Fasciola hepatica: a comparative survey of adult fluke resistance to triclabendazole, nitroxynil and closantel on selected upland and lowland sheep farms in Northern Ireland using faecal egg counting, coproantigen ELISA testing and fluke histology.

In order to investigate the incidence and distribution of adult fluke resistance to the fasciolicide tricalbendazole (TCBZ) amongst populations of Fasciola hepatica in sheep flocks in Northern Ireland (NI), individual rectal faeces samples were collected from 3 groups of 20 sheep, before (pre-dose), and 21 days after (post-dose) treatment of the animals with TCBZ, nitroxynil or closantel, on each of 13 well-managed sheep farms distributed across the province. The efficacy of each flukicide was determined for each farm, using faecal egg count reduction (FECRT) and F. hepatica coproantigen ELISA testing. In certain flocks, 2 sheep with high pre-dose faecal egg counts (FEC) were killed 3 days and 21 days respectively after TCBZ treatment, and the histology of the fluke reproductive organs was compared with that of flukes from untreated sheep, and from sheep treated with nitroxynil or closantel 2 days prior to death, using haematoxylin and eosin (H&E) staining and an in situ hybridisation method (TdT-mediated dUDP nick end labelling [TUNEL]) to demonstrate apoptosis. Results from FECRT revealed that in all flocks with a high fluke burden, TCBZ was ineffective in treating chronic fasciolosis, and this finding was generally supported by the results of the coproantigen reduction test (CRT). The histology of reproductive organs of flukes from TCBZ-treated sheep in these flocks was normal, when compared with untreated flukes, and this, together with the FECRT and CRT findings, indicated a likely diagnosis of TCBZ resistance in all the flocks with a high fluke burden. In contrast, nitroxynil and closantel were found to be fully effective against TCBZ-resistant flukes in each of the flocks bearing a high chronic fluke burden. All of the flocks with a high fluke burden and TCBZ resistance were managed on lowland in the South and East of NI. Upland flocks, in the North and West, had low fluke burdens, or were clear of infection; and FECs were too low to allow valid resistance testing. The study highlights the high level of penetration of TCBZ resistance throughout F. hepatica populations in areas of intensively managed sheep production with a high level of fluke challenge. Further, it emphasises the importance of pre-emptive chemotherapeutic action against chronic fasciolosis, using flukicides effective against the egg-producing adult flukes to minimise pasture contamination for the next season's lamb crop. This study also exemplifies the use of several complementary methods (FECRT; CRT; fluke histology; comparative anthelmintic efficacy testing) for confirmation of a diagnosis of fluke drug resistance.

Curcumin induces a nuclear factor-erythroid 2-related factor 2-driven response against oxidative and nitrative stress after praziquantel treatment in liver fluke-infected hamsters.

Praziquantel has been used for the treatment of liver fluke infection, but an oxidative/nitrative stress may occur after a short-term treatment and participate in side effects. In an attempt to reduce the adverse effects, we administered curcumin, an anti-inflammatory agent, to Opisthorchis viverrini-infected hamsters treated with praziquantel. At 12h after treatment, curcumin decreased eosinophil infiltration and increased mononuclear cell infiltration in parallel with nuclear factor-erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 expression at the transcriptional and protein levels. Curcumin also enhanced the expression of genes involved in the Nrf2-regulated stress pathway (Kelch-like ECH-associated protein 1, NAD(P)H:quinine oxidoreductase 1, glutamate cysteine ligase, and activating transcription factor 3, peroxiredoxin 3, peroxiredoxin 6, manganese superoxide dismutase, and catalase), leading to increased ferric antioxidant capacity in the plasma. In contrast, curcumin decreased the level of oxidative and nitrative stress markers such as urinary 8-oxo-7,8-dihydro-2'-deoxyguanosine, plasma levels of malondialdehyde and nitrate/nitrite, and activity of plasma alanine transaminase, a liver injury marker. This correlated with the suppression of nuclear factor-kappaB (NF-κB) and related molecules (cyclooxygenase-2 and inducible nitric oxide synthase) and pro-inflammatory cytokines (IL-1ß and TNF-α). In conclusion, curcumin may be an effective chemopreventive agent against oxidative and nitrative stress derived from praziquantel treatment during O. viverrini infection via induction of Nrf2 and suppression of NF-κB-mediated pathways. Nrf2 may also be a novel therapeutic target for not only parasitic diseases but other types of inflammation-mediated diseases.

