Fasciolicides: efficacy, actions, resistance and its management

Neutralization of Acidic Intracellular Vesicles by Niclosamide Inhibits Multiple Steps of the Dengue Virus Life Cycle In Vitro

Dengue fever is one of the most important mosquito-borne viral infections in large parts of tropical and subtropical countries and is a significant public health concern and socioeconomic burden. There is an urgent need to develop antivirals that can effectively reduce dengue virus (DENV) replication and decrease viral load. Niclosamide, an antiparasitic drug approved for human use, has been recently identified as an effective antiviral agent against a number of pH-dependent viruses, including flaviviruses. Here, we reveal that neutralization of low-pH intracellular compartments by niclosamide affects multiple steps of the DENV infectious cycle. Specifically, niclosamide-induced endosomal neutralization not only prevents viral RNA replication but also affects the maturation of DENV particles, rendering them non-infectious. We found that niclosamide-induced endosomal neutralization prevented E glycoprotein conformational changes on the virion surface of flaviviruses, resulting in the release of non-infectious immature virus particles with uncleaved pr peptide from host cells. Collectively, our findings support the potential application of niclosamide as an antiviral agent against flavivirus infection and highlight a previously uncharacterized mechanism of action of the drug.

Global serum proteomic changes in water buffaloes infected with Fasciola gigantica

BACKGROUND

The liver fluke Fasciola gigantica modulates several signaling pathways in infected buffaloes to facilitate its survival and establishment of persistent infection. In response to the parasite invasion, buffaloes activate innate and adaptive immune responses to counter the parasite infection. To detect new proteins that might be involved in the interaction between F. gigantica and the buffaloes, and that also might serve as biomarkers for fasciolosis, we used proteomic techniques to study the serum proteome of buffaloes during F. gigantica infection. Here, we used an isobaric tags for relative and absolute quantitation (iTRAQ)-based quantitative proteomic approach to identify serum proteins that are differentially expressed in infected buffaloes compared to uninfected control buffaloes. Additionally, we applied a parallel reaction monitoring (PRM) assay to validate specific proteins identified by the iTRAQ method.

RESULTS

A total of 313, 459 and 399 proteins were identified at 3, 42 and 70 days post-infection, respectively; of these 92, 93 and 138 were differentially abundant proteins. Some of the identified differentially abundant proteins, including complement factor H related 5, complement component C6, complement component C7, amine oxidase, plasma serine protease inhibitor and lysozyme, are known to be involved in complement system activation, blood coagulation, platelet activation, lymphocyte's adhesion and lysozyme hydrolysis. Analysis of data for all three time points after infection identified six significantly upregulated proteins in infected serum that separated infected and uninfected buffaloes into distinct clusters. Further PRM analysis confirmed the expression of five proteins, namely MHC class I antigen, Beta-2-microglobulin, NID2 protein, Fetuin-B and Fibrinogen gamma-B chain.

CONCLUSIONS

These findings provide novel insights into the serum proteomics signature of buffaloes during F. gigantica infection.

Preliminary Evidence for the Occurrence of β-tubulin Isotype 3 Polymorphisms in Fasciola Hepatica Isolates in Cattle and Sheep in Turkey

Fasciolosis caused by Fasciola hepatica is a common parasitic disease of livestock especially sheep and cattle. In this study molecular characterization of β-tubulin isotype 3 gene in Fasciola hepatica isolates from cattle and sheep in Turkey was carried out. For this purpose a total of 80 adult Fasciola hepatica isolates were collected from 20 sheep and 20 cattle in Kayseri and Erzurum provinces. PCR-RFLP was performed on β-tubulin isotype 3 gene and MboII revealed two fragments of approximately 350 bp and 390 bp, whereas HphI enzyme yielded 210, 340 and 540 bp bands, HindII yielded 380 and 450 bp bands in all samples. A total of 80 isolates were tested by SSCP and all of them presented the same band profiles. Six samples (4 sheep and 2 cattle) were randomly selected and DNA sequence of a 935 bp coding fragment of β-tubulin isotype 3 was performed. Sheep samples were more polymorphic than the cattle. This β-tubulin isotype 3 gene polymorphism of F.hepatica isolates from sheep and cattle of two distinct geographical areas of Turkey have been investigated for the first time.

Lack of efficacy of triclabendazole against Fasciola hepatica is present on sheep farms in three regions of England, and Wales

The liver fluke Fasciola hepatica is a parasitic trematode that has a major impact on livestock production and human health. Control of F hepatica is difficult and relies on anthelmintics, particularly triclabendazole, due to its efficacy against both adult and juvenile stages of the parasite. Emergence of triclabendazole-resistant F hepatica populations has been reported in a number of countries, including the UK, but the overall prevalence and distribution of triclabendazole resistance is unknown. In this study, the authors established the presence of reduced efficacy of triclabendazole in sheep flocks in England and Wales, using a validated composite faecal egg count reduction test. Seventy-four sheep farms were sampled from Wales, southwest, northwest and northeast England between Autumn 2013 and Spring 2015. F hepatica eggs were detected in samples from 42/74 farms. Evidence of a lack of efficacy of triclabendazole was detected on 21/26 farms on which the faecal egg count reduction test was completed, with faecal egg count reductions ranging from 89 per cent to 0per cent. Regression analysis suggested that both prevalence of F hepatica and lack of efficacy of triclabendazole were spatially correlated, with higher faecal egg counts and lower percentage reductions on farms located in the northwest of England, and Wales. Overall, the results show that reduced efficacy of triclabendazole is present across England and Wales, with a complete lack of therapeutic efficacy observed on 9/26 farms.

Screening the Pathogen Box for Identification of New Chemical Agents with Anti-Fasciola hepatica Activity

Fascioliasis is an infectious parasitic disease distributed globally and caused by the liver fluke Fasciola hepatica or F. gigantica This neglected tropical disease affects both animals and humans, and it represents a latent public health problem due to the significant economic losses related to its effects on animal husbandry. For decades, triclabendazole has been the unique anti-Fasciola drug that can effectively treat this disease. However, triclabendazole resistance in fascioliasis has more recently been reported around the world, and thus, the discovery of novel drugs is an urgent need. The aim of this study was to investigate the fasciocidal properties of 400 compounds contained in the Pathogen Box. The first stage of the screening was carried out by measuring the fasciocidal activity on metacercariae at a concentration of 33 μM each compound (the standard dose). Subsequently, the activities of the most active compounds (n = 33) at their 50% inhibitory concentration (IC₅₀) values against metacercariae were assayed, and the results showed that 13 compounds had IC₅₀s of ≤10 μM. The second stage queried the activities of these compounds at 33 μM against adult flukes, with seven of the compounds producing high mortality rates of >50%. Four hit compounds were selected on the basis of their predicted nontoxic properties, and the IC₅₀ values obtained for adult worms were <10 μM; thus, these compounds represented the best fasciocidal compounds tested here. A cytotoxicity assay on four types of cell lines demonstrated that three compounds were nontoxic at their most active concentration. In conclusion, three hit compounds identified in this proof-of-concept study are potential candidates in the discovery of new fasciocidal drugs. Further studies are warranted.

