Status of benzimidazole resistance in intestinal nematode populations of livestock in Brazil: a systematic review

Widespread occurrence of benzimidazole resistance single nucleotide polymorphisms in the canine hookworm, Ancylostoma caninum, in Australia

Canine hookworm (Ancylostoma caninum), a gastrointestinal nematode of domestic dogs, principally infects the small intestine of dogs and has the potential to cause zoonotic disease. In greyhounds and pet dogs in the USA, A. caninum has been shown to be resistant to multiple anthelmintics. We conducted a molecular survey of benzimidazole resistance in A. caninum from dogs at veterinary diagnostic centers in Australia and New Zealand. First, we implemented an internal transcribed spacer (ITS)-2 rDNA deep amplicon metabarcoding sequencing approach to ascertain the species of hookworms infecting dogs in the region. Then, we evaluated the frequency of the canonical F167Y and Q134H isotype-1 β-tubulin mutations, which confer benzimidazole resistance, using the same sequencing approach. The most detected hookworm species in diagnostic samples was A. caninum (90%; 83/92); the related Northern hookworm (Uncinaria stenocephala) was identified in 11% (10/92) of the diagnostic samples. There was a single sample with coinfection by A. caninum and U. stenocephala. Both isotype-1 β-tubulin mutations were present in A. caninum, 49% and 67% for Q134H and F167Y, respectively. Mutation F167Y in the isotype-1 β-tubulin mutation was recorded in U. stenocephala for the first known time. Canonical benzimidazole resistance codons 198 and 200 mutations were absent. Egg hatch assays performed on a subset of the A. caninum samples showed significant correlation between 50% inhibitory concentration (IC50) to thiabendazole and F167Y, with an increased IC50 for samples with > 75% F167Y mutation. We detected 14% of dogs with > 75% F167Y mutation in A. caninum. Given that these samples were collected from dogs across various regions of Australia, the present study suggests that benzimidazole resistance in A. caninum is widespread. Therefore, to mitigate the risk of resistance selection and further spread, adoption of a risk assessment-based approach to limit unnecessary anthelmintic use should be a key consideration for future parasite control.

Chitosan-ricobendazole complex: Synthesis, characterization and anthelmintic activity

Synthesis, characterization and assessment of therapeutic efficacy of chitosan-ricobendazole complex were carried out for the first time in this work. Study of physico-chemical properties revealed the optimal ratio of chitosan: ricobendazole (30:4). Quantum chemical modeling set the optimal parameters for the formation of the chitosan-ricobendazole molecular system (E = -3765.26 kcal/mol, η = 0.127 eV), which was confirmed by Fourier-transform infrared spectroscopy. Scanning electron microscopy showed spherical particles of chitosan-ricobendazole complex ranging in size from 100 to 200 μm. Study of therapeutic efficiency was conducted on sheep with dicroceliosis. Notably, the therapeutic efficiency of the chitosan-ricobendazole complex (4 mg/kg of ricobendazole) reached 89 %, while the therapeutic efficiency of the commercial preparation ricazole (8 mg/kg of ricobendazole) was 92 %. Biochemical blood test indicated equivalent normalization of hematological parameters in sheep after treatment with ricazole and the chitosan-ricobendazole complex. Histological examination of infected sheep liver revealed that treatment with the chitosan-ricobendazole complex leads to a decrease in the number of helminth eggs with subsequent therapeutic effect on the severity of the disease. This proves the enhanced solubility of ricobendazole at a dosage of 4 mg/kg, active interaction of the components and relatively high bioavailability without increasing the release rate of ricobendazole.

Tannins Can Have Direct Interactions with Anthelmintics: Investigations by Isothermal Titration Calorimetry

Plant tannins are known for their anthelmintic and antiparasitic activities and have been increasingly studied to battle the ever-growing problem of anthelmintic resistance. While tannins have been shown to exhibit these activities on their own, one approach would be to use them as complementary nutrients alongside commercial anthelmintics. So far, research on the interactions between tannins and anthelmintics is limited, and few studies have reported both synergistic and antagonistic effects depending on the type of tannin and the method used. These interactions could either strengthen or weaken the efficacy of commercial anthelmintics, especially if tannin-rich diets are combined with anthelmintics used as oral drenches. To study these interactions, a series of hydrolysable tannins (HTs) was selected, and their direct interactions with thiabendazole (TBZ) were evaluated by isothermal titration calorimetry (ITC), which allowed the detection of the exothermic interaction but also the roles and significances of different structural features of HTs in these interactions. Our results show that HTs can have a direct interaction with the benzimidazole anthelmintic TBZ and that the interaction is strengthened by increasing the number of free galloyl groups and the overall molecular flexibility of HTs.

