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PubMed1978

The identification of soluble adult antigen on the tegumental surface of juvenile Fasciola hepatica.

An antiserum was raised in rabbits against a soluble extract of fresh homogenized adult Fasciola hepatica of rat origin and was then absorbed with rat and mouse tissue antigens. This antiserum reacted specifically with the surface coat of adult flukes, of both rat and mouse origin, by indirect immunofluorescence to show the detail of surface spines. When tested against juvenile stages recovered from mice the reaction was positive with all but the earliest hepatic parenchyma stages. No reaction was present on the tegumental surface of newly excysted juveniles or stages 1 or 2 days post-infection (p.i.) whether recovered from the peritoneal cavity or the hepatic parenchyma.

Animals↗
PubMed1976

Origin, structure and function of subcuticular cells of Fasciola hepatica.

In the present paper the ultrastructure of the subcuticulare zone of the tegument of Fasciola hepatica and the distribution of thimidine-H3 for establishing the localization of DNA-synthesis in the tegument was studied. There were two types of subcuticular cells: 1) non-differentiated cells with presence of incorporated labelled thimidine in nuclei presented by DNA non-stable macromolecules, and 2) differentiated or definitive subcuticular cells without aggregates of silver grains. The results showed a high level of DNA replication leading to mitotic activity of the non-differentiated cells and absence of mitotic activity in the definitive cells. There was a morphological similarity between non-differentiated cells and the cells from the medular zone, supposing a relationship in their origin.

Animals↗
PubMed2003

Nitric oxide synthase activity in Fasciola hepatica: a radiometric study.

The activity of neuronal nitric oxide synthase (nNOS) in homogenates of adult Fasciola hepatica was measured by the direct radiometric assay of the production of L-[3H]citrulline. This is the first radiometric study of the activity of nNOS in a fluke. The effect of arginase was tested. In the presence of L-valine, which is an inhibitor of arginase, the formation of L-[3H]citrulline decreased from 12% to 38%, depending on the time of incubation. This means that the arginase activity in the worm is high, and has to be taken into consideration when measuring the activity of nNOS. When co-factors, such as H4B, and NADPH, were omitted the formation of L-[3H]citrulline decreased significantly (29%). The effects of several nNOS inhibitors were tested. N(omega)-nitro-L-arginine (L-NAME), aminoguanidine and S-methyl-L-thiocitrulline added at a concentration of 1 mM inhibited the L-[3H]citrulline formation by 28%, 15% and 14%, respectively. Chelation of Ca2+ with 1 mM EGTA resulted in a 40% decrease in the formation of L-[3H]citrulline. These results indicate the presence of nNOS activity in homogenates of F. hepatica.

Animals↗
PubMed2005

Fasciola hepatica procathepsin L3 protein expressed by a baculovirus recombinant can partly protect rats against fasciolosis.

Fasciola hepatica juveniles express immunodominant cathepsin L proteins, which are mainly found in their immature, procathepsin form. A gene encoding such a procathepsin L (FheCL3) was expressed by a baculovirus recombinant and by Saccharomyces cerevisiae. The glycosylated FheCL3 proteins obtained by both systems were used in a vaccination/challenge experiment in rats. Both antigens evoked similar antibody responses, but only the baculovirus expressed FheCL3 caused a significant protection against the number of liver flukes (52% protection, P=0.01), whereas the S. cerevisiae expressed FheCL3 did not. In a second experiment in rats, deglycosylated versions of both antigens were used, but this did not improve their efficacies.

Amino Acid Sequence↗
PubMed1998

Use of excretory/secretory antigens in a competition test to follow the kinetics of infection by Fasciola hepatica in cattle.

Eight 16-18-month-old Charolais heifers were experimentally infected with Fasciola hepatica. An antigen competition assay was used to follow the kinetics of the infection and was compared to antibody tires and serum liver enzymes. The antigen competition assay was able to detect the presence of infection as soon as 6 days after the start of the experimental infection which is considerably sooner than other methods. Consequently, this assay would be useful in diagnosing fasciolosis early in the prepatent period. The animals were slaughtered at the end of the experiment, the livers recovered and post-mortem fluke burdens determined. However, only serum liver enzyme levels gave any indication of the intensity of infection in the different animals.

Animals↗
PubMed1992

[Fasciola hepatica infestation. Biopathology and new diagnostic and therapeutic aspects].

We present here 6 patients with Fasciola hepatica infection, all from rural origin, and with the risk factors of eating wild watercress. The more common symptoms were: fever (83%), abdominal pain (100%), weight loss (83%) and generalized myalgia and joint pain (67%). All patients presented with an absolute eosinophil count above 1,000 cell/mm3. The diagnosis was established in five cases by means of serologic techniques (haemagglutination) and with direct visualization of adult worms while surgery in one case. A CT abdominal scan was performed in five patients, revealing specific lesions of tissue infiltration in four of them. Praziquantel was used in four patients, achieving clinical cure in three cases. In two patients, bithionol was used, with clinical cure in both cases. We review also some newer diagnostic and therapeutic approaches to this parasitic disease.