Fascioliasis

Fascioliasis is a major parasitic disease caused by the digenetic trematodes Fasciola hepatica and Fasciola gigantica. The disease is a well-known veterinary problem of worldwide distribution. Fascioliasis is the vector-borne parasitic disease presenting the widest latitudinal, longitudinal, and altitudinal distribution known at present. In the last two decades, many surveys have shown it to be an important public health problem as well, including estimations of 2.4 million, up to 17 million people, or even higher depending on the hitherto unknown situations mainly in several regions of Asia and Africa. In recent years, the increasing number of human case reports in many countries of the five continents and the results of studies on pathogenicity and immunity, mainly regarding the chronic period of the disease, were the reasons why it was decided to no longer consider fascioliasis merely a secondary zoonotic disease but an important human parasitic disease. In this chapter, we review the most relevant features in relation to fascioliasis, including from the most traditional to the most innovative aspects.

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.

Evaluating the effectiveness of trematocides against Fasciola gigantica and amphistomes infections in cattle, using faecal egg count reduction tests in Iringa Rural and Arumeru Districts, Tanzania

BACKGROUND

Fasciolosis, caused by the liver fluke Fasciola gigantica, and paramphistomosis are widespread in cattle in Tanzania, and the use of trematocides is encouraged by the Government livestock extension officers. However, reduced efficacy of oxyclozanide against Fasciola gigantica and amphistomes (rumen flukes), and albendazole against F. gigantica, has been reported in some regions. This study was conducted to assess the efficacy of different trematocides against F. gigantica and amphistome infections in cattle at Iringa Rural and Arumeru Districts.

METHODS

Cattle found with concurrent infection of F. gigantica and amphistomes were randomly grouped into six experimental groups. One control group was left untreated while five treatment groups were treated with one of five trematocides that include: albendazole, nitroxynil, oxyclozanide, closantel and triclabendazole. Post-treatment faecal sample collection was done on the day of treatment and again at 7, 14 and 28 days, from each cattle. The samples were processed by Flukefinder® method to recover and identify eggs. Assessment of the efficacy of the trematocides against F. gigantica and amphistomes was conducted using faecal egg count reduction (FECR) tests.

RESULTS

The findings of the present study in both districts indicate that nitroxynil, oxyclozanide, closantel and triclabendazole are effective against patent F. gigantica infection, as the calculated FECR% for each trematocide was 100% by day 14 post-treatment. However, albendazole found to have reduced efficacy of against F. gigantica, as FECR% was 49% in Arumeru District and 89% in Iringa Rural District by day 14 post-treatment. Oxyclozanide was the only trematocide found to be effective against amphistomes with FECR of 99%.

CONCLUSIONS

Albendazole had reduced efficacy against F. gigantica in cattle in Arumeru and Iringa Rural Districts, Tanzania. The reduced efficacy was prominent in Arumeru, where cattle are commonly treated with anthelmintics, than in Iringa Rural, where cattle are seldom treated.

Preferential Inhibition of Wnt/β-Catenin Signaling by Novel Benzimidazole Compounds in Triple-Negative Breast Cancer

Wnt/β-catenin signaling is upregulated in triple-negative breast cancer (TNBC) compared to other breast cancer subtypes and normal tissues. Current Wnt/β-catenin inhibitors, such as niclosamide, target the pathway nonspecifically and exhibit poor pharmacokinetics/pharmacodynamics in vivo. Niclosamide targets other pathways, including mTOR, STAT3 and Notch. Novel benzimidazoles have been developed to inhibit Wnt/β-catenin signaling with greater specificity. The compounds SRI33576 and SRI35889 were discovered to produce more cytotoxicity in TNBC cell lines than in noncancerous cells. The agents also downregulated Wnt/β-catenin signaling mediators LRP6, cyclin D1, survivin and nuclear active β-catenin. In addition, SRI33576 did not affect mTOR, STAT3 and Notch signaling in TNBC and noncancerous cells. SRI35889 inhibited mTOR signaling less in noncancerous than in cancerous cells, while not affecting STAT3 and Notch pathways. Compounds SRI32529, SRI35357 and SRI35361 were not selectively cytotoxic against TNBC cell lines compared to MCF10A cells. While SRI32529 inhibited Wnt/β-catenin signaling, the compound also mitigated mTOR, STAT3 and Notch signaling. SRI33576 and SRI35889 were identified as cytotoxic and selective inhibitors of Wnt/β-catenin signaling with therapeutic potential to treat TNBC in vivo.

Assessment of the effective dose of an experimental intramuscular formulation against immature and adult Fasciola hepatica in sheep

The effective dose of an injectable prodrug, named compound alpha prodrug, against immature and adult Fasciola hepatica in experimentally infected sheep was determined. In a first experiment, 30 sheep were infected with Fasciola hepatica on day 0 and 50. After microscopic detection of faecal eggs on day 80, groups (n = 6) 1 to 3 were treated with 6, 8 and 10 mg/kg of the experimental water-soluble prodrug compound alpha intramuscularly, respectively. Group 4 was treated with closantel and group 5 remained untreated. Copromicroscopical examinations were made on day 0, 80 and 108. On day 110, trematodes were collected from the bile ducts. Fasciolicide efficacy was assessed as a percentage of fluke-egg and adult-fluke reduction. Fluke length was also recorded. In a second experiment aimed to assess the fasciolicide activity of compound alpha prodrug against four-week-old flukes, 12 sheep were infected on day 0 and allocated into two groups (n = 6). On day 50 post infection, group A was treated with the experimental water-soluble prodrug compound alpha at 6 mg/kg/IM and B remained untreated. Fasciolicide activity was assessed on day 80 after collection, microscopic observation and measurement of flukes present in the parenchyma for immature stages and on day 108 for adults. Egg output decreased 91.2, 96.0, 98.8 and 94.9% for groups 1, 2, 3 and 4, respectively. Compound alpha prodrug cleared 97.6%, 98.51% and 100% of adult stages in a dose-dependent manner. Closantel killed 81.95% flukes. Regarding the second experiment, 81.2% efficacy was achieved. Immature flukes were significantly smaller in the treated group. It is concluded that the intramuscular application of compound alpha prodrug exerted fasciolicide efficacy against adults of Fasciola hepatica.

In vitro ovicidal activity of poly lactic acid curcumin-nisin co-entrapped nanoparticle against Fasciola spp. eggs and its reproductive toxicity

BACKGROUND

Curcumin and nisin have been widely reported for their antibacterial and anticancer potency. However, their therapeutic applications are hampered by several factors, which necessitate their development into nanosize ranges for improved delivery and activities. Their incorporation into a single nanosynthesized form may suggest desirable efficacy on parasites. The aim of the study was to assess the ovicidal activity of the curcumin-nisin polylactic acid (PLA) entrapped nanoparticle on the Fasciola eggs and its reproductive toxicity.

