Fasciola Hepatica Infection In Sheep Research Articles

Immunol detection of cathepsin L from Fasciola hepatica infection in sheep by monoclonal antibody-based colloidal gold test strip assay.

Immunol detection of cathepsin L from Fasciola hepatica infection in sheep by monoclonal antibody-based colloidal gold test strip assay.

A promising new target to control fasciolosis: Fasciola hepatica leucine aminopeptidase 2

Parasite M17 leucine aminopeptidases (LAPs) have been associated with critical roles in different key functions such as the nutrition, migration, and invasion of the natural host. Native or recombinant LAP used as a vaccine antigen has proved effective to elicit protection against Fasciola hepatica infection in sheep, pointing to potential vaccine candidates against fascioliasis in ruminant species. Previously, the FhLAP1, abundantly secreted in vitro by the mature adult parasite was used as a vaccine antigen obtaining promising protection results against F. hepatica challenge in small ruminants. Here, we report the biochemical characterization of a second recombinant LAP (FhLAP2) associated with the juvenile stage of F. hepatica. FhLAP2 showed aminopeptidase activity using different synthetic substrates, including leucine, arginine, and methionine and was increased in the presence of Mn+ 2 and Mg+ 2. The activity was inhibited by bestatin, 1,10-phenanthroline, and EDTA, specific inhibitors of aminopeptidase and/or metalloproteases. Finally, the recombinant FhLAP2 functional form was tested in combination with Freund’s incomplete adjuvant in an immunization trial in mice followed by an experimental challenge with F. hepatica metacercariae. The immunization with FhLAP2/FIA resulted in a significant reduction of parasite recovery compared to control groups. The immunized group elicited total specific IgG and subclasses IgG1 and IgG2 antibody responses. This study highlights the potential of a new candidate vaccine formulation with potential applications in natural ruminant hosts, especially those targeting the juvenile stage.

Coproscopical diagnosis of patent Fasciola hepatica infections in sheep – A comparison between standard sedimentation, FLUKEFINDER® and a combination of both

The liver fluke Fasciola hepatica is a highly pathogenic and zoonotic trematode with a cosmopolitan distribution. In livestock, infections may lead to significant economic losses if not diagnosed promptly and treated effectively. Particularly for small ruminants, the standard method for the detection of fluke infection is based on coproscopical methods such as the sedimentation method, which detects F. hepatica eggs in faecal samples. In this respect a recent innovative coproscopical approach to diagnose patent infections is the FLUKEFINDER® method, which relies on differential sieving before sedimentation. These two methods and a combination of both methods that allows larger amounts of faeces to be processed with the FLUKEFINDER® apparatus were compared, to assess which method is most appropriate to determine the prevalence and intensity of F. hepatica egg shedding. The methods were compared for their ability to recover eggs from ovine faecal samples containing different numbers of fluke eggs per gram (EPG) of faeces and diluting the samples further by mixing with faeces from uninfected sheep. To compare the specificity of the test procedures, positive and negative samples with a low EPG were analysed in parallel by an investigator blinded to the nature of the samples. Significant differences concerning the EPG outcome were found: The FLUKEFINDER® method demonstrated the highest EPG values (p < 0.001) in the undiluted samples as well as in all mixing levels, followed by the modified FLUKEFINDER® method. The standard sedimentation showed the lowest EPG values and the highest variability between technical replicates. The precision of the FLUKEFINDER® method and the modified FLUKEFINDER® method were significantly higher than the precision of the standard sedimentation as determined by comparison of variability between technical replicates. The highest raw egg counts were detected using the modified FLUKEFINDER® method. The FLUKEFINDER® method and the combined method showed a sensitivity of 100 % even at the lowest egg concentrations, whereas the sensitivity of the standard sedimentation was 98.1 % for the same set of samples (i.e. one false negative sample). In a separate investigation aiming to estimate the specificity no differences were found between the three methods: all protocols showed 100 % specificity and were able to correctly distinguish between truly positive and truly negative samples without any evidence of cross-contamination between positive and negative samples processed in parallel.

Field evaluation of the enhanced MM3-COPRO ELISA test for the diagnosis of Fasciola hepatica infection in sheep.