Adult↗
PubMed1997

[Diagnostic value of the demonstration of specific antigens of Fasciola hepatica by western blot technique].

A western blot assay was performed for the detection of Fasciola hepatica specific antigens for the diagnostic of fasciolasis; 72 sera were tested, 28 coming from patients with the parasitic disease and 44 from persons either healthy or presenting other diseases; 11 different antigenic bands were detected using sera from patients with fasciolasis. The 57 and 29 kDa specific antigens are considered like major, their specificity is about 100% and their respective sensibility, 79 and 93%. Band of 9-12 kDa is also appeared specific but is revealed only in 47% of the cases; 27 out of the 28 sera from patients with fasciolasis were able to recognize at least one of the 57, 29 or 9-12 kDa specific antigens. The present results suggest that western blot could be useful for the diagnosis of this parasitic disease as far as the criteria of positivity is based on the recognition of at least one of the major specific antigens.

Animals↗
PubMed1997

Effects of colchicine on the number of T2 vesicles in the tegument of Fasciola hepatica.

The role of microtubules in the secretory processes in the tegument of adult trematode Fasciola hepatica L. is studied by estimating the effects of colchicine, a substance known to disrupt microtubules, on the number of T2 vesicles. Tissue slices of the worm are incubated in Hedon-Fleig medium with or without 5 x 10(-4) M colchicine. The dynamics of the colchicine-provoked secretory block is examined by morphometry on samples processed for electron microscopy. T2 vesicles are estimated as a total number or separately within three levels (apical, sub-apical and central) of the distal tegument. The secretory block is demonstrated as reduction in the total number of T2 vesicles. The separate counting within three levels of the distal tegument demonstrates in control samples a trend of sub-apical condensation of T2 vesicles. This pattern of T2 distribution remains unchanged in colchicine-treated samples in spite of the reduction of the mean T2 counts within each of the levels examined. The data illustrate the role of microtubules in both the tegumental transport of secretory vesicles and the stratification of the organelles within the tegument.

Animals↗
PubMed1985

Fasciola hepatica: interaction of the tegument with poly-L-lysine and enzymes.

The tegument of Fasciola hepatica was treated with 0.5% pepsin (EC 3.4.4.1), 0.5% alpha-amylase (EC 3.2.1.1), and 0.5% sheep bile solutions both without and following preincubation in poly-L-lysine. Without poly-L-lysine preincubation, pepsin appeared to be breaking down limited areas of the tegumental surface but had no other marked effects on tegumental structure. alpha-Amylase and bile had no major effects on the tegument except for a reduction in matrix density by the latter. Incubation in poly-L-lysine alone resulted in some changes in surface morphology of the tegument and a limited amount of swelling of the basal infolds. When poly-L-lysine was followed by pepsin treatment, blebbing, microvillus-formation, and swelling of the basal infolds was greatly enhanced and led to surface destruction in some areas. alpha-Amylase following poly-L-lysine resulted in complete destruction and loss of the tegument, and left the basal lamina as the external surface, Incubation in bile after poly-L-lysine preincubation resulted in little change in tegumental morphology.

Animals↗
PubMedDate not supplied

Life-history traits of Fossaria cubensis (Gastropoda: Lymnaeidae) under experimental exposure to Fasciola hepatica (Trematoda: Digenea).

The effect of exposing the lymnaeid snail Fossaria cubensis to the trematode Fasciola hepatica on the snail population's life-history traits was studied under laboratory conditions. Exposed individuals showed a lower survival rate than control snails, although from week 7 onward a slower decrease of this parameter in relation to the control group was observed. There were higher values of fecundity rate for the controls compared to the exposed group except during weeks 9, 10, 11 and 12, which was the time that followed the period when almost all of the infected snails died. Both the intrinsic and finite rates of natural increase were significantly higher for the control group, but exposed snails still attained a lower mean generation time. Age-specific trade-offs were found, mainly for the weekly increase in size versus the number of eggs per mass, the weekly increase in size versus the number of viable eggs per mass, the number of masses versus the hatching probability and the number of eggs versus the hatching probability. All these negative associations were significant for juveniles of both control and exposed snails and not for adults; however, exposed young individuals exhibited much higher values of the correlation coefficient than control animals.

Animals↗
PubMed1990

Ontogenetic development of the brain of the platyhelminth Fasciola hepatica.

