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PubMed2004

Southernmost finding of Lymnaea viatrix orbigny, 1835 (Pulmonata: Lymnaeidae), intermediate host of Fasciola hepatica (Linnaeus, 1758) (Trematoda: Digenea), in urban and rural areas of Patagonia, Argentina.

We report the first finding of Lymnaea viatrix south of parallel 41 masculine S, in rural and urban areas from Argentina. Ninety snails were collected during year 2000, from a concrete pond at a Public Square in El Bolsón Village, Río Negro province, and 811 snails in November 1999, and during 2000 from waterbodies within a farm at Cholila locality, Chubut province. Fasciola hepatica infection was detected in 0.9% snails from the rural area. We discuss the potential risk of L. viatrix to public health in urban areas and its epidemiological importance in rural areas of the Andean Patagonian region.

Animals↗
PubMed1976

The effect of the molluscicide N-tritylmorpholine on transmission of Fasciola hepatica.

Field trials were carried out in north Devon to investigate the relationship between molluscicide treatment of pastures and control of liver fluke infection in sheep. Seven tracer lambs per plot were used to estimate the infectivity of 17 pairs of 0.20 hectare plots. One plot in each pair was treated with the molluscicide Frescon (N-tritylmorpholine). There was a highly significant difference (P less than 0.001) between the numbers of Fasciola hepatica recovered from lambs grazed on treated and untreated plots in the period after molluscicide treatment. The overall degree of snail control achieved by one application of molluscicide to 17 plots was about 90 per cent and this was matched by a comparable degree of liver fluke control. There was considerable variation between the plots and there was no simple correlation between snail numbers and liver fluke numbers (r = -0.03). The use of molluscicides is discussed in relation to the biotic potential of Lymnaea truncatula and environmental factors which limit its population growth.

Animals↗
PubMed2000

Inventory of wild rodents and lagomorphs as natural hosts of Fasciola hepatica on a farm located in a humid area in Loire Atlantique (France).

With the objective of studying the role of wild fauna in the epidemiology of fasciolosis disease, a definitive wild-host inventory was carried out in a french farm where infected domestic hosts (cows) cohabit with wild potential ones. Liver flukes, faecal eggs and antibodies were looked for in lagomorphs (Oryctolagus cuniculus) and rodents (Myocastor coypus, Ondatra zybethicus, Rattus norvegicus, Arvicola sapidus and micromammal species) trapped in the study area. Presence of Fasciola hepatica was detected in two species: O. cuniculus and M. coypus. Infection rates were respectively 34% (42/124) and 55% (106/193). Liver flukes were found in 78 M. coypus (n = 192) and 11 O. cuniculus (n = 35). No other species was infected by F. hepatica. The number of animals shedding fluke eggs was higher in M. coypus (49 out of 127 sampled; 38.6%) than in O. cuniculus (two out of 17 sampled; 11.7%). The results indicate that M. coypus may play a role in the maintenance and the dissemination of F. hepatica in various environments and open a discussion on the role of other natural wild hosts.

Agriculture↗
PubMed2003

Mucin-type O-glycosylation in Fasciola hepatica: characterisation of carcinoma-associated Tn and sialyl-Tn antigens and evaluation of UDP-GalNAc:polypeptide N-acetylgalactosaminyltransferase activity.