The Economic Impact of Parasitism from Nematodes, Trematodes and Ticks on Beef Cattle Production

Global human population growth requires the consumption of more meat such as beef to meet human needs for protein intake. Cattle parasites are a constant and serious threat to the development of the beef cattle industry. Studies have shown that parasites not only reduce the performance of beef cattle, but also negatively affect the profitability of beef agriculture and have many other impacts, including contributing to the production of greenhouse gases. In addition, some zoonotic parasitic diseases may also threaten human health. Therefore, ongoing cattle parasite research is crucial for continual parasite control and the development of the beef cattle industry. Parasitism challenges profitable beef production by reducing feed efficiency, immune function, reproductive efficiency, liveweight, milk yield, calf yield and carcass weight, and leads to liver condemnations and disease transmission. Globally, beef cattle producers incur billions (US$) in losses due to parasitism annually, with gastrointestinal nematodes (GIN) and cattle ticks causing the greatest economic impact. The enormity of losses justifies parasitic control measures to protect profits and improve animal welfare. Geographical differences in production environment, management practices, climate, cattle age and genotype, parasite epidemiology and susceptibility to chemotherapies necessitate control methods customized for each farm. Appropriate use of anthelmintics, endectocides and acaricides have widely been shown to result in net positive return on investment. Implementing strategic parasite control measures, with thorough knowledge of parasite risk, prevalence, parasiticide resistance profiles and prices can result in positive economic returns for beef cattle farmers in all sectors.

The 22nd Chromatography Component of the Fasciola gigantica Excretory-Secretory Products Decreased the Proliferation of Peripheral Blood Mononuclear Cells from Buffalo

The 22nd chromatography component (F22) of the Fasciola gigantica excretory-secretory products (FgESP) shows better diagnostic value than the FgESP, and diagnostic methods based on F22 have also been established. Thus, exploring its immunomodulatory function and potential as a molecular vaccine candidate is attractive. In the present study, the effect of F22 on the mitogen-induced proliferation of buffalo peripheral blood mononuclear cells (PBMCs) in the innate immune response was preliminarily studied using the FgESP as a control. PBMCs were incubated with concanavalin A (ConA) and phytohemagglutinin (PHA) at optimal (1 µg/well) or suboptimal (0.25 µg/well) doses coupled with FgESP and F22 at different doses (1-16 µg/well). Cell proliferation was then assessed by microenzyme reaction colorimetry (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium (MTT) assay). In addition, the components of F22 were also explored by mass spectrometry and then subjected to Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis to infer their functions. The results indicated that FgESP decreased the proliferation of PBMCs stimulated with ConA and PHA at specific doses, whereas F22 significantly decreased the proliferation of PBMCs stimulated with ConA and PHA at both optimal and suboptimal doses (p < 0.05). Two hundred and sixteen proteins were identified in F22, and these included 86 proteins that could be assigned to more than one pathway and some with robust immunomodulatory ability. Further studies should be performed to investigate the immunomodulatory function of F22 in the adaptive immune response, and the components of F22 can be further studied as potential vaccine candidate molecules.

Lentinula edodes extract increases goblet cell number and Muc2 expression in an intestinal inflammatory model of Trichinella spiralis infection

AHCC® is a standardized extract of cultured mushroom (Lentinula edodes) mycelia with a wide variety of therapeutic effects including anti-inflammatory, antitumor and antiviral effects. Trichinellosis, a food-borne parasitic zoonosis is caused by the nematode Trichinella spp. Infection with Trichinella is characterized by the induction of a Th1-type response at the beginning of the intestinal phase, followed by a dominant Th2-type response which is essential for parasite expulsion. The aim of this study was to evaluate the immunomodulatory effect of AHCC® in a murine model of Trichinella spiralis infection. Swiss CD1 mice were infected with T. spiralis larvae and treated with AHCC®. Standard treatment with albendazole (ABZ) was used as control in the assessment of parasite burden. The small intestine was taken out and the proximal segment was evaluated for several parameters: gene expression of immune and stress-reticulum mediators, histological damage score, goblet cell count and Mucin 2 (Muc2) gene expression. AHCC® modulated expression levels of both Th1 and Th2 cytokines and reduced histological damage score. In addition, AHCC® diminished the number of adults of T. spiralis in treated animals. AHCC® treatment anticipates T. spiralis expulsion and increases goblet cell number and Muc2 gene expression.