METHODS

The nanoparticle was formulated by double emulsion method. The eggs of the adult Fasciola spp. were exposed to different concentrations (0.3125-5 mg/mL) of the nanoparticle to monitor hatchability. Mice were exposed to 0.5 mL of the formulated drug at varying concentrations (10-20 mg/kg) and then sacrificed for sperm morphology assay.

RESULTS

The mean particle size, polydispersity index, and drug entrapment efficiency of the formulated drug were 288.4±24.3 nm, 0.232, and 51.7%, respectively. The highest nanoparticulate concentration (5 mg/mL) showed the least percentage egg hatching (41.7%) compared with the other treatment groups and positive control (albendazole) (45.1%). The aberrations observed in sperm cells were not concentration-dependent and no significant differences were observed in the mean aberrations between the nanoparticulate drug-exposed groups and the negative control (p>0.05).

CONCLUSIONS

The results confirmed the ovicidal activity of the curcumin-nisin nanoparticulate drug against the Fasciola species. The formulation also showed no toxicity to sperm cells. More robust studies on anti-fascioliasis activity of the drug on adult Fasciola spp. and in vivo and in vitro toxicity studies are recommended.

Pleiotropic alterations in gene expression in Latin American Fasciola hepatica isolates with different susceptibility to drugs

Background

Fasciola hepatica is the main agent of fasciolosis, a zoonotic disease affecting livestock worldwide, and an emerging food-borne disease in humans. Even when effective treatments are available, drugs are costly and can result in tolerance, liver damage and normally they do not prevent reinfection. Drug-resistant strains in livestock have been reported in various countries and, more worryingly, drug resistance in human cases has emerged in South America. The present study aims to characterize the transcriptome of two South American resistant isolates, the Cajamarca isolate from Peru, resistant to both triclabendazole and albendazole (TCBZR/ABZR) and the Rubino isolate from Uruguay, resistant to ABZ (TCBZS/ABZR), and compare them to a sensitive strain (Cenapa, Mexico, TCBZS/ABZS) to reveal putative molecular mechanisms leading to drug resistance.

Results

We observed a major reduction in transcription in the Cajamarca TCBZR/ABZR isolate in comparison to the other isolates. While most of the differentially expressed genes are still unannotated, several trends could be detected. Specific reduction in the expression levels of cytoskeleton proteins was consistent with a role of tubulins as putative targets of triclabendazole (TCBZ). A marked reduction of adenylate cyclase might be underlying pleiotropic effects on diverse metabolic pathways of the parasite. Upregulation of GST mu isoforms suggests this detoxifying mechanism as one of the strategies associated with resistance.

Conclusions

Our results stress the value of transcriptomic approaches as a means of providing novel insights to advance the understanding of drug mode of action and drug resistance. The results provide evidence for pleiotropic variations in drug-resistant isolates consistent with early observations of TCBZ and ABZ effects and recent proteomic findings.

Electronic supplementary material

The online version of this article (10.1186/s13071-017-2553-2) contains supplementary material, which is available to authorized users.

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.

Expression profiles of genes involved in TLRs and NLRs signaling pathways of water buffaloes infected with Fasciola gigantica

Infection of ruminants and humans with Fasciola gigantica is attracting increasing attention due to its economic impact and public health significance. However, little is known of innate immune responses during F. gigantica infection. Here, we investigated the expression profiles of genes involved in Toll-like receptors (TLRs) and NOD-like receptors (NLRs) signaling pathways in buffaloes infected with 500F. gigantica metacercariae. Serum, liver and peripheral blood mononuclear cell (PBMC) samples were collected from infected and control buffaloes at 3, 10, 28, and 70days post infection (dpi). Then, the levels of 12 cytokines in serum samples were evaluated by ELISA. Also, the levels of expression of 42 genes, related to TLRs and NLRs signaling, in liver and PBMCs were determined using custom RT² Profiler PCR Arrays. At 3 dpi, modest activation of TLR4 and TLR8 and the adaptor protein (TICAM1) was detected. At 10 dpi, NF-κB1 and Interferon Regulatory Factor signaling pathways were upregulated along with activation of TLR1, TLR2, TLR6, TLR10, TRAF6, IRF3, TBK1, CASP1, CD80, and IFNA1 in the liver, and inflammatory response with activated TLR4, TLR9, TICAM1, NF-κB1, NLRP3, CD86, IL-1B, IL-6, and IL-8 in PBMCs. At 28 dpi, there was increase in the levels of cytokines along with induction of NLRP1 and NLRP3 inflammasomes-dependent immune responses in the liver and PBMCs. At 70 dpi, F. gigantica activated TLRs and NLRs, and their downstream interacting molecules. The activation of TLR7/9 signaling (perhaps due to increased B-cell maturation and activation) and upregulation of NLRP3 gene were also detected. These findings indicate that F. gigantica alters the expression of TLRs and NLRs genes to evade host immune defenses. Elucidation of the roles of the downstream effectors interacting with these genes may aid in the development of new interventions to control disease caused by F. gigantica infection.

The in vitro anthelmintic activity of the ethanol leaf extracts of Terminalia catappa L. on Fasciola gigantica

At present, there are no medicinal plant extracts currently available for treatment and control of fasciolosis. The present work could provide, for the first study, conclusions on the in vitro fasciolicidal properties of the ethanol extract of Terminalia catappa L. (TcCE) leaves against adult Fasciola gigantica after incubation with RPMI-1640 medium containing the TcCE at various concentrations and times when compared with triclabendazole (TCZ). The relative motility and survival index values of the TcCE-treated flukes decreased at a more rapid rate than the TCZ-treated flukes. The death of the parasites was observed after exposed to TcCE at 3 h incubation with 400, 800 and 1000 µg mL−1, and at 6 h incubation in 100 and 200 µg mL−1. Vacuolization, blebbings and partial disruption on the parasites’ tegument were observed by light microscopy. When examined by scanning electron microscopy, TcCE caused similar tegumental alterations in the parasites as those observed in TCZ treatment but with larger damage at comparative incubation periods, consisting of swelling, blebbing, disrupted blebs, loss of spines, leading to the erosion, lesion and eventual disruption of the total tegument. Therefore, the TcCE may exert its fasciolicidal effect against F. gigantica by initially causing the tegumental alteration.

