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Andrew C Kotze - One of the best experts on this subject based on the ideXlab platform.
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acetylcholine receptor subunit genes from ancylostoma caninum altered transcription patterns associated with Pyrantel resistance
International Journal for Parasitology, 2009Co-Authors: Steven Kopp, G T Coleman, James S Mccarthy, Rebecca J Traub, Andrew C KotzeAbstract:The molecular mechanism of resistance to nicotinic agonist anthelmintics such as Pyrantel and levamisole in nematodes of medical and veterinary significance is poorly understood. The identification of Pyrantel-resistant isolates of the canine hookworm, Ancylostoma caninum, provides an opportunity to explore, at a molecular level, the mechanism of cholinergic resistance in a species that is a model for the human hookworms. Here we describe the cloning of three A. caninum genes orthologous to components of the Pyrantel-sensitive nicotinic acetylcholine receptor in Caenorhabditis elegans (UNC-29, -38, -63). Analysis of mRNA levels by quantitative PCR was also performed on these genes, plus an additional three nicotinic acetylcholine receptor subunit genes thought not to be constituents of the Pyrantel-sensitive receptor, for which a partial sequence was obtained. Gene sequences and mRNA levels were compared between two isolates of A. caninum showing either high- or low-level resistance to Pyrantel (as shown previously by in vivo efficacy and in vitro comparative studies). While no polymorphisms of likely significance between the two A. caninum isolates were observed, quantitative analysis of transcription revealed significantly lower levels for the three putative Pyrantel receptor subunits (AAR-29, -38 and -63) in the highly Pyrantel-resistant isolate compared with the isolate with low-level resistance. In contrast, transcription of the three subunits thought not to constitute the Pyrantel receptor (AAR-8, -15 and -19) was either not significantly different between the two isolates, or slightly higher in the highly-resistant isolate. This data suggests that reduced transcription of the mRNA coding for nicotinic acetylcholine receptor subunits that form the Pyrantel-sensitive receptors may be a component of the Pyrantel resistance mechanism in A. caninum.
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phenotypic characterization of two ancylostoma caninum isolates with different susceptibilities to the anthelmintic Pyrantel
Antimicrobial Agents and Chemotherapy, 2008Co-Authors: Steven Kopp, G T Coleman, James S Mccarthy, Andrew C KotzeAbstract:The anthelmintic Pyrantel plays an important role in the control of gastrointestinal helminths of humans and domestic animals. Despite the demonstration of Pyrantel resistance in several helminth species over the last 20 years, the resistance mechanism remains unclear. It has been hypothesized that resistance may arise as a consequence of changes to the relative proportions of subpopulations of nicotinic acetylcholine receptors (nAchRs). To test this hypothesis, we examined the responses of two isolates of the canine hookworm Ancylostoma caninum with low-level resistance (isolate NT) and high-level resistance (isolate PR) to Pyrantel to nicotinic agonist drugs reported to be selective for three nAchR subtypes. We used larval motility and conformation assays and force transduction experiments with adult worms. Pyrantel and levamisole were less potent against larvae of isolate PR than larvae of isolate NT (up to an 18-fold increase in the 50% inhibitory concentration); on the other hand, bephenium was more potent against larvae of isolate PR than larvae of isolate NT (twofold) and nicotine had the same potency against larvae of both isolates. In adults, Pyrantel, levamisole, and nicotine were less potent against isolate PR than isolate NT (two- to threefold), but the potency of bephenium against the two isolates was equivalent. Our data indicate a complex pattern of nAchRs in this species and suggest that the two isolates differ in their relative sensitivities to agonists targeting different nAchRs.
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Acetylcholine receptor subunit genes from Ancylostoma caninum: Altered transcription patterns associated with Pyrantel resistance ☆
International journal for parasitology, 2008Co-Authors: Steven Kopp, James S Mccarthy, Rebecca J Traub, Glen T. Coleman, Andrew C KotzeAbstract:The molecular mechanism of resistance to nicotinic agonist anthelmintics such as Pyrantel and levamisole in nematodes of medical and veterinary significance is poorly understood. The identification of Pyrantel-resistant isolates of the canine hookworm, Ancylostoma caninum, provides an opportunity to explore, at a molecular level, the mechanism of cholinergic resistance in a species that is a model for the human hookworms. Here we describe the cloning of three A. caninum genes orthologous to components of the Pyrantel-sensitive nicotinic acetylcholine receptor in Caenorhabditis elegans (UNC-29, -38, -63). Analysis of mRNA levels by quantitative PCR was also performed on these genes, plus an additional three nicotinic acetylcholine receptor subunit genes thought not to be constituents of the Pyrantel-sensitive receptor, for which a partial sequence was obtained. Gene sequences and mRNA levels were compared between two isolates of A. caninum showing either high- or low-level resistance to Pyrantel (as shown previously by in vivo efficacy and in vitro comparative studies). While no polymorphisms of likely significance between the two A. caninum isolates were observed, quantitative analysis of transcription revealed significantly lower levels for the three putative Pyrantel receptor subunits (AAR-29, -38 and -63) in the highly Pyrantel-resistant isolate compared with the isolate with low-level resistance. In contrast, transcription of the three subunits thought not to constitute the Pyrantel receptor (AAR-8, -15 and -19) was either not significantly different between the two isolates, or slightly higher in the highly-resistant isolate. This data suggests that reduced transcription of the mRNA coding for nicotinic acetylcholine receptor subunits that form the Pyrantel-sensitive receptors may be a component of the Pyrantel resistance mechanism in A. caninum.
