Anticoagulant rodenticide blood‐clotting dose‐responses and resistance factors for Tyrosine139Cysteine (Y139C) heterozygous‐ and homozygous‐resistant house mice (Mus musculus)

Abstract

Background The house mouse (Mus musculus) is a globally distributed rodent pest species against which anticoagulant rodenticides are widely used for the protection of human and animal health and the conservation of threatened wildlife. Anticoagulant‐resistant house mice have been known for more than half a century. A house mouse strain was developed in the laboratory that was homozygous resistant for the single nucleotide polymorphism (SNP) Tyrosine139Cysteine (Y139C) and, subsequently, heterozygous resistant animals were produced from this strain by crossing with the homozygous susceptible strain. Results Using blood clotting response tests, resistance factors at the ED50 level in the homozygous resistant strain for the first‐generation anticoagulants warfarin, chlorophacinone, diphacinone and coumatetralyl were in the range 31.5 to 628.0 for males (M) and 21.6 to 628.0 for females (F), thus indicating that Y139C house mice are substantially resistant to all these substances. Resistance factors at the ED50 level for the homozygous strain generated against the second‐generation compounds were: brodifacoum (M, 1.7; F, 1.9), bromadiolone (M, 16.6; F, 21.0), difenacoum (M, 1.2; F, 2.7), difethialone (M, 1.5; F, 1.5), and flocoumafen (M, 0.9; F, 1.2). Equivalent values for the heterozygous strain were: brodifacoum (M, 1.6; F, 1.4), bromadiolone (M, 5.6; F, 6.5), difenacoum (M, 1.0; F, 1.3), difethialone (M, 1.1; F, 1.1), flocoumafen (M, 0.9; F, 1.1). Conclusion Y139C SNP homozygous resistant mice are more resistant to anticoagulants than heterozygous resistant animals. All first‐generation anticoagulants are highly resisted and, among the second‐generation compounds, Y139C mice are resistant to bromadiolone and sometimes to difenacoum. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

The stop-feed effect of cholecalciferol (vitamin D3) and the efficacy of brodifacoum combined with cholecalciferol in Y139C-resistant Norway rats (Rattus norvegicus)

“…Laboratory and field trials confirmed that rats and mice of the Y139C strain are not only resistant to anticoagulants of the first generation, but also to the second-generation anticoagulant rodenticides (SGARs) bromadiolone and difenacoum (Buckle et al 2013;Endepols et al 2012). Such high level of resistance has not only been determined in Y139C strains, but also in a number of other rats and mouse strains (Baxter et al 2022;McGee et al 2020). Consequently, only three SGARs, brodifacoum, flocoumafen, and difethialone, are recommended for use against rats and house mice in such foci of resistance (RRAC 2021).…”