During ontogenetic development in the definitive host, the cerebral ganglia of the parasitic flatworm Fasciola hepatica lose their cell rind integrity and develop specialized nerve processes. The organization and cytological features of the central nervous system were examined during three developmental stages in the parasitic life cycle of F. hepatica to determine when the changes occur. The cerebral ganglion cell bodies of migrating juvenile worms (5 days post-infection) are organized into a one-cell-thick rind that surrounds a central neuropile composed of small unmyelinated nerve processes (less than 3 microns in diameter). In young, sexually-immature adult worms (30 days post-infection), the cell bodies of the ganglia are no longer organized into a complete or tight cell rind around the ganglia. In addition, large diameter ('giant') unmyelinated nerve processes (greater than 12 microns) are found in the neuropile area. These giant nerve processes are also found in the transverse commissure and the longitudinal nerve cords. In mature adult worms (4-6 months post-infection), the rind of nerve cell bodies has completely disappeared and cell bodies are scattered around and within the neuropile. More than half of the volume of the mature adult neuropile is composed of giant nerve processes. The three developmental stages of the parasite that were used in this study differ significantly in their sizes, behaviours and microhabitat locations in the host. The results suggest that the organizational and morphological changes in the ganglia reflect selective adaptations to changes in the parasitic microenvironment.

Animals↗
PubMed1988

Glutathione S-transferases in Fasciola hepatica.

Glutathione S-transferases (GST's) are widespread in the tissues of the liver fluke, Fasciola hepatica, and consist of multiple isozymes. Following purification to apparent homogeneity by affinity chromatography on glutathione agarose, fluke GST's were shown to comprise 2 components with molecular weights of about 25,000. Fluke GST's were immunogenic to rats, but when used as a vaccine conferred no protection on the animals against a challenge infection with F. hepatica metacercariae.

Animals↗
PubMed1981

Resistance to Fasciola hepatica in sheep harbouring primary Schistosoma bovis infections.

A substantial level of resistance to a heterologous challenge with Fasciola hepatica was demonstrated in sheep harbouring primary non-patent (two- to three-week-old) and newly patent (seven- to eight-week-old) Schistosoma bovis infections, the liver-fluke burdens being reduced by 70% and 93%, respectively, (p less than 0.01) in these groups compared with that of the challenge control group. The resistance was also reflected in less pronounced F. hepatica-induced liver damage and presumably also in a reduction of the egg-production capacity per established liver-fluke. In contrast, a corresponding heterologous resistance to challenge with F. hepatica could not be demonstrated in sheep harbouring primary 16- to 17-week-old S. bovis infections. Possible, presumably immunological, mechanisms involved in the observed cross-resistance are discussed, as is the possible practical relevance of this cross-resistance phenomenon in attempts to vaccinate sheep against F. hepatica.

Animals↗
PubMed1988

Antigenicity of a proteolytic enzyme of Fasciola hepatica.

The possibility was examined of using a haemoglobinase released during in vitro incubation of adult Fasciola hepatica for immunodiagnosis of fascioliasis. By SDS gel electrophoresis the enzyme appeared as two closely migrating bands with a molecular weight of approximately 27,000 daltons. After Western blotting the bands reacted with serum from rats infected with F. hepatica and mice infected with Schistosoma mansoni. The enzyme was therefore not a good antigen for immunodiagnosis.

Animals↗
PubMed2000

Variability of Fasciola hepatica infection in Lymnaea ovata in relation to snail population and snail age.

Bimiracidial infections of Lymnaea ovata with Fasciola hepatica were performed under laboratory conditions to determine the susceptibility of snails from six French populations to trematode infection. In five populations of L. ovata the prevalence of infection in the 1-mm groups ranged between 2.7% and 43.7% at day 35 postexposure; it decreased in the 2-mm snails and was zero in larger groups. In the snails from Thenay (periodically polluted brook) the prevalence of F. hepatica infection decreased from the 1-mm group to the 8-mm group (from 23.9% to 1.0%) and was zero in the 10-mm L. ovata. The total number of cercariae shed per snail was 18.3 in the 1-mm group, increasing to 117 in the 8-mm group. The latter findings could be interpreted as a consequence of periodic pollution in the brook of Thenay; pollution might disrupt the defense system of L. ovata and facilitate the subsequent larval development of F. hepatica.

Aging↗
PubMed1999

Bovine T cell responses to recombinant thioredoxin of Fasciola hepatica.

Fasciolosis is an economically significant disease of ruminants, caused by infection with the digenetic trematodes, Fasciola hepatica and F. gigantica. Some vaccination trials using irradiated metacercariae or isolated proteins have been shown to afford significant protection. However, the mechanisms of specific immunity against this pathogen have not been elucidated. We have identified thioredoxin, a tegument antigen of F. hepatica, among several proteins that are common to both the juvenile and adult fluke within the mammalian host and have undertaken studies to characterize bovine T cell responses to recombinant thioredoxin protein (FH 2020). Peripheral blood mononuclear cells from immune cattle proliferated specifically to crude F. hepatica antigenic extract but not to FH 2020. However, after repeated stimulation of lymphocytes by alternating crude extract and FH 2020, FH 2020-specific proliferation by T cell lines was observed. T cell clones were subsequently generated and found to respond specifically but weakly to both crude antigen and FH 2020. Thioredoxin appears to be only weakly antigenic for bovine T cells and is, therefore, an unpromising candidate for inducing resistance to F. hepatica.

Animals↗