Fasciolosis is a severe zoonosis responsible for major economic losses in livestock. The enhanced MM3-COPRO test (eMM3-COPRO) and the commercial version BIO K 201 (Bio-X Diagnostics, Rochefort, Belgium) are widely used as immunodiagnostic tools for the specific detection of coproantigens released by Fasciola during the late prepatent and patent stages of infection. However, performance of the eMM3-COPRO has never been evaluated under field conditions. To address this gap, a large number of ovine faecal samples, collected in a region where fasciolosis is endemic (Galicia, NW Spain), were analyzed. Two groups of sheep flocks were selected according to the Fasciola infection status: ‘Fasciola-free’ and ‘Fasciola-infected’ flocks. ‘Fasciola-free’ flocks were seronegative flocks with no history of fasciolosis detected by either coproscopy or necropsy in the last 5 years. Faecal samples from these sheep were used to calculate a cut-off value for infection (OD = 0.021). The cut-off was calculated using a bootstrap resampling method that enables estimation of the sampling distribution of the statistical parameters without making assumptions about the underlying data distribution. ‘Fasciola-infected’ flocks were characterized by high seroprevalence, a history of fasciolosis and periodical treatment with flukicides. Samples from these flocks were used to estimate the diagnostic accuracy of the eMM3-COPRO relative to coproscopy, which although limited by poor sensitivity is the only reference test available for diagnosing fasciolosis in vivo. To overcome this limitation, all animals classified positive by eMM3-COPRO were treated with triclabendazole and then retested. The eMM3-COPRO displayed higher sensitivity than coproscopy, as it detected coproantigens in all samples with positive coproscopy and in 12% of samples with negative coproscopy. The test also proved highly specific as coproantigens disappeared after the treatment. The eMM3-COPRO was less time consuming than coproscopy, particularly when the procedure involved numerous samples, and showed promise as a tool for monitoring flukicide efficacy.

Efficacy of a multivalent vaccine against Fasciola hepatica infection in sheep

In this work we report the protection found in a vaccination trial performed in sheep with two different vaccines composed each one by a cocktail of antigens (rCL1, rPrx, rHDM and rLAP) formulated in two different adjuvants (Montanide ISA 61 VG (G1) and Alhydrogel®(G2)). The parameters of protection tested were fluke burden, faecal egg count and evaluation of hepatic lesions. In vaccinated group 1 we found a significant decrease in fluke burden in comparison to both unimmunised and infected control group (37.2%; p = 0.002) and to vaccinated group 2 (Alhydrogel®) (27.08%; p = 0.016). The lower fluke burden found in G1 was accompanied by a decrease in egg output of 28.71% in comparison with the infected control group. Additionally, gross hepatic lesions found in vaccine 1 group showed a significant decrease (p = 0.03) in comparison with unimmunised-infected group. The serological study showed the highest level for both IgG1 and IgG2 in animals from group 1. All these data support the hypothesis of protection found in vaccine 1 group.

Comparative assessment of faecal diagnostics for detection and predictive modelling of endemic Fasciola hepatica infection in sheep and cattle on Australian farms

The diagnosis, monitoring and flukicide efficacy testing of fasciolosis on-farm is reliant on non-terminal methods. The coproantigen ELISA (cELISA) has been recommended for diagnosis of fasciolosis and associated flukicide efficacy testing as an alternative to fluke egg counts for monitoring parasitism. Recently experimental multi-age infections have suggested that the reliability of efficacy results can be improved by a second cELISA testing at 6 weeks post-treatment (wpt) in addition to the generally accepted 1 wpt. A field study was conducted to determine the suitability of faecal fluke egg counts (FFEC) and cELISA as diagnostic, drug efficacy testing and epidemiological tools on Australian sheep and cattle farms. Faecal samples from sheep and/or cattle on three endemic farms were taken at monthly intervals for 12 months and examined by both methods. Normal farm management was maintained during the study period and opportunistic efficacy testing, in line with each farm’s normal flukicide management was undertaken. Additionally, the suitability of the Ollerenshaw Index as a predictive model for fasciolosis under Australian conditions was examined. While both diagnostics demonstrated their value in the farm environment, the current data demonstrate a distinct and significant increase in diagnostic sensitivity for epidemiological studies by using the two tests in parallel. The agreement between the two diagnostics was found to be higher in cattle, despite the poor sensitivity of FFEC in this species. Similar levels of agreement between the two tests were demonstrated at both sheep properties, regardless of the marked difference in the intensity of F. hepatica challenge. Linear regression models demonstrated the results of the two diagnostics utilized in parallel were explained substantially (R2 = 0.91) as were series data (R2 = 0.88) when the respective models were fitted. In contrast, the fitted models for FFEC (R2 = 0.54) and cELISA (R2 = 0.58) were poor explanations for test outcomes. The outcomes of these models support previous findings that suggest that the two diagnostic tests are best utilized together, particularly in parallel. The application of the Ollerenshaw Index to Australian conditions requires further investigation.