Maximising Societal Benefit From the Control of Neglected Zoonoses: Identifying Synergies and Trade-Offs in the Control of Taenia solium

Interventions to control or eradicate neglected zoonoses are generally paid for through the public purse and when these interventions focus on the animal hosts, they are often expected to be performed and financed through the state veterinary service. The benefits of control, however, accrue across the human, animal, and environmental spaces and enhance both public and private interests. Additionally, disease control interventions do not take place in a vacuum and the indirect impacts of our actions should also be considered if the societal benefit of interventions is to be maximised. With the caveat that unintended consequences can and will occur, pre-identifying potential synergies and trade-offs in our disease control initiatives allows for them to be considered in intervention design and monitored during programme roll-out. In this paper, using a One Health approach with the example of Taenia solium control, we identify potential indirect impacts which may arise and how these may influence both our choice of intervention and opportunities to optimise the animal, environmental, and societal benefits of control through maximising synergies and minimising trade-offs.

Leaching of benzimidazole antiparasitics in soil columns and in soil columns amended with sheep excreta

Benzimidazoles are anthelmintics frequently used in sheep farming due to the high susceptibility of these animals to parasitic diseases. Sheep excreta are often disposed onto soils as a fertilizer, and they may contain benzimidazole residues that can contaminate soil and water. This work aimed to assess the leaching behavior of benzimidazole drugs (albendazole, fenbendazole, and thiabendazole) and their metabolites in two Brazilian soils of different textural classifications (sandy and clay), as well as sheep excreta-amended soils, following the OECD 312 Guidelines. Ewes received a single oral dose of 10 mg kg^-1 b.w. of either albendazole or fenbendazole. The feces were collected at 24, 48, 72, 96, and 120 h post-dose, and the parent drugs and their metabolites extracted using the QuEChERS approach and quantified by UHPLC-MS/MS. For the leaching assays, a benzimidazole solution was directly applied onto the soil columns, or an amount of 5 g of the medicated sheep feces was distributed over the top of the soil columns. In soil samples, benzimidazoles were extracted by solid-liquid extraction and quantified by UHPLC-MS/MS. For the leaching studies, atrazine was used as a reference substance to determine the relative mobility factor of the analytes of interest. Benzimidazoles were considered slightly to moderately mobile in both soils tested, with a leaching distance of up to 25 cm in a 30-cm soil column. Approximately 3 to 6% of the benzimidazoles present in ewe feces were able to leach into the soil columns. This finding is of concern since benzimidazoles are persistent in soil and may pose a risk to soil biota and induce the development of resistant strains of parasites.

Soybean (Glycine max) Is Able to Absorb, Metabolize and Accumulate Fenbendazole in All Organs Including Beans

Although manure is an important source of minerals and organic compounds it represents a certain risk of spreading the veterinary drugs in the farmland and their permeation to human food. We tested the uptake of the anthelmintic drug fenbendazole (FBZ) by soybean, a common crop plant, from the soil and its biotransformation and accumulation in different soybean organs, including beans. Soybeans were cultivated in vitro or grown in a greenhouse in pots. FBZ was extensively metabolized in roots of in vitro seedlings, where sixteen metabolites were identified, and less in leaves, where only two metabolites were found. The soybeans in greenhouse absorbed FBZ by roots and translocated it to the leaves, pods, and beans. In roots, leaves, and pods two metabolites were identified. In beans, FBZ and one metabolite was found. FBZ exposure did not affect the plant fitness or yield, but reduced activities of some antioxidant enzymes and isoflavonoids content in the beans. In conclusion, manure or biosolids containing FBZ and its metabolites represent a significant risk of these pharmaceuticals entering food consumed by humans or animal feed. In addition, the presence of these drugs in plants can affect plant metabolism, including the production of isoflavonoids.

