Multiple anthelmintic resistance in Haemonchus contortus infecting sheep in Gangetic plains of India.

The status of anthelmintic resistance against benzimidazole (BZ), levamisole (LV) and ivermectin (IVM) was assessed in Haemonchus contortus at ten sheep flocks in Gangetic plains of India by using larval development assay (LDA) and PCR based molecular assays like allele specific PCR (AS-PCR) targeting SNP at F200Y of β- tubulin isotype-1 gene of H. contortus (BZ resistance) and PCR targeting insertion or deletion of 63 bp in acr-8b gene of H. contortus (LV resistance). Resistance to benzimidazole was detected in 10/10 flocks, levamisole resistance in 3/10 flocks, and ivermectin resistance in 2/10 flocks. Multiple resistance to albendazole, levamisole and ivermectin was observed in both Ayodhya flocks, whereas resistance to albendazole and levamisole was observed in one Etah flock. The findings highlight the emergence of multiple anthelmintic resistance in H. contortus in Uttar Pradesh, India. Proper monitoring of anthelmintic resistance and sound managemental practices are urgently required to mitigate further spread of anthelmintic resistance across India.