Search

Summary: Background: Fasciola hepatica (liver fluke) affects grazing animals including horses but the extent to which it affects UK horses is unknown. Objectives: To define how liver fluke affects the UK horse population. Study design: Descriptive, cross‐sectional, observational study. Methods: An F. hepatica excretory‐secretory antibody detection ELISA with a diagnostic sensitivity of 71% and specificity of 97% was validated and used to analyse serum samples. An abattoir study was performed to determine prevalence. A case‐control study of 269 horses compared fluke exposure between horses with liver disease and controls. Data on clinical signs and blood test results were collected for sero‐positive horses. Genotyping of adult fluke was used to produce a multilocus genotype for each parasite. Results: Four (2.2%) of 183 horses registered in the UK, sampled in the abattoir, had adult flukes in the liver, and the sero‐prevalence of F. hepatica was estimated as 8.7%. In the case‐control study, horses showing signs consistent with liver disease had significantly higher odds of testing positive for F. hepatica on ELISA than control horses. In 23 sero‐positive horses, a range of non‐specific clinical signs and blood test abnormalities was reported, with a third of the horses showing no signs. Genotypic analysis of liver flukes from horses provided evidence that these came from the same population as flukes from sheep and cattle. Main limitations: Bias could have arisen in the prevalence and case‐control studies due to convenience sampling methods, in particular the geographic origin of the horses. Only a small number of horses tested positive so the data on clinical signs are limited. Conclusions: Exposure to liver fluke occurs frequently in horses and may be an under‐recognised cause of liver disease. Flukes isolated from horses are from the same population as those found in ruminants. When designing and implementing parasite control plans, fluke should be considered, and horses should be tested if appropriate. [ABSTRACT FROM AUTHOR]

The article discusses prevalence of fasciolosis in horses, which is caused by infection of Fasciola (F.) hepatica, the common liver fluke. Topics include prevalence of fluke infections in sheep and cattle in Great Britain; susceptibility of horses to fluke infections, as indicated by a study finding infection in yearlings in Australia; use of faecal egg counts for diagnosis of infections in sheep and cattle; and problems in diagnosing fluke in horses due to lack of pathognomic clinical signs.

A faecal egg count reduction test, using composite samples, was developed in order to assess the efficacy of the flukicide, triclabendazole (TCBZ) on commercial sheep farms in England and Wales. First, a comparison between individual counts and composite counts was conducted using sheep on two farms with different levels of infection. Faecal samples were collected from 50 sheep on each farm at the time of TCBZ treatment and 21 days later. The results showed that a composite fluke egg count (CFEC) was as sensitive as using individual samples, and the test was subsequently validated on an additional 18 sheep farms. The pre-and post-treatment CFECs using five composite samples were subjected to bootstrap analysis. The variance in fluke egg counts of composite samples was high, but analyses indicated that 20 individual samples analysed as two composites was as sensitive as using five composites. The two-composite assay was evaluated on another five farms. On seven out of 25 farms sampled, egg counts either did not decrease significantly or increased following treatment, suggesting TCBZ resistance on these farms. This assay represents a practical field test that can be used in the first instance to evaluate the efficacy of TCBZ on sheep farms where resistance is suspected. [ABSTRACT FROM AUTHOR]

Nematospiroides dubius, in common with many other species of metazoan parasite, induces an lgG1 hypergammaglobulinaemia during the course of infection. In the present study, immune sera raised in CFLP mice by repeated infection contained 24 ng/ml IgG1 compared with a resting level of 2.4 mg/ml. IgG2a and IgG2b levels were depressed following infection from 1.5 to 06 mg/ml and 0.64 to 0.42 mg/mI respectively. IgM levels were unaltered by infection (0.16 mg/ml) whilst IgA levels increased from 0.7 to 1.2 mg/mli. Immunochemical fractionation of immune sera by a combination of affinity chromatography and gel filtration revealed that the anti-parasite activity of the original serum could be largely accounted for by purified IgG1 fractions as assessed by immunoprecipitin and immunofluorescence assays. Purified IgG1 was shown to react with antigenic components common to both adult homogenate and adult excretory-secretory antigen. In addition, absorption studies revealed that as much as 48% of purified IgG1 from immune serum reacted with adult N. dubius antigen. In vivo, IgG1 was the only purified immunoglobulin isotype to cause significant reduction in worm numbers in the gastrointestinal tract when administered alone, and to have any noticeable co-operative effect when administered in conjunction with immune mesenteric lymph node cells. lgG1 also caused severe stunting of worms, and promoted the adherence of peritoneal exudate cells to the worm surface in vitro. It is suggested that one mechanism by which immune mesenteric lymph-node cells exert their protective activity following cell transfer is by elevating IgG1 levels in recipient mice. [ABSTRACT FROM AUTHOR]