Albendazole and Mebendazole as Anti-Parasitic and Anti-Cancer Agents: an Update

The use of albendazole and mebendazole, i.e., benzimidazole broad-spectrum anthelmintics, in treatment of parasitic infections, as well as cancers, is briefly reviewed. These drugs are known to block the microtubule systems of parasites and mammalian cells leading to inhibition of glucose uptake and transport and finally cell death. Eventually they exhibit ovicidal, larvicidal, and vermicidal effects on parasites, and tumoricidal effects on hosts. Albendazole and mebendazole are most frequently prescribed for treatment of intestinal nematode infections (ascariasis, hookworm infections, trichuriasis, strongyloidiasis, and enterobiasis) and can also be used for intestinal tapeworm infections (taeniases and hymenolepiasis). However, these drugs also exhibit considerable therapeutic effects against tissue nematode/cestode infections (visceral, ocular, neural, and cutaneous larva migrans, anisakiasis, trichinosis, hepatic and intestinal capillariasis, angiostrongyliasis, gnathostomiasis, gongylonemiasis, thelaziasis, dracunculiasis, cerebral and subcutaneous cysticercosis, and echinococcosis). Albendazole is also used for treatment of filarial infections (lymphatic filariasis, onchocerciasis, loiasis, mansonellosis, and dirofilariasis) alone or in combination with other drugs, such as ivermectin or diethylcarbamazine. Albendazole was tried even for treatment of trematode (fascioliasis, clonorchiasis, opisthorchiasis, and intestinal fluke infections) and protozoan infections (giardiasis, vaginal trichomoniasis, cryptosporidiosis, and microsporidiosis). These drugs are generally safe with few side effects; however, when they are used for prolonged time (>14-28 days) or even only 1 time, liver toxicity and other side reactions may occur. In hookworms, Trichuris trichiura, possibly Ascaris lumbricoides, Wuchereria bancrofti, and Giardia sp., there are emerging issues of drug resistance. It is of particular note that albendazole and mebendazole have been repositioned as promising anti-cancer drugs. These drugs have been shown to be active in vitro and in vivo (animals) against liver, lung, ovary, prostate, colorectal, breast, head and neck cancers, and melanoma. Two clinical reports for albendazole and 2 case reports for mebendazole have revealed promising effects of these drugs in human patients having variable types of cancers. However, because of the toxicity of albendazole, for example, neutropenia due to myelosuppression, if high doses are used for a prolonged time, mebendazole is currently more popularly used than albendazole in anti-cancer clinical trials.

Anthelmintic Activity of Extracts and Active Compounds From Diospyros anisandra on Ancylostoma caninum, Haemonchus placei and Cyathostomins

The present study aimed to evaluate the anthelmintic activity of leaf and bark extracts of Diospyros anisandra collected during different seasons and their major constituents on eggs of Ancylostoma caninum, Haemonchus placei, and cyathostomins. Specifically, the eclosion inhibition of the methanolic extracts of the leaves and bark of D. anisandra collected during the dry and rainy seasons (600–37.5 μg/ml) were evaluated in addition to the fractions, sub-fractions (300–37.5 μg/ml) and active major constituents (150–2.3 μg/ml). The rainy season bark extract had the highest percentage of eclosion inhibition (PEI) against the evaluated nematodes (≥ 90% at 75 μg/ml) along with high ovicidal activity (90.0 to 93.4% at 75 μg/ml). The purification of the rainy season bark extract showed that its biological activity came from the non-polar n-hexane fraction (≥ 93% at 75 μg/ml). The bioguided fractionation pointed to sub-fraction 5 as having the highest anthelmintic activity against the three evaluated genera of nematodes (PEI ≥ 93% at 37.5 μg/ml). Gas chromatography and mass spectrometry revealed that the major constituent in sub-fraction 5 was plumbagin. Upon evaluation, plumbagin was confirmed to be responsible for the anthelmintic activity of D. anisandra, with a PEI ≥ 90% at 2.3 μg/ml on the three evaluated nematodes. Additionally, the compounds betulin and lupeol in the bark of D. anisandra were evaluated but presented low anthelmintic activity (PEI ≤ 5.3% at 2.3 μg/ml). In conclusion, the rainy season bark extract of D. anisandra exerts a high ovicidal activity against the eggs of the three studied nematodes. Plumbagin is the active compound responsible for this activity and represents a potential alternative for the control of different genera of gastrointestinal nematodes given the current scenario of anthelmintic resistance.

