Genotyping of benzimidazole resistant and susceptible isolates of Haemonchus contortus from sheep by allele specific PCR
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Date
2016-06
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Abstract
Extensive and indiscriminate use of the benzimidazole
class of drugs has led to the onset of anthelmintic
resistance. In tropical countries like India, Haemonchus
contortus is the most pathogenic parasite infecting sheep
and goats. The widespread presence of resistant helminths
(especially H. contortus) threatens the livestock farming.
The use of various drugs has led to single nucleotide
polymorphism that causes specific amino acid substitutions
in b-tubulin protein of H. contortus to confer resistance.
This emphasizes the need for a survey on the present status
of resistance in India. In this study, allele specific PCR was
employed to screen the presence of a SNP, a thymine-toadenine
transversion which leads to substitution of amino
acid in codon 200 of b-tubulin gene that is correlated
specifically with BZ resistance. Third stage larvae (L3)
from pooled faecal cultures of four organized sheep farms
served as a source of genomic DNA for identification of H.
contortus and further genotype analysis. A total of 1000
larvae was screened, out of which 673 larvae were identified
as H. contortus. Among 673 H. contortus larvae, 539
larvae (80 %) were genotyped as homozygous resistant (rr)
and remaining 134 (20 %) were heterozygous susceptible
(Sr) by allele specific PCR. The concluded resistance status
reasons out the failure of anthelmintic drug in treating
ruminants. Immediate steps are needed to avoid further
aggravation of the problem. Target selective treatment by
reviewing the resistance status of individual drugs, appropriate
use of anthelmintic drugs and other control strategies
will provide a pragmatic option for delaying the further
spread of anthelmintic resistance.
Description
TNV_JPD_Jun2016_1-7
Keywords
Veterinary Science, Veterinary Parasitology