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

The Fasciola hepatica egg development and hatching test (EDHT) using commercial drugs: a simple protocol for tackling anthelminthic resistance and promoting cattle productivity

Fasciolosis is an important zoonotic disease caused by the trematode Fasciola hepatica, and it causes great losses in bovine production. The anthelmintic resistance is a major problem in the control of fasciolosis. In this study, the F. hepatica egg development and hatching test (EDHT) was used for the evaluation of the ovicidal activity of commercial drugs, commonly used for treating infected cattle, which reflects F. hepatica anthelminthic resistance in infected bovines, according to recent literature. Bile samples from F. hepatica naturally parasitized cattle were obtained from slaughterhouses in the cities of Lages and Otacílio Costa, Santa Catarina State, Brazil. The bile was washed, the eggs were recovered, quantified, and distributed in universal collectors, with a minimum of 1,000 eggs per vial. Four commercial drugs were used in this study, containing albendazole sulfoxide (ABDZ), closantel (CSTL), nitroxynil (NTXL), and triclabendazole with fenbendazole (TBZF). The drugs were diluted according to the manufacturer instructions. All drugs, and the respective control, were tested in triplicates, with the quantity of recovered eggs determining the number of drugs to be tested. The vials were incubated for 28 days at 27 °C, and the eggs were classified according to their degree of development under a stereomicroscope. In total, 121 egg samples were analyzed. Two samples were identified as resistant to TBZF. Undetermined resistance/susceptibility has been found in two isolates treated with ABDZ, one treated with NTXL and six treated with TBZF. CSTL did not present ovicidal activity and cannot be used in EDHT. This is the first time that commercial drugs were used in F. hepatica EDHT.

Efficacy of flukicides against Fasciola hepatica and first report of triclabendazole resistance on German sheep farms

Fasciola hepatica infections lead to severe health problems and production losses in sheep farming, if not treated effectively. Triclabendazole has been used extensively over decades due to its unique efficacy range against all definitive hostfluke stages but published data about the susceptibility of F. hepatica to anthelmintics in Germany are lacking. This study aimed to identify current F. hepatica infections in German sheep flocks by coproscopic examinations and to evaluate the efficacy of anthelmintics with a focus on triclabendazole in a field study conducted from 2020 to 2022. Initial screening included 71 sheep farms, many of them with known history of fasciolosis. In this highly biased sample set, the frequency of F. hepatica infection at individual sheep and farm level were 12.8% and 35.2%, respectively. Additionally, eggs of Paramphistominae were found at frequencies of 4.8% and 15.5% at individual sheep and farm level, respectively. Due to low egg shedding intensity, faecal egg count reduction (FECR) tests could only be conducted on a few farms. The efficacy of triclabendazole was tested on 11 farms and albendazole on one farm, including 3-53 sheep/farm. Individual faecal samples were collected before and two weeks after treatment to evaluate the FECR using the sedimentation or FLUKEFINDER® or a modified FLUKEFINDER® method. On all farms a coproantigen reduction test was conducted in parallel. Lacking efficacy of triclabendazole even at double dosage was shown on one farm associated with a high number of animal losses due to acute fasciolosis. On this farm, the Fasciola miracidium development test was additionally performed, revealing a high in vitro ovicidal activity of albendazole while closantel was effective in vivo. On all other farms, sufficient efficacy of triclabendazole was observed. In conclusion, triclabendazole resistance appears not to be widespread on German sheep farms but, when present, can have serious effects on animal health.

Fasciola hepatica antioxidant and protease-inhibitor cocktail recombinant vaccines administered five times elicit potent and sustained immune responses in sheep but do not confer protection

Our laboratory's vaccine development strategy against the livestock parasite Fasciola hepatica centres around disrupting key biological processes by combining groups of antigens with similar/complementary functional actions into a single vaccine cocktail. In this study the focus was on antioxidant protein vaccines and a protease inhibitor vaccine aimed at disrupting the parasite's ability to defend against oxidative stress and protease-inhibitor balance, respectively. Two combinations of recombinantly expressed antioxidants were assessed, namely peroxiredoxin (rFhPrx), thioredoxin (rFhTrx) and thioredoxin-glutathione reductase (rFhTGR) (Group 1) and rFhPrx, rFhTrx, and two superoxide dismutases (rFhSOD1 and rFhSOD3) (Group 2). The protease inhibitor vaccine cocktail included representatives of each of the key secreted protease inhibitor families, namely a Kunitz-type inhibitor (rFhKT1), a serpin (rFhSrp1) and a stefin, (rFhStf1) (Group 3). The vaccine combinations were formulated in adjuvant Montanide 61VG administered at five timepoints; two before experimental challenge with 60 F. hepatica metacercariae and three after infection. The vaccine combinations did not reduce the liver fluke burden, and only Group 2 displayed a marginal reduction in egg viability (8.2%). Despite previous results showing an effect of liver fluke vaccines on overall weight gain in infected animals, no significant (P value >0.05) impact on weight gain was observed in this study. Antibodies were elicited against all the vaccine antigens within the cocktails and were maintained at high levels to the end of the trial, due to our strategy of continuing vaccine administration after infection. However, these responses were not boosted by the challenge F. hepatica infection. A comparative analysis with previous vaccine data using a protease inhibitor vaccine found no repeat of the promising outcomes associated with this vaccine, indicating that the addition of rFhSrp1 to the vaccine cocktail did not improve vaccine efficacy. Assessment of liver pathology across the two trials using a modified liver enzyme score (glutamate dehydrogenase to platelet ratio) at eight weeks post infection suggests an association with liver fluke burden above 45 flukes, which could be used to predict liver pathology in future trials. The results reported in this study highlight the ambiguousness in liver fluke vaccine development and the difficulty in obtaining consistent and repeatable protection. This work stresses the need for repetition of trials and the use of sufficiently sized groups to assess vaccine efficacy with adequate statistical power.

Activity of cumin essential oil to control fascioliasis: Efficacy and changes in the tegument of Fasciola hepatica

Fasciola hepatica, the liver trematode, infects ruminants and causes economic loss. Because parasites are developing resistance to commercial drugs, the negative effects of parasitism are increasing. In this study, we aimed to evaluate the efficacy of cumin (Cuminum cyminum) essential oil against F. hepatica eggs and adults. The eggs were incubated with eight concentrations of the essential oil (0.031125-4.15 mg/mL), and viable eggs were counted after 14 days and classified as embryonated or non-embryonated. Adult flukes were incubated in Roswell Park Memorial Institute medium to ensure their viability and then incubated in essential oil. They were observed for 24 h after treatment. The adults were assessed with the two lowest effective oil concentrations used in the ovicidal test. Three controls were used for both tests: nitroxynil, a negative control, and Tween®80. After incubation in oil, the adult specimens were processed for histological analysis and stained with hematoxylin-eosin. In addition, the oil was tested for cytotoxicity using Madin-Darby bovine kidney cells to assess any possible effect on them. The oil was effective in ovicidal and adulticidal inhibition of the trematode, with statistically significant results. All concentrations assessed in the ovicidal test were 100% effective. The adult test was effective within 15 h and inactivated all the specimens at the highest concentration evaluated (0.06225 mg/mL). Histological analysis showed that cumin essential oil resulted in marked areas of vacuolization. The spines showed no structural changes but were surrounded by microvesicles. These findings indicated that cumin oil could be a potential compound in the control of fasciolosis.

