Prevalence of benzimidazole resistant beta- tubulin alleles in Haemonchus contortus larvae from sheep of Rajasthan

摘要

The study was conducted to find out the feasibility of community dilution strategy in worm population for reversion to susceptibility against benzimidazole (BZ) anthelmintics. The prevalence of BZ-resistant 6- tubulin alleles was determined through allele specific polymerase chain reaction (AS-PCR) in 1216 infective larvae of Haemonchus contortus isolated from sheep flocks of different origins. Both management of flocks and agro-climate has significant influence on the prevalence of homozygous BZ-resistant (rr) genotypes. The overall frequency of rr genotypes was relatively low in farm flocks and in arid Rajasthan. The maximum prevalence of BZ-susceptible was observed during winter (51.00%) and monsoon (24.59%) in arid and semi-arid farm. In field flocks, there was a moderate rise in proportion of BZ-susceptible genotypes during monsoon. The study exhibited that community dilution strategy for reversion of susceptibility to BZ anthelmintics in H. contortus could be feasible in farm conditions. Theperiod from September to November in semi-arid and from June to February in arid agroclimatic conditions seem to be appropriate in increasing the frequency of BZ-susceptible alleles in the refugia.