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application of in vitro anthelmintic sensitivity assays to canine parasitology detecting resistance to Pyrantel in ancylostoma caninum
Veterinary Parasitology, 2008Co-Authors: Steven Kopp, G T Coleman, James S Mccarthy, Andrew C KotzeAbstract:Resistance of the canine hookworm Ancylostoma caninum to anthelmintic therapy with Pyrantel is an emerging problem in canine veterinary practice. Detecting anthelmintic resistance in parasites of pets is problematic because traditional resistance-monitoring techniques used with livestock parasites, such as the faecal egg count reduction test, are often impractical for use in small animals. We used two field-collected isolates of A. caninum in an abbreviated critical trial to test their Pyrantel resistance status. The strains showed high-level and low-level resistance, with in vivo Pyrantel efficacies of 28% and 71%, respectively. We noted a distinct worm density dependence effect on faecal egg count during the critical trial; egg counts in the dogs containing the low-level resistant isolate were 41% higher 6 days after drug treatment, despite the removal of 71% of the adult worms by the drug treatment. We then assessed four candidate in vitro assays for their ability to detect Pyrantel resistance in A. caninum larvae, using these two isolates. The assays included a new format termed the larval arrested morphology assay (LAMA), based on observation of the effects of Pyrantel on the body shape adopted by infective stage A. caninum larvae in vitro. Our data suggests that three of these assays, the LAMA, the larval motility assay (LMA), and larval feeding inhibition assay (LFIA) show promise with regards to detection of Pyrantel resistance in A. caninum, but the complexity of the LFIA would likely limit its suitability for field studies. In vivo Pyrantel efficacies of 28% and 71% in the two A. caninum isolates were associated with a 17-fold shift in the in vitro IC50 values measured using the LAMA. Further testing with isolates of varying degrees of resistance is required to determine which of these assays is suitable as a rapid in vitro laboratory test for Pyrantel resistance in A. caninum. The present study also indicates that potential exists for the novel LAMA or the LMA to be of use in detecting Pyrantel resistance in the human hookworms, Necator americanus and Ancylostoma duodenale.
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Pyrantel in small animal medicine: 30 years on
Veterinary journal (London England : 1997), 2007Co-Authors: Steven Kopp, James S Mccarthy, Andrew C Kotze, Rebecca J Traub, Glen T. ColemanAbstract:Pyrantel, a tetrahydropyrimidine nicotinic agonist anthelmintic, has been used in companion animal medicine since the 1970s to control two important nematode groups, the hookworms and the roundworms. Given the zoonotic potential of these parasites, Pyrantel has served a dual role in helping to protect the health of both companion animals and the public for more than 30 years. This review describes the history and mechanism of action of this drug, and collates evidence that resistance to Pyrantel has developed in at least one canine nematode, the hookworm Ancylostoma caninum. The role of in vitro diagnosis tests in managing anthelmintic resistance in companion animal parasites is discussed, as are management practices that may reduce the rate at which resistance develops.
Jennifer Keiser - One of the best experts on this subject based on the ideXlab platform.
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Efficacy and tolerability of triple drug therapy with albendazole, Pyrantel pamoate, and oxantel pamoate compared with albendazole plus oxantel pamoate, Pyrantel pamoate plus oxantel pamoate, and mebendazole plus Pyrantel pamoate and oxantel pamoate
The Lancet. Infectious diseases, 2018Co-Authors: Wendelin Moser, Somphou Sayasone, Syda Xayavong, Bangon Bounheuang, Maxim Puchkov, Jörg Huwyler, Jan Hattendorf, Jennifer KeiserAbstract:Summary Background Albendazole and mebendazole are commonly used to control hookworm, but have shortcomings in their efficacy profiles. We assessed whether triple drug therapy (TDT) with albendazole, Pyrantel pamoate, and oxantel pamoate was more effective than the co-administration of two drugs for the treatment of hookworm infections. Methods A randomised, single-blind trial was done from Sept 27 until Nov 17, 2017, in Laos. Children (6–15 years) from six schools were invited to participate. Hookworm-positive children were randomly assigned (2:2:1:1) by a computer stratified list (block sizes of six and 12) to TDT with albendazole (400 mg), Pyrantel pamoate (20 mg/kg), and oxantel pamoate (20 mg/kg); albendazole plus oxantel pamoate; Pyrantel pamoate plus oxantel pamoate; or mebendazole (500 mg) combined with both Pyrantel pamoate and oxantel pamoate (used as proof of concept to compare the two TDTs). Two stool samples were collected at baseline and follow-up (17–30 days after treatment) and analysed with the Kato-Katz method. The primary outcome was the proportion of hookworm egg-negative children at follow-up in all Kato-Katz slides (cure rate [CR]) in the TDT with albendazole, Pyrantel pamoate, and oxantel pamoate group compared with the albendazole plus oxantel pamoate and Pyrantel pamoate plus oxantel pamoate groups. Secondary outcomes were tolerability 3 h and 24 h after treatment, egg reduction rates (ERRs) against hookworm, and efficacy against concomitant soil-transmitted helminth infections. Participating children and field and laboratory technicians were masked to treatment allocation. All children with follow-up data were included in the primary analysis. This trial is registered with ClinicalTrials.gov, number NCT03278431. Findings 1529 children were assessed for eligibility, of whom 533 provided complete baseline data and 414 provided complete outcome data. The CR was higher for the TDT albendazole, Pyrantel pamoate, and oxantel pamoate (116 [84%] of 138) than with albendazole plus oxantel pamoate (73 [53%] of 138; odds ratio 4·7, 95% CI 2·7–8·3; p Interpretation TDT with albendazole, Pyrantel pamoate, and oxantel pamoate could make a difference, in particular in the context of soil-transmitted helminth elimination. Pyrantel pamoate might be a useful alternative to prevent benzimidazole resistance; however, larger trials are needed to confirm this finding. Funding Swiss National Science Foundation.
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Pyrantel and oxantel pamoate
2017Co-Authors: Steven Kopp, Jennifer KeiserAbstract:Pyrantel, E-1,4,5,6-tetrahydro-1-methyl-2-[2-(2-thienyl) vinyl]-pyrimidine, is an imidazothiazole-derived tetrahydropyrimidine. Its anthelmintic activity was first identified in 1966 (Austin et al., 1966). It has been used as a broadspectrum anthelmintic in both veterinary and human medicine since the 1970s (Kopp et al., 2007b). In humans, it is clinically useful for therapy of three major nematode infections: hookworm (Ancylostoma duodenale and Necator americanus), roundworm (Ascaris lumbricoides), and pinworm (Enterobius vermicularis). In addition, Pyrantel pamoate appears to have activity against Trichinella spiralis and Trichostrongylus spp. Pyrantel pamoate is available as a tablet (including chewable) or oral suspension; common preparations include Combantrin (Pfizer), Antiminth (Goerig), and Pyrantrin (Niemeth).
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Effect of combinations of marketed human anthelmintic drugs against Trichuris muris in vitro and in vivo
Parasites & Vectors, 2012Co-Authors: Jennifer Keiser, Lucienne Tritten, Roberto Adelfio, Mireille VargasAbstract:Background Soil-transmitted helminth (STH) infections are responsible for a huge public health burden, however treatment options are limited. The discovery and development of novel efficacious drugs or drug combinations for the treatment of STH infections therefore has a high research priority. Methods We studied drug combination effects using the main standard anthelmintics, albendazole, mebendazole, levamisole, Pyrantel pamoate and ivermectin in the Trichuris muris model. Drug combinations were first tested in vitro and additive and synergistic combinations investigated further in vivo in female mice using ratios based on the ED_50 of the respective drugs. Results In vitro all 10 combinations of the standard anthelmintics tested against T. muris revealed synergistic behavior. We identified three drug combinations in vivo as strongly synergistic, namely mebendazole-ivermectin (Combination index (CI)=0.16), mebendazole-levamisole (CI=0.17) and albendazole-mebendazole (CI=0.23). For albendazole-ivermectin, moderate synergism was observed (CI=0.81) and for albendazole-levamisole a nearly additive effect was documented (CI=0.93) in vivo . Five combinations (albendazole-Pyrantel pamoate, mebendazole-Pyrantel pamoate, levamisole-Pyrantel pamoate, levamisole-ivermectin and Pyrantel pamoate-ivermectin) were antagonistic in vivo. Conclusion Our results strengthen the evidence that combination chemotherapy might play a role in the treatment of Trichuris infections. Albendazole-mebendazole should be studied in greater detail in preclinical studies.
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Efficacy of Current Drugs Against Soil-Transmitted Helminth Infections: Systematic Review and Meta-analysis
JAMA, 2008Co-Authors: Jennifer Keiser, Jürg UtzingerAbstract:Context More than a quarter of the human population is likely infected with soil-transmitted helminths (Ascaris lumbricoides, hookworm, and Trichuris trichiura) in highly endemic areas. Preventive chemotherapy is the mainstay of control, but only 4 drugs are available: albendazole, mebendazole, levamisole, and Pyrantel pamoate. Objective To assess the efficacy of single-dose oral albendazole, mebendazole, levamisole, and Pyrantel pamoate against A lumbricoides, hookworm, and T trichiura infections. Data Sources A systematic search of PubMed, ISI Web of Science, ScienceDirect, the World Health Organization library database, and the Cochrane Central Register of Controlled Trials (1960 to August 2007). Study Selection From 168 studies, 20 randomized controlled trials were included. Data Extraction and Data Synthesis Information on study year and country, sample size, age of study population, mean infection intensity before treatment, diagnostic method used, time between evaluations before and after treatment, cure rate (the percentage of individuals who became helminth egg negative following treatment with an anthelminthic drug), egg reduction rate, adverse events, and trial quality was extracted. Relative risk, including a 95% confidence interval (CI), was used to measure the effect of the drugs on the risk of infection prevalence with a random-effects model. Results Single-dose oral albendazole, mebendazole, and Pyrantel pamoate for infection with A lumbricoides resulted in cure rates of 88% (95% CI, 79%-93%; 557 patients), 95% (95% CI, 91%-97%; 309 patients), and 88% (95% CI, 79%-93%; 131 patients), respectively. Cure rates for infection with T trichiura following treatment with single-dose oral albendazole and mebendazole were 28% (95% CI, 13%-39%; 735 patients) and 36% (95% CI, 16%-51%; 685 patients), respectively. The efficacy of single-dose oral albendazole, mebendazole, and Pyrantel pamoate against hookworm infections was 72% (95% CI, 59%-81%; 742 patients), 15% (95% CI, 1%-27%; 853 patients), and 31% (95% CI, 19%-42%; 152 patients), respectively. No pooled relative risks could be calculated for Pyrantel pamoate against T trichiura and levamisole for any of the parasites investigated. Conclusions Single-dose oral albendazole, mebendazole, and Pyrantel pamoate show high cure rates against A lumbricoides. For hookworm infection, albendazole was more efficacious than mebendazole and Pyrantel pamoate. Treatment of T trichiura with single oral doses of current anthelminthics is unsatisfactory. New anthelminthics are urgently needed.
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efficacy of current drugs against soil transmitted helminth infections systematic review and meta analysis
JAMA, 2008Co-Authors: Jennifer Keiser, Jürg UtzingerAbstract:CONTEXT: More than a quarter of the human population is likely infected with soil-transmitted helminths (Ascaris lumbricoides, hookworm, and Trichuris trichiura) in highly endemic areas. Preventive chemotherapy is the mainstay of control, but only 4 drugs are available: albendazole, mebendazole, levamisole, and Pyrantel pamoate. OBJECTIVE: To assess the efficacy of single-dose oral albendazole, mebendazole, levamisole, and Pyrantel pamoate against A lumbricoides, hookworm, and T trichiura infections. DATA SOURCES: A systematic search of PubMed, ISI Web of Science, ScienceDirect, the World Health Organization library database, and the Cochrane Central Register of Controlled Trials (1960 to August 2007). STUDY SELECTION: From 168 studies, 20 randomized controlled trials were included. DATA EXTRACTION AND DATA SYNTHESIS: Information on study year and country, sample size, age of study population, mean infection intensity before treatment, diagnostic method used, time between evaluations before and after treatment, cure rate (the percentage of individuals who became helminth egg negative following treatment with an anthelminthic drug), egg reduction rate, adverse events, and trial quality was extracted. Relative risk, including a 95% confidence interval (CI), was used to measure the effect of the drugs on the risk of infection prevalence with a random-effects model. RESULTS: Single-dose oral albendazole, mebendazole, and Pyrantel pamoate for infection with A lumbricoides resulted in cure rates of 88% (95% CI, 79%-93%; 557 patients), 95% (95% CI, 91%-97%; 309 patients), and 88% (95% CI, 79%-93%; 131 patients), respectively. Cure rates for infection with T trichiura following treatment with single-dose oral albendazole and mebendazole were 28% (95% CI, 13%-39%; 735 patients) and 36% (95% CI, 16%-51%; 685 patients), respectively. The efficacy of single-dose oral albendazole, mebendazole, and Pyrantel pamoate against hookworm infections was 72% (95% CI, 59%-81%; 742 patients), 15% (95% CI, 1%-27%; 853 patients), and 31% (95% CI, 19%-42%; 152 patients), respectively. No pooled relative risks could be calculated for Pyrantel pamoate against T trichiura and levamisole for any of the parasites investigated. CONCLUSIONS: Single-dose oral albendazole, mebendazole, and Pyrantel pamoate show high cure rates against A lumbricoides. For hookworm infection, albendazole was more efficacious than mebendazole and Pyrantel pamoate. Treatment of T trichiura with single oral doses of current anthelminthics is unsatisfactory. New anthelminthics are urgently needed.
Peter Nansen - One of the best experts on this subject based on the ideXlab platform.
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Use of a migration assay for the separation of adult Pyrantel-susceptible and -resistant oesophagostomum dentatum.
Veterinary parasitology, 2000Co-Authors: Mads Bjelke Petersen, Henrik Bjørn, Jeff Craven, Peter NansenAbstract:Abstract A migration assay was used to separate a Pyrantel-susceptible and -resistant isolate of the pig nematode, Oesophagostomum dentatum. The experiment had three steps. In the first step, LD50 values for Pyrantel of the two isolates in the assay were established. In the second step, susceptible and resistant worms were mixed in various proportions prior to exposure to a fixed concentration of Pyrantel and thereafter assayed. The inhibition of migration showed to be linearly correlated with the proportion of resistant worms in a sample. In step three, this line was used as a standard curve to predict the number of resistant worms in samples from pigs infected with mixed samples of susceptible and resistant larvae.
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in vitro characterization of lines of oesophagostomum dentatum selected or not selected for resistance to Pyrantel levamisole and ivermectin
International Journal for Parasitology, 1997Co-Authors: M Varady, H Bjorn, Jeffrey Craven, Peter NansenAbstract:Lines of Oesophagostomum dentatum artificially selected or not selected for resistance to Pyrantel, levamisole and ivermectin were used in this study. From the 10th generation of selection eggs were collected from each line and subjected to an in vitro larval development assay (LDA) and an egg hatch assay (EHPA). Significant differences were observed between an unselected line of O. dentatum and the lines selected for resistance to levamisole or Pyrantel in both assays. The LDA was more sensitive than EHPA in detecting anthelmintic resistance in O. dentatum. The results obtained from the LDA confirmed side-resistance between levamisole and morantel/Pyrantel. The in vitro tests failed to show significant differences between ivermectin-sensitive and resistant lines.
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in vitro characterization of anthelmintic susceptibility of field isolates of the pig nodular worm oesophagostomum spp susceptible or resistant to various anthelmintics
International Journal for Parasitology, 1996Co-Authors: M Varady, Henrik Bjørn, Peter NansenAbstract:Abstract A larval development assay (LDA) and an egg hatch paralysis assay (EHPA) were used to measure the sensitivity to anthelmintics of eggs and larvae of nodular worms ( Oesophagostomum spp.) in pigs. The tests were carried out using in vivo defined resistant and susceptible isolates of Oesophagostomum dentatum, O. quadrispinulatum and Oesophagostomum spp. For measurement of pyrantei/morantel and levamisole sensitivity the LDA was found able to distingrich between susceptible or resistant isolates of Oesophagostomum . The EHPA was able to detect levamisole resistance, but the test failed to show differences in response to Pyrantel between Pyrantel susceptible and resistant lines. The possible routine application of LDA and EHPA in the diagnosis of anthelmintic resistance in Oesophagostomum spp. is discussed.
Steven Kopp - One of the best experts on this subject based on the ideXlab platform.
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Pyrantel and oxantel pamoate
2017Co-Authors: Steven Kopp, Jennifer KeiserAbstract:Pyrantel, E-1,4,5,6-tetrahydro-1-methyl-2-[2-(2-thienyl) vinyl]-pyrimidine, is an imidazothiazole-derived tetrahydropyrimidine. Its anthelmintic activity was first identified in 1966 (Austin et al., 1966). It has been used as a broadspectrum anthelmintic in both veterinary and human medicine since the 1970s (Kopp et al., 2007b). In humans, it is clinically useful for therapy of three major nematode infections: hookworm (Ancylostoma duodenale and Necator americanus), roundworm (Ascaris lumbricoides), and pinworm (Enterobius vermicularis). In addition, Pyrantel pamoate appears to have activity against Trichinella spiralis and Trichostrongylus spp. Pyrantel pamoate is available as a tablet (including chewable) or oral suspension; common preparations include Combantrin (Pfizer), Antiminth (Goerig), and Pyrantrin (Niemeth).
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acetylcholine receptor subunit genes from ancylostoma caninum altered transcription patterns associated with Pyrantel resistance
International Journal for Parasitology, 2009Co-Authors: Steven Kopp, G T Coleman, James S Mccarthy, Rebecca J Traub, Andrew C KotzeAbstract:The molecular mechanism of resistance to nicotinic agonist anthelmintics such as Pyrantel and levamisole in nematodes of medical and veterinary significance is poorly understood. The identification of Pyrantel-resistant isolates of the canine hookworm, Ancylostoma caninum, provides an opportunity to explore, at a molecular level, the mechanism of cholinergic resistance in a species that is a model for the human hookworms. Here we describe the cloning of three A. caninum genes orthologous to components of the Pyrantel-sensitive nicotinic acetylcholine receptor in Caenorhabditis elegans (UNC-29, -38, -63). Analysis of mRNA levels by quantitative PCR was also performed on these genes, plus an additional three nicotinic acetylcholine receptor subunit genes thought not to be constituents of the Pyrantel-sensitive receptor, for which a partial sequence was obtained. Gene sequences and mRNA levels were compared between two isolates of A. caninum showing either high- or low-level resistance to Pyrantel (as shown previously by in vivo efficacy and in vitro comparative studies). While no polymorphisms of likely significance between the two A. caninum isolates were observed, quantitative analysis of transcription revealed significantly lower levels for the three putative Pyrantel receptor subunits (AAR-29, -38 and -63) in the highly Pyrantel-resistant isolate compared with the isolate with low-level resistance. In contrast, transcription of the three subunits thought not to constitute the Pyrantel receptor (AAR-8, -15 and -19) was either not significantly different between the two isolates, or slightly higher in the highly-resistant isolate. This data suggests that reduced transcription of the mRNA coding for nicotinic acetylcholine receptor subunits that form the Pyrantel-sensitive receptors may be a component of the Pyrantel resistance mechanism in A. caninum.
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phenotypic characterization of two ancylostoma caninum isolates with different susceptibilities to the anthelmintic Pyrantel
Antimicrobial Agents and Chemotherapy, 2008Co-Authors: Steven Kopp, G T Coleman, James S Mccarthy, Andrew C KotzeAbstract:The anthelmintic Pyrantel plays an important role in the control of gastrointestinal helminths of humans and domestic animals. Despite the demonstration of Pyrantel resistance in several helminth species over the last 20 years, the resistance mechanism remains unclear. It has been hypothesized that resistance may arise as a consequence of changes to the relative proportions of subpopulations of nicotinic acetylcholine receptors (nAchRs). To test this hypothesis, we examined the responses of two isolates of the canine hookworm Ancylostoma caninum with low-level resistance (isolate NT) and high-level resistance (isolate PR) to Pyrantel to nicotinic agonist drugs reported to be selective for three nAchR subtypes. We used larval motility and conformation assays and force transduction experiments with adult worms. Pyrantel and levamisole were less potent against larvae of isolate PR than larvae of isolate NT (up to an 18-fold increase in the 50% inhibitory concentration); on the other hand, bephenium was more potent against larvae of isolate PR than larvae of isolate NT (twofold) and nicotine had the same potency against larvae of both isolates. In adults, Pyrantel, levamisole, and nicotine were less potent against isolate PR than isolate NT (two- to threefold), but the potency of bephenium against the two isolates was equivalent. Our data indicate a complex pattern of nAchRs in this species and suggest that the two isolates differ in their relative sensitivities to agonists targeting different nAchRs.
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Acetylcholine receptor subunit genes from Ancylostoma caninum: Altered transcription patterns associated with Pyrantel resistance ☆
International journal for parasitology, 2008Co-Authors: Steven Kopp, James S Mccarthy, Rebecca J Traub, Glen T. Coleman, Andrew C KotzeAbstract:The molecular mechanism of resistance to nicotinic agonist anthelmintics such as Pyrantel and levamisole in nematodes of medical and veterinary significance is poorly understood. The identification of Pyrantel-resistant isolates of the canine hookworm, Ancylostoma caninum, provides an opportunity to explore, at a molecular level, the mechanism of cholinergic resistance in a species that is a model for the human hookworms. Here we describe the cloning of three A. caninum genes orthologous to components of the Pyrantel-sensitive nicotinic acetylcholine receptor in Caenorhabditis elegans (UNC-29, -38, -63). Analysis of mRNA levels by quantitative PCR was also performed on these genes, plus an additional three nicotinic acetylcholine receptor subunit genes thought not to be constituents of the Pyrantel-sensitive receptor, for which a partial sequence was obtained. Gene sequences and mRNA levels were compared between two isolates of A. caninum showing either high- or low-level resistance to Pyrantel (as shown previously by in vivo efficacy and in vitro comparative studies). While no polymorphisms of likely significance between the two A. caninum isolates were observed, quantitative analysis of transcription revealed significantly lower levels for the three putative Pyrantel receptor subunits (AAR-29, -38 and -63) in the highly Pyrantel-resistant isolate compared with the isolate with low-level resistance. In contrast, transcription of the three subunits thought not to constitute the Pyrantel receptor (AAR-8, -15 and -19) was either not significantly different between the two isolates, or slightly higher in the highly-resistant isolate. This data suggests that reduced transcription of the mRNA coding for nicotinic acetylcholine receptor subunits that form the Pyrantel-sensitive receptors may be a component of the Pyrantel resistance mechanism in A. caninum.
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application of in vitro anthelmintic sensitivity assays to canine parasitology detecting resistance to Pyrantel in ancylostoma caninum
Veterinary Parasitology, 2008Co-Authors: Steven Kopp, G T Coleman, James S Mccarthy, Andrew C KotzeAbstract:Resistance of the canine hookworm Ancylostoma caninum to anthelmintic therapy with Pyrantel is an emerging problem in canine veterinary practice. Detecting anthelmintic resistance in parasites of pets is problematic because traditional resistance-monitoring techniques used with livestock parasites, such as the faecal egg count reduction test, are often impractical for use in small animals. We used two field-collected isolates of A. caninum in an abbreviated critical trial to test their Pyrantel resistance status. The strains showed high-level and low-level resistance, with in vivo Pyrantel efficacies of 28% and 71%, respectively. We noted a distinct worm density dependence effect on faecal egg count during the critical trial; egg counts in the dogs containing the low-level resistant isolate were 41% higher 6 days after drug treatment, despite the removal of 71% of the adult worms by the drug treatment. We then assessed four candidate in vitro assays for their ability to detect Pyrantel resistance in A. caninum larvae, using these two isolates. The assays included a new format termed the larval arrested morphology assay (LAMA), based on observation of the effects of Pyrantel on the body shape adopted by infective stage A. caninum larvae in vitro. Our data suggests that three of these assays, the LAMA, the larval motility assay (LMA), and larval feeding inhibition assay (LFIA) show promise with regards to detection of Pyrantel resistance in A. caninum, but the complexity of the LFIA would likely limit its suitability for field studies. In vivo Pyrantel efficacies of 28% and 71% in the two A. caninum isolates were associated with a 17-fold shift in the in vitro IC50 values measured using the LAMA. Further testing with isolates of varying degrees of resistance is required to determine which of these assays is suitable as a rapid in vitro laboratory test for Pyrantel resistance in A. caninum. The present study also indicates that potential exists for the novel LAMA or the LMA to be of use in detecting Pyrantel resistance in the human hookworms, Necator americanus and Ancylostoma duodenale.
James S Mccarthy - One of the best experts on this subject based on the ideXlab platform.
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acetylcholine receptor subunit genes from ancylostoma caninum altered transcription patterns associated with Pyrantel resistance
International Journal for Parasitology, 2009Co-Authors: Steven Kopp, G T Coleman, James S Mccarthy, Rebecca J Traub, Andrew C KotzeAbstract:The molecular mechanism of resistance to nicotinic agonist anthelmintics such as Pyrantel and levamisole in nematodes of medical and veterinary significance is poorly understood. The identification of Pyrantel-resistant isolates of the canine hookworm, Ancylostoma caninum, provides an opportunity to explore, at a molecular level, the mechanism of cholinergic resistance in a species that is a model for the human hookworms. Here we describe the cloning of three A. caninum genes orthologous to components of the Pyrantel-sensitive nicotinic acetylcholine receptor in Caenorhabditis elegans (UNC-29, -38, -63). Analysis of mRNA levels by quantitative PCR was also performed on these genes, plus an additional three nicotinic acetylcholine receptor subunit genes thought not to be constituents of the Pyrantel-sensitive receptor, for which a partial sequence was obtained. Gene sequences and mRNA levels were compared between two isolates of A. caninum showing either high- or low-level resistance to Pyrantel (as shown previously by in vivo efficacy and in vitro comparative studies). While no polymorphisms of likely significance between the two A. caninum isolates were observed, quantitative analysis of transcription revealed significantly lower levels for the three putative Pyrantel receptor subunits (AAR-29, -38 and -63) in the highly Pyrantel-resistant isolate compared with the isolate with low-level resistance. In contrast, transcription of the three subunits thought not to constitute the Pyrantel receptor (AAR-8, -15 and -19) was either not significantly different between the two isolates, or slightly higher in the highly-resistant isolate. This data suggests that reduced transcription of the mRNA coding for nicotinic acetylcholine receptor subunits that form the Pyrantel-sensitive receptors may be a component of the Pyrantel resistance mechanism in A. caninum.
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phenotypic characterization of two ancylostoma caninum isolates with different susceptibilities to the anthelmintic Pyrantel
Antimicrobial Agents and Chemotherapy, 2008Co-Authors: Steven Kopp, G T Coleman, James S Mccarthy, Andrew C KotzeAbstract:The anthelmintic Pyrantel plays an important role in the control of gastrointestinal helminths of humans and domestic animals. Despite the demonstration of Pyrantel resistance in several helminth species over the last 20 years, the resistance mechanism remains unclear. It has been hypothesized that resistance may arise as a consequence of changes to the relative proportions of subpopulations of nicotinic acetylcholine receptors (nAchRs). To test this hypothesis, we examined the responses of two isolates of the canine hookworm Ancylostoma caninum with low-level resistance (isolate NT) and high-level resistance (isolate PR) to Pyrantel to nicotinic agonist drugs reported to be selective for three nAchR subtypes. We used larval motility and conformation assays and force transduction experiments with adult worms. Pyrantel and levamisole were less potent against larvae of isolate PR than larvae of isolate NT (up to an 18-fold increase in the 50% inhibitory concentration); on the other hand, bephenium was more potent against larvae of isolate PR than larvae of isolate NT (twofold) and nicotine had the same potency against larvae of both isolates. In adults, Pyrantel, levamisole, and nicotine were less potent against isolate PR than isolate NT (two- to threefold), but the potency of bephenium against the two isolates was equivalent. Our data indicate a complex pattern of nAchRs in this species and suggest that the two isolates differ in their relative sensitivities to agonists targeting different nAchRs.
