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

Estimation of diagnostic sensitivity and specificity of abattoir registrations and bulk tank milk ELISA as herd-level tests for Fasciola hepatica using Bayesian latent class modelling

The common liver fluke, Fasciola hepatica, is a trematode parasite found worldwide, typically with a focal distribution due to its requirement for suitable climatic and environmental conditions to complete its lifecycle. Bovine fasciolosis causes suboptimal production and economic losses, including liver condemnation at slaughter. The lack of reliable diagnostic methods is a disadvantage to the increasing demand for surveillance and control. The aim of this study was to evaluate the diagnostic accuracy of bulk tank milk (BTM) antibody testing and aggregated abattoir registrations (AAR) of liver fluke as herd-level tests for F. hepatica infection using Bayesian latent class models. Data from the abattoirs in 2019-2021 and BTM, sampled in the winter of 2020/2021, were collected from 437 herds on the southwest coast of Norway. The BTM samples were analysed with the SVANOVIR® F. hepatica-Ab ELISA test, with results given as an optical density ratio (ODR), and later dichotomized using the recommended cut-off value from the test manufacturer (ODR ≥0.3). Based on the BTM ELISA test, 47.8% of the herds tested positive. The AAR test was defined as the herd-level proportion of female slaughtered animals registered with liver fluke infection during the study period. For this test, three cut-offs were used (a proportion of 0.05, 0.1 and 0.2). The herds were split into two subpopulations ("Coastal" and "Inland"), which were expected to differ in true prevalence of F. hepatica infection based on climate-related and geographical factors. The diagnostic accuracies of both tests were estimated using Bayesian latent class models with minimally informative priors. Post-hoc analysis revealed that the maximum sum of sensitivity (Se) and specificity (Sp) of the tests was achieved with a herd-level proportion of ≥0.1 registered with liver fluke as the AAR test. Using this cut-off, the median estimate for the diagnostic accuracy of the BTM ELISA was 90.4% (84.0-96.2 95% Posterior Credible Interval (PCI)) for Se and 95.3% (90.6-100% PCI) for Sp, while the median estimate of Se for AAR was 87.5% (81.4-93.1% PCI) and the median estimate of Sp for AAR was 91.0% (85.2-96.5% PCI). The cut-off evaluation of the SVANOVIR® F. hepatica-Ab ELISA test for BTM confirmed the manufacturer's recommended cut-off of ODR ≥0.3 to denote positive and negative herds. This study suggests that AAR and BTM ELISA test can be used as herd-level tools to monitor liver fluke infection, so that appropriate interventions against infection can be implemented as necessary.

Blood parameters and parasite burden in cattle with chronic fascioliasis

Fascioliasis is a trematodiasis that affects domestic and wild animals as well as humans worldwide. It is a well-recognized disease in livestock, were it produces serious economic losses. Yet in cattle, there is limited information about the burden of liver flukes and its relation to the eggs per gram shed to the environment. There is also lack of knowledge on the effect of parasite load in blood parameters of infected animals, which is important to evaluate the severity and progression of the disease. The objective of this work was to gain insight in these aspects. Cattle from Mendoza province, Argentina, were inspected at a farm and at the abattoir determining the presence or absence of Fasciola hepatica. Each animal was sampled for blood and feces and in the slaughterhouse the livers were inspected. Hematology and blood chemistry parameters were determined, feces were examined for F. hepatica eggs by a quantitative sedimentation technique and livers were thoroughly inspected to determine the number of flukes. Infected cattle presented a mild burden of liver flukes per animal, strongly correlated (r = 0.72) to the number of eggs per gram of feces. The total number of eggs (X̄=35,100) shed per animal to the environment and the type of livestock management techniques in the region exacerbate the role of cattle as efficient reservoirs of this disease. Statistically significant lower red blood cell, lymphocyte and neutrophil counts were observed in infected compared to uninfected animals. All hepatic parameters tested showed highly statistically significant differences (p < 0.001) as well as proteins by cause of rise of globulins in infected cattle. The correlation between the amount of flukes in the liver and the number of eggs per gram of faces indicates coprology as a reliable and cost-effective method to infer parasite burden. The impact of fascioliasis on blood parameters can be of aid for the veterinary practitioner on the assessment of this disease on cattle.