Understanding the main route of drug entry in adult Fasciola hepatica: Further insights into closantel pharmacological activity

Closantel (CLS) is highly effective against adult liver flukes after its oral or subcutaneous (sc) administration in ruminants. Trans-tegumental diffusion and oral ingestion are the two potential routes available for the entry of drugs into Fasciola hepatica. The work reported here contributes to improve the understanding of CLS pharmacology. The main goals of were: I) to determine the pattern of in vivo CLS accumulation into adult F. hepatica and relevant tissues in CLS-treated sheep; II) to investigate the influence of the physicochemical composition of the incubation medium on the CLS diffusion process into adult F. hepatica; III) to assess the ovicidal activity of CLS against F. hepatica eggs; and IV) to investigate the in vivo effect of CLS treatment on glutathione S-transferases activity in adult liver flukes exposed to CLS. Fourteen healthy sheep were each orally infected with 75 F. hepatica metacercariae. Sixteen (16) weeks after infection, animals were treated with CLS by oral (n = 6, 10 mg/kg) or sub-cutaneous (sc) (n = 6, 5 mg/kg) route. At 12, 24 and 36 h post-treatment, animals were sacrificed (n = 2) and samples of blood, bile and adult F. hepatica were collected. In addition, flukes recovered from non-treated sheep (n = 2) were ex vivo incubated (60 min) in the presence of CLS in either RPMI or bile as incubation medium. CLS concentration was measured by HPLC. The ovicidal activity of CLS was investigated using eggs obtained from the bile of untreated sheep. Finally, glutathione S-transferase activity in F. hepatica recovered from untreated and CLS-treated sheep was assessed. In the in vivo studies, the highest CLS concentrations were measured in plasma and adult liver flukes. A positive correlation was observed between CLS concentration in plasma and in F. hepatica. Results obtained in the current work indicate that the in vivo accumulation of CLS into adult liver flukes occurs mainly by the oral route. After ex vivo incubation, the uptake of CLS by the parasite was markedly diminished in the presence of bile compared with that observed in the presence of RPMI as incubation medium. CLS lacks ovicidal activity at therapeutically relevant concentrations. Lastly, CLS significantly increased glutathione S-transferase activity in flukes recovered at 12 h (oral treatment) and 24 h (sc treatment), compared to the control liver flukes.

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.

Benzimidazole inhibitors from the Niclosamide chemotype inhibit Wnt/β-catenin signaling with selectivity over effects on ATP homeostasis

The Wnt signaling pathway plays a key role in organ and tissue homeostasis, and when dysregulated, can become a major underlying mechanism of disease, particularly cancer. We reported previously that the anthelmintic drug Niclosamide inhibits Wnt/β-catenin signaling and suppresses colon cancer cell growth in vitro and in vivo. To define Niclosamide's mechanism of Wnt/β-catenin inhibition, and to improve its selectivity and pharmacokinetic properties as an anticancer treatment, we designed a novel class of benzimidazole inhibitors of Wnt/β-catenin signaling based on SAR studies of the Niclosamide salicylanilide chemotype. Niclosamide has multiple biological activities. To address selectivity in our design, we interrogated a protonophore SAR model and used the principle of conformational restriction to identify novel Wnt/β-catenin inhibitors with less effect on ATP cellular homeostasis. These studies led to the identification of 4-chloro-2-(5-(trifluoromethyl)-1H-benzo[d]imidazol-2-yl) phenol (4) and related derivatives with greater selectivity for Wnt/β-catenin signaling inhibition vs. differential effects on cellular ATP homeostasis. This is the first report that the Wnt signaling inhibitory activity of Niclosamide can be translated into a new chemical class and to show that its effects on ATP homeostasis can be separated from its inhibitory effects on Wnt signaling. These compounds could be useful tools to elucidate the mechanism of Niclosamide's inhibition of Wnt signaling, and aid the discovery of inhibitors with improved pharmacologic properties to treat cancer and diseases in which Niclosamide has important biological activity.

De novo transcriptome sequencing and analysis of the juvenile and adult stages of Fasciola gigantica

Fasciola gigantica is regarded as the major liver fluke causing fasciolosis in livestock in tropical countries. Despite the significant economic and public health impacts of F. gigantica there are few studies on the pathogenesis of this parasite and our understanding is further limited by the lack of genome and transcriptome information. In this study, de novo Illumina RNA sequencing (RNA-seq) was performed to obtain a comprehensive transcriptome profile of the juvenile (42days post infection) and adult stages of F. gigantica. A total of 49,720 unigenes were produced from juvenile and adult stages of F. gigantica, with an average length of 1286 nucleotides (nt) and N50 of 2076nt. A total of 27,862 (56.03%) unigenes were annotated by BLAST similarity searches against the NCBI non-redundant protein database. Because F. gigantica needs to feed and/or digest host tissues, some proteases (including cysteine proteases and aspartic proteases), which play a role in the degradation of host tissues (protein), have been paid more attention in the present study. A total of 6511 distinct genes were found differentially expressed between juveniles and adults, of which 3993 genes were up-regulated and 2518 genes were down-regulated in adults versus juveniles, respectively. Moreover, stage-specific differentially expressed genes were identified in juvenile (17,009) and adult (6517) F. gigantica. The significantly divergent pathways of differentially expressed genes included cAMP signaling pathway (226; 4.12%), proteoglycans in cancer (256; 4.67%) and focal adhesion (199; 3.63%). The transcription pattern also revealed two egg-laying-associated pathways: cGMP-PKG signaling pathway and TGF-β signaling pathway. This study provides the first comparative transcriptomic data concerning juvenile and adult stages of F. gigantica that will be of great value for future research efforts into understanding parasite pathogenesis and developing vaccines against this important parasite.

Exploration of interaction zones of β-tubulin colchicine binding domain of helminths and binding mechanism of anthelmintics

Numerous studies postulated the possible modes of anthelmintic activity by targeting alternate or extended regions of colchicine binding domain of helminth β-tubulin. We present three interaction zones (zones vide -1 to -3) in the colchicine binding domain of Haemonchus contortus (a helminth) β-tubulin homology model and developed zone-wise structure-based pharmacophore models coupled with molecular docking technique to unveil the binding hypotheses. The resulted ten structure-based hypotheses were then refined to essential three point pharmacophore features that captured recurring and crucial non-covalent receptor contacts and proposed three characteristics necessary for optimal zone-2 binding: a conserved pair of H bond acceptor (HBA to form H bond with Asn226 residue) and an aliphatic moiety of molecule separated by 3.75±0.44Å. Further, an aliphatic or a heterocyclic group distant (11.75±1.14Å) to the conserved aliphatic site formed the third feature component in the zone-2 specific anthelmintic pharmacophore model. Alternatively, an additional HBA can be substituted as a third component to establish H bonding with Asn204. We discern that selective zone-2 anthelmintics can be designed effectively by closely adapting the pharmacophore feature patterns and its geometrical constraints.