Artemisia vulgaris anthelmintic activities to ova and adult stages of Fasciola gigantica in vitro

Background and Aim

Fasciolosis due to Fasciola gigantica is endemic to tropical countries and Fasciola hepatica in temperate climates, highly detrimental to livestock and known as foodborne zoonotic diseases. The strategic control of the disease is mainly the use of chemical anthelmintic. This study aimed to evaluate the anthelmintic properties of Artemisia vulgaris extract on the ova and adult stages of F. gigantica.

Materials and Methods

Samples were collected from the Ampel Abbatoir, Boyolali District, Central Java, Indonesia. The ova from 20-gallbladders of cattle which were naturally infected with F. gigantica and 270 living F. gigantica worms were used in this study. The ovicidal assay was performed by incubating the ova with A. vulgaris in different concentrations, that is, 5%, 2.5%, and 1.25% for 5, 9, 11, 14, and 16 days. The efficacies were evaluated by quantification of ova degeneration during developmental stages in different time points and egg-hatch assay. The flukicidal effects were observed by mortality assay in 5, 10, 20, 40, 80, 160, 320, and 640 min incubations followed by scanning electron microscopy for surface morphology and histology of the fluke's transversal sections.

Results

The concentration of 5% A. vulgaris showed the strongest ovicidal activities. The percentage of hatching ova on day 16 at concentrations of 5%, 2.5%, and 1.25% were 3.33%, 6.67%, and 16.67%. These ova hatch assay showed a significant reduction (p < 0.001) compared to untreated control. The flukicidal effect was significant (p < 0.001) at a concentration of 20%, with a mortality rate reaching 66.67% in the 40 min of incubation time. The surface properties of the adult worms, including the spine, tegument, acetabulum, intestine, and vitelline follicles, were disintegrated.

Conclusion

The results showed that A. vulgaris has the potential ovicidal and flukicidal properties to F. gigantica. The active compounds remained necessary to be elucidated further and its modes of action would be interesting to be predicted by molecular docking modeling.

Microscopic alterations in Fasciola hepatica treated with the essential oils of Pelargonium graveolens and Citrus aurantium

Fasciolosis is one of the most important parasitic diseases in animal health, affecting mainly ruminants, causing economic and productivity losses. This study aimed to evaluate the in vitro ovicidal and adulticidal activity of essential oils (EOs) from Pelargonium graveolens (geranium) and Citrus aurantium (sour orange) on Fasciola hepatica. Performed Gas Chromatography of EOs P. graveolens and C. aurantium, with major compound, citronellol (31.37 %) and limonene (93.89 %), respectively. For the cytotoxicity assay, the sour orange EO showed to be promising when used in lower concentrations. For the ovicidal tests, the eggs were incubated with geranium EOs at concentrations from 4.5 to 0.03375 mg/mL and sour orange at concentrations from 4.25 to 0.031875 mg/mL, along with controls. The viable eggs were counted on the 14th day post-incubation. Adult forms of F. hepatica were incubated containing the EOs and observed for 24 h after treatment, as well as the control groups. Later the specimens were fixed for histological analysis. Geranium and sour orange EOs in trematode eggs at the concentrations tested were 100 % effective in inactivating hatching (p < 0.05) when compared to the untreated control. In the adulticidal test, the essential oil of P. graveolens at both concentrations tested (0.0675 and 0.03375) within 15 h, promoted the death of flukes. For C. aurantium, 18 h was enough to inactivate all specimens, up to a concentration of 0.06375. The histological analysis, observed the accumulation of liquid in the tegument in the specimens incubated in C. aurantium and P. graveolens, with vacuolization in the tegument and spines, preventing externalization. The results of the study present OEs with efficient ovicidal and adulticidal activity.

Efficacy of flukicides on Fasciola gigantica, a food-borne zoonotic helminth affecting livestock in Bangladesh

Fasciola gigantica, the causative agent of tropical fasciolosis, is a food-borne zoonotic trematode that affects around 80% livestock of Bangladesh. Triclabendazole (TCBZ), nitroxynil (NTON) and oxyclozanide (OCZN) are frequently used against fascioliasis; however, the current status of potency of these flukicides was unknown. In this study, in vitro efficacy of TCBZ, NTON and OCZN at various concentrations on F. gigantica has been evaluated by relative motility (RM), morphological distortions of apical cone through an inverted microscope, architectural and ultra-structural changes through histopathological and scanning electron microscopy (SEM). It is observed that TCBZ, NTON and OCZN at higher concentrations significantly (P < 0.05) reduced RM of the flukes compared to untreated control. NTON at 150 μg mL−1 was the most potent to reduce the motility within 4 h whereas TCBZ and OCZN were much delayed. Histopathological changes showed swollen, extensive cracking, numerous vacuoles and splitting of the tegument surrounding the spines; spine dislodged from its socket in treated flukes compared to untreated worms. Histopathological changes were more conspicuous at higher doses of TCBZ, NTON and OCZN. SEM has shown the disruption of the apical cone, apart from swelling of the tegument on the ventral surface corrugation and disruption of the ventral apical cone. All these changes indicate that NTON is the most potent in killing flukes in vitro among the tested flukicides and suggest the presence of TCBZ-resistant fluke populations in Bangladesh. It is imperative to explore the in vivo effects of these flukicides and subsequently their molecular mechanisms.

Transcriptomic and proteomic profiling of peptidase expression in Fasciola hepatica eggs developing at host's body temperature

Fasciola hepatica is a global parasite of livestock which also causes a neglected zoonosis in humans. The parasite’s communication with the host during its complicated lifecycle is based on an ingenious enzymatic apparatus which includes a variety of peptidases. These enzymes are implicated in parasite migration, pathogenesis of the disease, and modification of host immune response. Although the dynamics of proteolytic machinery produced by intra-mammalian F. hepatica life stages has been previously investigated in great detail, peptidases of the eggs so far received little scientific attention. In this study, we performed a comparative RNA-seq analysis aimed at identification of peptidases expressed in F. hepatica eggs, cultured at 37 °C to represent gall bladder retained eggs, for different time periods and employed mass spectrometry in order to identify and quantify peptidases translated in F. hepatica egg lysates. We demonstrated that F. hepatica eggs undergo significant molecular changes when cultured at the physiological temperature of the definitive host. Egg transcriptome is subject to numerous subtle changes while their proteome is even more variable. The peptidase profile is considerably modified on both transcriptome and proteome level. Finally, we measured and classified proteolytic activities in extracts from F. hepatica eggs using a library of fluorogenic substrates and peptidase class-selective inhibitors. Activities of threonine peptidases were detected constantly, while the cysteine peptidases prevailing in freshly laid eggs are substituted by aspartic peptidase and metallopeptidase activities in the later stages of egg development.