Simple mucin-type cancer-associated O-glycan structures, such as the Tn antigen (GalNAc-O-Ser/Thr), are expressed by certain helminth parasites. These antigens are involved in several types of receptor-ligand interactions, and they are potential targets for immunotherapy. The aim of this work was to study the initiation pathway of mucin-type O-glycosylation in Fasciola hepatica, performing a biochemical and immunohistochemical characterisation of Tn and sialyl-Tn antigens, and evaluating the ppGaNTase activity, which catalyses the first step in O-glycan biosynthesis. Using ELISA, both Tn and sialyl-Tn antigens were detected predominantly in the somatic and deoxycholate extracts. Immunofluorescence analysis revealed that Tn antigen is preferentially expressed in testis, while sialyl-Tn glycoproteins were more widely distributed, being present in parenchymal cells, basal membrane of the tegument, and apical surface of epithelial cells lining the caeca. On the basis of their electrophoretic mobility, Tn glycoproteins were resolved as six components of 10, 37, 76, 125, 170 and 205 kDa, and sialyl-Tn components showed an apparent molecular mass of 28 and 32 kDa, and two broad bands of 90-110 and 170-190 kDa. The observation that only the 76 kDa Tn-glycoprotein remained in the 0.6 N perchloric acid-soluble fraction suggests that it could be a good candidate for mucin characterisation in this parasite. The ppGaNTase activity showed its maximal activity at pH 7-7.5 and 37 degrees C, showing that Mn(2+) was the best divalent cation activator. Using a panel of nine synthetic peptides as acceptor substrates, we found that F. hepatica ppGaNTase was able to glycosylate both threonines and serines, the best substrates being the peptides derived from the tandem repeat region of human mucins (MUC2 and MUC6), and from Trypanosoma cruzi and Trypanosoma brucei glycoproteins. The results reported here constitute the first evidence on O-glycosylation pathways in F. hepatica, and may help to identify new biological characteristics of this parasite as well as of the host-parasite relationship.

Animals↗
PubMed1988

Neurocytology of the cerebral ganglion of Fasciola hepatica (Platyhelminthes).

An ultrastructural study of the organization and fine structure of the nervous system of the parasitic flatworm Fasciola hepatica was undertaken. The brain consists of paired cerebral ganglia, located just posterior to the oral sucker, that are connected by a transverse commissure which crosses over the dorsal surface of the pharynx. The cell bodies of the cerebral ganglia are not organized into a clearly defined rind around the neuropile but are loosely scattered around and within the neuropile area. The neuropile consists of two morphologically distinct types of unmyelinated nerve processes. The small nerve processes, with smooth cell membranes, are less than 2 micron in diameter, whereas the "giant" processes are greater than 12 micron in diameter and have extensively invaginated cell membranes. Giant processes make up the bulk of the nerve fibers in the transverse commissure and longitudinal nerve cords. Four morphological types of vesicles are present in the small processes; small clear vesicles (which were found associated with synapses), spheroidal and ellipsoidal dense vesicles, and dense-core vesicles. Two types of synapses are found in the neuropile: simple synapses characterized by pre- and postsynaptic membrane densities, clusters of small clear vesicles, and a clear synaptic cleft; and wedge-shaped synapses or divergent diads each having one presynaptic process synapsing onto two postsynaptic processes. Synaptic contacts were observed only between small processes; no synapses were observed on the cell bodies or on giant processes.

Animals↗
PubMed1993

Type I hypersensitivity reactions in intestinal mucosae from rats infected with Fasciola hepatica.

Type I hypersensitivity reactions in the intestinal tract of sensitized animals may contribute to resistance to reinfection with Fasciola hepatica. Colonic mucosae isolated from previously infected rats were voltage clamped in Ussing chambers. Antigen was prepared as a crude homogenate from adult liver fluke. Assay of serum antibodies against fluke antigen confirmed sensitization. Antigen challenge evoked a rapid onset, transient inward current in sensitized but not in control preparations. Chloride secretion accounted for at least part of the response since the loop diuretic bumetanide reduced the effect of antigen by 61%. Anti-rat IgE mimicked the response to antigen and desensitized tissues to subsequent antigen challenge. Local synthesis of eicosanoids may mediate the response to antigen since the cyclo-oxygenase inhibitor piroxicam reduced the response by 76%. In contrast, mepyramine which is a histamine receptor antagonist did not alter the ion transport response evoked by antigen. Tetrodotoxin reduced the response to antigen by 53% implicating intrinsic neurons within the lamina propria as effector cells in the responses of this tissue to antigen. We propose that antigen stimulation of electrogenic chloride movement and consequent fluid secretion in vivo may contribute to a local effector mechanism in prevention of reinfection of previously sensitized hosts.

Acetylcholine↗
PubMed1996

Rhodoquinone is synthesized de novo by Fasciola hepatica.