Anthelmintic Potential of Thymoquinone and Curcumin on Fasciola gigantica

Fasciolosis an economically important global disease of ruminants in the temperate and tropical regions, caused by Fasciola hepatica and F. gigantica, respectively, also poses a potential zoonotic threat. In India alone it causes huge losses to stakeholders. Anthelmintics including triclabendazole have been used to control this menace but the emerging resistance against the available compounds necessitates identification of novel and alternative therapeutic measures involving plant derived natural compounds for their anthelmintic potential. Thymoquinone (T) and curcumin (C), the active ingredients of Nigella sativa and Curcuma longa respectively have been used as antiparasitic agents but the information on their flukicidal effect is very limited. Adult flukes of F. gigantica were in vitro exposed to different concentrations of thymoquinone and curcumin separately for 3h at 37+ 1°C. A significant (p<0.05) reduction in the worm motility at 60 μM concentration of both T and C was observed though all the worms remained alive after 3h exposure, whereas the effect on egg shedding was statistically insignificant. Pronounced tegumental disruptions and erosion of spines in the posterior region and around the acetabulum was evident. A significant (p<0.05) decrease in glutathione-S-transferase and superoxide dismutase activity and reduced glutathione (GSH) level was observed, while protein carbonylation increased differentially. A significant inhibition of CathepsinL (CatL) gene expression in thymoquinone treated worms was also evident. Further, in silico molecular docking of T and C with CatL revealed a stronger interaction of curcumin with the involvement of higher number of amino acids as compared to thymoquinone that could be more effective in inhibiting the antioxidant enzymes of F. gigantica. It is concluded that both the compounds understudy will decrease the detoxification ability of F. gigantica, while inhibition of CatL will significantly affect their virulence potential. Thus, both thymoquinone and curcumin appeared to be promising anthelmintic compounds for further investigations.

Transcriptomic responses of water buffalo liver to infection with the digenetic fluke Fasciola gigantica

Background

Fasciola gigantica, the tropical liver fluke, infects buffaloes in Asian and African countries and causes significant economic losses and poses public health threat in these countries. However, little is known of the transcriptional response of buffaloes to infection with F. gigantica. The objective of the present study was to perform the first transcriptomic analysis of buffalo liver infected by F. gigantica. Understanding the mechanisms that underpin F. gigantica infection in buffaloes will contribute to our ability to control this parasite.

Methods

We challenged buffaloes with 500 viable F. gigantica metacercariae and collected liver samples through a time course at 3, 42 and 70 days post-infection (dpi). Then, we performed gene expression analysis on liver samples using RNA sequencing (RNA-Seq) Illumina technology and confirmed the RNA-Seq data by quantitative RT-PCR analysis.

Results

Totals of 496, 880 and 441 differentially expressed transcripts were identified in the infected livers at 3, 42 and 70 dpi, respectively. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis revealed that transcriptional changes in the liver of infected buffaloes evolve over the course of infection. The predominant response of buffaloes to infection was mediated by certain pathways, such as MHC antigen processing and presentation, Toll-like receptor 4 (TLR4), transforming growth factor beta (TGF-β), and the cytochrome P450. Hepatic drug metabolizing enzymes and bile secretion were also affected.

Conclusions

Fasciola gigantica can induce statistically significant and biologically plausible differences in the hepatic gene expression of infected buffaloes. These findings provide new insights into the response of buffaloes to F. gigantica over the course of infection, which may be useful in determining pathways that can modulate host-parasite interaction and thus potentially important for clearance of the parasite.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-017-1990-2) contains supplementary material, which is available to authorized users.

Development of Fasciola Vaccine in an Animal Model

Fasciola hepatica and F. gigantica are the parasites that cause the zoonotic parasitic disease called fasciolosis. Although several anthelmintic drugs have been used to treat these parasitic infections, recombinant protein vaccines have been developed to overcome the anthelmintic resistance that has recently been reported in many regions of the world. These vaccines have been shown to induce high levels of immune responses and high percentages of protection in experimental and large animals. Efficacies of these vaccines suggest they could be an alternative and sustainable strategy to prevent fasciolosis in animals as well as humans in the future. The purpose of this chapter is to provide a protocol to develop a recombinant protein-based vaccine against Fasciola infection in mice. Moreover, this method can also be used as a guideline when the vaccination is performed in larger animals.

Six-year longitudinal study of Fasciola hepatica bulk milk antibody ELISA in the dairy dense region of the Republic Ireland

Completion of the F. hepatica lifecycle is dependent on suitable climatic conditions for development of immature stages of the parasite, and its snail intermediate host. Few investigations have been conducted regarding temporal variations in F. hepatica status in Irish dairy herds. The current study aimed to conduct a longitudinal study examining annual and seasonal trends in bulk milk seropositivity over six years, while also investigating associations with soil temperature, rainfall and flukicide treatment. Monthly bulk milk samples (BTM) were submitted by 28 herds between March 2009 and December 2014. In all, 1337 samples were analysed using a Cathepsin L1 ELISA. Soil temperature, rainfall and management data were obtained for general estimating equation and regression analyses. A general decrease in milk seropositivity was observed over the six year study period and was associated with an increased likelihood of treating for liver fluke (OR range=2.73-6.96). Annual and seasonal analyses of rainfall and F. hepatica BTM status yielded conflicting results. Higher annual rainfall (>1150mm) yielded a lower likelihood of being BTM positive than annual rainfall of <1000mm (OR=0.47; P=0.036). This was most likely due to farmers being more proactive in treating for F. hepatica in wetter years, although a 'wash effect' by high rainfall of the free living stages and snails cannot be ruled out. Higher seasonal rainfall (>120mm), however, was associated with increased ELISA S/P% values (Coefficient=9.63S/P%; P=0.001). Soil temperature was not found to influence F. hepatica to the same extent as rainfall and may reflect the lack of severe temperature fluctuations in Ireland. Flukicides active against both immature and mature F. hepatica were approximately half as likely to record a positive F. hepatica herd BTM status than a flukicide active against only the mature stage of the parasite (OR≅0.45; P<0.01). This study highlights the importance of examining both annual and seasonal F. hepatica data, which can vary significantly. Additionally, it highlights the progress that can be achieved in fluke control by application of a continuous BTM monitoring program.

Fasciolosis in South America: epidemiology and control challenges

Fasciolosis caused by Fasciola hepatica severely affects the efficiency of livestock production systems worldwide. In addition to the economic impact inflicted on livestock farmers, fasciolosis is an emergent zoonosis. This review emphasizes different aspects of the disease in South America. Available data on epidemiology in bovines and ovines in different countries, as well as a growing body of information on other domestic and wildlife definitive hosts, are summarized. The issue of drug resistance that compromises the long-term sustainability of current pharmacological strategies is examined from a regional perspective. Finally, efforts to develop a single-antigen recombinant vaccine in ruminants are reviewed, focusing on the cases of leucine aminopeptidase or thioredoxin glutathione reductase.

