Abstract
Anthelmintic resistance is an increasing problem that threatens livestock production worldwide. Understanding of the genetic basis of benzimidazole resistance recently allowed the development of promising molecular diagnostic tools. In this study, isolates of Haemonchus contortus obtained from goats, sheep and buffaloes raised in Brazil were screened for presence of the polymorphism Phe200Tyr in the β-tubulin 1 gene, which confers resistance to benzimidazole. The allelic frequency of the mutation conferring resistance ranged from 7% to 43%, and indicated that resistance to benzimidazole could be found in nematodes isolated from all the ruminant species surveyed. Although significant variation in the frequency of the F200Y mutation was observed between different herds or host species, no significant variation could be found in populations isolated from animals within the same herd. These findings suggest that screening of samples from a few animals has the potential to provide information about the benzimidazole resistance status of the entire herd, which would enable a considerable reduction in the costs of diagnosis for the producer. Molecular diagnosis has practical advantages, since it can guide the choice of anthelmintic drug that will be used, before its application in the herd, thus reducing the economic losses driven by anthelmintic resistance.
Highlights
Gastrointestinal parasites of the genus Haemonchus constitute a major cause of economic losses in livestock production in tropical and subtropical areas (AMARANTE, 2011)
Isolates of Haemonchus contortus obtained from goats, sheep and buffaloes raised in Brazil were screened for presence of the polymorphism Phe200Tyr in the β-tubulin 1 gene, which confers resistance to benzimidazole
Significant variation in the frequency of the F200Y mutation was observed between different herds or host species, no significant variation could be found in populations isolated from animals within the same herd
Summary
Gastrointestinal parasites of the genus Haemonchus constitute a major cause of economic losses in livestock production in tropical and subtropical areas (AMARANTE, 2011). In Brazil, the species Haemonchus contortus prevails in small ruminants, while Haemonchus placei and Haemonchus similis mainly affect cattle (BRASIL et al, 2012). These nematodes, especially the species H. contortus, affect the development of young animals by impairing weight gain and increasing mortality. Nematode control was achieved through application of anthelmintics until recent years (AHID et al, 2008; SILVA et al, 2010), the widespread use of these drugs has led to emergence of resistant parasites (KAPLAN, 2004; GETACHEW et al, 2007). The efficacy of the anthelmintic chosen for use in the herd should be proved (WALLER, 1999)
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