Application of a coproantigen ELISA as an indicator of efficacy against multiple life stages of Fasciola hepatica infections in sheep

At present diagnosis of true resistance and determination of drug efficacy in Fasciola hepatica infection rely solely on terminal experiments. The coproantigen ELISA (cELISA) has been reported previously as a sensitive and specific tool appropriate to detect treatment failure, and potentially drug resistance. Two studies were conducted to determine whether the cELISA was appropriate for on-farm efficacy and resistance testing in Australian Merino sheep. In Study 1 sheep were infected orally with 50 F. hepatica metacercariae on three occasions, twelve, six and two weeks prior to a single flukicide treatment with triclabendazole, closantel or albendazole. Sheep were sampled weekly for a further seven weeks prior to necropsy. Following effective treatment, no faecal antigen was detected from 1 week. When immature stages (≤6 weeks) survived treatment, coproantigen reappeared from 6 weeks post-treatment. Therefore, cELISA conducted 1–4 weeks after treatment will demonstrate obvious treatment failure against adult F. hepatica, but is not sufficiently sensitive to detect survival of immature fluke until these reach maturity. In study 2, fluke burdens of sheep necropsied 13 weeks post single infection were compared to fecal worm egg counts (FWEC) and cELISA at necropsy. Regression analysis demonstrated that cELISA correlated strongly with fluke burden, whilst FWEC correlated weakly with cELISA. The correlation between FWEC and fluke burden was also weak, although stronger than that of FWEC with cELISA. The cELISA is an appropriate tool for monitoring effectiveness of treatments against Fasciola hepatica if an adult infection is present, however when immature stages of the parasite are present it is not as reliable. Where immature parasites are present it is recommended that initial cELISA be followed with a secondary cELISA at least 6 weeks after treatment to ensure resistance to immature stages is detected. Further testing is justified for monitoring the effectiveness of control programs by detecting adult populations that have survived a treatment regime.

Network Analysis of the Systemic Response to Fasciola hepatica Infection in Sheep Reveals Changes in Fibrosis, Apoptosis, Toll-Like Receptors 3/4, and B Cell Function.

The Trematode Fasciola hepatica is an important cause of disease in livestock and in man. Modulation of immunity is a critical strategy used by this parasite to facilitate its long-term survival in the host. Understanding the underlying mechanisms at a system level is important for the development of novel control strategies, such as vaccination, as well as for increasing general understanding of helminth-mediated immunoregulation and its consequences. Our previous RNA sequencing work identified a large number of differentially expressed genes (DEG) from ovine peripheral blood mononuclear cells (PBMCs) at acute and chronic stages of F. hepatica infection, and yielded important information on host–parasite interaction, with particular reference to the immune response. To extend our understanding of the immunoregulatory effects of this parasite, we employed InnateDB to further analyze the DEG dataset and identified 2,458 and 224 molecular interactions in the context of innate immunity from the acute and chronic stages of infection, respectively. Notably, 458 interactions at the acute stage of infection were manually curated from studies involving PBMC-related cell-types, which guaranteed confident hypothesis generation. NetworkAnalyst was subsequently used to construct and visualize molecular networks. Two complementary strategies (function-first and connection-first) were conducted to interpret the networks. The function-first approach highlighted subnetworks implicated in regulation of Toll-like receptor 3/4 signaling in both acute and chronic infections. The connection-first approach highlighted regulation of intrinsic apoptosis and B-cell receptor-signaling during acute and chronic infections, respectively. To the best of our knowledge, this study is the first system level analysis of the regulation of host innate immunity during F. hepatica infection. It provides insights into the profound changes induced by F. hepatica infection that not only favors parasite survival into chronic infection but also impedes the host’s immune response to other pathogens, and render vaccination against fasciolosis a difficult challenge. The information provided will be useful in the design of specific vaccine protocols to overcome parasite-mediated immunoregulation and in furthering general understanding of the interplay between helminth infection and host immune systems.

