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Occurence of benzimidazole resistant Haemonchus contortus in Norwegian sheep. detected by droplet digital PCR
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International audience. The aim of this study was to investigate the occurrence of BZ-resistant Haemonchus contortus in Norwegian sheep flocks. Screening was performed based on detection of one of the resistance-conferring mutations in the β tubulin isotype 1 gene. Fecal samples were collected in 2021 from flocks in the northern (n=3), coastal (n=5), and inland (n=22) areas of Norway. Flocks were recruited from the Norwegian sheep recording system, using data previously obtained by a questionnaire. In total, 25 flocks were randomly selected from the dataset. Additionally, five flocks were enrolled due to suspicion of AR. Individual faecal samples were collected from 10 randomly selected ewes (spring) and 10 lambs (autumn). From each flock samples, 4X5 (lambs and ewes pooled separately) faeces, were pooled and cultured for L3development. After harvest of larvae with the Baermann method, DNA was extracted and then analyzed using droplet digital PCR. The assay was performed using primer/probe sets targeting the F200Y (TAC) mutation. The mutation was found in 20 of the total 30 flocks (67%). In positive flocks, median allele frequencies were 100% in both age groups, with a range of 23-100 and 82-100% in lambs and ewes, respectively. The mutation was only found in flocks from the coastal (n=5) or inland (n=15) areas (including the AR-suspected flocks). However, so far, few flocks have been investigated from northern Norway. Samples collection from additional flocks in this region will therefore continue in 2022
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