Dr. Priya M. NMERIN DAS V. J2024-09-282024-09-282023-03-23https://krishikosh.egranth.ac.in/handle/1/5810215152The present study was carried out to evaluate benzimidazole resistance in gastrointestinal nematodes of cattle. A total of 497 faecal samples were collected from 17 organised cattle farms and 23 small holder farmers’ herd in Thrissur district and adjoining areas. Microscopical examination of the faecal samples revealed an overall incidence of 36.01 per cent of gastrointestinal parasitism in cattle. The incidence of strongylosis among the samples examined was 10.66 per cent with incidence rates of 6.94 and 17.22 per cent in organised and small holder farmers’ herd respectively. There was no significant difference between mean incidence of strongyles in organised farm (11.34±5.60 per cent) and that of small holder farmers’ herd (22.95±4.83). However, there was a significant difference between mean faecal egg count (FEC) in organised farm (1559.09±731.789) and that of small holder farmers’ herd (134.38±27.719). The prevalent genera of strongyles identified by coproculture were Haemonchus spp., Mecistocirrus spp. and Oesophagostomum spp. Detection of anthelmintic resistance was done by in vivo faecal egg count reduction method (FECRT), in vitro egg hatch assay (EHA) and molecular genotyping by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Based on FECRT with albendazole, resistance was detected in all organised farms and 33.33 per cent of the small holder farmers’ herd whereas 66.67 per cent of the small holder farmers’ herd were susceptible to benzimidazole. Pooled samples from three organised and one small holder farmers’ herd were utilised for EHA and resistance was observed in two organised farms and one small holder farmers’ herd with ED50 greater than 0.1µg/mL and Hdd greater than 0.5 µg/mL whereas one organised farm was detected as susceptible to benzimidazole. Molecular detection by PCR-RFLP was done by using single larvae of Haemonchus spp. from pooled faecal sample of three organised and one small holder farmers’ herd followed by restriction digestion with Eco1051, HpyCH4V and HpyCh4III to determine resistance associated SNPs at codon 167, 198 and 200, respectively at isotype 1 β- tubulin gene. The results of PCR-RFLP with 102 Haemonchus spp. larvae revealed 95.10per cent of the larvae carried resistant genotype (rr) and 4.9 per cent carried susceptible genotype (SS) at codon 198 of isotype 1 β tubulin gene. All the larvae carried susceptible genotype (SS) at codon 167 and 200 of the β tubulin gene. The association of clinical benzimidazole resistance by FECRT with molecular genotyping was done and revealed that benzimidazole resistant organised farms showed 97.7 per cent homozygous resistant genotype (rr) and 2.30 per cent homozygous susceptible genotype (SS). The benzimidazole resistant small holder farmers’ herd showed 81.25 per cent rr genotype and 18.75 per cent SS genotype. In conclusion, the present research work reports the detection of benzimidazole resistance in cattle by in vivo FECRT, in vitro EHA and molecular genotyping by PCR-RFLP to identify the SNPs at isotype 1 β- tubulin gene of Haemonchus spp. To the best of our knowledge, this study forms the first report of anthelmintic resistance in cattle in South India.EnglishThesis