Survival and Fecundity of Anopheles stephensi and Anopheles albimanus Mosquitoes (Diptera: Culicidae) After Ingesting Bovine Blood Containing Various Veterinary Systemic Parasiticides

Systemic parasiticides in livestock can control zoophilic malaria vectors that contribute to residual malaria transmission. Membrane feeding techniques were used to screen seven systemic parasiticidic drugs currently in veterinary use for livestock and dogs. Drugs were tested in two laboratory strains of zoophilic Anopheles - A. stephensi (South Asian vector) and A. albimanus (Central American vector). To assess the relative potentials of these drugs, the resultant LC-50 for each drug was compared with what is known about the pharmacokinetic of the drug. Drugs with LC-50 values below the reported maximum plasma concentration of treated animals were considered as showing the most promise for use in the field. Ivermectin and fipronil showed the greatest promise for use in cattle against A. stephensi. Fipronil showed the greatest promise for use in cattle against A. albimanus. Both fluralaner and afoxolaner were highly effective against both mosquito species but pharmacokinetic data for these drugs in cattle are lacking. Eprinomectin, moxidectin and abamectin showed marginal to no promise for either mosquito species. At sublethal doses, ivermectin, fipronil, and afoxolaner (but not fluralaner) significantly reduced the larval production of surviving A. stephensi and A. albimanus. Further testing of candidate systemic parasiticides, including their product formulations, in livestock against field-collected populations of Anopheles is the next logical step toward full implementation of this strategy to manage zoophilic vectors.

Liver function markers and haematological dynamics during acute and chronic phases of experimental Fasciola hepatica infection in cattle treated with triclabendazole

Fasciola hepatica, a worldwide-distributed liver fluke, is one of the causative agents of fasciolosis, a zoonotic disease that affects livestock and humans. In livestock, fasciolosis causes huge economic losses worldwide, reducing animal fertility, milk production, weight gain and condemnation of livers. In spite of the availability of drugs, such as triclabendazole (TCZ), for the treatment of fasciolosis, they do not necessarily prevent liver damage or parasite reinfection and can eventually increase parasite resistance. The aim of this research was to relate the hepatic function, haematological parameters, leukocyte counts in circulation and parasite egg shedding during F. hepatica acute and chronic phases of infection in cattle as well as to determine how these parameters change with TCZ-treatment of chronically infected cattle. Our results show that increased levels of serum aspartate aminotransferase (AST) and gamma glutamyltransferase (GGT) were detected in early stages of the experimental infection. Moreover, high circulating eosinophil count and plateletcrit levels were correlated with fluke number in livers from infected cattle. On the other hand, although TCZ-treatment in the chronic phase of infection reduced parasite burden and damage in the liver, it was not able to completely avoid them. In conclusion, our work sheds light into the physiopathological mechanisms induced during fluke infection in cattle, revealing the complexity of the host response to the infection, together with the effects of TCZ-treatment in chronically infected animals.

Grazier perceptions and management practices for liver fluke control in north eastern NSW, Australia

A survey of livestock producers (graziers) located in north eastern NSW Australia, collected information on perceptions and management practices for liver fluke control in livestock. The total area farmed by the 161 respondents was 195,600 ha (ranging in size from 4 to 10,522 ha) with cattle and sheep being the dominant livestock enterprises. Overall, 80% of graziers relied exclusively on anthelmintics for liver fluke control and few of these graziers (9%) integrated parasite management (IPM) strategies to reduce disease prevalence. Of those relying on anthelmintic control, triclabendazole (TCBZ) was preferentially chosen by 75% of graziers. Fifty five percent of these graziers used TCBZ in combination with oxfendazole (46%), ivermectin (5%) or abamectin (4%) whilst 45% used TCBZ as a single active ingredient. Thirty eight percent of graziers drenched livestock one or more times per year for liver fluke despite claiming they had no liver fluke or confirmed knowledge of infection. Fifty one percent of graziers based anthelmintic dose on the known weight of the heaviest animal in the herd whilst 43% visually guessed livestock bodyweight to calculate anthelmintic dose. Choice of anthelmintic was predominately based on perceived efficacy (45%) despite very few graziers (2%) having conducted post-treatment fluke egg counts. The majority of graziers (76%) were unsure if they had anthelmintic resistance, 21% claimed they had no resistance whilst 3% of graziers had confirmed resistance. Most graziers (97%) also reported farms were cohabited by kangaroos highlighting additional grazing pressures on-farm. This current survey has revealed that graziers rely on anthelmintics as their primary choice for liver fluke control. Reluctance to adopt IPM strategies and a continued heavy reliance on TCBZ, whilst basing anthelmintic decisions on perception rather than measurement and testing, pose threats for the future control of liver fluke in livestock within this endemic area.

