Benzimidazole resistance of sheep nematodes in Norway confirmed through controlled efficacy test

Atle V Meling Domke,Christophe Chartier,Bjørn Gjerde,Snorre Stuen

doi:10.1186/1751-0147-54-48

Abstract

BackgroundResistance against benzimidazoles (BZ) has recently been detected in Norwegian sheep flocks through a large scale prevalence survey based on the faecal egg count reduction test (FECRT). The use of this test in combination with bulk larval culture only gives an indication of which gastrointestinal nematodes genera that are involved and these results have to be confirmed by a controlled efficacy test (CET) to get accurate information about resistant nematodes populations at species level. A CET was therefore performed with larvae from two flocks where BZ resistance was previously detected through FECRT.ResultsThe latter test confirmed the previous results in both flocks. In flock A, the BZ resistant nematode population consisted solely of Haemonchus contortus, whereas H. contortus and Teladorsagia circumcincta comprised the resistant worm population in flock B.ConclusionsSome discrepancies that have been recorded between FECRT and CET results regarding time for post-treatment coproscopical examination and a temporary suppression of faecal egg excretion are discussed.

Highlights

Resistance against benzimidazoles (BZ) has recently been detected in Norwegian sheep flocks through a large scale prevalence survey based on the faecal egg count reduction test (FECRT)
As FECRTs may give false-positive results in relation with drug administration issues and does not identify the resistant species properly [5], a controlled efficacy test (CET) was performed in two selected flocks with previously reported BZ resistance both to confirm the presence of resistance and to further characterize the nematode populations involved
Selection and characteristics of the tested flocks Based on the results from the FECRT performed by Domke et al [4], gastrointestinal nematode (GIN) populations from two of the eight sheep flocks with BZ resistance were sampled for a controlled efficacy test

Summary

Introduction

Resistance against benzimidazoles (BZ) has recently been detected in Norwegian sheep flocks through a large scale prevalence survey based on the faecal egg count reduction test (FECRT) The use of this test in combination with bulk larval culture only gives an indication of which gastrointestinal nematodes genera that are involved and these results have to be confirmed by a controlled efficacy test (CET) to get accurate information about resistant nematodes populations at species level. As FECRTs may give false-positive results in relation with drug administration issues and does not identify the resistant species properly [5], a controlled efficacy test (CET) was performed in two selected flocks with previously reported BZ resistance both to confirm the presence of resistance and to further characterize the nematode populations involved

Methods

Results

Discussion

Conclusion