Molecular evidence of hybridization between pig and human Ascaris indicates an interbred species complex infecting humans

Human ascariasis is a major neglected tropical disease caused by the nematode Ascaris lumbricoides. We report a 296 megabase (Mb) reference-quality genome comprised of 17,902 protein-coding genes derived from a single, representative Ascaris worm. An additional 68 worms were collected from 60 human hosts in Kenyan villages where pig husbandry is rare. Notably, the majority of these worms (63/68) possessed mitochondrial genomes that clustered closer to the pig parasite Ascaris suum than to A. lumbricoides. Comparative phylogenomic analyses identified over 11 million nuclear-encoded SNPs but just two distinct genetic types that had recombined across the genomes analyzed. The nuclear genomes had extensive heterozygosity, and all samples existed as genetic mosaics with either A. suum-like or A. lumbricoides-like inheritance patterns supporting a highly interbred Ascaris species genetic complex. As no barriers appear to exist for anthroponotic transmission of these 'hybrid' worms, a one-health approach to control the spread of human ascariasis will be necessary.

Teladorsagia circumcincta beta tubulin: the presence of the E198L polymorphism on its own is associated with benzimidazole resistance

BACKGROUND

Benzimidazole resistance is associated with isotype-1 β-tubulin gene F200Y, E198A and F167Y SNPs. In this study, the recently described polymorphism E198L was reported and analysed in Teladorsagia circumcincta.

METHODS

The benzimidazole phenotypic resistance was measured by the faecal egg count reduction test (FECRT) and the egg hatch test (EHT) using a discriminating dose (DD) in 39 sheep flocks. Around 1000 larvae collected before and after treatment were used for DNA extraction. The resistant species identified in all flocks was T. circumcincta. The resistance alleles frequencies were measured for F200Y and E198A. A 371-bp fragment of the isotype-1 β-tubulin gene was analysed, including the three codons of interest, and a new pyrosequencing assay was designed for testing E198L.

RESULTS

The percentage of resistant flocks was 35% by FECRT or 26% by EHT; however, F200Y and E198A SNPs were absent in T. circumcincta. The amplification of a 371-bp fragment confirmed the absence of F167Y and F200Y in 6 resistant flocks. Regarding codon 198, all samples after treatment carried a leucine (CTA). A pyrosequencing assay analysed the allele frequencies for the first two bases at codon 198 independently, G/C and A/T. The correlation between C and T frequencies was almost 1 (r = 0.929, P < 0.0001) and the mean value of both was calculated to measure the leucine frequency; this value ranged between 10.4-80.7% before treatment, and 82.3-92.8% after treatment. High and similar correlations were reported between the genotypic variables (C frequency, T frequency or mean of both frequencies) and phenotypic resistance (r > 0.720, P < 0.0001), although negatively associated with the FECRT and positively with the EHT. According to multivariate linear regression analysis, the T frequency was the most significant variable influencing the phenotypic resistance (FECRT or EHT; P < 0.0001). In the EHT, 67.1% of the phenotypic variability is associated with the T frequency but in the FECRT only 33.4%; therefore, the EHT using a DD seems to detect the genotypic resistance more accurately than the FECRT.

CONCLUSIONS

The E198L polymorphism can confer BZ resistance on its own in T. circumcincta.

The Identification of Metabolites and Effects of Albendazole in Alfalfa (Medicago sativa)

Albendazole (ABZ), a widely used anthelmintic drug, enters the environment mainly via livestock excrements. To evaluate the environmental impact of ABZ, the knowledge of its uptake, effects and metabolism in all non-target organisms, including plants, is essential. The present study was designed to identify the metabolic pathway of ABZ and to test potential ABZ phytotoxicity in fodder plant alfalfa, with seeds and in vitro regenerants used for these purposes. Alfalfa was chosen, as it may meet manure from ABZ-treated animals in pastures and fields. Alfalfa is often used as a feed of livestock, which might already be infected with helminths. The obtained results showed that ABZ did not inhibit alfalfa seed germination and germ growth, but evoked stress and a toxic effect in alfalfa regenerants. Alfalfa regenerants were able to uptake ABZ and transform it into 21 metabolites. UHPLC-MS/MS analysis revealed three new ABZ metabolites that have not been described yet. The discovery of the parent compound ABZ together with the anthelmintically active and instable metabolites in alfalfa leaves shows that the contact of fodder plants with ABZ-containing manure might represent not only a danger for herbivorous invertebrates, but also may cause the development of ABZ resistance in helminths.

