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PubMed2000

Fasciola hepatica: lithogenic capacity in experimentally infested rats and chemical determination of the main stone components.

A study was done of the possible association between the development of common bile-duct stones and the presence of worms in rats experimentally infected with Fasciola hepatica. A total of 157 rats were individually infected with 20 metacercariae, and another 40 animals served as controls. The rats were dissected at 100, 200, 300, and 400 days postinfection (p.i.). A significant association was observed between the observation of stones and the presence of F. hepatica adults. The global frequency of bile-duct lithiasis in the parasitized rats was 22%, with a significantly lower incidence being observed in the younger group (100 days p.i.). Different analytical techniques were used to determine the main stone components. Energy-dispersive X-ray microanalysis showed calcium to be the main component in all cases (82-94%). Scanning electron microscopy, nuclear magnetic resonance ([1H]- and [13C]-NMR), and mass spectrometry revealed the predominance of palmitic (C-16) and stearic (C-18) acid.

Animals↗
PubMed2000

Prevalence of Haplometra cylindracea infection in three species of Lymnaea snails in central France.

Field investigations were performed over a 2- or 3-year period at five sites in central France to determine the prevalence of Haplometra cylindracea infection in three species of adult Lymnaea, and to compare it with that of Fasciola hepatica infection recorded in the same snails. L. glabra, L. palustris, and L. truncatula harboured Haplometra larval forms but the prevalence of this infection varied according to the site and snail species studied. The prevalences in May ranged over 0-66.9% in L. glabra, 3-7.7% in L. palustris, and 0-31.5% in L. truncatula. The mean intensity of H. cylindracea infection in May did not show any significant variation, whatever the site and species studied. The prevalence of F. hepatica infection was significantly lower in snails collected in sites known for H. cylindracea infection than in those originating from nearby meadows (0-1% instead of 1-5%). H. cylindracea could develop in some Lymnaea species and its occurrence had an impact in snails by decreasing the prevalence of F. hepatica infection.

Animals↗
PubMed1996

Acquired resistance of merino sheep against Fasciola gigantica.

Merino sheep acquired resistance against Fasciola gigantica, which is contrary to previous observations of infections with F. hepatica in that breed. The acquired resistance was manifest against young adult parasites. St. Croix sheep had previously been shown to have more resistance than European sheep against F. hepatica after primary infection; however, in F. gigantica infections in the present study there was no difference between the resistance levels of the breeds. Antigenic analysis of the host:parasite relationships could lead to identification of protective antigens suitable for use as vaccines.

Animals↗
PubMed1997

Fasciola hepatica: in vitro production of daughter rediae and cercariae from first- and second-generation rediae.

Fasciola hepatica mother rediae belonging to the first generation and the first cohort of the second generation were extracted from their snail intermediate host (Lymnaea truncatula) and maintained in vitro for 16 days to determine the quantity of daughter rediae and cercariae produced by each generation. L-15 Leibovitz medium with a saline fraction adjusted to that of the L. truncatula hemolymph was used for experiments. A total of 35 daughter rediae exited from the 21 mother rediae of the first and second generations, which were 14-32 days old at the onset of culture. Microscope examination of the mother rediae demonstrated the presence of numerous redial embryos and differentiating daughter rediae, whereas no cercaria was seen within their body. A total of 49 cercariae exited from the 17 mother rediae of the first and second generations, which were 29-50 days old at the onset of culture. No differentiating daughter redia was seen in these last mother rediae. The productivity of the first or second generation (first cohort) was nearly identical in terms of cercariae.

Animals↗
PubMed1999

Oviposition of Lymnaea truncatula infected by Fasciola hepatica under experimental conditions.

