Genetic Variability in ß-tubulin-l in Benzimidazole Resistant Haemonchus contortus from Sheep in North-East Punjab, Pakistan.

Benzimidazole is a synthetic anthelmintic against which nematode resistance especially in Haemonchus contortus, is emerging at a alarming speed. The mechanism of benzimidazole resistance appears to involve mutations in the gene encoding ß-tubulin isotype 1 (ß-tubulin-1). The present study was carried out to find out the variation existing in ß-tubulin-1 which is directly involved with drug binding capacity involving microtubules polymerization. DNA of adult nematode H. contörtus was extracted, amplified and sequenced. Out of 50 worms investigated, 37 showed benzimidazole susceptible gene while 13 were resistant indicating single nucleotide mutation at amino acid 200 TTC/TAC. In addition, 12 worms showed several regions of consistent difference indicating single nucleotide polymorphism (SNPs) at various positions in coding region. It has been concluded that resistant alleles conferring anthelmintic resistance is prevalent in the local population of H. contortus of north-east Punjab, Pakistan. [ABSTRACT FROM AUTHOR]