In vitro ovicidal activity of Peganum harmala seeds extract on the eggs of Fasciola hepatica

Peganum harmala seeds extract has been previously reported to have antimicrobial and other medicinal properties. The aim of this study was to evaluate the ovicidal activity of the methanolic extract of P. harmala seeds against the eggs of F. hepatica. The phenolic compounds of the methanolic extract of P. harmala seeds were identified by HPLC analysis. Catechin, rutin, p-Coumaric acid, chloregenic acid and hesperetin were found to be the major phenolic compounds. F. hepatica eggs were collected from the gall bladder of naturally infected sheep. The eggs were exposed to two concentrations of P. harmala seeds extract (1 and 3 mg/mL) for 24 and 48 h. To investigate the effect of the P. harmala seeds extract on the miracidial formation, the treated eggs were incubated at 28 °C for 14 days. The results indicated that F. hepatica eggs were susceptible to the methanolic extract of P. harmala seeds. Following 24 h exposure of the eggs to P. harmala seeds extract with concentrations of 1 and 3 mg/mL, the miracidial formation reduced to 5 and 2.2 % respectively (compared with 60 % for the control group). Following 48 h of exposure of the eggs to P. harmala seeds extract with 1 mg/mL concentration, the miracidial formation reduced to 0.5 %. In this exposure time, no miracidial formation was observed in the eggs exposed to P. harmala seeds extract with concentration of 3 mg/mL. Therefore, the results of this study indicated that P. harmala seeds extract has high ovicidal activity against the eggs of F. hepatica. Accordingly, this extract may have the potential flukicidal activity against the immature and mature F. hepatica.

Exploring and Expanding the Fatty-Acid-Binding Protein Superfamily in Fasciola Species

The liver flukes Fasciola hepatica and F. gigantica infect livestock worldwide and threaten food security with climate change and problematic control measures spreading disease. Fascioliasis is also a foodborne disease with up to 17 million humans infected. In the absence of vaccines, treatment depends on triclabendazole (TCBZ), and overuse has led to widespread resistance, compromising future TCBZ control. Reductionist biology from many laboratories has predicted new therapeutic targets. To this end, the fatty-acid-binding protein (FABP) superfamily has proposed multifunctional roles, including functions intersecting vaccine and drug therapy, such as immune modulation and anthelmintic sequestration. Research is hindered by a lack of understanding of the full FABP superfamily complement. Although discovery studies predicted FABPs as promising vaccine candidates, it is unclear if uncharacterized FABPs are more relevant for vaccine formulations. We have coupled genome, transcriptome, and EST data mining with proteomics and phylogenetics to reveal a liver fluke FABP superfamily of seven clades: previously identified clades I-III and newly identified clades IV-VII. All new clade FABPs were analyzed using bioinformatics and cloned from both liver flukes. The extended FABP data set will provide new study tools to research the role of FABPs in parasite biology and as therapy targets.

Extracellular pH Modulates Neuroendocrine Prostate Cancer Cell Metabolism and Susceptibility to the Mitochondrial Inhibitor Niclosamide

Neuroendocrine prostate cancer is a lethal variant of prostate cancer that is associated with castrate-resistant growth, metastasis, and mortality. The tumor environment of neuroendocrine prostate cancer is heterogeneous and characterized by hypoxia, necrosis, and numerous mitoses. Although acidic extracellular pH has been implicated in aggressive cancer features including metastasis and therapeutic resistance, its role in neuroendocrine prostate cancer physiology and metabolism has not yet been explored. We used the well-characterized PNEC cell line as a model to establish the effects of extracellular pH (pH 6.5, 7.4, and 8.5) on neuroendocrine prostate cancer cell metabolism. We discovered that alkalinization of extracellular pH converted cellular metabolism to a nutrient consumption-dependent state that was susceptible to glucose deprivation, glutamine deprivation, and 2-deoxyglucose (2-DG) mediated inhibition of glycolysis. Conversely, acidic pH shifted cellular metabolism toward an oxidative phosphorylation (OXPHOS)-dependent state that was susceptible to OXPHOS inhibition. Based upon this mechanistic knowledge of pH-dependent metabolism, we identified that the FDA-approved anti-helminthic niclosamide depolarized mitochondrial potential and depleted ATP levels in PNEC cells whose effects were enhanced in acidic pH. To further establish relevance of these findings, we tested the effects of extracellular pH on susceptibility to nutrient deprivation and OXPHOS inhibition in a cohort of castrate-resistant prostate cancer cell lines C4-2B, PC-3, and PC-3M. We discovered similar pH-dependent toxicity profiles among all cell lines with these treatments. These findings underscore a potential importance to acidic extracellular pH in the modulation of cell metabolism in tumors and development of an emerging paradigm that exploits the synergy of environment and therapeutic efficacy in cancer.

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.

A growing degree-day model for determination of Fasciola hepatica infection risk in New Zealand with future predictions using climate change models

Infections of ruminants with Fasciola hepatica are considered to be of regional importance within New Zealand but there is very little recent information on its prevalence or severity other than anecdotal reports. Generally they are considered to be of secondary importance compared to gastrointestinal nematode infections. Utilizing data from Virtual Climate Stations (n=11491) distributed on a 5km grid around New Zealand a growing degree-day model was used to describe the risk of infection with liver fluke from 1972 to 2012 and then to apply the predictions to estimate the risk of fluke infections within New Zealand for the years 2040 and 2090. The growing degree-day model was validated against the most recent survey of infection within New Zealand in 1984. A strong positive linear relationship for 1984 between F. hepatica prevalence in lambs and infection risk (p<0.001; R²=0.71) was found indicating the model was effective for New Zealand. A linear regression for risk values from 14 regions in New Zealand for 1972-2012 did not show any discernible change in risk of infection over this time period (p>0.05). Post-hoc comparisons indicate the risk in Westland was found to be substantially higher (p<0.05) than all other regions with Northland ranked second highest. Notable predicted changes in F. hepatica infection risk in 2040 and 2090 were detected although they did vary between different climate change scenarios. The highest average percentage changes in infection risk were found in regions with low initial risk values such as Canterbury and Otago; in these regions 2090 infection risk is expected to rise by an average of 186% and 184%, respectively. Despite the already high levels of infection risk in Westland, values are expected to rise by a further 76% by 2090. The model does show some areas with little change with Taranaki predicted to experience only very minor increases in infection risk with average 2040 and 2090 predicted changes of 0% and 29%, respectively. Overall, these results suggest the significance of F. hepatica in New Zealand farming systems is probably underestimated and that this risk will generally increase with global warming following climate change.

Use of bait containing triclabendazole against Fasciola gigantica in a herd of captive wild impala (Aepyceros melampus)

Although the efficacy of triclabendazole treatment against Fasciola gigantica has been shown before in cattle and buffaloes, there appears to be no published report on the efficacy of triclabendazole in impala or other antelope species. As part of a health monitoring programme at Mulungushi International Conference Centre, Lusaka, Zambia, a coprological examination was undertaken to investigate the helminthological status of captive impala (Aepyceros melampus). Of 39 fresh coprological samples, 46% contained F. gigantica. The source of infection was identified to be a fountain within the grounds of the conference centre. Lymnaea natalensis, collected from the study site, were induced to shed cercariae, and were thus confirmed as the snail intermediate host. In managing this disease, triclabendazole at 6 mg/kg was administered together with the feed bait. Water from the pond was drained; vegetation within it cleared and the pond allowed to dry for 1 week before water was replaced. Three weeks post-treatment, faecal examination revealed that the Fasciola had been cleared. To the best of our knowledge, this is a first case of Fasciola spp. infection reported in captive wild impala in Zambia and provides evidence that triclabendazole may be delivered to free-ranging antelope using medicated bait.