Efficacy of an injectable combination anthelmintic (nitroxynil+clorsulon+ivermectin) against early immature Fasciola hepatica compared to triclabendazole combination flukicides given orally or topically to cattle.

The objective was to compare the efficacy against artificially induced 2- and 4-week old early immature triclabendazole-susceptible liver flukes (Fasciola hepatica) of an injectable combination of nitroxynil, clorsulon and ivermectin with oral and pour-on combination formulations containing triclabendazole. Groups of yearling Angus or Angus cross cattle were confirmed fluke free before being artificially infected with 500 Sunny Corner strain triclabendazole-susceptible liver fluke metacercariae. Two or four weeks after infection, cattle were treated with the test combination Nitromec (10.2mg/kg nitroxynil, 2.0mg/kg clorsulon, 0.2mg/kg ivermectin), or oral Flukazole C+Se (triclabendazole/oxfendazole/Selenium), oral Fasimec C (triclabendazole/ivermectin) or Genesis Ultra Pour-On (triclabendazole/abamectin). At intervals cattle were weighed, faecal sampled for liver fluke egg counts and blood sampled for liver serum enzyme analysis. Cattle were slaughtered 14 weeks after infection for recovery of adult flukes; fluke egg counts and liver pathology assessment. All cattle increased in body weight by 0.4-0.8kg/day but there were no significant differences between control and treated groups or between the treatment groups. Geometric mean 14-week fluke egg counts and total fluke counts for all treatments, were significantly less (p<0.05) than the control group, except for the group treated with Genesis Ultra Pour-On, 2 weeks after infection. Nitromec treatment of 2-week old flukes was 83% and 95% effective as assessed by 14-week egg and fluke counts, respectively, compared to Flukazole C; 96% and 99%, Fasimec C; 70% and 46%, and Genesis Pour-On, which was ineffective, with egg and fluke count reductions of 0% and 8%, respectively. Against 4-week old flukes, Nitromec treatment was 88% and 99% effective when assessed by 14-week egg and fluke counts, respectively, with Flukazole C; 98% and 99%, Genesis Pour-On; 98% and 82% and Fasimec C; 91% and 61% effective, respectively. Group mean levels of the bile duct-associated enzyme gamma glutamyl transpeptidase (GGT) and the parenchymal associated enzymes, aspartate amino-transferase (AST) and glutamate dehydrogenase (GLDH) increased above the normal range 8 and 11 weeks after infection in the untreated control animals and the group treated 2 weeks after infection with Genesis Pour-On. The groups treated with Fasimec at 2 or 4 weeks after infection, also had elevated enzyme levels. The use of liver-associated enzyme assay is supported as supplementary indicators of fluke-induced pathology.

[Liver fluke infestation in New World camelids. Parasitology, pathology, clinical findings and therapy]. / Leberegelbefall bei Neuweltkameliden. Parasitologie, Pathologie, Klinik und Therapie.

In Llamas and Alpacas infestation with Fasciola hepatica or Dicrocoelium dendriticum can cause liver damage, sometimes even with lethal outcome. Once infected South American Camelids (SACs) react more sensitively to these parasites than other domestic ruminants. We report here on the pathology, parasitology, clinics and therapy of this disease. Concerning Dicrocoelium dendriticum we describe own clinical results and therapeutic outcome in addition to the pathological investigation. According to anatomic corrosion casts, the bile ducts of SACs show more similarity with the equine bile system than with the bile system of domestic ruminants.