Field study on the determination of the effective dose of injectable fosfatriclaben prodrug in sheep naturally infected with Fasciola hepatica

The aim of the present study was to determine the effective dose of fosfatriclaben through a field study in sheep naturally infected with F. hepatica. Thirty crossbred sheep positive for fluke eggs were selected for inclusion in the trial. On day 0, 5 groups of 6 animals each were formed for treatments: group 1 (G1), G2, and G3 received fosfatriclaben at 4, 6, and 8 mg/kg/IM, respectively. G4 received triclabendazole at 10 mg/kg/PO, and G5 was the untreated control group. Fecal samples of the sheep were analyzed to count the number of fluke eggs to evaluate the percentage of egg reduction. Twenty-one days after treatment, all sheep were humanely euthanized to extract the flukes from the bile ducts. They were counted to assess the percentage of fluke reduction. Fosfatriclaben reduced fluke eggs by 99.6, 99.6, and 100% and flukes by 94.3, 100, and 100%, respectively. Triclabendazole reduced fluke eggs by 95.2% and flukes by 100%. The fosfatriclaben injectable prodrug showed a high fasciolicidal efficacy similar to triclabendazole, with advantages over its predecessor, since only half the dose as compared to triclabendazole was required to remove eggs and flukes in the sheep that were studied.

The Pattern of Blood-Milk Exchange for Antiparasitic Drugs in Dairy Ruminants

Simple Summary

This review article is focused on the description of the plasma–milk partition coefficients for different antiparasitic drug classes in dairy ruminants, and it contributes to rational pharmaco-therapy in lactating dairy animals, which is critical to understand the pattern of drug excretion in milk as well as the residual concentration patterns in dairy products elaborated by processing milk from drug-treated animals.

Abstract

The prolonged persistence of milk residual concentration of different antiparasitic drugs in lactating dairy animals should be considered before recommending their use (label or extra-label) for parasite control in dairy animals. The partition blood-to-milk ratio for different antiparasitic compounds depends on their ability to diffuse across the mammary gland epithelium. The high lipophilicity of some of the most widely used antiparasitic drugs explains their high partition into milk and the extended persistence of high residual concentrations in milk after treatment. Most of the antiparasitic drug compounds studied were shown to be stable in various milk-related industrial processes. Thus, the levels of residues detected in raw milk can be directly applicable to estimating consumer exposure and dietary intake calculations when consuming heat-processed fluid milk. However, after milk is processed to obtain milk products such as cheese, yogurt, ricotta, and butter, the residues of lipophilic antiparasitic drugs are higher than those measured in the milk used for their elaboration. This review article contributes pharmacokinetics-based information, which is useful to understand the relevance of rational drug-based parasite control in lactating dairy ruminants to avoid undesirable consequences of residual drug concentrations in milk and derived products intended for human consumption.

Current Challenges for Fasciolicide Treatment in Ruminant Livestock

Pharmacological treatment remains essential to control fasciolosis in areas where infection is endemic. However, there are major constraints to treating food-producing animals. Of particular concern is the lack of flukicides for treating early Fasciola infections in ruminant livestock in some countries. In addition, the information provided in package leaflets, particularly regarding withdrawal periods, is often incomplete, confusing, and/or contradictory. International regulatory bodies should harmonize the use of flukicides in livestock in favor of fairer, safer international trade. In addition, monitoring the efficacy of fasciolicides on farms is also essential to minimize the spread of drug-resistant populations of Fasciola. The current situation regarding flukicide formulations in the European Union and other, non-European countries is analyzed in this review paper.