Targeting Secreted Protease/Anti-Protease Balance as a Vaccine Strategy against the Helminth Fasciola hepatica

The liver fluke Fasciola hepatica is an economically important global pathogen of humans and their livestock. To facilitate host invasion and migration, F. hepatica secretes an abundance of cathepsin peptidases but prevents excessive damage to both parasite and host tissues by co-secreting regulatory peptidase inhibitors, cystatins/stefins and Kunitz-type inhibitors. Here, we report a vaccine strategy aimed at disrupting the parasite’s protease/anti-protease balance by targeting these key inhibitors. Our vaccine cocktail containing three recombinant stefins (rFhStf-1, rFhStf-2, rFhStf-3) and a Kunitz-type inhibitor (rFhKT1) formulated in adjuvant Montanide 61VG was assessed in two independent sheep trials. While fluke burden was not reduced in either trial, in Trial 1 the vaccinated animals showed significantly greater weight gain (p < 0.05) relative to the non-vaccinated control group. In both trials we observed a significant reduction in egg viability (36–42%). Multivariate regression analyses showed vaccination and increased levels of IgG2 antibodies specific for the F. hepatica peptidase inhibitors were positive indicators for increased weight gain and levels of haemoglobin within the normal range at 16 weeks post-infection (wpi; p < 0.05). These studies point to the potential of targeting peptidase inhibitors as vaccine cocktails for fasciolosis control in sheep.

Prevalence and gross pathology of liver fluke in macropods cohabiting livestock farms in north eastern NSW, Australia, and diagnosis using cELISA

Liver fluke (Fasciola hepatica) is a parasite of herbivores including wildlife. Macropods, such as Eastern grey kangaroo (Macropus giganteus) and Common wallaroo (Osphranter robustus), are frequently observed sharing grazing sites with domestic livestock. The impact of Macropods, as reservoirs of infection, on livestock production and risks to cross-species transmission are largely unknown. In Phase 1 of this study, liver and faecal samples were collected from 245 Macropods (181 Eastern grey kangaroos, 64 Common wallaroos) cohabiting livestock farms (n = 7) in the Northern Tablelands regions of New South Wales. Total fluke (TFC) and fluke eggs (FEC) were counted in the liver and faeces, respectively, to assess prevalence. Faecal antigens were also measured using the commercial Bio-X Diagnostic Monoscreen AgELISA Fasciola hepatica kit (cELISA) to assess suitability as a diagnostic tool. In Phase 2, Macropod faecal samples were collected from 60 livestock farms to conduct FEC and assess prevalence by region. Liver fluke was prevalent in 22% of Eastern grey kangaroo and 20% of Common wallaroos with prevalence as high as 45% in the Eastern grey kangaroo. Fluke burdens ranged from 1 to 122 flukes (mean = 9 flukes) with a FEC range of 0–195 eggs per gram (epg) of faeces (mean = 18 epg). Evidence of dead and live flukes trapped within fibrotic capsules confirms the ability of Macropods to resolve infections. cELISA proved highly specific (100%) and sensitive (98%) in liver fluke detection however fibrotic capsules observed in the liver may reduce the correlation of coproantigens with fluke burden. Phase 2 revealed that 27% of livestock farms had Macropods infected with liver fluke. Overall, this study confirmed Eastern grey kangaroo and Common wallaroo are susceptible hosts and potential reservoirs for liver fluke and, monitoring infections in Macropods would assist in livestock disease management.

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Eastern grey kangaroo and Common wallaroo harbouring liver fluke in north eastern Australia.

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Macropods with liver fluke may limit effectiveness of integrated parasite management strategies for liver fluke control.

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Monitoring Macropod populations within liver fluke endemic regions may assist livestock disease management.

Kangaroos and liver fluke: The role played in cross-species transmission and drug resistance

Australian livestock are challenged by liver fluke (Fasciola hepatica) in grazing regions endemic to the intermediate snail host. Liver fluke infests a wide range of herbivores including free-roaming wildlife such as kangaroos (Macropods). The role played by Macropods in cross-species transmission and as vectors for anthelmintic resistance is largely unknown. In Phase 1 of this study, liver fluke of Eastern grey kangaroo (Macropus giganteus Shaw, 1790) origin (Kangaroo isolate) were artificially infected in sheep to confirm establishment and cross-species transmission. In Phase 2, the efficacy of triclabendazole (TCBZ) was assessed in vivo against the Kangaroo isolate to identify any drug resistance. Forty (40) merino sheep were housed in pens and allocated to one of 4 groups (Groups 1-4). Groups 1 and 2 were artificially infected with a TCBZ resistant liver fluke isolate (Oberon) originating from sheep whilst Groups 3 and 4 were infected with the Kangaroo isolate (Phase 1). At 9 weeks post infection (wpi), sheep in Groups 2 and 4 were treated with 10 mg/kg TCBZ (Phase 2). Sheep were subsequently euthanased at 11 wpi to conduct total fluke counts (TFC) in the liver. Faecal samples were collected fortnightly to measure fluke egg counts and coproantigens. Individual blood samples were collected, concurrently with faecal sampling, to monitor haematocrit and plasma proteins levels. Liver fluke of kangaroo origin established to patent infections in sheep with similar establishment and pathogenicity to the Oberon isolate. TCBZ achieved an 86 % reduction in TFC (99.8 % - adult fluke, 0 % - immature fluke) in sheep with the Kangaroo isolate and a 28 % reduction in the Oberon isolate (37 % - adult, 0 % - immature fluke). An 89 % reduction in faecal coproantigens was observed in sheep with the Kangaroo isolate and no reduction in sheep with Oberon. This study confirmed cross-species transmission of liver fluke from a kangaroo to sheep. When cohabiting the livestock grazing environment, kangaroos may act as reservoirs for liver fluke and vectors for drug resistance within liver fluke endemic areas.

Vaccination with cathepsin L phage-exposed mimotopes, single or in combination, reduce size, fluke burden, egg production and viability in sheep experimentally infected with Fasciola hepatica

Fascioliasis is a worldwide emergent zoonotic disease that significantly constrains the productivity of livestock. In this study, fluke burdens, liver fluke size and biomass, faecal eggs counts, serum levels of hepatic enzymes and immune response were assessed in sheep vaccinated with peptide mimotopes of cathepsin L and infected with metacercariae. A total of 25 sheep were allocated randomly into five groups of five animals each, and experimental groups were immunised with 1 × 10¹³ filamentous phage particles of cathepsin L1 (CL1) (TPWKDKQ), CL2 (YGSCFLR) and mixtures of CL1 + CL2 mimotopes, in combination with Quil A adjuvant, and wild-type M13KE phage in a two-vaccination scheme on weeks 0 and 4. The control group received phosphate-buffered saline. All groups were challenged with 300 metacercariae two weeks after the last immunisation and euthanised 16 weeks later. The CL1 vaccine was estimated to provide 57.58% protection compared with the control group; no effect was observed in animals immunised with CL2 and CL1 + CL2 (33.14% and 11.63%, respectively). However, animals receiving CL2 had a significant reduction in parasite egg output. Vaccinated animals showed a significant reduction in fluke length and width and wet weights. In the CL1 group, there was a significant reduction in the total biomass of parasites recovered. Egg development was divided into seven stages: dead, empty, unembryonated, cell division, eyespot, hatched and hatching. The highest percentage of developmental stages was detected for vaccinated sheep administered CL1 + CL2 with cell division, and the lowest percentage was observed in the hatching stage. Furthermore, a significant difference in all developmental stages was observed between vaccinated animals and the control group (P < 0.01). The levels of anti-phage total IgG in immune sera increased significantly at four weeks after immunisation and were always significantly higher for cathepsin L vaccine group than in the challenged control group. Total IgG was inversely and significantly correlated with worm burden in the CL1 group.

