Experimental evidence for the lack of sensitivity of in vivo faecal egg count reduction testing for the detection of ear
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HELMINTHOLOGY - ORIGINAL PAPER
Experimental evidence for the lack of sensitivity of in vivo faecal egg count reduction testing for the detection of early development of benzimidazole resistance Alžbeta Königová 1 & Michaela Urda Dolinská 1 & Michal Babják 1 & Georg von Samson-Himmelstjerna 2 & Michaela Komáromyová 1,3 & Marián Várady 1 Received: 17 July 2020 / Accepted: 3 November 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The objective of this study was to compare the results of an in vitro egg hatch test (EHT), micro-agar larval development test (MALDT) and in vivo faecal egg count reduction test (FECRT) between worm strains obtained from goats and sheep identically infected with the gastrointestinal parasitic nematode Haemonchus contortus. Results from the in vivo and in vitro tests were compared with benzimidazole (BZ)-resistance-associated β-tubulin allele frequencies determined using Pyrosequencing™. BZ resistance was not detected by the in vivo FECRT, where reductions of > 99% for both the resistant and the susceptible H. contortus strains were detected in both species. Discriminating doses in EHT and MALDT for the resistant strain indicated a low level (approx. 25%) of resistant individuals. Genotyping indicated that the susceptible strain had 10% BZ-resistant βtubulin codon 200 alleles and the resistant strain had 26% respective resistant alleles. The in vitro tests and allele-frequency distribution suggested low levels of resistance in both strains; however, the FECRT did not support the evidence of resistant individuals of either strain in either species, suggesting a potential underestimation of low-level resistance in sheep and goats when employing this test. Keywords Haemonchus contortus . Anthelmintic resistance . In vitro tests . In vivo tests . Goats . Sheep
Introduction The occurrence of anthelmintic resistance (AR) on smallruminant farms is rapidly increasing worldwide, and new cases are frequently being reported (Van Den Brom et al. 2013; Cintra et al. 2016; Arece-García et al. 2017; Nagata et al. 2019). Most new surveys still focus on the occurrence of AR in sheep herds. Imbalances between ovine and caprine studies were noted by Hoste et al. (2010), where only 20–25% of Handling Editor: Julia Walochnik * Marián Várady [email protected] 1
Institute of Parasitology of the Slovak Academy of Sciences, Hlinkova 3, 040 01 Košice, Slovakia
2
Institute for Parasitology and Tropical Veterinary Medicine, Freie Universität Berlin, Robert-von-Ostertag-Str. 7-13, 14163 Berlin, Germany
3
University of Veterinary Medicine and Pharmacy in Košice, Komenského 73, 041 81 Košice, Slovakia
references about gastrointestinal nematode species studied caprines. Goat farming is increasing, because goats can efficiently convert low-quality forages to quality meat and milk (Hoste et al. 2010). Immunological, behavioural, and physiological differences between sheep and goats are well known (TorresAcosta and Hoste 2008), and goats need higher dose rates for effective anthelmintic treat
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