Common rodent poisons may be becoming less effective, scientists warn, as research suggests that mice and rats are increasingly evolving resistance to them.
Data from a new study revealed that an alarming number of house mice carry a genetic mutation associated with rodenticide resistance, which makes them more likely to survive poisons commonly relied upon for pest control.
Among house mice sampled from urban areas in Northeast America, nearly 70 per cent were found to carry genetic mutations already known to help them survive common rodenticides, while roughly 35 per cent of Norway rats – often called brown or sewer rats – carried mutations in the same gene.
Reports from flummoxed pest control professionals of increasingly stubborn rodent populations caused researchers at Rutgers University to investigate.
“Pest management professionals often told us that rodent control was becoming more difficult in some areas, even though they applied the effective rodenticides,” said Jin-Jia Yu, the first author of the study.
Researchers examined DNA from 147 house mice and 143 Norway rats collected in a number of Northeastern states, including New York and Washington DC.
They found that a staggering percentage of rodents have mutations of a gene called Vkorc1, which is linked with resistance to the most widely used poison in the US, anticoagulant rodenticides.
"We found that resistance appears to be much more widespread in house mice than many people realised,” Yu said. “Norway rats also carried genetic mutations, but scientists do not yet know whether most of those mutations affect Norway rats' susceptibility to rodenticides.”
Rodents are more than just a nuisance, according to study co-author Changlu Wang – they're a public health concern.
“As resistance becomes more common, it becomes even more important to use science-based management strategies that protect both public health and the environment,” he said.
“Studies like this help us understand how rodent populations are changing and how our management strategies need to evolve with them.”
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