Apoptosis of peritoneal leucocytes during early stages of Fasciola hepatica infections in sheep

Several immunomodulatory properties have been described in Fasciola hepatica infections. Apoptosis has been shown to be an effective mechanism to avoid the immune response in helminth infections. The aim of the present work was to study apoptosis in peritoneal leucocytes of sheep experimentally infected with F. hepatica during the early stages of infection. Five groups (n=5) of sheep were used. Groups 2–5 were orally infected with 200 metacercariae (mc) and sacrificed at 1, 3, 9 and 18days post-infection (dpi), respectively. Group 1 was used as the uninfected control (UC). Apoptosis was detected using three different methods 1) immunocytochemistry (ICC) with a polyclonal antibody anti-active caspase-3; 2) an annexin V flow cytometry assay using the Annexin V-FITC/propidium iodide (PI); and 3) transmission electron microscopy (TEM). The differential leucocyte count revealed that the majority of peritoneal granulocytes were eosinophils, which increased significantly at 9 and 18 dpi with respect to the uninfected controls. The ICC study revealed that the percentage of caspase-3+ apoptotic peritoneal leucocytes increased significantly from 3 dpi onwards with respect to the uninfected controls. The flow cytometry annexin V assay detected a very significant (P<0.001) increase of apoptotic peritoneal macrophages, lymphocytes and granulocytes, which remained higher than in the UC until 18 dpi. Transmission electron microscopy studies also confirmed the presence of apoptosis in peritoneal eosinophils at 18 dpi. This is the first report of apoptosis induced by F. hepatica in the peritoneal leucocytes of sheep in vivo. The results of this work suggest the importance of apoptosis induction for the survival of the juvenile parasites in the peritoneal migratory stages of infection.

Serologic detection of antibodies against Fasciola hepatica in sheep in the middle Black Sea region of Turkey.

The aim of the present study was to estimate the prevalence of Fasciola hepatica infection in sheep in the Black Sea region of Turkey. Samples from 213 sheep were collected randomly in Samsun, Tokat, and Sinop from September 2005 to January 2007 and tested by indirect enzyme-linked immunosorbent assay (ELISA) and Western blot analysis using F. hepatica excretory-secretory (E/S) antigens. The distribution of ELISA-positive samples for F. hepatica infections out of a total of 213 sheep serum samples was 23/71 (32.4%), 15/59 (25.4%), and 29/83 (34.9%) in Samsun, Sinop, and Tokat, respectively. The immunodominant proteins were determined by Western blot analysis using molecular weight markers of 14kDa, 20kDa, 24kDa, 27kDa, 33kDa, 45kDa, and 66kDa and extracted from sera of sheep that were positive for Fasciola spp. eggs and also hyperimmune sera from rabbits immunized with E/S antigens. The ELISA-positive results were confirmed by Western blot analysis. As a result, seroprevalence of F. hepatica infection was found in 31.4% of sheep from the Karayaka breed in the Middle Black sea region of Turkey.

The recombinant gut-associated M17 leucine aminopeptidase in combination with different adjuvants confers a high level of protection against Fasciola hepatica infection in sheep

Fasciola hepatica M17 leucine aminopeptidase (FhLAP) is thought to play a role in catabolizing peptides generated by the concerted activity of gut-associated endopeptidases on host polypeptides, thus releasing amino acids to be used in protein anabolism. In this study, a recombinant functional form of this homo hexameric metallopeptidase produced in Escherichia coli was used in combination with adjuvants of different types in a vaccination trial in Corriedale sheep against experimental challenge with F. hepatica metacercariae. The experimental assay consisted of 6 groups of 10 animals; 5 of the groups (1-5) were subcutaneously inoculated at weeks 0 and 4 with 100 μg of rFhLAP mixed with Freund's complete plus incomplete adjuvant (group 1), Alum (group 2), Adyuvac 50 (group 3), DEAE-D (group 4) and Ribi (group 5); the adjuvant control group (group 6) received Freund's adjuvant. Two weeks after the booster, the sheep were orally challenged with 200 metacercariae. Immunization with rFhLAP induced significant reduction in fluke burdens in all vaccinated groups: 83.8% in the Freund's group, 86.7% in the Alum group, 74.4% in the Adyuvac 50 group, 49.8% in the Ribi group and 49.5% in the DEAE-D group compared to the adjuvant control group. Morphometric analysis of recovered liver flukes showed no significant size modifications in the different vaccination groups. All vaccine preparations elicited specific IgG, IgG1 and IgG2 responses. This study shows that a liver fluke vaccine based on rFhLAP combined with different adjuvants significantly reduced worm burden in a ruminant species that was high in animals that received the enzyme along with the commercially approved adjuvants Alum and Adyuvac 50.