Transcriptome and Secretome Analysis of Intra-Mammalian Life-Stages of Calicophoron daubneyi Reveals Adaptation to a Unique Host Environment

Paramphistomosis, caused by the rumen fluke, Calicophoron daubneyi, is a parasitic infection of ruminant livestock, which has seen a rapid rise in prevalence throughout Western Europe in recent years. After ingestion of metacercariae (parasite cysts) by the mammalian host, newly excysted juveniles (NEJs) emerge and invade the duodenal submucosa, which causes significant pathology in heavy infections. The immature flukes then migrate upward, along the gastrointestinal tract, and enter the rumen where they mature and begin to produce eggs. Despite their emergence, and sporadic outbreaks of acute disease, we know little about the molecular mechanisms used by C. daubneyi to establish infection, acquire nutrients, and avoid the host immune response. Here, transcriptome analysis of four intramammalian life-cycle stages, integrated with secretome analysis of the NEJ and adult parasites (responsible for acute and chronic diseases, respectively), revealed how the expression and secretion of selected families of virulence factors and immunomodulators are regulated in accordance with fluke development and migration. Our data show that while a family of cathepsins B with varying S2 subsite residues (indicating distinct substrate specificities) is differentially secreted by NEJs and adult flukes, cathepsins L and F are secreted in low abundance by NEJs only. We found that C. daubneyi has an expanded family of aspartic peptidases, which is upregulated in adult worms, although they are under-represented in the secretome. The most abundant proteins in adult fluke secretions were helminth defense molecules that likely establish an immune environment permissive to fluke survival and/or neutralize pathogen-associated molecular patterns such as bacterial lipopolysaccharide in the microbiome-rich rumen. The distinct collection of molecules secreted by C. daubneyi allowed the development of the first coproantigen-based ELISA for paramphistomosis which, importantly, did not recognize antigens from other helminths commonly found as coinfections with rumen fluke.

Fasciolosis in India: An overview

Fasciolosis in ruminants is a relentless constraint in the livestock industry across the world. Immuno-prophylactic vaccines against fasciolosis may not come up in near future, rendering the control of this scourge with chemotherapy and snail population control. With the alarming threats of anti-fasciolid drug resistance reported from certain parts of the world; the control of fasciolosis should be directed towards the development of rapid and reliable diagnostic tools to execute the specific and discrete treatment. Understanding the epidemiology of Fasciola, its genomics and proteomics, host-parasite interplay, and advances in drug design research is vital for improving animal health that would ultimately succour to meet the ever-increasing demand for food. Due to possible differences in immune response depending on the species of the host and parasite, immuno-prophylactic studies in India should aim at achieving protective efficacy in buffalo against F. gigantica as workers from other countries concentrate primarily on vaccination of cattle and sheep against F. hepatica. This manuscript focused on the research that has been carried out in India for understanding the epidemiology, genetic diversity, immuno-diagnosis, and possible control measure in terms of immuno-prophylaxis and drug designing against tropical fasciolosis caused by Fasciola gigantica.

Fascioliasis and fasciolopsiasis: Current knowledge and future trends

Food-borne zoonotic trematodiases are classified as neglected diseases by the World Health Organization. Among them, fascioliasis is caused worldwide by Fasciola hepatica and F. gigantica, and represent a huge problem in livestock production and human health in endemic areas. Fasciolopsis buski, restricted to specific regions of Asia, causes fasciolopsiasis. The incidence of these trematodiases is underestimated due to under-reporting and to the lack of sensitive and widely accepted tool for their diagnosis. This, together with a rising trend in reporting of drug resistance and the need for an effective vaccine against these parasites, pose a challenge in the effective control of these diseases. Here, the latest reports on fascioliasis outbreaks between 2000 and 2020 and the most recent advances in their epidemiology, diagnosis, treatment and control are revised. Finally, future needs in the field of fascioliasis and fasciolopsiasis are presented, which could be addressed based on current knowledge and by means of new emerging technologies.

Evaluation of anthelmintic drugs against egg development of rumen flukes recovered from cattle raised in the humid tropics of Mexico

Paramphistomosis is a parasitic disease endemic in ruminants nearly worldwide. In the present study, an in vitro screening of the main anthelmintics used in Mexico was carried out to determine the mean lethal dose for rumen fluke eggs from cattle in a humid, warm region. Rumen flukes were obtained from cattle slaughtered in the states of Tabasco and Chiapas in Mexico. Eggs were collected using a 37-μm sieve and quantified. Then, an in vitro incubation study was performed: 100 eggs were placed into the wells of polystyrene microtiter plates. Anthelmintic products were tested on the eggs at concentrations ranging from 0.0015 to 3.0 mg/ml for rafoxanide, 0.0025 to 10.20 mg/ml for nitroxinil and 0.0015 to 3 mg/ml for closantel to determine the median lethal dose (LD50) and maximum lethal dose (LD99). A control group (water) was included in each plate. Three different species of rumen flukes (Calicophoron brothriophoron, Calicophoron clavula and Paramphistomum cervi) belonging to five isolates were identified. Nitroxinil had the highest efficacy against rumen fluke eggs, with an LD50 of 0.11 to 65 μg/ml, whereas rafoxanide showed the lowest efficacy with an LD50 ranging from 500 to 1713 μg/ml. Closantel showed high variability in the LD50 among the different analysed isolates (17 to 122 μg/ml). The evaluated flukicidal drugs presented differential efficacy against the development of rumen fluke eggs. The efficacy of the drugs will vary depending on the geographical area of origin of the animals.

Rumen fluke, Fischoederius elongatus (Trematoda: Gastrothylacidae): Preliminary investigation of suitable conditions for egg hatching

Various temperatures may have different effects on the distribution of paramphistomes that cause amphistomosis in cattle, including Fischoederius elongatus. Therefore, this study aimed to investigate the effects of different temperature treatments on F. elongatus hatching, with specific identification using morphological, histological, and phylogenetic analysis. All specimens were collected from two buffalo (Bubalus bubalis) rumens in a slaughterhouse in Pathum Thani province, Thailand. F. elongatus adults were kept in phosphate buffered saline solution for egg collection. The egg specimens were incubated in tap water under four different temperature conditions: 4 °C, room temperature, 35 °C, and 55 °C. For 31 days, egg specimens of approximately 50 eggs per observation were randomly classified into three stages (undeveloped, developing (or pre-hatching), and hatched). To test the change of temperature, cold water was used for thermal shocking the egg specimens. The results indicated that rates of egg development and hatching were highest at 35 °C and significantly higher than in the other treatments (P < 0.001). In addition, statistical investigation of pre-thermal shock results also suggesting that 35 ºC may be a suitable condition for hatching F. elongatus eggs and could enhance the developing and hatching by longer periods of incubation for more than 26 days. Even changing the temperature could affect development and hatching but initial environment temperature remains an important factor. These data could be used for efficient epidemiological prediction of F. elongatus and applied in livestock management.