Experimental infections of Lymnaea truncatula by Fasciola hepatica (one, two, or three miracidia per snail) were carried out under laboratory conditions to analyze the oviposition of infected snails and determine the characteristics of their egg masses. In the infected snails from the three groups, egg-laying steadily decreased until week 4 postexposure and stopped afterward until the end of the experiment, except for the cercaria-shedding snails from the one-miracidium group, for which low numbers of egg masses were noted between weeks 9 and 12. In uninfected snails the number of egg masses decreased until week 4 and remained low during subsequent weeks. At weeks 11 and 12 postexposure the natality rate was 98.9% in controls, 56% in the cercaria-shedding snails from the one-miracidium group, and 59.2-68.5% in uninfected snails. In the cercaria-shedding snails from the one-miracidium group the restoration of reproduction activity after week 8 may be explained by a lower parasite burden in these snails than in those from the two- and three-miracidium groups.

Animals↗
PubMed1999

Subclass profile of specific IgG antibodies in rats challenged during acute and chronic primary infection with Fasciola hepatica.

The influence of a previous infection (acute and chronic) on the kinetics of the immune humoral response in rats challenged with Fasciola hepatica was studied. Two infected groups were reinfected at different times--one, at 4 weeks after primary infection (w.a.p.i.); and the other, at 11 w.a.p.i. Signs of reinfection were observed in the two challenged groups as evidenced by an increment in glutamate dehydrogenase and gamma-glutamyl transpeptidase activity after secondary infection. IgG subclass (IgG1, IgG2a, IgG2b, IgG2c) responses to F. hepatica excretory/secretory products (FhESP) differed, depending on the time of challenge infection, but no difference was observed between the reinfected groups. A predominance of the IgG1 subclass was noted in the group challenged at 4 w.a.p.i., and IgG2b and IgG2c were prominent in the group reinfected at 11 w.a.p.i. These results indicate that the presence of juvenile or adult flukes in the liver at the time of challenge seems to influence the immune response to a secondary infection.

Acute Disease↗
PubMed2001

The definitive and intermediate hosts of Fasciola hepatica in the natural watercress beds in central France.

Field investigations were carried out over a two-year period in 52 natural watercress beds located in the Limousin region of central France to list the mammal and bird species that frequented these sites. This enabled detection of the definitive hosts of Fasciola hepatica and determination of the prevalence of natural infection in snails. A total of 13 mammal and five bird species were listed in these watercress beds. Adult flukes were found in Lepus capensis (39.2%), Oryctolagus cuniculus (42.0%), and Sylvilagus floridanus (25.0%). No infection with F. hepatica was noted in the five species of rodents studied. Snails infected with F. hepatica were found in 14 watercress beds. The global prevalence of natural infection was 1.1% in Lymnaea truncatula and 0.3% in L. glabra. Among the other trematode larval forms detected, the most frequent was Haplometra cylindracea (0.5%). In the Limousin region, the presence of hares and rabbits in watercress beds ensured the continuation of the F. hepatica life cycle and permitted the subsequent infection of humans when this wild watercress was eaten.

Animals↗
PubMed2001

Effect of fasciolicides on the antigenaemia in sheep naturally infected with Fasciola hepatica.

A study was developed to evaluate the influence of triclabendazole (Fasinex) and netobimin (Hapasil) the antigenaemia in sheep naturally infected with Fasciola hepatica during 16 weeks. A sandwich-ELISA (enzyme-linked immunosorbent assay) using a rabbit polyclonal IgG antibody to F. hepatica antigens was employed and the data obtained were compared to those from coprological and indirect-ELISA techniques. Triclabendazole reduced the values of circulating antigens at weeks 2-4 post-treatment and faecal output at weeks 2-8 post-treatment, but antibodies showed positive values until the end of the study. Netobimin did not reduce circulating antigens of the trematode nor egg-excretion; and IgG antibodies did not decrease throughout the study.

Animals↗
PubMed2001

Fasciola hepatica: the characteristics of experimental infections in Lymnaea truncatula subjected to miracidia differing in their mammalian origin.