The effect of Quil A adjuvant on the course of experimental Fasciola hepatica infection in sheep

Fasciola hepatica infection causes significant clinical disease in ruminants. Current control methods, based on flukicidal drugs, are becoming less useful because of resistance in fluke populations. Vaccination would be a viable alternative, but as yet no vaccine to protect ruminants against liver fluke infection has been commercialised. Adjuvants can be used to enhance and promote protective immune responses by vaccines. In previous vaccination trials, we have observed a distinct adjuvant effect, or a degree of protection, in animals administered adjuvant alone in the absence of any specific F. hepatica antigen. Understanding this effect will be important for continuing efforts to develop vaccines effective against fasciolosis. This study investigated the effects of three adjuvants (Quil A, Freund's Incomplete and TiterMax Gold) on the course of experimental F. hepatica infection in 6-month-old sheep ( n = 33). At completion of the trial, all animals were necropsied to determine fluke burden and fluke weight. Quil A administration led to a significant reduction in faecal egg count ( P < 0.0001) and significantly higher parasite-specific serum antibody activity for all isotypes measured ( P < 0.01). This suggests that Quil A, which promotes a Th1 response, may be useful as an adjuvant in anti- Fasciola vaccines. Furthermore, it reinforces the results of our previous studies indicating that enhanced Th1 responsiveness to vaccine antigens is required to achieve protection against challenge by F. hepatica.

Efficacy and safety of artemether against a natural Fasciola hepatica infection in sheep

Triclabendazole is the current drug of choice against Fasciola spp. infections in livestock, but resistance has become a major problem. In this study, we assessed the efficacy and safety of artemether, a derivative of artemisinin, in sheep with a low natural Fasciola hepatica infection. Artemether was administered orally or intramuscularly; sheep were monitored for 8 h posttreatment and then once daily for adverse events, and drug efficacy was estimated by fecal egg count reductions and worm burden reductions. Single 40- and 80-mg/kg oral doses of artemether showed no effect on F. hepatica egg and worm burden. Treatment with a single 160-mg/kg intramuscular dose of artemether significantly reduced the egg burden (64.9%) and worm burden (91.3%). At half this dose, a worm burden reduction of 65.3% was obtained, which was still statistically significant (P < 0.05). The lowest intramuscular dose of artemether investigated (40 mg/kg) yielded no effect on egg counts and worm burden. There were no adverse events due to artemether; however, two abortions were observed 7 days posttreatment. In conclusion, artemether shows interesting fasciocidal properties in sheep, but embryotoxicity is of concern. Further studies are warranted to assess the potential of additional artemisinin derivatives and other peroxidic compounds for the treatment of Fasciola spp. infections in different ruminants.

Discovery and validation of serum biomarkers expressed over the first twelve weeks of Fasciola hepatica infection in sheep