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.

Inhibitory Activities of Ethanolic Extracts of Two Macrofungi Against Eggs and Miracidia of Fasciola Spp

Fascioliasis is a disease of livestock which is now recognized as an emerging disease in humans. Cantharellus cibarius and Ganoderma applanatum are known for their medicinal properties. The use of ethanolic extracts of these macrofungi against the eggs and miracidia of Fasciola spp. is a promising method to break the parasite transmission cycle. The aim of the study is to evaluate the inhibitory effects of ethanolic extracts of the mushrooms on eggs and miracidia of Fasciola spp. Concentrated eggs and miracidia of Fasciola spp. were exposed to different concentrations (1-8 mg/ml) of extracts of Ganoderma applanatum (GEE) and Cantharellus cibarius (CEE) at different time intervals. GEE showed superior antiparasitic activities when compared to CEE at all concentrations tested. Significant positive correlations were observed between the concentration of GEE and mortality in miracidia (r=0.980, P <0.05) and CEE and mortality in miracidia (r= 0.968, P <0.05). The study showed that ethanolic extracts of G. applanatum and C. cibarius have ovicidal and miracicidal activities. While G. applanatum showed excellent activities, activities in C. cibarius were moderate. Therefore, these mushroom extracts can be regarded as promising sources of bioactive compounds that could be developed into ovicides and miracicides.

Ovicidal in vitro activity of 2-aryl-3-(2-morpholinoethyl)thiazolidin-4-ones and 2-aryl-3-(3-morpholinopropyl)thiazolidin-4-ones against Fasciola hepatica (Linnaeus, 1758)

Although there is a variety of biological activity reports regarding compounds derived from thiazolidin-4-ones, no data related to ovicidal activity against trematodes, particularly Fasciola hepatica are available. Since there are reports about anthelmintic resistance in F. hepatica, new drugs are required. Thus, this study evaluated ovicidal action in vitro against F. hepatica eggs in two systematic series of thiazolidin-4-ones: 2-aryl-3-(2-morpholinoethyl)thiazolidin-4-ones (1a-h) and 2-aryl-3-(3-morpholinopropyl)thiazolidin-4-ones (2a-h) at different concentrations (20, 2, 0.2, 0.02 and 0.002 μg/ml). The egg hatch assay (EHA) was used to evaluate the ovicidal action property of such compounds. In addition, potential negative effects of the compounds on metabolic activity of bovine kidney (MDBK) cells were evaluated by determining mitochondrial dehydrogenase activity. The eggs used in the EHA were obtained from parasites removed from the liver of cattle, which were discarded by slaugh after sanitary inspection. The results of EHA showed that compounds 2a-h exhibited ovicidal activity, especially compounds 2b which showed 90% ovicidal activity and viability of 93% MDBK cells at the concentration of 2 μg/ml; and 2e with 96-99% ovicidal activity at 0.2 μg/ml, 0.02 μg/ml and 0.002 μg/ml. The results show the potential of compound 2b to continue the studies in the production of new compounds with anthelmintic action.

Fasciola and fasciolosis in ruminants in Europe: Identifying research needs

Fasciola hepatica is a trematode parasite with a global distribution, which is responsible for considerable disease and production losses in a range of food producing species. It is also identified by WHO as a re-emerging neglected tropical disease associated with endemic and epidemic outbreaks of disease in human populations. In Europe, F. hepatica is mostly associated with disease in sheep, cattle and goats. This study reviews the most recent advances in our understanding of the transmission, diagnosis, epidemiology and the economic impact of fasciolosis. We also focus on the impact of the spread of resistance to anthelmintics used to control F. hepatica and consider how vaccines might be developed and applied in the context of the immune-modulation driven by the parasite. Several major research gaps are identified which, when addressed, will contribute to providing focussed and where possible, bespoke, advice for farmers on how to integrate stock management and diagnosis with vaccination and/or targeted treatment to more effectively control the parasite in the face of increasing the prevalence of infection and spread of anthelmintic resistance that are likely to be exacerbated by climate change.

Comparative ovicidal activity of Moringa oleifera leaf extracts on Fasciola gigantica eggs

BACKGROUND

Fasciolosis is an important zoonotic disease affecting the productive performance of farm animals in Egypt.

AIM

The aim of the present study was comparing the ovicidal effect of different extracts as an alcoholic (Methanolic and Ethanolic) and aqueous Moringa oleifera leaf extracts on Fasciola gigantica non-embryonated and developed eggs.

MATERIALS AND METHODS

Tested concentrations of extracts ranged from 12.5 to 800 mg/ml. Nitroxynil was used as reference drug with a dose of 100 mg/ml.

RESULTS

M. oleifera alcoholic and aqueous extracts showed a concentration-dependent ovicidal effect on F. gigantica non-embryonated and developed eggs. Based on LC50 values, water extract showed the highest ovicidal activity since it registered the lowest values of 2.6 mg/ml on non-embryonated eggs. Non-embryonated eggs were more susceptible to aqueous extract than developed eggs. On the other hand, the developed eggs were more susceptible to ethanolic extract than non-embryonated eggs even the lowest LC50 (12.38 mg/ml).

CONCLUSION

M. oleifera leaf extracts especially aqueous extract could be a promising step in the field of controlling fascioliasis. Further, in vivo studies are needed to enlighten the therapeutic potential of M. oleifera extracts in treating F. gigantica infection.

Disruption of egg production by triclabendazole-resistant Fasciola hepatica following treatment with a commercial preparation of myrrh (Mirazid)

An in vitro study has been carried out to monitor changes to the female reproductive system in adult triclabendazole (TCBZ)-resistant Fasciola hepatica following treatment with a commercial preparation of myrrh ("Mirazid"). Flukes were immersed for 6 h and 24 h in myrrh extract at a concentration of 200 µg/ml, then processed for histological and transmission electron microscope (TEM) examination of the uterus, Mehlis' gland, ovary and vitellaria. Egg production had become abnormal at 6 h post-treatment (pt), with the uterine lumen being filled with free vitelline cells and masses of shell protein material; few eggs were present. At 24 h pt, no eggs were present. Distinct changes to the ovary and Mehlis' gland were only observed after 24 h incubation in Mirazid. The ovary contained numbers of apoptotic oogonia and oocytes. In the Mehlis' gland, the S1 cells were disorganised and the processes from them were vacuolated, although the disruption was not significant. More severe changes were observed in the vitelline cells and follicles. After 6 h incubation in Mirazid, although the gross organisation of the vitelline follicles appeared to be normal, nuclear changes indicative of the early stages of apoptosis were observed in the stem cells and shell protein production by the mature cells had decreased. At 24 h pt, a distinct shift in cell population was evident, with the follicles containing mainly mature cells and spaces were present between the cells. The shell globule clusters in the mature cells were disorganised. In more severely-affected follicles, cells were seen to be breaking down, with karyolytic nuclei and disintegrating cytoplasm. Overall, the results have shown that exposure to Mirazid treatment had a severe impact on egg production by TCBZ-resistant flukes, an effect that was mediated by disruption of the vitelline cells and of the mechanism co-ordinating egg formation in the ootype.

