Overview
- A Rutgers-led DNA study published June 24, 2026 tested 147 house mice and 143 Norway rats from New York, New Jersey, Pennsylvania and Washington, D.C., and found about 84% of mice and roughly 35% of rats carried mutations linked to rodenticide resistance.
- Researchers identified several previously undescribed genetic variants in both species and said laboratory work is needed to determine which new mutations actually reduce susceptibility to anticoagulant poisons.
- The study found species-specific adaptation: house mice show high frequencies of genetic changes—notably in the Vkorc1 pathway that anticoagulants target—while many Norway rats display learned avoidance of baits and traps.
- Experts warn continued reliance on anticoagulant rodenticides risks reduced control of disease-carrying rodents and secondary poisoning of predators and scavengers, and they recommend switching to sanitation, sealing entry points, trapping and integrated pest management.
- The sampling came from pest-control submissions in the Northeast, so researchers caution results may vary by place and say cities should prepare for higher control costs, more emphasis on prevention, and follow-up studies to guide local policy.