Distribution and frequency of <scp> <i>Vkorc1</i> </scp> polymorphisms in house mice and Norway rats in the northeastern United States

BACKGROUND: Modern commensal rodent pest control often relies on anticoagulant rodenticides (ARs), yet the development of resistance driven by mutations in the Vkorc1 gene has become a growing challenge in rodent management. Surveying the mutations in the Vkorc1 gene in rodents is essential to understanding the rodenticide resistance profile and its impacts on the environment. This study aimed to assess the distribution and frequency of Vkorc1 polymorphisms in house mice and Norway rats in New York, New Jersey, Pennsylvania, and Washington, DC, USA. RESULTS: A total of 147 house mice (Mus musculus domesticus Schwarz and Schwarz) and 143 Norway rats (Rattus norvegicus [Berkenhout]) were sampled from urban areas. Five nonsynonymous single nucleotide polymorphisms (nsSNPs) were identified in house mice, including A32V, W59L, L128S, Y139C, and Y139F. The A32V and Y139F mutations were reported for the first time in M. musculus domesticus. Among all mice examined, 84% carried at least one mutation, with Y139C (42%) and L128S (33%) being the most prevalent. At least 69% of the mice carried mutations that are known to confer resistance. In Norway rats, 35% carried mutations including two synonymous mutations (H68H, I82I) that have been previously reported and one nsSNP (L128V) that was newly identified in this study. However, H68H is not associated with AR resistance and whether the other two mutations contribute to AR resistance remains unknown. CONCLUSION: The high prevalence of resistance-associated mutations in house mice suggests that different types of rodenticides should be alternated and integrated management approaches need to be emphasized in rodent control. © 2026 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.