Experiments on anthelmintic control of Fasciola hepatica in Brazil.

Two separate field trials involving naturally infected cattle were carried out on two farms known to have a history of Fasciola hepatica infection. On the first farm, 15 animals per group were allocated as follows: G1, triclabendazole (TCBZ) four times a year; G2, TCBZ twice a year (May and September); G3, untreated control. All groups grazed together and after 3.5 years the animals were slaughtered and their livers examined by federal meat inspectors who condemned 100% of livers in G3 and 8.3% in G2 owing to the presence of lesions of fasciolosis. In G1 no livers were condemned. Significant differences in weight gains were not detected and fluke counts remained at low levels in the treated groups. Also, in the control group, egg counts started to decrease when animals were 2 years old. On the second farm, groups of 20 animals were treated as follows: G1, TCBZ three times a year (May, September and December); G2, TCBZ twice a year (May and September); G3, nitroxynil twice a year (May and September); G4, rafoxanide twice a year (May and September); G5, untreated controls. All animals were weighed and faecal samples examined at approximately 28-day intervals. During the period of the study, larger weight gains were detected in the TCBZ treated groups than in the others. TCBZ treatment kept F. hepatica egg counts at a lower level for longer periods than the other drugs and significant differences in weight gains were only obtained between the group receiving TCBZ three times a year and the control group.     

Fasciola in horses in the Republic of South Africa: a single natural case of Fasciola hepatica and the failure to infest ten horses either with F. hepatica or Fasciola gigantica

The faeces of 11 horses were examined for Fasciola spp. eggs. One of them was positive for Fasciola hepatica, a finding which was confirmed post-mortem. The 10 negative horses were subsequently infested with either F. hepatica or Fasciola gigantica, each animal receiving orally from 500-9,500 metacercariae. No clinical signs were observed and no fluke eggs were detected in the faeces, and neither immature nor adult Fasciola worms were recovered from the horses slaughtered 16-26 weeks post-infestation with F. hepatica and 28-34 weeks post-infestation with F. gigantica, respectively. The results indicate that horses have a high level of resistance to both South African Fasciola spp. Factors which can probably explain the conflicting reports for the prevalences of fascioliasis in horses throughout the world and the varying results obtained in experimental infestations are briefly considered.     

Prevalence of Fasciola hepatica and Dicrocoelium dendriticum in the cow: inspection in an east Switzerland abattoir

On the basis of meat inspection in an abattoir in the eastern part of Switzerland, the incidence of liverflukes in cattle was recorded weekly during one year. The prevalence was compared with surveys from the seventies and nineties. The average incidence of Dicrocoelium dendriticum infection did not change. Although the prevalence of Fasciola hepatica apparently slightly decreased, an actual decrease of liverflukes could not be demonstrated.     

实验感染肝片吸虫山羊的病理生理学——Ⅲ.细胞因子水平的变化

试验选择6只健康白山羊（经粪便学检查和Dot-ELISA检测，确认无肝片吸虫感染）随机分成Ⅰ、Ⅱ、Ⅲ组，其中Ⅰ、Ⅱ组山羊每只分别1次口服接种200、500个肝片吸虫囊蚴，Ⅲ组作为不感染对照组，每周颈静脉采血1次，连续11周，检测肝片吸虫感染后山羊血清中IL-2、TNF-α水平的变化和外周血淋巴细胞分泌IL-2的能力。结果表明，山羊试验感染肝片吸虫后，Ⅰ组山羊血清IL-2水平在感染后有所下降，而Ⅱ组山羊血清IL-2水平在感染后有所升高；感染不同剂量肝片吸虫的山羊血清TNF-α水平和淋巴细胞IL-2分泌水平均有不同程度的升高，在感染后第1周淋巴细胞就有反应，并且对非特异性刺激原和特异性刺激原的应答都有显著升高。这一结果提示，TNF-α可能参与肝片吸虫对肝的损伤过程，肝片吸虫感染剂量对宿主的IL-2含量影响较大，同时IL-2在宿主防御免疫中有重要作用。     

Evaluation of an ELISA to assess the intensity of Fasciola hepatica infection in cattle

An elisa with a diagnostic sensitivity of 98 per cent and specificity of 96 per cent was evaluated as a means of assessing the intensity of Fasciola hepatica infection in cattle. A total of 294 blood samples were collected from infected cattle at a local abattoir, and the level of infection in each animal was assessed on the basis of the extent of liver pathology and the presence of flukes; 120 blood samples were also collected from uninfected cattle kept on a farm known to be free of F hepatica. The results indicated that there was a significant correlation (P<0.001) between the elisa values and the intensity of infection. Values between 15 and 28 per cent of a positive control sample indicated a low intensity of infection, values between 28 and 50 per cent indicated a medium intensity of infection and values above 50 per cent indicated a high intensity of infection.     