Use of a multiple choice questionnaire to assess UK prescribing channels' knowledge of helminthology and best practice surrounding anthelmintic use in livestock and horses

Grazing livestock and equines are at risk of infection from a variety of helminths, for which the primary method of control has long been the use of anthelmintics. Anthelmintic resistance is now widespread in a number of helminth species across the globe so it is imperative that best practice control principles be adopted to delay the further spread of resistance. It is the responsibility of all who prescribe anthelmintics (in the UK, this being veterinarians, suitably qualified persons (SQPs) and pharmacists) to provide adequate information on best practice approaches to parasite control at the point of purchase. Poor uptake of best practice guidelines at farm level has been documented; this could be due to a lack of, or inappropriate, advice at the point of anthelmintics purchase. Therefore, the aim here was to evaluate levels of basic knowledge of helminthology, best practice guidelines and dispensing legislation among veterinarians and SQPs in the UK, through a Multiple Choice Question (MCQ) test, that was distributed online via targeted emails and social media sites. For each respondent, the percentage correct was determined (for the MCQ test overall and for subsections) and the results analysed initially using parametric and non-parametric statistics to compare differences between prescribing channels. The results showed that channels generally performed well; veterinarians achieved a mean total percentage correct of 79.7% (range 34.0-100%) and SQPs, a mean total percentage correct of 75.8% (range 38.5-100%) (p=0.051). The analysis indicated that veterinarians performed better in terms of knowledge of basic helminthology (p=0.001), whilst the SQP group performed better on legislation type questions (p=0.032). There was no significant difference in knowledge levels of best practice between the two channels. Multivariable linear regression analysis showed that veterinarians and those answering equine questions only performed significantly better than those answering all questions. Based on information gaps identified by analysis of individual questions, a number of areas for improvement in knowledge transfer to both channels are suggested to improve the quality of advice at the point of anthelmintics purchase.

Current Threat of Triclabendazole Resistance in Fasciola hepatica

Triclabendazole (TCBZ) is the only chemical that kills early immature and adult Fasciola hepatica (liver fluke) but widespread resistance to the drug greatly compromises fluke control in livestock and humans. The mode of action of TCBZ and mechanism(s) underlying parasite resistance to the drug are not known. Due to the high prevalence of TCBZ resistance (TCBZ-R), effective management of drug resistance is now critical for sustainable livestock production. Here, we discuss the current status of TCBZ-R in F. hepatica, the global distribution of resistance observed in livestock, the possible mechanism(s) of drug action, the proposed mechanisms and genetic basis of resistance, and the prospects for future control of liver fluke infections using an integrated parasite management (IPM) approach.

Diagnosis of human fascioliasis in Arusha region, northern Tanzania by microscopy and clinical manifestations in patients

Background

Human fascioliasis (HF) is a zoonotic disease that has been identified in many countries worldwide. This report concerns the identification and clinical management of cases of human fascioliasis in the suburbs of Arusha city, northern Tanzania in 2013. Fascioliasis is included among the WHO’s Neglected Tropical Diseases as a plant transmitted trematode infection. Human fascioliasis has not been described before in the East Africa region, including Tanzania.

Methods

Patients presenting at a primary healthcare centre in Arusha Region, northern Tanzania provided fresh stool samples for routine ova and parasite screening (saline and iodine preparations). Subsequent stool samples were preserved in 5 % formalin in saline and subjected to ether sedimentation for examination.

Results

Out of 1460 patients, 305 (21 %) were diagnosed positive for fascioliasis based on the demonstration of brownish, oval eggs with inconspicuous opercula in stool. Two distinct egg sizes were identified; large 170–212.5 by 115–150 μm (mean 194.5 by 130.5 μm) and smaller eggs 120–150 by 87.5 – 112.5 μm (mean 138.8 by 101 μm). Clinically, patients presented with fever (39 - 40 °C) and abdominal pain. Some patients had pruritis around the mouth and their lips were swollen. 3 patients were treated and cured with single dose Triclabendazole. The remaining 302 patients were treated with Nitazoxanide and 122 (40 %) were cleared of infection with a single course. Snails of the genus Lymnaea were found in the surroundings.

Conclusions

This report serves to remind medical professionals in East Africa that HF is a probable differential diagnosis in patients presenting with similar symptoms. It is possible to diagnose fascioliasis by light microscopy although specific antigen tests are required for confirmation. Human fascioliasis however, has not been described or reported in Tanzania before and begs further investigation.

Closantel nano-encapsulated polyvinyl alcohol (PVA) solutions

The influence of closantel on the rheological and physicochemical properties (particle size and by UV-Vis absorption spectroscopy) of PVA aqueous solutions is studied here. About 1% PVA aqueous solutions were prepared by varying the closantel content. The increase of closantel content led to a reduction in the particle size of final solutions. All the solutions were buffered at pH 7.4 and exhibited shear-thinning behavior. Furthermore, in oscillatory flow, a "solid-like" type behavior was observed for the sample containing 30 μg/mL closantel. Indicating a strong interaction between the dispersed and continuous phases and evidencing an interconnected network between the nanoparticle and PVA, this sample also showed the highest shear viscosity and higher shear thinning slope, indicating a more intrincate structure disrupted by shear. In conclusion, PVA interacts with closantel in aqueous solution and the critical concentration for closantel encapsulation by PVA was about 30 μg/mL; above this concentration, the average particle size decreased notoriously which was associated to closantel interacting with the surface of the PVA aggregates and thus avoiding to some extent direct polymer-polymer interaction.

Fascioliasis: An Ongoing Zoonotic Trematode Infection

Zoonotic trematode infections are an area of the neglected tropical diseases that have become of major interest to global and public health due to their associated morbidity. Human fascioliasis is a trematode zoonosis of interest in public health. It affects approximately 50 million people worldwide and over 180 million are at risk of infection in both developed and underdeveloped countries. The one health paradigm is an area that seeks to address the problem of zoonotic infections through a comprehensive and sustainable approach. This review attempts to address the major challenges in managing human and animal fascioliasis with valuable insights gained from the one health paradigm to global health and multidisciplinary integration.

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.

