Abstract: Anthelmintic resistance detection of ruminant gastroenteric parasitic nematode Heamonchus contortus, can be achieved by molecular probes and DNA amplification assays, this advanced methodologies are faster and cheaper to apply than conventional bioassays, however for better accuracy of a DNA-based test, it is necessary first to clarify the details of the molecular mechanisms underlying anthelmintic resistance. β-tubulin is Benzimidazoles (BZ) anthelmintic target, several anthelmintic detection methods rely on the identification of mutations within the coding gene leading to BZ tolerance or resistance. H. contortus, β-tubulin genes are highly variable and new alleles are frequently detected in small ruminant livestock infected with this parasite. This research was done with the objective to identify geographical allelic variants of β-tubulin genes in Mexican H. contortus field isolates. Specific DNA was obtained from the nematodes by RT-PCR starting from mRNA, amplicons were cloned, submitted to automate DNA sequencing and translated to aminoacid (aa) sequences that were analyzed by multiple sequence alignment software and compared against similar nematodes proteins reported at the GenBank. Six allelic variations were identified in the analyzed sequences one at aa position 200 conferring a change from Phe to Tyr regarded as responsible for BZ resistance in H. contortus. Five more allelic variations not previously identified were found at position: 64, Val to Ala., 170 Val to Ala., 190 His to Gln,, 198 Asp to Glu and 343 Asp to Glu, this findings corroborate the allelic variability of H. contortus β-tubulin and highlight the necessity to identify new geographic alleles useful for DNA-based anthelmintic resistance assays.
Estefan Miranda-Miranda , Raquel Cossio-Bayugar and Enrique Liebano-Hernandez , 2008. Genotyping of Athelmintic Resistant Haemonchus contortus Reveals New β-tubulin Allelic Variants. Journal of Animal and Veterinary Advances, 7: 27-31.