Drug resistance in liver flukes

Liver flukes include Fasciola hepatica, Fasciola gigantica, Clonorchis sinensis, Opisthorchis spp., Fascioloides magna, Gigantocotyle explanatum and Dicrocoelium spp. The two main species, F. hepatica and F. gigantica, are major parasites of livestock and infections result in huge economic losses. As with C. sinensis, Opisthorchis spp. and Dicrocoelium spp., they affect millions of people worldwide, causing severe health problems. Collectively, the group is referred to as the Food-Borne Trematodes and their true significance is now being more widely recognised. However, reports of resistance to triclabendazole (TCBZ), the most widely used anti-Fasciola drug, and to other current drugs are increasing. This is a worrying scenario. In this review, progress in understanding the mechanism(s) of resistance to TCBZ is discussed, focusing on tubulin mutations, altered drug uptake and changes in drug metabolism. There is much interest in the development of new drugs and drug combinations, the re-purposing of non-flukicidal drugs, and the development of new drug formulations and delivery systems; all this work will be reviewed. Sound farm management practices also need to be put in place, with effective treatment programmes, so that drugs can be used wisely and their efficacy conserved as much as is possible. This depends on reliable advice being given by veterinarians and other advisors. Accurate diagnosis and identification of drug-resistant fluke populations is central to effective control: to determine the actual extent of the problem and to determine how well or otherwise a treatment has worked; for research on establishing the mechanism of resistance (and identifying molecular markers of resistance); for informing treatment options; and for testing the efficacy of new drug candidates. Several diagnostic methods are available, but there are no recommended guidelines or standardised protocols in place and this is an issue that needs to be addressed.

In vitro and in vivo effects of 3-bromopyruvate against Echinococcus metacestodes

While searching for novel anti-echinococcosis drugs, we have been focusing on glycolysis which is relied on by Echinococcus for energy production and intermediates for other metabolic processes. The aim of this study was to investigate the potential therapeutic implication of glycolytic inhibitors on Echinococcus. Our results demonstrate that at an initial concentration of 40 μM, all inhibitors of glycolysis used in the current experiment [3-bromopyruvate (3-BrPA), ornidazole, clorsulon (CLS), sodium oxamate and 2,6-dihydroxynaphthalene (NA-P₂)] show considerable in vitro effects against Echinococcus granulosus protoscoleces and Echinococcus multilocularis metacestodes. Among them, 3-BrPA exhibited the highest activity which was similar to that of nitazoxanide (NTZ) and more efficacious than albendazole (ABZ). The activity of 3-BrPA was dose dependent and resulted in severe ultrastructural destructions, as visualized by electron microscopy. An additional in vivo study in mice infected with E. multilocularis metacestodes indicates a reduction in parasite weight after the twice-weekly treatment of 25 mg/kg 3-BrPA for 6 weeks, compared to that of the untreated control. In particular, in contrast to ABZ, the administration of 25 mg/kg 3-BrPA did not cause toxicity to the liver and kidney in mice. Similarly, at the effective dose against Echinococcus larvae, 3-BrPA showed no significant toxicity to human hepatocytes. Taken together, the results suggest that interfering with the glycolysis of the parasite may be a novel chemotherapeutical option and 3-BrPA, which exhibited a remarkable activity against Echinococcus, may be a promising potential drug against cystic echinococcosis (CE) and alveolar echinococcosis (AE).

