Proceedings of the Vertebrate Pest Conference

The widespread use of anticoagulant rodenticide for controlling commensal rodent pests over the past 50 years has raised concerns about the development of genetic resistance that could diminish the efficacy of these toxicants. These rodenticides primarily target the VKORC1 protein synthesized by the Vkorc1 gene. Mutations in the 139 codon altering binding sites and conferring resistance. While studies in Europe and Asia have documented such Vkorc1 mutations and associated anticoagulant rodenticide resistance in commensal rodents, few investigations have explored this issue in the Americas according to the Rodenticide Resistance Action Committee (RRAC). This study is one of the first efforts to survey Vkorc1 resistance mutations in commensal rodents in eastern North America. The lack of genetic mutations in sampled Norway rats collected from Richmond, Virginia and Helsinki Finland provides a baseline for future monitoring as anticoagulant rodenticide selection pressure continues. However, as Norway rat populations continue to grow, regular screening will be critical for early detection of rodenticide resistant genotypes. Municipalities should incorporate Vkorc1 resistance testing into integrated pest management (IPM) programs for rodents. If resistance alleles emerge, control strategies may need to transition towards alternative toxicant modes of control and greater emphasis on IPM tactics that reduce food and harborage resources for these rodents.