A review of bovine fasciolosis and other trematode infections in Nigeria

Trematode infections cause serious economic losses to livestock worldwide. Global production losses due to fasciolosis alone exceed US$3 billion annually. Many trematode infections are also zoonotic and thus a public health concern. The World Health Organization has estimated that about 56 million people worldwide are infected by at least one zoonotic trematode species, and up to 750 million people are at risk of infection. Fasciolosis caused by the fluke Fasciola gigantica is endemic in Nigeria and is one of the most common causes of liver condemnation in abattoirs. Total cattle losses from Fasciola infection in Nigeria have been estimated to cost £32.5 million. Other trematode infections of cattle, including paramphistomosis, dicrocoeliasis and schistosomiasis, have all been reported in various parts of Nigeria, with varying prevalence. Most publications on trematode infections are limited to Nigerian local and national journals, with very few international reports. This paper therefore summarized the current data on distribution, control and zoonotic trematode infections in Nigeria and other African countries. We also identified research gaps and made recommendations for future research and areas for funding for policy/planning.

Ultrastructural changes to the tegumental system and gastrodermal cells of adult Fasciola hepatica following treatment in vivo with a commercial preparation of myrrh (Mirazid)

An in vivo study in the laboratory rat model has been carried out to monitor changes to the tegument and gut of adult Fasciola hepatica following treatment with myrrh ('Mirazid'). Rats infected with the triclabendazole-resistant Dutch isolate were dosed orally with Mirazid at a concentration of 250 mg/kg and flukes recovered 2, 3 and 7 days post-treatment (pt). The flukes were processed for examination by scanning and transmission electron microscopy. A variety of changes to the external surface were observed, culminating in the sloughing of the tegumental syncytium. Internal changes to the syncytium and tegumental cell bodies were more severe and were evident from 2 days pt onwards. Swelling of the basal infolds (leading to flooding of the surface layer) and a decline in secretory body production were the major changes seen. The gastrodermal cells were less severely affected than the tegument, pointing to a trans-tegumental route of uptake for Mirazid by the fluke. Some loss of muscle fibres in the main somatic muscle layers was observed, which may be correlated with the decline in movement of flukes seen at recovery.

Assessment of flukicide efficacy against Fasciola hepatica in sheep in Sweden in the absence of a standardised test

Anthelmintic resistance (AR) to Fasciola hepatica is emerging worldwide. Recently, AR to the adulticide compound albendazole (ABZ) was shown in Argentina and Spain. In Sweden, ABZ treatment failure against F. hepatica was first reported in sheep in 2012. The present study tested the efficacy of ABZ and triclabendazole (TCBZ) in sheep naturally infected with F. hepatica using a combination of three different diagnostic methods: faecal egg counts (FEC), coproantigen ELISA (cELISA) and Fasciola egg hatch test (FEHT). Two deworming trials, in November 2014 and January 2015, were performed on two sheep farms (farms A and B) in south-western Sweden. Except ABZ in November, treatment with ABZ or TCBZ achieved sufficient efficacy (97-100%) against adult F. hepatica on farm A. In contrast, ABZ treatment failed in the sheep flock on farm B, despite low initial faecal egg output. On farm B, ABZ efficacy based on FEC was 67% (95% CI: 35-84) and four of eight ewes tested were coproantigen-positive 21 days post-treatment. Ovicidal activity of ABZ against Fasciola eggs in isolates from both farms and one additional bovine isolate were tested by FEHT to exclude the presence of juvenile flukes and other factors such as dosing failure and poor quality of drug product. Irrespective of drug trial, data from FEHT showed significantly lower ovicidal activity of ABZ for the ovine farm B isolate than for the isolate from farm A. This confirms that the low efficacy of ABZ in sheep flock B was associated with ABZ resistance. Overall, the usefulness of three complementary methods for detection of ABZ resistance in the field was demonstrated.

Disruption of spermatogenesis in the liver fluke, Fasciola hepatica by two artemisinin derivatives, artemether and artesunate

An in vivo study in the laboratory rat model has been carried out to monitor changes to the spermatogenic cells in the testis tubules of adult Fasciola hepatica following treatment with the artemisinins, artemether and artesunate. Rats infected with the triclabendazole (TCBZ)-resistant Sligo isolate were dosed orally with artemether at a concentration of 200 mg/kg and flukes recovered at 24, 48 and 72 h post treatment (pt). Rats infected with the TCBZ-resistant Oberon isolate were dosed orally with artesunate at a concentration of 200 mg/kg and flukes recovered 24, 48, 72 and 96 h pt. The flukes were processed for histological and transmission electron microscope (TEM) examination. Changes to the spermatogenic cells were evident at 24 h pt with artemether. The spermatogonial and spermatocyte cells contained abnormal mitochondria, there were fewer spermatids and spermatozoa in the tubules than normal, and a number of cells showed signs of apoptosis. There was a further decline in cell numbers at 48 h pt and the organization of the spermatocyte and spermatid rosettes was atypical. Sperm formation had become abnormal and those spermatozoa present possessed only a single axoneme. By 72 h pt, the testis tubules were vacuolated and filled with abnormal cells and cell debris. Only spermatogonial cells could be identified and there was widespread evidence of apoptosis in the cells. Distinct cellular changes following artesunate treatment did not become apparent until 48 h pt. The changes seen were similar to those described for artemether, but were generally less severe at matching time-periods. The fine structural changes occurring in the spermatogenic cells were compared to those observed in other cell types and fluke tissues and the overall information was collated to identify the cellular targets for artemisinin action and to establish the time-line for drug action.

Screening anthelmintic resistance to triclabendazole in Fasciola hepatica isolated from sheep by means of an egg hatch assay

Background

In the present study, the detection of anthelmintic resistance to triclabendazole (TCBZ) in sheep infected by Fasciola hepatica was studied using an egg hatch assay (EHA). F. hepatica eggs were recovered from bile and faeces of infected animals by isolates with different grade of anthelmintic resistance to TCBZ: i) a resistant isolate (RT); ii) a susceptible isolate (ST); iii) naturally infected sheep by a susceptible field strain (FST). In the EHA the percentage of hatched eggs were calculated according to the following concentrations of TCBZ diluted in dimethyl-sulfoxide (DMSO): 0.05, 0.2, 1, 5, and 25 μg/ml.

Results

In relation to the EHAs carried out with the eggs from bile of sheep infected by ST, differences were found in the percentage of hatched eggs between the control well, only with DMSO, and the two highest concentrations of TCBZ (5 and 25 μg/m) (p < 0.05). However, when we tested the drug with the eggs from the bile of sheep infected by RT, the percentage of hatched eggs was similar among all concentrations. Since the range of hatching varied between isolates, we calculated the ratio of the results of each concentration to its control value confirming the higher hatching in RT than in ST.

