Abstract

Benzimidazole (BZ) drugs are frequently used to treat infections with the equine ascarid Parascaris univalens due to increasing resistance to macrocyclic lactones and pyrantel. Benzimidazole resistance is rare in ascarids in contrast to strongyle parasites where this resistance is widespread. In strongyles, single nucleotide polymorphisms (SNPs) at codons 167, 198 and 200 in a 13-tubulin gene have been correlated to BZ resistance, but little is known about the 13-tubulin genes and their possible involvement in BZ resistance in P. univalens and other ascarids. Previously two 13-tubulin genes have been identified in P. univalens. In this study, we present five additional 13-tubulin genes as well as the phylogenetic relationship of all seven genes to 13-tubulins of other clade III and V nematodes. In addition, the efficacy of fenbendazole for treatment of P. univalens on a Swedish stud farm was studied in 2019 and 2020 using faecal egg count reduction test. Reductions varied from 73% to 88%, indicating the presence of a resistant P. univalens population on the farm. The emergence of BZ resistance emphasizes the need for development of molecular markers for rapid and more sensitive detection of resistant populations. We therefore investigated whether possible SNPs at positions 167, 198 or 200 in any of the 13-tubulin genes could be used to distinguish between resistant and susceptible P. univalens populations. Amplicon sequencing covering the mutation sites 167, 198 and 200 in all seven 13-tubulin genes revealed an absence of SNPs in both resistant and susceptible populations, suggesting that the mechanism behind BZ resistance in ascarids is different from that in strongyle nematodes and the search for a molecular marker for BZ resistance in P. univalens needs to continue.

Keywords

Amplicon sequencing; Anthelmintic resistance; Equine; Fenbendazole

Published in

International Journal for Parasitology: Drugs and Drug Resistance
2021, Volume: 17, pages: 84-91
Publisher: ELSEVIER SCI LTD

SLU Authors

• Martin, Frida

  • Department of Animal Biosciences, Swedish University of Agricultural Sciences
    

• Halvarsson, Peter

  • Department of Animal Biosciences, Swedish University of Agricultural Sciences
    

• Delhomme, Nicolas

  • Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences
    

• Höglund, Johan

  • Department of Animal Biosciences, Swedish University of Agricultural Sciences
    

• Tyden, Eva

  • Department of Animal Biosciences, Swedish University of Agricultural Sciences
    

Associated SLU-program

AMR: Parasite


UKÄ Subject classification

Genetics


Publication identifier

DOI: https://doi.org/10.1016/j.ijpddr.2021.08.004

Permanent link to this page (URI)

https://res.slu.se/id/publ/113745