During primary tsetse-transmitted challenge of Boran (Bos indicus) cattle with Trypanosoma congolense ILNat 3.1, a transient parasite antigen-specific T-cell proliferative response was observed in peripheral blood mononuclear cells and splenic mononuclear cells stimulated in vitro. A response was also observed with cells of N'Dama (Bos taurus) cattle, but in this case higher stimulation indices were observed and the response was maintained until the termination of the experiment at 40 days post-infection (p.i.). The highest parasite antigen-specific proliferative responses were observed at 20 days post-infection. At this time N'Dama cattle not only responded to the antigens derived from the infecting clone (ILNat 3.1), but also to antigens from a clone of a different serodeme (ILNaR 2), whereas Boran cattle only recognized antigens from the infecting clone of parasites. To determine the molecular mass of the antigenic trypanosome proteins, whole trypanosome lysates made from T. congolense ILNat 3.1 were fractionated by SDS-PAGE and transferred onto nitrocellulose membranes. The major protein bands were isolated and used directly in T-cell proliferation assays, In this instance, no differences in the antigen recognition profiles of Boran and N'Dama cattle were observed. The variable surface glycoprotein did not induce T-cell proliferation in infected cattle despite the presence of serum antibodies to this variable antigenic type. [ABSTRACT FROM AUTHOR]

Epitopes specific for IgM on peripheral blood lymphocytes from 47 cattle were examined with three class-specific monoclonal antibodies, IL-A30, IL-A50 and B5/4. In all 47 animals tested, mAb IL-A30 detected a similar percentage of peripheral blood lymphocytes as a mAb that recognizes all immunoglobulin classes. However, in some animals mAbs IL-A50 and B5/4 detected a lower percentage of B cells compared with IL-A30 or the mAb against total Ig. They both reacted with a proportion of the serum IgM from these animals, while IL-A30 reacted with all serum IgM. Therefore, it is probable that mAb-A30 recognizes an IgM isotypic determinant and mAbs IL-A50 and B5/4 recognize different IgM allotypic determinants. Using mAb IL-A30 it was found that the percentage of peripheral blood IgM+ lymphocytes varied widely between healthy cattle (4-31%) but remained constant, with only minor variations, within individual animals. [ABSTRACT FROM AUTHOR]

IgG1 immunoglobulin purified from sera 3 weeks following primary infection with 400 L3 larvae of Nematospiroides dubius was shown to be protective against challenge infection as assessed by worm recovery and worm length. No evidence was seen of blocking activity either using primary infection sera or IgG1 purified from primary infection sera in a variety of assay systems both in vivo and in vitro. In addition, immune complexes precipitated from primary infection sera by polyethylene glycol failed to inhibit the capacity of immune mesenteric lymph node cells to transfer immunity. It is concluded that an explanation for the prolonged survival of Nematospiroides dubius must be sought in mechanisms other than circulating blocking factors. [ABSTRACT FROM AUTHOR]

The zoonotic liver flukes Fasciola hepatica and F. gigantica co-exist in parts of Africa and Asia. The two species have similar life-cycles but different transmission characteristics. Although the identification of adult Fasciola to species level is traditionally based on differences in size and shape, recent studies have demonstrated this method to be unreliable. Species of Fasciola can be distinguished by staining and comparing the morpho-anatomy of the gut and ovaries or by iso-enzyme analysis but such approaches are time-consuming and require specialist skills. Two primer sets, based on RAPD-derived sequences from English F. hepatica and Ghanaian F. gigantica, can now be used, in two separate PCR, to distinguish F. hepatica from F. gigantica. When the PCR were used to investigate 10 flukes (five from the U.K. and five from Peru) morpho-anatomically identified as F. hepatica and 10 (five from Ghana and five from Sudan) morpho-anatomically identified as F. gigantica, all 20 flukes were correctly identified to species level. The PCR were validated using 175 flukes collected, over a 12-year period, from different countries and both cattle and sheep. [ABSTRACT FROM AUTHOR]

Fasciola hepatica is a common parasite of livestock in Ireland, causing significant economic losses and affecting animal welfare. A previous abattoir study of 200 horses led to an estimated 9.5 % prevalence of infection in horses slaughtered in Ireland. However, the epidemiology and pathogenic significance of this infection in this species is not well-described. The objectives of this study were to determine the susceptibility of horses to oral challenge infection with F. hepatica metacercariae, and to document the course of the infection along with serological and biochemical response. We attempted an experimental infection of horses (n = 10; 9 geldings and 1 mare) with F. hepatica. Four were given 1000 metacercariae, four 500 metacercariae and two were sham-infected. Blood and faecal samples were taken at intervals up to 18 weeks post-infection (wpi). ELISA assays were used to assess sero-conversion in the experimental horses and also in a panel of sera from horses of known fluke status. No flukes were recovered from any of the livers, and neither were any lesions that could be attributed to F. hepatica infection observed. Coproantigen ELISA was negative throughout for all horses. Three antibody detection ELISAs, useful in diagnosing fasciolosis in other species, had limitations as diagnostic aids as determined using a panel of sera from horses of known F. hepatica infection status. This study is limited by the relatively small number of animals included, and the relatively short duration of the study period. Failure to establish infection after oral challenge raises fundamental questions on the pathophysiology and epidemiology of equine fasciolosis., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)