The Uptake of Ivermectin and Its Effects in Roots, Leaves and Seeds of Soybean (Glycine max)

In recent years interest has grown in the occurrence and the effects of pharmaceuticals in the environment. The aim of this work is to evaluate the risk of fertilizing crops with manure from livestock treated with anthelmintics. The present study was designed to follow the fate of the commonly used anthelmintic drug, ivermectin (IVM) and its metabolites in soybeans (Glycine max (L.) Merr.), a plant that is grown and consumed world-wide for its high content of nutritional and health-beneficial substances. In vitro plantlets and soybean plants, cultivated in a greenhouse, were used for this purpose. Our results showed the uptake of IVM and its translocation to the leaves, but not in the pods and the beans. Four IVM metabolites were detected in the roots, and one in the leaves. IVM exposure decreased slightly the number and weight of the beans and induced changes in the activities of antioxidant enzymes. In addition, the presence of IVM affected the proportion of individual isoflavones and reduced the content of isoflavones aglycones, which might decrease the therapeutic value of soybeans. Fertilization of soybean fields with manure from IVM-treated animals appears to be safe for humans, due to the absence of IVM in beans, the food part of plants. On the other hand, it could negatively affect soybean plants and herbivorous invertebrates.

Assessment of the F200Y mutation frequency in the β tubulin gene of Haemonchus contortus following the exposure to a discriminating concentration of thiabendazole in the egg hatch test

The ruminant livestock production sector is under threat due to the infections with gastrointestinal nematode parasites and the subsequent development of anthelmintic resistance. One of most common and pathogenic species in small ruminants is Haemonchus contortus. The ability to control the infections with this and other gastrointestinal nematodes relies heavily on the use of anthelmintic drugs. Although resistance to all major classes of anthelmintics has been shown in H. contortus, the precise mechanism of resistance acquisition is only known for benzimidazoles. F200Y (TAC) is a common point mutation in the isotype 1 β tubulin gene which is associated with an effective increase in the resistance towards benzimidazole drugs. Here, we show the utility of using this mutation as a marker in a droplet digital PCR assay to track how two H. contortus laboratory strains, characterized by different resistance levels, change with respect to this mutation, when subjected to increasing concentrations of thiabendazole. Additionally, we wanted to investigate whether exposure to a discriminating dose of thiabendazole in the egg hatch test resulted in the death of all H. contortus eggs with a susceptible genotype. We found the MHco5 strain to maintain an overall higher frequency of the F200Y mutation (80-100%) over all drug concentrations, whilst a steady, gradual increase from around 30%-60% was observed in the case of the MHco4 strain. This is further supported by the dose-response curves, displaying a much higher tolerance of the MHco5 strain (LD₅₀ = 0.38 μg/ml) in comparison to the MHco4 strain (LD₅₀ = 0.07 μg/ml) to the effects of thiabendazole. All things considered, we show that the F200Y mutation is still a viable and reliable marker for the detection and surveillance of benzimidazole drug resistance in H. contortus in Europe.

Accelerated microdroplet synthesis of benzimidazoles by nucleophilic addition to protonated carboxylic acids

We report a metal-free novel route for the accelerated synthesis of benzimidazole and its derivatives in the ambient atmosphere. The synthetic procedure involves 1,2-aromatic diamines and alkyl or aryl carboxylic acids reacting in electrostatically charged microdroplets generated using a nano-electrospray (nESI) ion source. The reactions are accelerated by orders of magnitude in comparison to the bulk. No other acid, base or catalyst is used. Online analysis of the microdroplet accelerated reaction products is performed by mass spectrometry. We provide evidence for an acid catalyzed reaction mechanism based on identification of the intermediate arylamides. Their dehydration to give benzimidazoles occurs in a subsequent thermally enhanced step. It is suggested that the extraordinary acidity at the droplet surface allows the carboxylic acid to function as a C-centered electrophile. Comparisons of this methodology with data from thin film and bulk synthesis lead to the proposal of three key steps in the reaction: (i) formation of an unusual reagent (protonated carboxylic acid) because of the extraordinary conditions at the droplet interface, (ii) accelerated bimolecular reaction because of limited solvation at the interface and (iii) thermally assisted elimination of water. Eleven examples are shown as evidence of the scope of this chemistry. The accelerated synthesis has been scaled-up to establish the substituent-dependence and to isolate products for NMR characterization.