We developed an EHA with eggs recovered from faeces in order to avoid the slaughter of sheep. The results of the EHAs with the isolate ST showed differences in the percentage of hatching between the highest concentration (25 μg/ml) and the control well (p < 0.05); however, these differences were not confirmed under field conditions with the strain FST.

Conclusions

The ovicidal effect of TCBZ in F. hepatica eggs from bile was shown using a commercial formulation diluted in DMSO with a minimum concentration of 5 μg/ml. However, in eggs recovered from faeces the results are not conclusive. The cleaning of eggs recovered from faeces is an important issue that should be reviewed and standardized before comparing results between susceptible and resistant isolates in this kind of EHA.

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.

A comparative study on the impact of two artemisinin derivatives, artemether and artesunate, on the female reproductive system of Fasciola hepatica

An in vivo study in the laboratory rat model has been carried out to monitor changes to the female reproductive system in adult Fasciola hepatica following treatment with the artemisinins, artemether and artesunate. Rats infected with the triclabendazole (TCBZ)-resistant Sligo isolate were dosed orally with artemether at a concentration of 200mg/kg and flukes recovered at 24, 48 and 72 h post-treatment (pt). Rats infected with the TCBZ-resistant Oberon isolate were dosed orally with artesunate at a concentration of 200mg/kg and flukes recovered 24, 48, 72 and 96 h pt. The flukes were processed for histological and transmission electron microscope (TEM) examination of the uterus, Mehlis' gland, ovary and vitellaria. After treatment with artemether, egg production had become abnormal by 72 h pt, with free vitelline cells and masses of shell protein material within the uterus; spermatozoa were absent. The Mehlis' gland and ovary retained a normal morphology over the 3-day period. A change in the cell population in the vitelline follicles was seen at 48 h pt, with a decline in the number of immature cells. This became more marked by 72 h and the follicles became progressively vacuolated over the 3-day period. At the TEM level, there were changes in the immature vitelline cells at 24h pt, as evidenced by a decrease in shell protein production and the presence of lipid droplets and abnormal mitochondria. Spaces in the follicles separated the cells from each other. The changes became progressively more severe with time, so that, by 72 h pt, the follicles were very disrupted, containing cells in the advanced stages of apoptotic breakdown. In extreme cases, the follicles were scarcely recognisable and had become filled with cellular debris. Fine structural changes to the vitelline cells induced by artesunate treatment were similar to those described for artemether, but generally occurred more quickly and were greater; this was particularly true of the swelling of the ger cisternae. Overall, the results have shown that artemisinin treatment has a severe impact on egg production by TCBZ-resistant flukes, an effect that is mediated by disruption of the vitelline cells.

Disruption of vitellogenesis and spermatogenesis by triclabendazole (TCBZ) in a TCBZ-resistant isolate of Fasciola hepatica following incubation in vitro with a P-glycoprotein inhibitor

A study has been carried out to investigate whether the action of triclabendazole (TCBZ) against Fasciola hepatica is altered by inhibition of P-glycoprotein (Pgp)-linked drug efflux pumps. The Sligo TCBZ-resistant fluke isolate was used for these experiments and the Pgp inhibitor selected was R(+)-verapamil [R(+)-VPL]. In the first experiment, flukes were initially incubated for 2 h in R(+)-VPL (100 μm), then incubated in R(+)-VPL+triclabendazole sulphoxide (TCBZ.SO) (50 μg mL−1, or 133·1 μm) until flukes ceased movement (at 9 h post-treatment). In a second experiment, flukes were incubated in TCBZ.SO alone and removed from the incubation medium following cessation of motility (after 15 h). In the third experiment, flukes were incubated for 24 h in R(+)-VPL on its own. Changes to the testis tubules and vitelline follicles following drug treatment and following Pgp inhibition were assessed by means of light microscope histology and transmission electron microscopy. Incubation of the Sligo isolate in either R(+)-VPL or TCBZ.SO on their own had a limited impact on the morphology of the two tissues. Greater disruption was observed when the drugs were combined, in terms of the block in development of the spermatogenic and vitelline cells and the apoptotic breakdown of the remaining cells. Sperm formation was severely affected and abnormal. Large spaces appeared in the vitelline follicles and synthesis of shell protein was disrupted. The results of this study support the concept of altered drug efflux in TCBZ-resistant flukes and indicate that drug transporters may play a role in the development of drug resistance.

Motility of Fasciola hepatica miracidia assessed with a computer-assisted sperm analyser

The motility parameters of Fasciola hepatica miracidia were assessed at different temperatures and times post-hatching using computer-assisted sperm analysis. Eggs were incubated at 22°C or 25°C for 14 days. Five motion parameters were evaluated at different incubation temperatures up to 10 h post-hatching. No differences were observed in the percentage that hatched after incubation at the two different temperatures. However, the straight-line velocity of miracidia following incubation at 22°C was significantly different from that observed at 25°C (P< 0.01). All miracidium motion parameters at different post-hatching temperatures showed an overall decrease at the end of the experiment. Those miracidia hatching from eggs incubated at 25°C had a higher velocity of 1673.3 μm/s compared with 1553.3 μm/s at 22°C. Velocity parameters increased as the post-hatching temperature increased from 22°C to 37°C.

The anti-fasciolasis properties of silver nanoparticles produced by Trichoderma harzianum and their improvement of the anti-fasciolasis drug triclabendazole

Recently, new strains of Fasciola demonstrated drug resistance, which increased the need for new drugs or improvement of the present drugs. Nanotechnology is expected to open some new opportunities to fight and prevent diseases using an atomic scale tailoring of materials. The ability to uncover the structure and function of biosystems at the nanoscale, stimulates research leading to improvement in biology, biotechnology, medicine and healthcare. The size of nanomaterials is similar to that of most biological molecules and structures; therefore, nanomaterials can be useful for both in vivo and in vitro biomedical research and applications. Therefore, this work aimed to isolate fungal strains from Taif soil samples, which have the ability to synthesize silver nanoparticles. The fungus Trichoderma harzianum, when challenged with silver nitrate solution, accumulated silver nanoparticles (AgNBs) on the surface of its cell wall in 72 h. These nanoparticles, dislodged by ultrasonication, showed an absorption peak at 420 nm in a UV-visible spectrum, corresponding to the plasmon resonance of silver nanoparticles. The transmission electron micrographs of dislodged nanoparticles in aqueous solution showed the production of reasonably monodisperse silver nanoparticles (average particle size: 4.66 nm) by the fungus. The percentage of non hatching eggs treated with the Triclabendazole drug was 69.67%, while this percentage increased to 89.67% in combination with drug and AgNPs.

Identification of putative markers of triclabendazole resistance by a genome-wide analysis of genetically recombinant Fasciola hepatica

Despite years of investigation into triclabendazole (TCBZ) resistance in Fasciola hepatica, the genetic mechanisms responsible remain unknown. Extensive analysis of multiple triclabendazole-susceptible and -resistant isolates using a combination of experimental in vivo and in vitro approaches has been carried out, yet few, if any, genes have been demonstrated experimentally to be associated with resistance phenotypes in the field. In this review we summarize the current understanding of TCBZ resistance from the approaches employed to date. We report the current genomic and genetic resources for F. hepatica that are available to facilitate novel functional genomics and genetic experiments for this parasite in the future. Finally, we describe our own non-biased approach to mapping the major genetic loci involved in conferring TCBZ resistance in F. hepatica.