Most adult parasitic helminths have an anaerobic energy metabolism in which fumarate is reduced to succinate by fumarate reductase. Rhodoquinone (RQ) is an essential component of the electron transport associated with this fumarate reduction, whereas ubiquinone (UQ) is used in the aerobic energy metabolism of parasites. Not known yet, however, is the RQ and UQ composition during the entire life cycle nor the origin of RQ in parasitic helminths. This report demonstrates the essential function of RQ in anaerobic energy metabolism during the entire life cycle of Fasciola hepatica, as the amount of RQ present reflected the importance of fumarate reduction in various stages. We also studied the origin of RQ, as earlier studies on the protozoan Euglena gracilis suggested that RQ is synthesized from UQ. Therefore, in parasitic helminths RQ might be synthesized by modification of UQ obtained from the host. However, we demonstrated that in F. hepatica adults RQ was not produced by modification of UQ obtained from the host but that RQ was synthesized de novo, as (i) the chain-length of the quinones of F. hepatica adults was not related to the chain length of the quinone of the host, (ii) despite many attempts we could never detect any in vitro conversion of UQ9 into RQ9 or into UQ10, neither by intact adult flukes nor by homogenates of F. hepatica adults and (iii) F. hepatica adults used mevalonate as precursor for the synthesis of RQ. We also showed that the rate of quinone synthesis in F. hepatica adults was comparable to that in the free-living nematode Caenorhabditis elegans. These results prompted the suggestion that RQ is synthesized via a pathway nearly identical to that of UQ biosynthesis: possibly only the last reaction differs.

Animals↗
PubMed2001

Pharmacokinetics and microsomal oxidation of praziquantel and its effects on the P450 system in three-month-old lambs infested by Fasciola hepatica.

Praziquantel (PZQ) is a broadly effective trematocide and cestocide, widely employed in veterinary and human medicine. In view of several differences in both its pharmacokinetic profile in different animal species and in the cytochrome P450-dependent system between ruminant and nonruminant species, the present study was undertaken to determine the pharmacokinetics of this drug, its effects on the P450 system and the involvement of cytochrome P450 in its metabolism in 3-month-old lambs infested by Fasciola hepatica. Following both oral and i.m. administration, PZQ disposition was best described by a linear one-compartment open model with a rapid absorption and elimination. Although the PZQ dose used by the i.m. route was only half of that used by the oral route, the mean PZQ plasma concentration was higher after i.m. than after oral treatment. Oral treatment with 30 mg/kg/day of PZQ did not modify the mono-oxygenase activities tested, whilst the administration of PZQ at a dose of 60 mg/kg/day for 2 days caused a significant decrease in the P450 3A-dependent erythromycin N-demethylase and 6beta testosterone hydroxylase activities. From the incubation of microsomes from lambs not treated with PZQ, a single metabolite (PZQ 11b-OH or PZQ 1-OH) was identified by GC/MS analysis. By selective inhibition of the 3A subfamily performed with triacetyloleandromycin, the production of this metabolite declined by about 90% suggesting a prominent role of P450 3A isoforms in this oxidation. These features indicate that agents or drugs which are able to modulate P450 3A-dependent catalysis may interfere with the metabolism, bioavailability and therapeutic effects of PZQ.

Administration, Oral↗
PubMed1992

Host influence on the banding profiles of whole-body protein and excretory-secretory product of Fasciola hepatica (Trematoda) by isoelectric focusing.

Various protein separation techniques have been used as alternative means of differentiating species and strains of parasites. Of these techniques, isoelectric focusing (IEF) has proved to be specific and reproducible with cestodes, protozoa and trematodes. As with the traditional morphological approach, there is, however, the potential for host influence. For a particular separation technique to be useful, it is important that banding profiles differentiating parasites be consistent, regardless of host species. To test for host influence, Fasciola hepatica were maintained in four definitive hosts. Soluble proteins of flukes from different hosts and their respective excretory-secretory product (ESP) were then subjected to IEF together with respective host tissues, and the resulting banding patterns were compared. Protein banding profiles of fluke body protein from llama, rat and mouse were very similar, while those of flukes from calves were distinct. Banding patterns of fluke ESP from different hosts were dissimilar. Overall banding patterns of body protein and ESP of flukes from different hosts were distinct from those of respective host tissues. The unique banding patterns of the body protein of flukes from calves indicate that there was host influence in their protein banding patterns, and the uniqueness of the calf fluke is discussed relative to host's resistance to the fluke.

