacies of 99.8% in the susceptible and 10.8% in the resistant strain. Since the resistant strain was isolated from a mixed cattle and sheep farm, it confirms the presence of triclabendazole resistance in the Netherlands.

Animals↗

PubMed2001

Cathepsin L proteinases as vaccines against infection with Fasciola hepatica (liver fluke) in ruminants.

Fasciolosis, caused by trematodes of the genus Fasciola, is one of the most important diseases of farmed ruminants in temperate and tropical zones. The appearance of Fasciola hepatica populations that are resistant to common flukicidal drugs means that new methods of treatment will soon be required. The future prospect for the development of anti-liver fluke vaccines is optimistic and given their consumer acceptability and environmental friendliness, offer the best way forward. Cathepsin L proteases (Fhe CL 1 and Fhe CL 2), secreted by liver flukes at all stages of their development in the mammalian host, are believed to play important roles in facilitating parasite migration (tissue degradation), feeding and immuno-evasion. The authors consider them prime targets for which new vaccines can be developed. Vaccine studies in cattle and sheep have shown that protection levels of up to 72 and 79 per cent, respectively, can be obtained with immunisations of cathepsin Ls in Freunds' adjuvant. The vaccine also exhibited high anti-embryonation/anti-fecundity effects on parasites that survived in vaccinated animals and thus could have a major impact on the transmission of disease to the intermediate host. While natural infections in sheep and cattle appear to elicit non-protective Th2 immune responses, the authors' studies indicate that the protection induced by vaccination involves elements of a Th1 response.

Animals↗

PubMed1985

Forskolin activation of serotonin-stimulated adenylate cyclase in the liver fluke Fasciola hepatica.

Properties of forskolin activation of adenylate cyclase in the liver fluke Fasciola hepatica are described. Forskolin stimulated adenylate cyclase activity in cell-free fluke particles to levels more than 30-fold above the basal rate. This activation was not dependent on guanine nucleotides and, upon washing of the particles, was rapidly reversed. Forskolin potentiated the activation of adenylate cyclase by serotonin (5-HT) and lysergic acid diethylamide (LSD), resulting in both an increase in the maximal level of enzyme activity and a decrease in the apparent activation constant (KA). The 5-HT antagonist 2-bromo-LSD did not inhibit enzyme activation by forskolin. Furthermore, forskolin had no effect on specific [3H]LSD binding to fluke particles. Activation of adenylate cyclase by sodium fluoride or guanine nucleotides was modified in a complex manner by forskolin with both stimulatory and inhibitory effects present. The results suggest that forskolin does not interact directly with the 5-HT receptor coupled to adenylate cyclase. Instead, it appears that forskolin effects are, at least in part, due to its ability to alter the interaction between the regulatory and catalytic components of adenylate cyclase. Incubation of intact flukes with forskolin increased their cAMP levels 2- to 3-fold. The concentration dependence of this response was similar to that for forskolin activation of adenylate cyclase in fluke particles, with 300 microM forskolin giving the maximum response. Forskolin and other agents that increased fluke cAMP levels also stimulated fluke motility.

Adenylyl Cyclases↗

PubMed1987

Differences in intermediary energy metabolism between juvenile and adult Fasciola hepatica.

A comparison of glucose catabolism by juvenile and adult liver flukes, Fasciola hepatica, showed that in the adult the cytosolic degradation of glucose via phosphoenolpyruvate carboxykinase (PEPCK) was the most important route, whereas in the freshly excysted juvenile a large part was degraded via pyruvate kinase (PK). However, it was also shown that the adult did not exclusively use the PEPCK pathway, nor did the juvenile exclusively use the PK pathway. When the juvenile was forced to anaerobic functioning it produced propionate and acetate just like the adult, but this did not imply that it switched to the pathways of the adult: the pathway via PK remained important. Malic enzyme (NADP(H)-dependent) was demonstrated to be present in the cytosol and in the mitochondria of both juveniles and adults. These enzyme activities enable the parasite to use a mixture of malate and pyruvate in any ratio as substrate for the mitochondrial production of propionate and acetate. Pyruvate dismutation was important in the anaerobically functioning juvenile, whereas in the adult malate was the major, but not the only mitochondrial substrate. The pH profiles of PK and PEPCK showed that the pathway of PEP metabolism at the PK/PEPCK branchpoint can be regulated by the pH. However, the end products of glucose breakdown were not dependent on the pH. During its development, the liver fluke will gradually be forced to anaerobic functioning. At first, the acidic end product will favour a partitioning of PEP at the PK/PEPCK branchpoint towards malate formation. Later, a lasting predominance of the PEPCK pathway occurs as PK activity almost completely disappears.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetates↗

PubMed1980

The parasitic castration and gigantism of Lymnaea truncatula infected with the larval stages of Fasciola hepatica.