Testing albendazole resistance in Fasciola hepatica: validation of an egg hatch test with isolates from South America and the United Kingdom

The main goal of the current work was to develop and validate an in vitro fluke egg hatch test, as a method for the detection of albendazole (ABZ) resistance in the liver fluke, Fasciola hepatica. Fluke eggs (200/ml, n= 5) from six different isolates were used in the current experimental work. They were obtained from different geographical locations and named Cullompton (UK), CEDIVE (Chascomus, Argentina), INTA-Bariloche (Bariloche, Argentina), Rubino (Uruguay), Cajamarca (Perú) and Río Chico (Catamarca, Argentina). The fluke eggs were incubated (25°C) for a 12-h period in the presence of either ABZ or its sulphoxide metabolite (ABZ.SO) (5, 0.5 or 0.05 nmol/ml). Untreated eggs were incubated as a control. Incubated eggs (with or without drug present) were kept in darkness at 25°C for 15 days. Afterwards, the trematode eggs were exposed to daylight over a 2-h period. Hatched and unhatched eggs were evaluated using an optical microscope, and the ovicidal activity was assessed for each fluke isolate. A very low ovicidal activity ( ≤ 13.4%) was observed in the ABZ-resistant CEDIVE isolate for both ABZ and ABZ.SO. Conversely, in the INTA-Bariloche and Río Chico isolates, which are suspected to be susceptible to ABZ, ovicidal activities ≥ 70.3% were observed after incubation with ABZ at the lowest concentration tested (0.05 nmol/ml). This finding correlates with that previously described for the ABZ-susceptible Cullompton. Finally, the Cajamarca and Rubino isolates behaved as ABZ resistant, since no ovicidal activity was observed after eggs were incubated with ABZ at 0.5 nmol/ml. Considering the specific results obtained for each isolate under assessment, the egg hatch test described here may be a suitable method for detection of ABZ resistance in F. hepatica.

Inactivation of exogenous endoparasite stages by chemical disinfectants: current state and perspectives

Chemical disinfection is common practice and inevitable to achieve sufficient control over parasites particularly in intensive animal housing systems. To identify suitable chemicals, reliable data on antiparasitic efficacy of disinfectants are required. This review summarizes recently published experience with procedures applied to evaluate the viability of a variety of endoparasites following physical or chemical stress. It is concluded that laboratory models used to assess antiparasitic efficacy of e.g. commercial disinfectants should consider the most resistant stages of both helminths and protozoa, i.e. ascarid eggs and coccidia oocysts. To ensure reproducibility and transparency, standardized protocols are pivotal. Such protocols are established on a national level (e.g. DVG guidelines in Germany); however, internationally accepted certification procedures are currently lacking.

Identification of the rumen fluke, Calicophoron daubneyi, in GB livestock: possible implications for liver fluke diagnosis

The liver fluke, Fasciola hepatica, is common in many parts of Great Britain. To detect liver fluke infection and to assess whether fasciolicide treatment has been successful, the faecal egg count (FEC) and faecal egg count reduction test (FECRT) are widely used. Rumen fluke is also increasingly reported from Great Britain, but its species identity is yet to be determined. Liver fluke and rumen fluke eggs are morphologically similar, which may lead to erroneous diagnoses of liver fluke infection or treatment failure. As an alternative to FEC, a coproantigen ELISA (cELISA) can be used. The potential for this test to cross-react with rumen fluke species from Great Britain has not been evaluated. Rumen fluke specimens from cattle and sheep in Scotland were identified to species level using DNA sequencing of the ITS-2 region. Subsequently, rumen and liver fluke obtained from naturally co-infected sheep were subjected to immunohistochemistry using antibodies from a commercially available cELISA kit for F. hepatica. Finally, faecal samples from naturally co-infected sheep flocks were examined by FEC and cELISA. Rumen fluke from imported and home-bred cattle and sheep in Scotland belonged to the species Calicophoron daubneyi, rather than Paramphistomum cervi, the species presumed to be most common in Great Britain. Intense staining of the gastrodermis was observed in F. hepatica but cross-reactivity with C. daubneyi was not seen. Faecal samples that contained rumen fluke eggs but not liver fluke eggs were all negative by cELISA. We conclude that C. daubneyi is the most common rumen fluke of domestic ruminants in Scotland and that cELISA reduction testing may be a valuable alternative to FECRT in herds or flocks that are co-infected with liver and rumen fluke.

Update on trematode infections in sheep

Trematode parasites live in the liver, fore stomachs or blood vessels of a wide range of animals and humans. Most of them have a special economic and veterinary significance. Liver fluke disease of sheep and other animal species is caused by the common liver fluke Fasciola hepatica. Hepatic fasciolosis occurs throughout the world, where climatic conditions are suitable for the survival of aquatic intermediate host snails. Also of importance for ruminants, in some parts of the world, are Fasciola gigantica and Fascioloides magna. Other trematodes infecting ruminants include Dicrocoelium dendriticum; Eurytrema pancreaticum and Eurytrema coelomaticum. Among the Paramphistomidae, some species can infect sheep and other ruminants. Finally, Schistosoma spp. are found in the blood vessels of ruminants and are of minor importance in temperate regions. The manuscript concentrates on trematode species of veterinary importance for domestic sheep.

Impact of compound alpha treatment in vivo on egg production by the liver fluke, Fasciola hepatica

Sheep infected with the triclabendazole-susceptible Cullompton isolate of Fasciola hepatica were treated with compound alpha at a dosage of 15 mg/kg at 12 weeks post-infection. Adult flukes were recovered from the bile ducts at 24h, 48 h and 72 h post-treatment (pt). They were processed for whole mount analysis, histology and transmission electron microscopy of the female reproductive system: specifically, the uterus, Mehlis' gland, ovary and vitellaria. As judged by the appearance of the uterus, normal egg production ceased within 24h of treatment; this phenomenon preceded significant changes to the other reproductive organs. Over the 3-day pt period, there was a progressive decline in the number of oogonia in the ovary, together with an increase in the number of eosinophilic and apoptotic oocytes and vacuolation and shrinkage of the ovarian tubules. There was a shift in the cell population within the vitelline follicles at 48 h pt, with relatively greater numbers of mature vitelline cells and fewer immature cells. The follicles were vacuolated and the shell globule clusters in the mature cells were disorganised. Greater disruption was seen at 72 h pt, with a reduction in the size of the follicles and rupture of cells, releasing their content into the lumen of the follicles. These histological observations were confirmed and extended at the TEM level. Thus, examination of electron micrographs showed that disruption of the shell globule clusters was evident at 48 h pt, which coincided with the start of the breakdown of the mature cells and of the nurse cell network. These degenerative changes were more conspicuous at 72 h pt. In the Mehlis' gland, shrinkage and vacuolation of the cells and their cytoplasmic extensions became progressively greater from 48 h to 72 h pt, and secretory activity declined. The changes in the reproductive organs and inhibition of egg production are put in context of the overall time-course of drug action.