author(s)
D Choudhury, SC Phukan, S Islam, RK Sarmah, A Baruah, DC Milli and KH Bulbul

abstract
Faecal egg count reduction test (FECRT) and molecular techniques were employed to diagnose the anthelmintic resistance (AR) against naturally infected gastrointestinal nematodes in cattle of both organized and unorganized farm of in and around Guwahati, Assam. Twenty-four animals of each from organized and unorganized farm having more than 200 eggs per gram (EPG) of faeces were selected randomly and divided into four groups of six animals each to record the AR by FECRT. Animals of Group I, II, III were treated with levamisole (@7.5mg/kg body weight orally), fenbendazole (@5mg/kg body weight orally), albendazole (@7.5mg/kg body weight orally), respectively and group IV was kept as infected untreated control. Faecal samples were collected per-rectally on “0^th” day (pre-treatment) and 10 and 14^th day post-treatment from animals of all groups and individual faecal egg counts were determined by Modified McMaster technique. The study revealed FECR% of 100.00, 90.00 and 93.00% was in animals of Group I, II and III, respectively in organized farm while in unorganized farm it was 100.00, 92.00 and 92.00% in animals of Group I, II and III, respectively. It was observed that BZ group were found to develop resistance while levamisole treated group was 100% effective. The adult Haemonchus parasites was collected obtained from slaughtered male animals of the respective farm without any anthelmintic treatment and confirmed based on morphological features of the parasites and subjected to DNA extraction as per standard protocol. The partial b-tubulin isotype-1 gene encoding the codon 200, which was found to be responsible for BZ resistance, was amplified with the combination of P₁ and P₂ primers. An aliquot of first PCR amplicon was used for nested PCR with Pn3 and Pn4 primers combination and product size of 820 bp was visualised in 1.5% agarose gel electrophoresis. The Allele specific PCR was used for diagnosis of BZ resistance, which yielded 550 and 774 bp products in susceptible parasite and 250 and 774 bp in resistant parasite population.