Juvenile-specific cathepsin proteases in Fasciola spp.: their characteristics and vaccine efficacies

Fasciolosis, caused by Fasciola hepatica and Fasciola gigantica, is one of the most neglected tropical zoonotic diseases. One sustainable control strategy against these infections is the employment of vaccines that target proteins essential for parasites' invasion and nutrition acquiring processes. Cathepsin proteases are the most abundantly expressed proteins in Fasciola spp. that have been tested successfully as vaccines against fasciolosis in experimental as well as large animals because of their important roles in digestion of nutrients, invasion, and migration. Specifically, juvenile-specific cathepsin proteases are the more effective vaccines because they could block the invasion and migration of juvenile parasites whose immune evasion mechanism has not yet been fully developed. Moreover, because of high sequence similarity and identity of cathepsins from juveniles with those of adults, the vaccines can attack both the juvenile and adult stages. In this article, the characteristics and vaccine potentials of juvenile-specific cathepsins, i.e., cathepsins L and B, of Fasciola spp. were reviewed.

Fasciola hepatica vaccine: we may not be there yet but we're on the right road

Major advances have been made in identifying potential vaccine molecules for the control of fasciolosis in livestock but we have yet to reach the level of efficacy required for commercialisation. The pathogenesis of fasciolosis is associated with liver damage that is inflicted by migrating and feeding immature flukes as well as host inflammatory immune responses to parasite-secreted molecules and tissue damage alarm signals. Immune suppression/modulation by the parasites prevents the development of protective immune responses as evidenced by the lack of immunity observed in naturally and experimentally infected animals. In our opinion, future efforts need to focus on understanding how parasites invade and penetrate the tissues of their hosts and how they potentiate and control the ensuing immune responses, particularly in the first days of infection. Emerging 'omics' data employed in an unbiased approach are helping us understand liver fluke biology and, in parallel with new immunological data, to identify molecules that are essential to parasite development and accessible to vaccine-induced immune responses.

The effects of farm management practices on liver fluke prevalence and the current internal parasite control measures employed on Irish dairy farms

Fasciolosis caused by Fasciola hepatica is responsible for major production losses in cattle farms. The objectives of this study were to assess the effect of farm management practices on liver fluke prevalence on Irish dairy farms and to document the current control measures against parasitic diseases. In total, 369 dairy farms throughout Ireland were sampled from October to December 2013, each providing a single bulk tank milk (BTM) sample for liver fluke antibody-detection ELISA testing and completing a questionnaire on their farm management. The analysis of samples showed that cows on 78% (n=288) of dairy farms had been exposed to liver fluke. There was a difference (P<0.05) between farms where cows were positive or negative for liver fluke antibodies in (a) the total number of adult dairy cows in herds, (b) the number of adult dairy cows contributing to BTM samples, and (c) the size of the total area of grassland, with positive farms having larger numbers in each case. There was no difference (P>0.05) between positive and negative farms in (a) the grazing of dry cows together with replacement cows, (b) whether or not grazed grassland was mowed for conservation, (c) the type of drinking water provision system, (d) spreading of cattle manure on grassland or (e) for grazing season length (GSL; mean=262.5 days). Also, there were differences (P<0.001) between drainage statuses for GSL with farms on good drainage having longer GSL than moderately drained farms. The GSL for dairy cows on farms with good drainage was 11 days longer than for those with moderate drainage (P<0.001). The percentage of farmers that used an active ingredient during the non-lactating period against liver fluke, gastrointestinal nematodes, lungworm, and rumen fluke was 96%, 85%, 77% and 90%, respectively. Albendazole was the most frequently used active ingredient for treatment against gastrointestinal nematodes (57%), liver fluke (40%) and lungworm (47%), respectively. There was a difference (P<0.05) in the use of triclabendazole and albendazole between positive and negative farms, with triclabendazole use being more common in positive farms. This study highlighted differences in dairy management practices between Irish farms with dairy herds exposed or not exposed to liver fluke and stressed the need of fine-scale mapping of the disease patterns even at farm level to increase the accuracy of risk models. Also, comprehensive advice and professional support services to farmers on appropriate farm management practices are very important for an effective anthelmintic control strategy.

A highly water soluble benzimidazole derivative useful for the treatment of fasciolosis

This study describes the synthesis of compound (7), a highly hydrosoluble phosphonooxymethyl prodrug of compound alpha (4). Compound (7) improved the aqueous solubility of its precursor compound (4) by 50,000 times and it is stable at neutral pH. The prodrug showed faciolicidal activity when evaluated in vitro against excysted Fasciola hepatica metacercariae. The in vivo evaluation of (7) was carried out via oral, intramuscular and subcutaneous administration in sheep artificially infected with F. hepatica metacercariae. At an intramuscular dose of 4 mg/kg, the activity of (7) was similar to that of compound alpha (4) at an oral dose of 15 mg/kg.

Ovicidal effect of the methanolic extract of ginger (Zingiber officinale) on Fasciola hepatica eggs: an in vitro study

Fasciolosis is of considerable economic and public health importance worldwide. Little information is available on the ovicidal effects of anthelminthic drugs. The use of ovicidal anthelmintics can be effective in disease control. In this study, the effectiveness of the methanolic extract of ginger (Zingiber officinale) on the eggs of Fasciola hepatica is investigated. Fasciola hepatica eggs were obtained from the gall bladders of naturally infected sheep and kept at 4 °C until use. The eggs were exposed to varying concentrations of ginger extract (1, 5, 10, 25 and 50 mg/mL) for 24, 48 and 72 h. To investigate the effect of the ginger extracts on the miracidial formation, the treated eggs were incubated at 28 °C for 14 days. The results indicated that F. hepatica eggs are susceptible to the methanolic extract of Z. officinale. The ovicidal effect of ginger extract at a concentration of 1 mg/mL with 24, 48 and 72 h treatment time was 46.08, 51.53 and 69.09 % respectively (compared with 22.70 % for control group). The ovicidal effect of ginger extract at a concentration of 5 mg/mL after 24 h was 98.84 %. One hundred percent ovicidal efficacy was obtained through application of ginger extract at concentrations of 5 and 10 mg/mL with a 48 and 24 h treatment time respectively. The in vitro ovicidal effect of the methanolic extract of Z. officinale was satisfactory in this study, however, in vivo efficacy of this extract, remains for further investigation. To the best of our knowledge, this is the first report on the ovicidal effect of Z. officinale against F. hepatica eggs.

In vitro tegumental alterations on adult Fasciola gigantica caused by mefloquine

Emergence of drug-resistant Fasciola strains has drawn the attention of many authors to alternative drugs. The purpose of this study is to explore the in vitro effect of the antimalarial mefloquine against adult Fasciola gigantica. Light and scanning electron microscopic observations could be used to determine the target of the drug following 6 and 12 h of incubation in medium containing mefloquine at three different concentrations 10, 20 and 30 μg/mL, as morphological changes could be observed. These changes occurred in definite sequences in response to mefloquine, and were consisted of swelling, vacuolization that was later disrupted, leading to desquamation of the tegument, resulting in exposure and disruption of basal lamina and the dislodging of spines. It is concluded that mefloquine presented itself as a drug that might become important in trematode chemotherapy, with the tegument being an important drug target.