牛羊东毕血吸虫病与肝片吸虫病混合感染

牛羊东毕血吸虫病是由东毕血吸虫引起牛羊的一种慢性传染病,可引起牛羊贫血、消瘦、水肿及母畜不孕或流产,甚至因恶病质而大批死亡。牛羊肝片吸虫病是由肝片吸虫引起牛羊急性或慢性肝炎和胆囊炎、并伴有全身性中毒和营养障碍的一种寄生虫病。牛羊东毕血吸虫病很少发生,牛羊肝片     

Comparison of an indirect haemagglutination assay and an ELISA for diagnosing Fasciola hepatica in experimentally and naturally infected sheep.

An enzyme-linked immunosorbent assay (ELISA) with somatic (S) or excretory-secretory antigens (ES) was compared with an indirect haemagglutination assay (IHA) for ability to detect antibodies against Fasciola hepatica in sheep. The specificity of both assays was determined by testing sera collected from sheep experimentally or naturally mono-infected with Fasciola hepatica, Haemonchus contortus, Ostertagia circumcincta, Cooperia curticei, Taenia ovis, Eimeria spp., Trichostrongylus vitrinus, Trichostrongylus colubriformis or Nematodirus battus respectively. With S or ES antigens the specificity of the ELISA was 98% or 95% respectively, whereas the specificity of the IHA was 86%. Antibodies directed against Fasciola hepatica were detected by the ELISA with S or ES antigens from 2 weeks after infection until the end of the experiment, whereas the IHA detected antibodies from week 3. We conclude that the ELISA with S antigens compares favourably with the IHA and can be used for the serodiagnosis of ovine fasciolosis in the Netherlands.     

Temporal studies on Fasciola hepatica in Galba truncatula in the west of Ireland

The population dynamics and prevalence of Fasciola hepatica in Galba truncatula were investigated on the Teagasc hill sheep farm in Country Mayo, Ireland from August 2006 until March 2008. Galba truncatula (n=974) were collected at fortnightly intervals in 4 snail habitats on the farm, their relative density and mean monthly rainfall and temperature were recorded. Snail abundance was associated with rainfall and temperature. G. truncatula abundance was generally low during winter 2006/2007 (December 2006-February 2007), mid spring and summer 2007 (April-July) and late autumn and winter 2007/2008 (October 2007-February 2008). Overall, two peaks in G. truncatula abundance were evident during the study period, an early spring (March) and late summer/autumn (late August-October) peak. Seasonal differences were observed in the prevalence of F. hepatica in G. truncatula, the greatest prevalence was evident in 2007 during the summer (25%) and autumn (16%). Two seasonal transmission peaks, as evident by the presence of mature infections in snails, one in summer/autumn and the other in late winter/early spring. Not unsurprising, cercariae (28%) and rediae (29%) were the predominant developmental stages observed in mature and pre-adult snails respectively. Worthy of note in this study, cercariae were also evident in pre-adult snails. The present study highlights the influence of milder temperatures and wetter conditions on both snail and fluke development. If the trend in mild and wet weather conditions continues, there is the potential for an increase in the number of G. truncatula habitats and ultimately the prevalence of fasciolosis in grazing livestock in Ireland.     

The effects of nitroxynil on the survival, growth and morphology of Fasciola hepatica in sheep.

Groups of sheep were experimentally infected with Fasciola hepatica and treated with nitroxynil at 10 mg/kg given subcutaneously at intervals of up to 70 days later. Effects on fluke burden, weight, morphology, egg production and hatchability were recorded. The results showed that the efficacy of nitroxynil and the occurrence of structurally abnormal flukes were directly proportional to the age of infection at treatment. Treatment also deleteriously affected fluke growth and egg hatchability and reduced faecal egg counts.     