Epidemiological and ultrasonographic investigation of bovine fascioliasis in smallholder production system in Eastern Nile Delta of Egypt

Regular updating of our knowledge on the epidemiological determinants of bovine fascioliasis is necessary to increase the awareness of the disease's significance and subsequently, improve the control measures. The objectives of this study were (1) to estimate the prevalence of bovine fascioliasis, and identify the association of epidemiological characteristics under traditional householders' production systems, (2) to describe the association between the clinical picture, Fasciola spp. egg count and hepatobiliary ultrasonography findings. In total, 270 faecal samples were examined microscopically for the presence or absence of Fasciola spp. egg, using the sedimentation-flotation method. Copro-positive animals were subjected to ultrasonographic examination. Overall prevalence of copro-positive animals was 27.4% (22.4-33.0%, 95% CI). The final multivariate analysis showed that there was a significant association between fascioliasis and animal species (P < 0.03), and administration of anthelmintic (P < 0.0001). Cattle have a less chance of being positive to Fasciola spp. by 0.55 (95% CI: 0.30 - 0.99) compared to water buffaloes. Administration of anthelmintic to animals on a regular basis decreased the risk of copro-positivity to Fasciola spp by 0.17 (95% CI: 0.07 - 0.36) compared to animals received anthelmintic on an irregular basis. Infected animals having different Fasciola spp. egg burden revealed different clinical symptoms associated with hepatobiliary changes on ultrasonographic examination ranged from normal hepatic parenchyma and bile system in low faecal egg load to hyperechogenic hepatic parenchyma, hyperechogenic with distal shadowing bile duct, and distended gallbladder in high faecal egg load of Fasciola spp. In conclusion, the prevalence of bovine fascioliasis is high under the traditional household's production system. Regular administration of anthelmintic significantly reduces the animal's chance of being copro-positive to Fasciola spp. Ultrasound poses a valuable prognostic technique for assessment of bovine fascioliasis.

Farm-level risk factors for Fasciola hepatica infection in Danish dairy cattle as evaluated by two diagnostic methods

Background

The prevalence of bovine fasciolosis in Denmark is increasing but appropriate guidelines for control are currently lacking. In order to help develop a control strategy for liver fluke, a risk factor study of farm management factors was conducted and the utility of bulk tank milk (BTM ELISA) as a tool for diagnosis in Danish dairy cattle farms was assessed.

Methods

This case-control study aimed to identify farm-level risk factors for fasciolosis in Danish dairy farms (> 50 animals slaughtered in 2013) using two diagnostic methods: recordings of liver condemnation at slaughter, and farm-level Fasciola hepatica antibody levels in BTM. A case farm was defined as having a minimum of 3 incidents of liver condemnation due to liver fluke at slaughter (in any age group) during 2013, and control farms were located within 10 km of at least one case farm and had no history of liver condemnation due to liver fluke during 2011–2013. The selected farmers were interviewed over telephone about grazing and control practices, and BTM from these farms was collected and analysed by ELISA in 2014. The final complete dataset consisting of 131 case and 63 control farms was analysed using logistic regression.

Results

Heifers grazing on wet pastures, dry cows grazing on wet pastures, herd size, breed and concurrent beef cattle production were identified as risk factors associated with being classified as a case farm. With the categorised BTM ELISA result as the response variable, heifers grazing on wet pastures, dry cows grazing on wet pastures, and purchase of cows were identified as risk factors. Within the case and control groups, 74.8 and 12.7% of farms were positive for fasciolosis on BTM ELISA, respectively. The differences are likely to be related to the detection limit of the farm-level prevalence by the BTM ELISA test, time span between slaughter data and BTM, and the relatively low sensitivity of liver inspection at slaughter.

Conclusions

Control of bovine fasciolosis in Denmark should target heifers and dry cows through grazing management and appropriate anthelmintic treatment, and BTM ELISA can be a useful diagnostic tool for fasciolosis in Danish dairy farms.

Electronic supplementary material

The online version of this article (10.1186/s13071-017-2504-y) contains supplementary material, which is available to authorized users.

