Genotyping of benzimidazole resistant and susceptible isolates ofHaemonchus contortusfrom sheep by allele specific PCR.
Extensive and indiscriminate use of the benzimidazole class of drugs has led to the onset of anthelmintic resistance. In tropical countries like India,Haemonchus contortusis the most pathogenic parasite infecting sheep and goats. The widespread presence of resistant helminths (especiallyH. contortus) threatens the livestock farming. The use of various drugs has led to single nucleotide polymorphism that causes specific amino acid substitutions in β-tubulin protein ofH. contortusto 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-to-adenine transversion which leads to substitution of amino acid in codon 200 of β-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 ofH. contortusand further genotype analysis. A total of 1000 larvae was screened, out of which 673 larvae were identified asH. contortus. Among 673H. contortuslarvae, 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.
Department of Veterinary Parasitology, Madras Veterinary College, Tamil Nadu Veterinary and Animal Sciences University, Chennai, Tamil Nadu 600 007 India.
Karthik
K
Mohanraj
Department of Veterinary Parasitology, Madras Veterinary College, Tamil Nadu Veterinary and Animal Sciences University, Chennai, Tamil Nadu 600 007 India.
Subhra
S
Subhadra
Department of Veterinary Parasitology, Madras Veterinary College, Tamil Nadu Veterinary and Animal Sciences University, Chennai, Tamil Nadu 600 007 India.
Aravindan
A
Kalyanasundaram
Department of Veterinary Parasitology, Madras Veterinary College, Tamil Nadu Veterinary and Animal Sciences University, Chennai, Tamil Nadu 600 007 India.
Manikkavasagan
M
Ilangopathy
Department of Veterinary Parasitology, Madras Veterinary College, Tamil Nadu Veterinary and Animal Sciences University, Chennai, Tamil Nadu 600 007 India.
Muthusamy
M
Raman
Allele specific-PCR; Anthelmintic resistance; Benzimidazole; Haemonchus contortus; Nematode; Sheep