Anthelmintic resistance in ruminants: challenges and solutions

Effectiveness of Anthelmintic Treatments in Small Ruminants in Germany

“…In order to reach the broadest possible participation, some compromises had to be made in methodology, as performance of the classical FECRT [ 29 ] is impracticable for large-scale field studies [ 31 , 38 , 39 ], and an optimal degree of standardization cannot be achieved in studies relying on farmer participation. Simplified protocols were therefore necessary to gain access to sufficient farm numbers representing the variety of the target population and to gain a realistic impression of the current situation regarding the effectiveness of treatments performed in the field.…”

“…While 57.7% of the treatment assessments were based on ten or 15 animals, a considerable percentage of the treatment outcomes could only be assessed based on one sample pool, representing five individual animals. For the performance of a FECRT for assessment of anthelmintic resistance, ten to 15 animals need to be sampled [ 26 , 29 , 31 ]. Treatment assessments based on less than ten animals may be less accurate and potentially over-estimate treatment effectiveness, particularly if initial egg counts are low.…”

“…Inclusion criteria for assessment of treatment effectiveness were: >200 epg in initial submission, use of an anthelmintic product licensed for treatment of GIN, correct dose rate (or higher) for the relevant small ruminant species, and corresponding post-treatment sample collection from identical animal groups as for the initial submission. Collection of these samples between seven and 21 days post treatment was considered acceptable depending on the anthelmintic class used [ 31 ]. For the purposes of this study, the accepted treatment-to-sampling interval was set at 7–16 days for levamisole, 10–21 days for avermectins and moxidectin, 10–19 days for monepantel and benzimidazoles, and 8–19 days for the closantel and mebendazole combination product.…”

“…Despite major scientific advances in this field since the publication of the World Association for the Advancement of Veterinary Parasitology (WAAVP) guidelines in 1992, which defined standardized methods for the detection of anthelmintic resistance in ruminants [ 29 ], and their re-evaluation in 2006 [ 30 ], the faecal egg count reduction test (FECRT) and its recent adaptations remain the only method applicable to all anthelmintic classes and suitable for field conditions [ 26 ]. New WAAVP guidelines for the diagnosis of anthelmintic resistance in ruminants are currently being developed, but have not yet been published at the time of writing [ 31 , 32 ]. According to Charlier et al (2022) [ 31 ], these are likely to include guidelines for the performance of a FECRT in farmed ruminants consistent with the latest recommendations by Kaplan (2020) [ 26 ].…”

“…New WAAVP guidelines for the diagnosis of anthelmintic resistance in ruminants are currently being developed, but have not yet been published at the time of writing [ 31 , 32 ]. According to Charlier et al (2022) [ 31 ], these are likely to include guidelines for the performance of a FECRT in farmed ruminants consistent with the latest recommendations by Kaplan (2020) [ 26 ]. General guidelines for the evaluation of efficacy of anthelmintics have recently been published [ 32 ].…”