First report of closantel treatment failure against Fasciola hepatica in cattle

Control of Fasciola hepatica infection in livestock is based on annual treatment using flukicides such as triclabendazole, albendazole and closantel. However, triclabendazole resistant F. hepatica populations are emerging worldwide and resistance is emerging to albendazole, whereas it has until now never been described for closantel. In Sweden, a topical formulation containing a combination of closantel and ivermectin (Closamectin Pour On) has been registered for use in cattle only since 2011. This study evaluated the efficacy of closantel against F. hepatica in naturally infected beef cattle using both coproantigen and faecal egg count reduction tests. Faecal egg counts (FEC) and coproantigen ELISA examinations were conducted in February 2014 in three beef cattle herds (A, B, C) in south-western Sweden. On each farm, 10 F. hepatica coproantigen-positive and F. hepatica egg-positive animals were allocated after 12-16 weeks of housing into groups and treated topically with a minimum of 20 mg closantel per kg body weight. Faecal samples were collected from selected animals on 0, 7 and 21 day post-treatment (PT). Based on FEC, closantel efficacy 21 days PT was 72% (95% CI: 65-77%) and 97% (95% CI: 95-98%) on farms A and B, respectively. No FEC reduction at all was observed on farm C. In total, 4, 1 and 6 animals remained coproantigen-positive at 21 days PT on farms A, B and C, respectively. Closantel treatment failure was confirmed on two of the farms. As the animals were housed 12-16 weeks before treatment and thereafter during the entire study, failure due to the presence of juvenile flukes was excluded. Although the cause of closantel failure currently remains unclear, development of resistance or/and absorption failure of topical administration should be considered. To our knowledge, this is the first report of closantel treatment failure against F. hepatica in cattle.

Bovine fasciolosis: control strategies based on the location of Galba truncatula habitats on farms

Infection of livestock with Fasciola hepatica is a worldwide, economically important and increasing problem. Even though, bovine fasciolosis can be a disease associated with particular regions, there are usually epidemiological issues on individual farms. For this reason, it is recommended to find the source of infection by examination of definite hosts and pastures on a farm. The following factors which promote the transmission of bovine fasciolosis are usually found: (A) Snail habitats are present on pastures used for young stock (prior to first calving) or dry cows only. Pastures for dairy cows are not affected. (B) Snail habitats are present on all pastures for dairy cows. (C) Snail habitats are present on single pastures used for dairy cows. (D) Snail habitats are present on hayfields. For each of these epidemiological situations an individual control strategy is advised. When a control strategy is tailored according to the specific epidemiology found on the individual farm, egg shedding and F. hepatica-seroprevalence can be reduced significantly. This approach can support the responsible use of the available flukicides.

In vitro efficacy of triclabendazole and clorsulon against the larval stage of Echinococcus multilocularis

Alveolar echinococcosis (AE) caused by the cestode Echinococcus multilocularis (E. multilocularis) is endemic in wide areas of the Northern hemisphere. Untreated AE progresses and leads to death in more than 90% of cases. Until the advent of benzimidazoles, no antihelminthic drugs were available to cure AE. Benzimidazoles have greatly improved the prognosis of patients with AE. However, benzimidazoles have only a parasitostatic effect on E. multilocularis. Albendazole (ABZ) must sometimes be withdrawn because of adverse events. Alternative drugs are urgently needed. The antihelminthic triclabendazole (TCZ) and clorsulon (CLS) are more effective than ABZ to cure infections by the liver flukes Fasciola spp. The efficacy of TCZ and CLS was investigated on an in vitro culture of E. multilocularis larval tissue. E. multilocularis vesicles were evaluated for their morphology before and after adding TCZ, TCZ sulfoxide (TCZSX) and CLS to the larval tissue culture. TCZ at the concentrations of 20 μg/ml culture solution led to maximum vesicle damage within 12 days and of 25 μg/ml within 13 days, and TCZSX at the concentrations of 20 μg/ml within 20 days and of 25 μg/ml within 14 days. Contrary, CLS added at 5, 10 and 15 μg/ml to culture solution did not lead to any vesicle damage. TCZ is a promising further candidate drug for the treatment of AE.