The shells of Lymnaea truncatula infected with the larval stages of Fasciola hepatica were significantly longer than those of comparable uninfected controls. The dry mass (tissue, shell + parasite) of the same infected snails, 56 days after infection, was approximately twice that of the controls (tissue + shell). The increased mass of infected snails was not due to a disproportionate increase in shell weight relative to tissues. Infected snails maintained at 20 degrees C had virtually ceased egg production by 21 days post-infection whereas control snails continued to lay eggs steadily for the duration of the experiment. The dry mass of snail tissue plus the cumulative dry weight of eggs produced was taken as an indication of the ability of control snails to generate biomass. Similarly the tissue mass plus cumulative egg weight and parasite weight was taken as an indication of the ability of the infected snails to generate biomass. The control and infected snails were not significantly different in this respect indicating that the gigantism of infected snails could be the result of a switch in nutrient supply from reproduction to somatic tissue growth and parasite growth. Castration was brought about 17-21 days after infection as a result of the direct consumption of the ovotestis by a proportion of the redial population. In a separate experiment it was demonstrated that a population of infected snails maintained at 20 degrees C survived as long as a similar group of control snails. The findings with this host-parasite system are discussed in relation to possible mechanisms causing castration and gigantism in other digene-snail interactions, and in relation to parasitic castration in other groups. It is concluded that the observed gigantism of infected snails is more likely to have a nutritional rather than endocrine origin.

Animals↗

PubMed2000

A field study of natural infections in three freshwater snails with Fasciola hepatica and/or Paramphistomum daubneyi in central France.

Natural infections of three freshwater snails with Fasciola hepatica and/or Paramphistomum daubneyi were studied during two periods in 1996 and 1997 (June-July and September-October) on 18 farms located in the departments of Vienne and Haute Vienne (central France), and known for low prevalences of F. hepatica infections in ruminants. A total of 1573 Lymnaea glabra and 1421 L. truncatula 6 mm high or more were collected in the meadows of 13 farms and dissected under laboratory conditions. Snails with single or concurrent infections of F. hepatica and/or

Animals↗

PubMed2000

Cercarial productivity of redial generations in single-miracidium infections of Lymnaea truncatula with Paramphistomum daubneyi or Fasciola hepatica.

Single-miracidium infections of Lymnaea truncatula with Paramphistomum daubneyi or with Fasciola hepatica were carried out under laboratory conditions to count free rediae, their germinal embryos, and to determine the cercarial productivity of each redial generation. In snails infected by P. daubneyi, the cercariae were produced by the first (8.7 cercariae per redia) and second (8.9 per redia) generations. At day 63 post-exposure, they corresponded, respectively, to 53.9% and 46.1% of cercariae produced by all rediae. In snails infected by F. hepatica, the majority of cercariae were produced by the R2a group (18.2 cercariae per redia) and corresponded to 66.0% of cercariae produced all rediae. The cercariae produced by the other redial groups were more limited in number: 17.5 per redia in the R1b group (28.7%) and 2.0 per redia in the R2b/R3a group (5.3%). Cercarial productivity of P. daubneyi until day 63 post-exposure was more limited in number than that of F. hepatica: a total of 145 cercariae per snail versus 427 per snail.

Animals↗

PubMed2001

Effect of parasite burden on the detection of Fasciola hepatica antigens in sera and feces of experimentally infected sheep.

The effect of Fasciola hepatica parasite burden on the detection of excretory/secretory (E/S) antigens in sera and feces of experimentally infected sheep was evaluated using a double antibody-based capture enzyme-linked immunosorbent assay (ELISA). Four groups of five sheep each were used. The first three groups were infected with 50, 100 and 200 metacercariae of F. hepatica, and the fourth group remained as non-infected control. On the day of infection and weekly thereafter, serum and fecal samples were taken. ELISA detected F. hepatica E/S antigen levels in serum from the first week post-infection (wpi) and in fecal supernatant from the fourth wpi, which were significantly (p<0.05) higher than controls. F. hepatica eggs were not detected until after the eighth wpi. The correlation between absorbance of E/S antigens in serum with the fluke burden was 0.77 (p<0.0001) and in feces 0.76 (p<0.0001) at 12th wpi. The sensitivity of the assay to detect E/S antigens in serum was 86.6% and in feces 93.3%. It is concluded that the ELISA technique used in this study offers a diagnostic alternative for detecting early infections of F. hepatica in sheep.

Animals↗