Serum biomarkers associated with Fasciola hepatica infection of Corriedale sheep were analysed during the first 12 weeks of infection using surface-enhanced laser desorption ionisation time of flight mass spectrometry (SELDI-TOF MS). In the discovery phase of analysis, pooled sera collected at week 0 and at each week p.i. to week 12 were fractionated by anion-exchange chromatography and the protein mass fingerprints obtained in individual fractions were in the M/z range 1.5–150kDa. A total of 2302 protein clusters (peaks) were identified that varied between time-points following infection with peaks increasing or decreasing in intensity, or showing transient variation in intensity, during the 12 weeks of parasite challenge. In the validation phase, candidate biomarkers in sera of individual sheep at weeks 3 and 9 p.i. were analysed, identifying 100 protein peaks, many of which are small peptides <10kDa in size: 54% of these peaks were up-regulated in intensity at week 3 or 9 p.i. Twenty-six biomarkers were chosen for further study, ranging in size from 1832 to 89,823Da: six biomarkers were up-regulated at weeks 3 and 9 p.i., 16 biomarkers were up-regulated only at week 9 p.i. and four biomarkers were down-regulated at week 9 p.i. Two biomarkers up-regulated at week 9 were identified as transferrin (77.2kDa) and Apolipoprotein A-IV (44.3kDa), respectively. The results show that the interaction between the host and F. hepatica is complex, with changes in biomarker patterns beginning within 3 weeks of infection and either persisting to weeks 9–12 or showing transient changes during infection. Identification of biomarkers expressed during ovine fasciolosis may provide insights into mechanisms of pathogenesis and immunity to Fasciola and may assist in the rational development and delivery of vaccines.

Fasciola hepatica and Fasciola gigantica: Comparison of cellular response to experimental infection in sheep

Cellular responses to Fasciola gigantica and to Fasciola hepatica infection in sheep were compared. Eosinophil numbers increased more quickly and strongly in F. gigantica-infected sheep than in F. hepatica-infected sheep. In both groups, peripheral blood mononuclear cell (PBMC) proliferation in response to the parasitic excretory–secretory products (ESP) showed similar kinetics. Interferon-gamma (IFN-γ) production by ESP-stimulated PBMC was early and showed similar kinetics in both groups. Interleukin-10 (IL-10) production by FhESP-stimulated PBMC was very high throughout infection even at 0 weeks post-infection (WPI) in F. hepatica-infected sheep, while in F. gigantica-infected sheep, IL-10 production by FgESP-stimulated PBMC increased between 1 and 4 WPI. IL-10 production in F. gigantica-infected sheep was significantly lower than in F. hepatica-infected sheep during infection. The lower susceptibility to F. gigantica infection in sheep could be explained by the more intense cellular response induced by the parasite and the weaker capacity of F. gigantica to evade the immune response.

Diagnostic imaging in sheep hepatic fascioliasis: ultrasound, computer tomography and magnetic resonance findings.

Radiological features and biochemical changes were investigated during the parenchymal and ductal phases of chronic Fasciola hepatica infection in sheep. The activities of plasma aspartate aminotransferase (AST), lactate dehydrogenase (LDH) and gamma-glutamyl transpeptidase (GGT), plasma levels of IgG anti- F. hepatica and serial ultrasound, computed tomography (CT) and magnetic resonance imaging (MRI) findings were studied in eight sheep infected with 150 F. hepatica metacercariae. Experimental fluke infection provoked an increase in plasma level of IgG directed against F. hepatica and in plasma LDH and AST activities from 4 weeks after infection. Enzyme activities did not significantly differ from the baseline after 15 and 12 weeks for LDH and AST, respectively. GGT activity increased from 9 weeks postinfection and still remained significantly elevated at 18 weeks. In the parenchymal phase, both CT and MRI showed nodular lesions in five animals and MRI could also detect early tracks in the subcapsular area in three sheep. Ultrasound findings were nonspecific in this phase. Ductal dilatation was shown by ultrasound, CT and MRI in almost all animals, although MRI was inferior to CT in depicting a mild ductal dilatation. Moving echogenic forms in the dilated bile ducts were observed by ultrasound from 9 weeks postinfection in seven of the eight sheep. Moving worms were only demonstrated in four sheep at CT and in a single sheep at MRI. This study shows that radiological findings may be useful in studies of fluke-induced liver damage.