Evaluation of the comparative efficacy of a moxidectin plus triclabendazole pour-on solution against adult and immature liver fluke, Fasciola hepatica, in cattle

The objective of this study was to evaluate the efficacy of a pour-on solution containing moxidectin plus triclabendazole (MOX plus TCBZ) against immature and adult stages of the liver fluke in cattle and compare the efficacy with other commercially available preparations. To this end, 104 male Holstein-Friesian calves aged between 3 and 4 months, were randomly allocated to 13 groups of eight animals each, and infected with approximately 500 Fasciola hepatica metacercariae. One group remained untreated, four groups were treated with MOX plus TCBZ at a dose rate of 0.1 mL/kg, four other groups were treated with ivermectin (IVM) plus clorsulon injectable at a dose rate of 0.02 mL/kg, and the remaining four groups were treated with IVM plus closantel pour-on at a dose rate of 0.1 mL/kg. Each treatment was applied to one of the groups at 4 weeks, 6 weeks, 8 weeks and 12 weeks after the experimental infection. At necropsy (99-102 days after infection), all untreated animals were infected with a minimum of 30 flukes. The MOX plus TCBZ treated animals had significantly (P<0.0001) lower fluke counts compared to the untreated control animals at all time points after treatment. Efficacy against 8-week old and adult flukes was >99.5%. For 6-week old immature fluke, the efficacy was 98.0% and for 4-week old immature fluke the efficacy was 90.9%. The IVM plus closantel pour-on treated animals had significantly lower fluke counts compared to the untreated control animals for adult and 8-week old flukes (P<0.0001), and for 6-week old flukes (P=0.002). The efficacy was 26.8%, 68.2%, 90.6% and 99.3% against 4-week, 6-week and 8-week old immature flukes, and adult flukes respectively. The IVM plus clorsulon treated animals had significantly lower fluke counts compared to the untreated control animals for adult (P<0.0001) and 8-week old (P<0.05) flukes. The efficacy was 29.7%, 43.4%, 53.2% and 99.2% against 4-week, 6-week and 8-week old immature flukes, and adult flukes respectively. For treatments at 4, 6 and 8 weeks after infection, the fluke counts were significantly (P<0.0001) lower for the MOX plus TCBZ treatment than for IVM plus closantel or IVM plus clorsulon. The results confirm the high efficacy (>90%) of the MOX plus TCBZ pour-on combination against 4-week old to adult liver fluke in cattle. The IVM plus closantel pour-on combination was effective (>90%) against 8-week old and adult flukes, but had low efficacy against 4- and 6-week old fluke. The IVM plus clorsulon injectable combination was effective (>90%) against adult fluke only.

Liver fluke isolates: a question of provenance

A survey of literature on experimental infections with the liver fluke, Fasciola hepatica published between 2005 and 2009 has revealed a general lack of information on where fluke material (i.e. metacercariae) was sourced from. Even less information was given on the drug status of the fluke isolate used, which is a particular concern for those studies that involved anthelmintics. In these two respects, information on the liver fluke lags far behind that for nematodes, where such information is given almost as a matter of course. Of additional concern is that, at times, information about the source and drug history of fluke isolates was incorrect. The overall aim of the review is to demonstrate why it is important to provide as much information as possible on what fluke material is being used. It also attempts to correct some of the errors in the literature and gather together what information is available about the provenance of those isolates that have been used in recent experimental studies.

The drugs we have and the drugs we need against major helminth infections

Parasitic worms (helminths) have accompanied humans for thousands of years and, still today, they are pervasive where poverty persists, including large parts of Southeast Asia and the Western Pacific Region. The global strategy for the control of helminth infections is morbidity control and elimination as a public health problem. Regular administration of anthelminthic drugs to at-risk populations (e.g. school-aged children) serves as the backbone of interventions in areas where helminth infections are highly endemic. In this review, we focus on soil-transmitted helminthiasis (ascariasis, hookworm disease, strongyloidiasis and trichuriasis) and food-borne trematodiasis (clonorchiasis, fascioliasis, intestinal fluke infections, opisthorchiasis and paragonimiasis) and discuss the few drugs that are currently available for their treatment and control. Emphasis is placed on efficacy with new light shed on multiple dosing and combination therapy. We summarise recent advances made with anthelminthic drugs that might become the future armentarium for the control of major helminthiasis (e.g. artemisinins, cyclooctadepsipeptides, mefloquine, monepantel, nitazoxandide, synthetic peroxides and tribendimidine). Issuing from our review are current research gaps and the need for concerted efforts to discover, develop and deploy the next generation of anthelminthic drugs.