Animals↗
PubMed1969

The mode of action of carbon tetrachloride on Fasciola hepatica.

1. A biliary fistula was prepared in twelve sheep.2. Each animal was given 2 ml. of (14)C-carbon tetrachloride (specific activity 15 mc/m-mole) and bile collected at 2, 4, 24 and 48 hr.3. Specific activity was measured by liquid scintillation counting before and after each specimen had been heated to 75 degrees C for 10 min to drive off volatile content (carbon tetrachloride).4. Only traces of activity were present in the bile and heating did not alter this.5. There was no difference in the survival times of adult Fasciola hepatica incubated in Hedon Flieg medium with and without 25% bile from non-medicated sheep, or with carbon tetrachloride in a concentration of 0.03%, but 25% of bile from sheep given 2 ml. of carbon tetrachloride 24 hr before greatly increased lethality in vitro.6. The anthelmintic action of carbon tetrachloride on F. hepatica does not result from a direct action due to excretion in bile of unchanged carbon tetrachloride but of an unidentified toxic element not necessarily derived from the drug but which arises as a result of its administration.

Animals↗
PubMed1990

Efficacy of thiophanate and albendazole against natural infections of Dicrocoelium dentriticum, Fasciola hepatica, and gastrointestinal nematodes and cestodes in sheep.

The anthelmintic efficacy of thiophanate and albendazole was compared in sheep with heavy infestations of Dicrocoelium dentriticum. The effectiveness of each drug was determined by counting the numbers of D. dentriticum in animals killed 21 days after treatment. In one group, the dose of thiophanate recommended for use against gastrointestinal (GI) nematodes (50 mg kg-1 live weight) was found to be 74.4% effective against D. dentriticum. Two tablets (each containing 76 mg of active ingredient) of albendazole per 30 kg live weight were given to a second group and the dose repeated after 1 week. Under this regime, albendazole was found to be 12.7% effective against D. dentriticum. The effect of each drug on other parasites was as follows; thiophanate had no effect against Fasciola hepatica or cestodes, while albendazole was 71.5% effective against F. hepatica and 100% effective against cestodes. Both drugs were highly effective against GI nematodes.

Albendazole↗
PubMed1990

Efficacy of concomitant early summer treatment with fenbendazole and clorsulon against Fasciola hepatica and gastrointestinal nematodes in calves in Louisiana.

The efficacy, safety, and compatibility of fenbendazole (FBZ) and clorsulon (CLN) were tested after oral administration of label recommended and of higher (5x) dosage rates to calves naturally infected with gastrointestinal nematodes and Fasciola hepatica. Results for 42 calves allotted to 4 treatment groups indicated a similar efficacy against mature F hepatica by FBZ (5 mg/kg of body weight) and CLN (7 mg/kg) in a combined oral suspension, compared with CLN (7 mg/kg) alone (100 vs 99% reduction). A lesser efficacy was observed against immature flukes (88.6 and 84.9% reduction, respectively). Calves given 25 mg of FBZ/kg and 35 mg of CLN/kg had nearly complete reduction of both mature (99.6%) and immature flukes (99.1%). Fasciola egg counts were reduced by greater than 99.5% in all treated groups. Against Ostertagia ostertagi, the percentage of efficacy of the combined FBZ (5 mg/kg) and CLN (7 mg/kg) treatment was 94.3% against adults and 81.3% against inhibited larvae. Efficacy against all other nematodes was 100%, except against Cooperia spp adults (98.3%) and immature Oesaphagostomum radiatum (88.0%). At 5 x dosage rates for FBZ and CLN, percentage of removal of adults and inhibited larvae of O ostertagi was 99.3 and 99.0%, respectively, and 99 to 100% for other nematodes. Results indicate that FBZ and CLN are compatible when mixed together and administered as an oral suspension to cattle and that the efficacy is similar to that of the drugs individually. On the basis of further results, we suggest that summer treatment may be superior in preventive value for gastrointestinal nematodes and F hepatica, compared with spring treatment, because of seasonal infection dynamics of the major cattle parasites in Louisiana.