Development of an egg hatch assay for the diagnosis of triclabendazole resistance in Fasciola hepatica: proof of concept

The aim of this study was to develop an Egg Hatch Assay (EHA) test for the detection of triclabendazole (TCBZ) resistance in Fasciola hepatica. A number of fluke isolates were used, of differing sensitivity to TCBZ. Eggs were exposed to solutions of triclabendazole sulphoxide (TCBZ.SO) for 14 days, then triggered to hatch. Egg development was divided into 6 distinct and easily identifiable stages: dead, empty, unembryonated, cell division, eye spot and hatched. The number of eggs reaching those stages was recorded. Initially, the discriminating dose (1% hatch) was determined for the Cullompton isolate, used as TCBZ-susceptible (TCBZ-S) standard. Once this concentration had been resolved, the response of different isolates to this concentration was examined. The hatch rate of the Fairhurst isolate was not significantly different from that of the Cullompton isolate, confirming its TCBZ-S status. The Patagonia isolate has not been exposed to TCBZ in the field and should be TCBZ-S: the results of the EHA supported this. The egg hatch response of the Oberon and Dutch isolates differed significantly from that of the Cullompton isolate; the former isolates are regarded as TCBZ-resistant (TCBZ-R) and the results confirmed this. Another isolate, the Leon isolate, was originally described as being TCBZ-R, but has since been shown to be TCBZ-S. There was no difference in its response to TCBZ.SO in the EHA from the Cullompton (and Fairhurst and Patagonia) isolate(s), further indicating its TCBZ-S status. The impact of TCBZ.SO treatment on the component stages of egg development was determined and revealed differences between the isolates. In conclusion, the results of the study have shown that it is possible to discriminate between TCBZ-S and TCBZ-R isolates of F. hepatica on the basis of the response of their eggs to an EHA and the test could be used to evaluate the TCBZ sensitivity of unknown field isolates.     

肝片吸虫对奶牛生理生化水平的影响及分析

[目的]试验选择济南地区3个奶牛场中5头感染肝片吸虫的奶牛和5头健康奶牛为试验动物,对感染肝片吸虫的奶牛生理生化指标进行了探讨。[方法]通过对奶牛体温、呼吸、心率和血液中红细胞、白细胞、血红蛋白和红细胞压积的测定来观察奶牛机体生理指标的影响;通过对血清中血糖、谷丙转氨酶和总胆红素的测定来观察肝片吸虫对奶牛血液生化指标的影响。[结果]感染肝片吸虫的奶牛体温、呼吸和心跳与对照组相比显著升高,血液红细胞总数、红细胞压积、血红蛋白降低,白细胞总数升高;血清中血糖、谷丙转氨酶和总胆红素的含量与健康组相比显著升高。[结论]肝片吸虫对奶牛的生理和生化水平都有一定程度的影响。     

comparison of an indirect haemagglutination assay and an Elisa for diagnosing Fasciola hepatica in experimentally and naturally infected sheep

Summary

An enzyme‐linked immunosorbent assay (ELISA) with somatic (S) or excretory‐secretory antigens (ES) was compared with an indirect haemagglutination assay (IHA) for ability to detect antibodies against Fasciola hepatica in sheep. The specificity of both assays was determined by testing sera collected from sheep experimentally or naturally mono‐infected with Fasciola hepatica, Haemonchus contortus, Ostertagia circumcincta, Cooperia curticei, Taenia ovis, Eimeria spp., Trichostrongylus vitrinus, Trichostrongylus colubriformis or Nematodirus battus respectively. With S or ES antigens the specificity of the ELISA was 98% or 95% respectively, whereas the specificity of the IHA was 86%. Antibodies directed against Fasciola hepatica were detected by the ELISA with S or ES antigens from 2 weeks after infection until the end of the experiment, whereas the IHA detected antibodies from week 3. We conclude that the ELISA with S antigens compares favourably with the IHA and can be used for the serodiagnosis of ovine fasciolosis in the Netherlands.     

The effect of albendazole and triclabendazole on colchicine binding in the liver fluke Fasciola hepatica

Albendazole (ABZ) and its sulfoxide (SX) and sulfone (SO) metabolites inhibit the binding of 3H-colchicine, a ligand with high affinity for tubulin to homogenate preparations of the liver fluke Fasciola hepatica. The relative potency of these compounds is SX greater than ABZ greater than SO. The benzimidazoles (cambendazole, parbendazole, oxibendazole and mebendazole), when tested at a concentration of 10 microM, also inhibited colchicine binding to fluke homogenates. However, a potent new benzimidazole flukacide, triclabendazole (TCB), was without effect on colchicine binding to F. hepatica homogenates. When intact flukes were exposed in vitro to 10(-5)M SX for as little as 5 min the subsequent binding of 3H-colchicine to fluke homogenates was significantly reduced. However, flukes recovered from sheep either 12 or 24 h after treatment with ABZ did not have a decreased ability to bind colchicine, although the non-specific binding was higher in flukes from treated sheep, suggesting some interaction of drug with tubulin in vivo. ABZ, SX and SO were effective in preventing embryonation of fluke eggs at doses as low as 0.01 microM, but TCB was without effect at concentrations as high as 10 microM. The results suggest that ABZ exerts at least part of its anthelmintic effect by interaction with fluke tubulin.