Experimental infections of Lymaea truncatula, using two susceptible snail populations (Berneuil, or Migné, central France) and four isolates of Fasciola hepatica miracidia differing in their mammalian host of origin (cattle, nutrias, rabbits, or sheep), were performed under laboratory conditions to determine whether the host of origin had an effect on the daily production of cercariae. Snails were each subjected to bimiracidial exposures and were then reared under semi-natural conditions (a constant temperature of 20 degrees C and natural photoperiod). Significantly lower values were noted in the rabbit groups for survival rates at day 30 post-exposure, as well as for prevalences of infection, snail growth. duration of shedding period, and the total numbers of cercariae these snails shed. The total number of cercariae shed by both nutria groups was significantly higher than those recorded in the six other infected groups. In the cattle, rabbit, and sheep (Berneuil only) groups, the peaks in the daily distribution of cercariae occurred between day 2 and day 4 after the first shedding, and the number of cercaria-shedding snails decreased with increasing number of shedding waves. In contrast, in the three other groups, the peaks were only observed between days 20 and 45. Snails shedding their cercariae during nine or more waves were numerous in these last groups. No infradian-type rhythm in the daily distribution of cercarial numbers over the shedding period was noted for any snail group. The highest production of F. hepatica cercariae in both nutria groups would be a consequence of a higher success rate of miracidia when they infected an allopatric population of snails. The absence of an infradian-type rhythm in the distribution of daily cercarial numbers in the eight groups suggests that this rhythm, if it occurs, would only be influenced by temperature and thus be limited to periods with optimal conditions for cercarial shedding.

Animals↗
PubMed2000

Precancerous lesions of intrahepatic cholangiocarcinoma.

Intrahepatic cholangiocarcinoma (ICC), also known as cholangiocellular carcinoma or peripheral bile duct carcinoma, is an intrahepatic malignant tumor that consists of cells resembling the biliary epithelium. The proportion of ICC among primary hepatic malignancies is approximately 10% worldwide. Although the etiology and pathogenesis remain unclear in a great majority of cases, preceding pathologic conditions or etiologies in the development of ICC are known or suspected in a proportion of these patients. Some forms of ICC, such as those associated with hepatolithiasis or liver fluke infestation, are endemic in parts of the world, particularly in East Asia. ICC is reportedly a late complication of primary sclerosing cholangitis. Most of these preceding pathologic conditions are forms of chronic cholangitis, and longstanding inflammation, chronic injury, and regenerative hyperplasia of the biliary epithelium may be causally related to malignant transformation. Biliary epithelial dysplasia is encountered in the intrahepatic bile ducts both near and remote from ICC foci in the liver and near and remote from the chronically inflamed biliary tree. This lesion could be a precancerous lesion, and it shows telomerase activity and increased proliferative activities. Furthermore, congenital and developmental disorders of the biliary system, such as Caroli's disease, congenital hepatic fibrosis, and pancreatico-biliary malformation are occasionally associated with ICC. Benign biliary tumors, such as biliary papillomatosis, may eventually undergo malignant transformation. These lesions could be regarded as precancerous or borderline lesions. Some ICCs may also develop in nonbiliary viral cirrhosis. In the majority of cases of ICC, however, the etiology, pathogenesis, and developmental processes and precancerous lesions of the ICC remain unclear.

Bile Duct Neoplasms↗
PubMed2002

Markovian chemicals "in silico" design (MARCH-INSIDE), a promising approach for computer aided molecular design II: experimental and theoretical assessment of a novel method for virtual screening of fasciolicides.

A novel method for in silico selection of fluckicidal drugs is introduced. Two QSARs that permit us to discriminate between fasciolicide and non-fasciolicide drugs (the first) and to outline some conclusions about the possible mechanism of action of a chemical (the second) are performed. The first model correctly classified 93.85% of compounds in the training series and 89.5% of the compounds in the predicting one. This model correctly classified 87.7, 93.8, 92.2 and 93.9% of compounds in leave- n-out cross validation procedures when n takes values from 2 to until 6. The model seems to be stable in around 92% of good classification in leave- n-out cross validation analysis when n>6. The second model correctly classified 70% of non-fasciolicide compounds, 85.71% of beta-tubulin inhibitors and 100% of proton ionophores in the training set. This model recognizes as proton ionophores 100% of any nitrosalicylanilides in the predicting series. Both models have a low p-level <0.05. Finally, the experimental assay of six organic chemicals by an in vivo test permit us to carry out an assessment of the model with a fairly good 100% agreement between experiment and theoretical prediction.

