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Year 2011 - Volume 31, Number 9
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Weak phenotypic reversion of ivermectin resistance in a field resistant isolate of Haemonchus contortus by verapamil, 31(9):731-736
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ABSTRACT.- Borges F.A., Rossini J.B., Velludo P.P., Buzzulini C., Costa G.H., Molento M.B. & Cos-ta A.J. 2011. Weak phenotypic reversion of ivermectin resistance in a field resistant isolate of Haemonchus contortus by verapamil. Pesquisa Veterinária Brasileira 31(9):731-736. Departamento de Medicina Veterinária, Faculdade de Medicina Veterinária e Zootecnia, Universidade Federal de Mato Grosso do Sul, Campo Grande, MS 79070-900, Brazil. E-mail: fernando.borges@ufms.br
Recent advances in anthelmintic resistant phenotype reversion by Pgp modulating drugs in ruminant nematodes indicate that this can be a useful tool to helminth control. The aim of the present study was to evaluate the efficacy of ivermectin (IVM) in combination with verapamil (VRP), in oil or water-based vehicle, against an IVM-resistant field isolate of Haemonchus contortus through a larval migration assay and experimental infection trial. In the in vitro assay was observed a phenotypic reversion of H. contortus resistance to ivermectin at a high concentration of VRP, increasing IVM efficacy from 53.1% to 94.3. In the in vivo trial, IVM + VRP demonstrated 36.02% efficacy compared to the 7.75% of IVM alone. The vehicle formulation showed no influence in efficacy. These are the first results demonstrating the effect of VRP as a partial IVM-resistance phenotype reverser in a field isolate of IVM-resistant H. contortus experimentally inoculated in sheep. |
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