Paula Ehnert (Berlin / DE), Dr. Jürgen Krücken (Berlin / DE), Dr. Stefan Fiedler (Berlin / DE), Fabian Horn (Berlin / DE), Christina Helm (Berlin / DE), Sabrina Ramünke (Berlin / DE), Tanja Bartmann (Berlin / DE), Alexandra Kahl (Berlin / DE), Ann Neubert (Berlin / DE), Dr. Wiebke Weiher (Berlin / DE), Ricarda Daher (Berlin / DE), Werner Terhalle (Berlin / DE), Alexandra Klabunde-Negatsch (Berlin / DE), Dr. Stephan Steuber (Berlin / DE), Prof. Dr. Georg von Samson-Himmelstjerna (Berlin / DE)
Abstract text
Introduction
Anthelmintic resistance (AR) of strongyle nematodes against all available drug classes is a worldwide problem in small ruminants and horses and is rapidly spreading in cattle. Particularly, multi-drug resistant parasites pose a high risk for animal health and production. However, since most strongyle eggs are not distinguishable, it is difficult to identify the particular species that has evolved drug resistance.
Objectives
Since no recent data on the occurrence of AR in German ruminants are available, the faecal egg count reduction test (FECRT) and deep amplicon sequencing (nemabiome) were used to identify resistant strongyle populations and species.
Materials and methods
The FECRT was conducted using Mini-FLOTAC with fenbendazole (FEB), ivermectin (IVM) and moxidectin (MOX) on eight, eight and twelve sheep farms, respectively. Susceptibility to FEB and eprinomectin (EPR) was investigated with FLOTAC on eight and seven cattle farms, respectively. The FECR with 95% confidence intervals was calculated with the R package eggCounts. Internal transcribed spacer 2 PCR products with 5'-Illumina adapters were barcoded and sequenced on a MiSeq (V3 2x300). Reads were assigned to strongyle species using the nemabiome database and species composition was calculated.
Results
In sheep, resistance was found on 6/8 farms for FEB, 6/8 farms for IVM, 3/12 farms for MOX and 3/8 farms for all three drugs. Nemabiome data were obtained for eleven farms before treatment and Teladorsagia circumcincta (5.8-91.1% of the larvae) was found on all of them. Trichostrongylus colubriformis (≤41.6%) and Haemonchus contortus (≤42.1%) occurred on 10/11 farms. Chabertia ovina (51.5%) and Oesophagostomum venulosum (27.3%) represented the most abundant species on one farm each. On three farms, triple resistant H. contortus and T. circumcincta were detected. Resistance to FEB and IVM was detected in T. colubriformis, Trichostrongylus vitrinus, Trichostrongylus axei, Cooperia curticei and Cooperia fuelleborni. In cattle, FEB was fully active on all eleven farms while EPR resistance was detected on 1/7 farms. Ostertagia ostertagi and Cooperia oncophora were the most abundant species but Bunostomum phlebotomum and T. axei were the most abundant species on one farm each. No post treatment nemabiome data were obtained.
Conclusions
In sheep, highly pathogenic parasite species with triple resistance occurred on multiple farms while anthelmintics in cattle were still fully active on most farms.