Rodenticide resistance testing halted by lab closure

Testing for rodenticide resistance in rats and mice has been suspended due to coronavirus-related closure of the laboratory where DNA analysis was being done. Funded by the Campaign for Responsible Rodenticide Use, this annual surveillance is a formal requirement of the UK Rodenticide Stewardship Regime.

CRRU chairman Dr Alan Buckle has confirmed that a new laboratory contractor is being sought. Meanwhile, he asks pest controllers, farmers and gamekeepers not to send rat or mouse tail samples to the University of Reading’s Vertebrate Pests Unit.

In the past two years, this surveillance found new hotspots of resistance genes in Northumberland and County Durham, Tyneside and North Yorkshire, Greater Manchester and along the River Severn valley from north-west Shropshire to Somerset, Devon and East Anglia.

An online national map (bit.ly/2PsM8Pl) plots the known distribution of resistance in rats and mice. Resistance genes have become widespread across central southern England over a number of years. But Dr Buckle says there remains a lack of data from central England and most parts of Scotland, