Sequences of β-tubulin cDNA from benzimidazole-susceptible and -resistant strains of Teladorsagia circumcincta, a nematode parasite of small ruminants

Elard, Loïc; Comes, Ana M.; Humbert, Jean‐François

doi:10.1016/0166-6851(96)02664-3

Cited by 91 publications

(59 citation statements)

References 16 publications

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“…These authors also showed that changes in allele frequencies rather than novel rearrangements induced by exposure to the drug explained changes associated with BZ resistance. A similar stepwise selection of BZ resistance also occurs in some Trichostrongylus colubriformis and Ostertagia circumcincta populations (45,68). Furthermore, Kerboeuf et al (84) recently provided indirect evidence that P-glycoproteins (P-gp) also play a role in BZ resistance in H. contortus.…”

Section: Mechanisms Of Drug Resistancementioning

confidence: 94%

Drug Resistance in Human Helminths: Current Situation and Lessons from Livestock

Geerts

Gryseels

2000

Clinical Microbiology Reviews

231

130

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Section: Mechanisms Of Drug Resistancementioning

confidence: 94%

Drug Resistance in Human Helminths: Current Situation and Lessons from Livestock

Geerts

Gryseels

2000

Clinical Microbiology Reviews

231

130

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“…Benzimidazole resistance in H. contortus results from selection on both the isotype-I and isotype-II β-tubulin genes [6,56,66]. In H. contortus and Ostertagia (Teladorsagia) circumcincta, BZ resistance has been linked to a single Phe to Tyr mutation at amino acid 200 in the isotype-I β-tubulin [38,57,58]. Additionally, BZ-resistant populations of H. contortus have been identified with a Phe at position 200, but with a Tyr or His at position 167 [78].…”

Section: Mechanisms Of Resistance In Equine Cyathostomesmentioning

confidence: 99%

Anthelmintic resistance in nematodes of horses

2002

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-Suppressive anthelmintic treatment strategies originally designed to control Strongylus vulgaris in horses were extremely successful in reducing morbidity and mortality from parasitic disease. Unfortunately, this strategy has inadvertently resulted in the selection of drug-resistant cyathostomes (Cyathostominea), which are now considered the principal parasitic pathogens of horses. Resistance in the cyathostomes to benzimidazole drugs is highly prevalent throughout the world, and resistance to pyrantel appears to be increasingly common. However, there are still no reports of ivermectin resistance in nematode parasites of horses despite 20 years of use. It is unknown why resistance to ivermectin has not yet emerged, but considering that ivermectin is the single most commonly used anthelmintic in horses most parasitologists agree that resistance is inevitable. The fecal egg count reduction test is considered the gold standard for clinical diagnosis of anthelmintic resistance in horses, but diagnosis is complicated by lack of an accepted standard for the performance of this test or for the analysis and interpretation of data. Presently there is very little data available on the molecular mechanisms of anthelmintic resistance in cyathostomes; β-tubulin gene is the only anthelmintic-resistance associated gene that has been cloned. The increasingly high prevalence of anthelmintic-resistant cyathostomes must be taken into account when designing worm control programs for horses. Strategies to decelerate further selection for drug resistance thereby extending the lifetime of currently effective anthelmintics should be implemented whenever possible. Considering the nature of the equine industry in which horses often graze shared pastures with horses from diverse locations, transmission and widespread dispersal of resistant parasites is virtually assured. A proactive approach to this problem centered on understanding the molecular basis of anthelmintic resistance in cyathostomes is required if we are to expect chemical control of nematodes in horses to remain a viable element of parasite control in the future.cyathostome / anthelmintic / resistance / nematode / horse Résumé -La résistance aux anthelmintiques chez les nématodes des chevaux. Les stratégies des traitements anthelmintiques mises en place à l'origine pour contrôler Strongylus vulgaris chez les chevaux ont été extrêmement efficaces pour réduire la morbidité et la mortalité dues aux maladies 491

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“…A controlled trial was conducted on the experimental infections of sheep with a T. circumcincta strain, partially resistant to benzimidazoles. A recessive point mutation in the β-tubulin gene is responsible for benzimidazole resistance [6,38,39,61,62]. At the therapeutic dosage, only homozygous mutant nematodes survive benzimidazole treatment [38].…”

Section: Under-dosingmentioning

confidence: 99%

Sheep and goat nematode resistance to anthelmintics: pro and cons among breeding management factors

et al. 2002

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-Although the molecular bases of resistance to anthelmintic families have been intensively studied, the contributing factors for the development of anthelmintic resistance are less well known. Clear recommendations must be given to farmers in order to delay the onset of anthelmintic resistance. Until now, the main advice has concerned the reduction of treatment frequency in order to slow down the spread of resistance. Anthelmintic resistance development depends mostly on an efficient selection pressure. This means that a high treatment frequency is neither necessary nor sufficient to select for resistance. The contribution of resistant worms, which have survived an anthelmintic treatment, to the subsequent generation is the key factor that controls resistance spread. This point is illustrated by five surveys conducted on sheep and goat farms from France and Morocco. In the 52 farms studied, less than three anthelmintic treatments were given each year. Three characteristics of breeding management can be identified in the build up of anthelmintic resistance: (1) the introduction of resistant worms through the purchase of sheep/goats or the use of common pastures, grazed by several herds/flocks, (2) under-dosing of hosts and the repeated use of one class of drugs, (3) the size of the population in refugia (infective larvae on pastures) at the time of the treatment. The role played by these breeding management factors in selecting for resistance is discussed. The most efficient way to limit the increase of anthelmintic resistance remains the reduction of the selection pressure by drugs, and optimal timing to maximise their efficacy. Bien que les bases moléculaires de la résistance aux différentes familles d'anthelminthiques aient été très étudiées, les facteurs permettant le développement de la résistance anthelminthique sont moins bien connus. Des recommandations claires sont nécessaires aux éleveurs si l'on souhaite retarder l'apparition de la résistance aux anthelminthiques. La principale recommandation a consisté à réduire la fréquence des traitements de façon à ralentir le développement de la résis-tance. Le développement de la résistance anthelminthique dépend essentiellement d'une pression de sélection efficace. Cela signifie qu'une forte fréquence de traitements n'est ni nécessaire ni suffisante pour sélectionner la résistance. La contribution des vers résistants, qui ont survécu au traitement anthelminthique, à la génération suivante est le facteur clé qui contrôle le développement de la résis-tance. Ce point est illustré par cinq enquêtes réalisées dans des élevages ovins et caprins de France et du Maroc. Dans les 52 élevages étudiés, moins de trois traitements anthelminthiques par an étaient réalisés. Trois conditions d'élevage ont pu être mises en évidence comme étant impliquées dans le dé-veloppement de la résistance anthelminthique :

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Sequences of β-tubulin cDNA from benzimidazole-susceptible and -resistant strains of Teladorsagia circumcincta, a nematode parasite of small ruminants

Cited by 91 publications

References 16 publications

Drug Resistance in Human Helminths: Current Situation and Lessons from Livestock

Drug Resistance in Human Helminths: Current Situation and Lessons from Livestock

Anthelmintic resistance in nematodes of horses

Sheep and goat nematode resistance to anthelmintics: pro and cons among breeding management factors

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