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Acetylcholine receptor subunit genes from Ancylostoma caninum: Altered transcription patterns associated with Pyrantel resistance ☆
International journal for parasitology, 2008Co-Authors: Steven Kopp, James S Mccarthy, Rebecca J Traub, Glen T. Coleman, Andrew C KotzeAbstract:The molecular mechanism of resistance to nicotinic agonist anthelmintics such as Pyrantel and levamisole in nematodes of medical and veterinary significance is poorly understood. The identification of Pyrantel-resistant isolates of the canine hookworm, Ancylostoma caninum, provides an opportunity to explore, at a molecular level, the mechanism of cholinergic resistance in a species that is a model for the human hookworms. Here we describe the cloning of three A. caninum genes orthologous to components of the Pyrantel-sensitive nicotinic acetylcholine receptor in Caenorhabditis elegans (UNC-29, -38, -63). Analysis of mRNA levels by quantitative PCR was also performed on these genes, plus an additional three nicotinic acetylcholine receptor subunit genes thought not to be constituents of the Pyrantel-sensitive receptor, for which a partial sequence was obtained. Gene sequences and mRNA levels were compared between two isolates of A. caninum showing either high- or low-level resistance to Pyrantel (as shown previously by in vivo efficacy and in vitro comparative studies). While no polymorphisms of likely significance between the two A. caninum isolates were observed, quantitative analysis of transcription revealed significantly lower levels for the three putative Pyrantel receptor subunits (AAR-29, -38 and -63) in the highly Pyrantel-resistant isolate compared with the isolate with low-level resistance. In contrast, transcription of the three subunits thought not to constitute the Pyrantel receptor (AAR-8, -15 and -19) was either not significantly different between the two isolates, or slightly higher in the highly-resistant isolate. This data suggests that reduced transcription of the mRNA coding for nicotinic acetylcholine receptor subunits that form the Pyrantel-sensitive receptors may be a component of the Pyrantel resistance mechanism in A. caninum.
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application of in vitro anthelmintic sensitivity assays to canine parasitology detecting resistance to Pyrantel in ancylostoma caninum
Veterinary Parasitology, 2008Co-Authors: Steven Kopp, G T Coleman, James S Mccarthy, Andrew C KotzeAbstract:Resistance of the canine hookworm Ancylostoma caninum to anthelmintic therapy with Pyrantel is an emerging problem in canine veterinary practice. Detecting anthelmintic resistance in parasites of pets is problematic because traditional resistance-monitoring techniques used with livestock parasites, such as the faecal egg count reduction test, are often impractical for use in small animals. We used two field-collected isolates of A. caninum in an abbreviated critical trial to test their Pyrantel resistance status. The strains showed high-level and low-level resistance, with in vivo Pyrantel efficacies of 28% and 71%, respectively. We noted a distinct worm density dependence effect on faecal egg count during the critical trial; egg counts in the dogs containing the low-level resistant isolate were 41% higher 6 days after drug treatment, despite the removal of 71% of the adult worms by the drug treatment. We then assessed four candidate in vitro assays for their ability to detect Pyrantel resistance in A. caninum larvae, using these two isolates. The assays included a new format termed the larval arrested morphology assay (LAMA), based on observation of the effects of Pyrantel on the body shape adopted by infective stage A. caninum larvae in vitro. Our data suggests that three of these assays, the LAMA, the larval motility assay (LMA), and larval feeding inhibition assay (LFIA) show promise with regards to detection of Pyrantel resistance in A. caninum, but the complexity of the LFIA would likely limit its suitability for field studies. In vivo Pyrantel efficacies of 28% and 71% in the two A. caninum isolates were associated with a 17-fold shift in the in vitro IC50 values measured using the LAMA. Further testing with isolates of varying degrees of resistance is required to determine which of these assays is suitable as a rapid in vitro laboratory test for Pyrantel resistance in A. caninum. The present study also indicates that potential exists for the novel LAMA or the LMA to be of use in detecting Pyrantel resistance in the human hookworms, Necator americanus and Ancylostoma duodenale.
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Pyrantel in small animal medicine: 30 years on
Veterinary journal (London England : 1997), 2007Co-Authors: Steven Kopp, James S Mccarthy, Andrew C Kotze, Rebecca J Traub, Glen T. ColemanAbstract:Pyrantel, a tetrahydropyrimidine nicotinic agonist anthelmintic, has been used in companion animal medicine since the 1970s to control two important nematode groups, the hookworms and the roundworms. Given the zoonotic potential of these parasites, Pyrantel has served a dual role in helping to protect the health of both companion animals and the public for more than 30 years. This review describes the history and mechanism of action of this drug, and collates evidence that resistance to Pyrantel has developed in at least one canine nematode, the hookworm Ancylostoma caninum. The role of in vitro diagnosis tests in managing anthelmintic resistance in companion animal parasites is discussed, as are management practices that may reduce the rate at which resistance develops.