Assessing anthelmintic resistance risk in the post-genomic era: a proof-of-concept study assessing the potential for widespread benzimidazole-resistant gastrointestinal nematodes in North American cattle and bison

As genomic research continues to improve our understanding of the genetics of anthelmintic drug resistance, the revolution in DNA sequencing technologies will provide increasing opportunities for large-scale surveillance for the emergence of drug resistance. In most countries, parasite control in cattle and bison has mainly depended on pour-on macrocyclic lactone formulations resulting in widespread ivermectin resistance. Consequently, there is an increased interest in using benzimidazole drugs which have been used comparatively little in cattle and bison in recent years. This situation, together with our understanding of benzimidazole resistance genetics, provides a practical opportunity to use deep-amplicon sequencing to assess the risk of drug resistance emergence. In this paper, we use deep-amplicon sequencing to scan for those mutations in the isotype-1 β-tubulin gene previously associated with benzimidazole resistance in many trichostrongylid nematode species. We found that several of these mutations occur at low frequency in many cattle and bison parasite populations in North America, suggesting increased use of benzimidazole drugs in cattle has the potential to result in widespread emergence of resistance in multiple parasite species. This work illustrates a post-genomic approach to large-scale surveillance of early emergence of anthelmintic resistance in the field.

High Endemicity of Soil-Transmitted Helminths in a Population Frequently Exposed to Albendazole but No Evidence of Antiparasitic Resistance

INTRODUCTION

Soil-transmitted helminths (STHs) are gastrointestinal parasites widely distributed in tropical and subtropical areas. Mass drug administration (MDA) of benzimidazoles (BZ) is the most recommended for STH control. These drugs have demonstrated limited efficacy against Trichuris trichiura and the long-term use of single-dose BZ has raised concerns of the possible emergence of genetic resistance. The objective of this investigation was to determine whether genetic mutations associated with BZ resistance were present in STH species circulating in an endemic region of Honduras.

METHODS

A parasitological survey was performed as part of this study, the Kato-Katz technique was used to determine STH prevalence in children of La Hicaca, Honduras. A subgroup of children received anthelminthic treatment in order to recover adult parasite specimens that were analyzed through molecular biology techniques. Genetic regions containing codons 200, 198, and 167 of the -tubulin gene of Ascaris lumbricoides and Trichuris trichiura were amplified and sequenced.

RESULTS

Stool samples were collected from 106 children. The overall STH prevalence was 75.47%, whereby T. trichiura was the most prevalent helminth (56.6%), followed by A. lumbricoides (17%), and hookworms (1.9%). Eighty-five sequences were generated for adjacent regions to codons 167, 198, and 200 of the -tubulin gene of T. trichiura and A. lumbricoides specimens. The three codons of interest were found to be monomorphic in all the specimens.

CONCLUSION

Although the inability to find single-nucleotide polymorphisms (SNPs) in the small sample analyzed for the present report does not exclude the possibility of their occurrence, these results suggest that, at present, Honduras's challenges in STH control may not be related to drug resistance but to environmental conditions and/or host factors permitting reinfections.

Albendazole and Praziquantel: Review and Safety Monitoring in Korea

Albendazole (ADZ) and praziquantel (PZQT) have been used as anthelmintics for over 30 years. Worldwide, hundreds of millions tablets are administered to people and livestock every year. ADZ is poorly orally absorbed (<5%), and its uptake is enhanced by high-fat meals, while PZQT is well absorbed (>75%) and uptake is enhanced by carbohydrate-rich meals. Both ADZ and PZQT are safe, but not recommended for children <2 years or for women in the first trimester of pregnancy. Serious adverse events occur following high dose and prolonged administration of these drugs for treatment of echinococcosis or neurocysticercosis, especially in patients with poor liver function. The adverse events may be induced by the drugs, or by the dead worms themselves. The Korea Institute of Drug Safety & Risk Management monitors drug-related adverse events in Korea, and its database included 256 probable or possible ADZ-associated events and 108 PZQT-associated events between 2006 and 2015. Such low incidence rates in Korea are due to the low single dose treatments of ADZ, and the short-term use of PZQT. The number of serious adverse events due to drug interaction induced by ADZ and PZQT were six and two, respectively. We conclude that ADZ and PZQT are generally safe drugs, but they must be used with caution in people with poor liver function or those being comedicated for gastroesophageal reflux disease.