Genotype characterization of strains of Haemonchus contortus susceptible or resistant to benzimidazole treatments in Argentina

M. GUZMÁN; C. FIEL; P. STEFFAN; E. RIVA; S. SCARCELLA; P. LUCHESSI

Buenos Aires

Congreso; XXIII Congreso Internacional De La Asociación Mundial Para el Avance de la Parasitología Veterinaria; 2011

The resistance of worm populations to anthelmintics is a spread phenomenon in sheep farms all over the world. Resistance of trichostrongyles to benzimidazole derivates (BZ) has a high prevalence being the mutation in β-tubuline genes the most frequent change observed in populations of worms in small ruminants. The aim of this study was to characterize the genotype of two Haemonchus contortus strains, which had been shown to be susceptible or resistant to benzimidazole treatments. The Amplification Refractory Mutation System- Polymerase Chain Reaction (ARMS-PCR) was used to detect eventual mutations in the 200 site of isotype 1 β-tubuline. For this purpose two strains of H. contortus resistant or susceptible to BZ treatments and named as Ayacucho and Cedive respectively, were utilized. From adult male worms recovered from the abomasums of infected lambs, the genomic DNA was obtained by use of a phenol-chloroform protocol for each individual. For ARMS-PCR technique four primers were used to amplify two different alleles in a single PCR reaction. Two primers HcF1 (forward) and HcR1 (reverse) direct the amplification of the control band (296 bp) from isotype 1 β-tubulina. The forward primer HcF1 with reverse primer HcSu direct to amplification of the region without mutation (146 bp) in susceptible to BZ strains. The reverse primer HcR1 with forward primer HcRT direct the amplification of the region containing mutation (198 bp) in resistant to BZ strains. Control band was observed either in resistant or susceptible to BZ strains. Only bands of 198 bp were observed in Ayacucho strain Bands of 198 bp and 146 bp were observed in the Cedive strain. These results showed that in the Ayacucho strain the mutation towards resistance to BZ compounds involved 100% of homozygote genes whereas a major proportion of heterocygote genes were observed in the Cedive strain. The knowledge of worm populations proportions that have muted to resistance to Bz derivates might be of a great and useful approach to implement rational control programs throughout the use of proper compounds and selective treatments along the year.