Animals↗
PubMed1999

Fasciola hepatica suppresses a protective Th1 response against Bordetella pertussis.

Fasciolosis, like other helminth infections, is associated with the induction of T-cell responses polarized to the Th2 subtype. Respiratory infection with Bordetella pertussis or immunization with a pertussis whole-cell vaccine (Pw) induces a potent Th1 response, which confers a high level of protection against bacterial challenge. We have used these two pathogens to examine bystander cross-regulation of Th1 and Th2 cells in vivo and provide evidence of immunomodulation of host T-cell responses to B. pertussis by a concomitant infection with Fasciola hepatica. Mice with a coinfection of F. hepatica and B. pertussis exhibited a Th2 cytokine profile in response to F. hepatica antigens, similar to those infected with F. hepatica alone. By contrast, the Th1 response to B. pertussis antigens was markedly suppressed and the bacterial infection was exacerbated following infection with F. hepatica. Furthermore, an established Th1 response induced in mice by infection with B. pertussis or by parenteral immunization with Pw was also suppressed following infection with F. hepatica. This immunomodulatory effect of B. pertussis-induced responses by F. hepatica infection is significantly reduced, but not completely abrogated, in IL-4 knockout mice. Our findings demonstrate that Th2-inducing parasites can exert bystander suppression of protective Th1 responses to infection or vaccination with a bacterial pathogen and that the modulation is mediated in part by IL-4 and, significantly, is effective at both the induction and effector stages of the Th1 response.

Animals↗
PubMed1996

Distribution of potential intermediate hosts for Fasciola hepatica and Fascioloides magna in Montana, USA.

A collection of lymnaeid snails in Montana was made over a 3 year period, in conjunction with a state-wide survey of the distribution of liver flukes in Montana. Collection areas were selected based on reports of infected cattle, sheep or wildlife, and with the intent of covering all geographic regions of the state. Snails were found at all 97 of the locations chosen for collections, with lymnaeids collected at 71 of the locations. The 97 sites were located in 28 of Montana's 56 counties. Nine lymnaeid species were collected, five of which have been reported either as natural or experimental intermediate hosts for Fasciola hepatica or Fascioloides magna. The two snail species most widely distributed over the areas enzootic for the flukes were Lymnaea modicella and Lymanaea caperata.

Animals↗
PubMed1975

Oxidative enzymes in the development of Fasciola hepatica L. V. Activity of oxidases and dehydrogenases in the Cercaria and Metacercaria.

The object of the study was the investigation of the occurrence and localization of oxidative enzymes in the 4th and 5th larval stages of the liver fluke, i. e. in the cercaria and metacercaria. The following enzymes were detected: cytochrome oxidase, peroxidase, NADH and NADPH tetrazolium reductases/diaphorases) as well as succinate, isocitrate, malate, lactate, alpha-glycerophosphate, glyceraldehyde phosphate, glucose-6-phosphate, 6-phosphogluconate, beta-hydroxybutyrate, L-glutamate and alcohol dehydrogenases. The occurrence and localization of the enzymes were investigated histochemically in the cercaria still unreleased from the snail tissues, in the free natatorial cercaria, and in the encysted specimen, i.e. metacercaria. Among the enzymes studied only peroxidase was found to be absent from the cercaria and metacercaria, the latter larva being deprived of alcohol and L-glutamate dehydrogenases as well. The aerobic path, i.e. the Krebs cycle, was ascertained as the principal mode of obtaining energy in the free natatorial cercaria and metacercaria, and glycolysis as the main energy path for the undetached larva. The analysis of the above-mentioned oxidative enzymes was the basis for the description, within the available range, of the function and metabolism of individual organs of cercaria in different periods of its development. In the recapitulation the author discusses the effect of the parasitic way of life of the larval forms of Fasciola hepatica on their energy metabolism.

Alcohol Oxidoreductases↗