Animals↗
PubMed2005

Control of fasciolosis in stall-fed buffaloes by managing the feeding of rice straw.

Fasciolosis, caused by Fasciola gigantica, presents major disease and production problems, particularly in the rice producing areas of South and South-East Asia. In Nepal, buffaloes are commonly stall-fed and the most usual fodder is rice straw, which is produced in large quantities in the area. Here we describe a relatively simple way of controlling fasciolosis in these animals. We demonstrate that infectious metacercariae of F. gigantica are concentrated in the bottom part of the rice straw and that infection can be controlled by cutting the rice straw in half, and then feeding the parasite free top half of the straw first. The bottom part of the rice straw should ideally be stored for at least 4 months after harvest to allow the parasites to die before it is used as fodder.

Animals↗
PubMed2006

The effect of temperature and humidity on longevity of metacercariae of Fasciola gigantica.

Studies were undertaken on the viability of the metacercariae of Fasciola gigantica when stored in water at 13 degrees C for periods up to 23 weeks, exposed to the sunlight for up to 8 h or stored at a range of temperatures and humidities for up to 10 weeks. Excysted metacercariae were catergorized microscopically as viable (motile and undamaged), dubious (not motile and undamaged) or dead (visible necrosis). The infectivity of viable and dubious metacercariae and unselected reference metacercariae held in water at 7 degrees C for 20 days or longer was assessed by comparing numbers of flukes recovered from infected Merino sheep. Mean recovery rates were 54.6%, 7.2% and 37.2%, respectively, for viable, dubious and unselected metacercariae. Metacercariae immersed in water remained viable longer than those allowed to desiccate. Viability was promoted by decreasing temperature and increasing humidity. Exposure to direct sunlight killed metacercariae within 8 h. Results indicated that in lowland Indonesian irrigated rice paddies, metacercariae immersed in water are likely to survive for less than 5 weeks while those that become desiccated will survive less than 2 weeks. This information, together with the option of exposing fresh rice stalks to direct sunlight before feeding them to livestock, can assist farmers in reducing infection with F gigantica.

Animal Feed↗
PubMed2006

Cross-sectional prevalence of helminth infections in cattle on traditional, small-scale and large-scale dairy farms in Iringa district, Tanzania.

A cross-sectional study was carried out to determine the prevalence of gastrointestinal (GI) nematodes and flukes (Fasciola and amphistomes) infection in communally grazed traditional cattle, zero-grazed small-scale dairy cattle and intensively grazed large-scale dairy cattle through examination of helminth eggs in faeces. Results indicated that the type of management, especially the grazing habit, has a significant influence on the prevalence and intensity of GI nematodes and flukes. The prevalence of GI nematodes in traditional, large-scale dairy and small-scale dairy cattle was 67%, 44.4% and 37%, respectively, with the highest faecal egg counts in calves. The overall prevalence of Fasciola gigantica in traditional, large-scale dairy and small-scale dairy cattle was 63.8%, 46.2% and 28.4%, respectively. The prevalence of amphistomes was 81.9%, 55.5% and 41.1% in traditional, large-scale dairy and small-scale dairy cattle, respectively. The high prevalence of flukes in the traditional system was attributed to communal grazing and watering management practices. Stomach flukes recovered in examined cattle at the abattoir were Calicophoron microbothrium and Cotylophoron jacksoni. About 42.1% of infected animals had both Fasciola and amphistomes. The prevalence of both GI nematodes and flukes varied greatly among villages and farms. The prevalence of both Fasciola and amphistomes was higher in adults (58.5%, 75.2%) than in yearlings (36.5%, 51.5%) or calves (24.9%, 47.2%). The variation in the prevalence of both GI nematodes and flukes among management and age groups within systems can be used as an entry point towards rational use of anthelmintics for each management system. More studies on seasonal transmission pattern of all these parasites are required in order to design rational, economic and locally sustainable parasite control programmes.

Animal Husbandry↗