Eicosanoid production by adult Fasciola hepatica and plasma eicosanoid patterns during fasciolosis in sheep

Fasciola hepatica infection in sheep is known to cause anaemia, fever and elevated levels of liver enzymes. It was hypothesised that eicosanoids play a role in these pathophysiological changes, so the pattern of plasma eicosanoids during the course of acute and chronic fasciolosis was studied in sheep infected with a single dose of 800 F. hepatica metacercariae. Blood plasma was collected weekly until week 17 p.i. from infected sheep, and from uninfected controls. Adult F. hepatica were then recovered from bile ducts and incubated for production of ES products. Eicosanoids were determined by enzyme immuno-assay in blood plasma, fluke homogenates and ES products after chromatographic purification of the samples. Fever and anaemia were seen from 3 to 12 weeks p.i. and from 8 to 17 weeks p.i., respectively. Onset of fever was accompanied by elevated liver enzyme activities (aspartate amino transferase and gamma glutamyl transferase) in the plasma. In general, the plasma levels of prostaglandin E2 (PGE2), prostaglandin I2 (PGI2) and leukotriene B4 (LTB4) were reduced during the acute and chronic stages of the infection, whereas thromboxane B2 (TXB2) was reduced only at 8 weeks p.i. The TXB2/PGI2 ratio was increased in favour of TXB2 at 3 and 11 weeks p.i. Additionally, TXB2, PGI2, PGE2 and LTB4 were detected both in ES products and in homogenates of F. hepatica. It was concluded that eicosanoid depletion in the plasma is caused by parasite-induced liver damage. The changes in eicosanoid levels are highly correlated to the clinical signs of the disease. Changes in the pattern of host plasma eicosanoids during fasciolosis, as well as parasite-derived eicosanoids, may reflect or contribute to the pathology of the disease.

Serum and bile antibody responses (IgG and IgA) during subclinical Fasciola hepatica infection in sheep

The kinetics of serum and bile immunoglobulins (IgG and IgA) directed against Fasciola hepatica in the course of subclinical infection induced experimentally was investigated in sheep. Serum activities of glutamate dehydrogenase and gamma-glutamyltransferase were used as markers of the different fluke stages during infection and associated liver damage. Specific serum and bile immunoglobulins followed a similar kinetic pattern, increasing progressively from infection throughout the prepatent period and tended to decrease when adult flukes became established in the bile duct. IgA titres were lower than those of IgG. Specific IgG and IgA bile titres reached maximum values at 14 weeks postinfection that were considerably lower than the serum titres during the whole experimental period. The major bile immunoglobulins are probably derived directly from plasma. The immunoglobulin kinetic pattern could be related to changes in serum liver enzyme activities.

Fasciola hepatica infection in sheep: changes in liver metabolism

Several aspects of liver function during infection with Fasciola hepatica were examined in sheep four weeks after infection and compared with the changes observed in infected rats. Previously reported respiratory abnormalities in mitochondria isolated from the left lobe of the liver of infected sheep were characterised further. Evidence is presented that the respiratory lesion is located in the mitochondrial electron transport chain and that the aberrant respiratory behaviour is not associated with an increase in non-esterified fatty acids and the depletion of mitochondrial phospholipids, as is the case in the rat. Microsomal membranes, which have also been shown to be depleted of phospholipids in the fluke-infected rat liver, showed no such changes in the sheep. However, in common with the rat, a substantial loss of cytochrome P 450 was recorded in microsomes prepared from the left lobe, and the glycogen content of the left lobe was found to be less than 50 per cent of control values. No change was observed in glucose 6-phosphatase activity. All these changes were localised effects, confined to areas of fluke infiltration.

Herd evaluation by enzyme-linked immunosorbent assay for the determination of Fasciola hepatica infection in sheep and cattle from the Altiplano of Bolivia

A study was designed to determine by ELISA the seroprevalence of fasciolosis both in sheep (29 herds totaling 184 sheep), in samples collected in 1988, and in cattle (41 herds totaling 299 animals, samples collected in 1988: 34 herds totaling 147 animals, samples collected in 1989) in the same area of Corapata in which a seroprevalence survey had been done in humans. The results show high seropositivity in sheep (89%) and lower seropositivity in cattle (58% in 1988, and 57% in 1989). The seroprevalence in cattle in 1988 was essentially identical to that detected in 1989. Faecal examinations were also done in the 1988 sheep and 1989 cattle. Results of the study showed that of the 184 sheep examined, 22 positive for F. hepatica eggs, while 163 were positive by serology. All of the 22 sheep which were positive parasitologically were also positive serologically for a sensitivity of 100%. On the other hand, of 147 cattle tested, 38 were positive parasitologically while 84 were positive serologically. Of the 38 positives for F. hepatica eggs, 31 were positive by serology (sensitivity 82%).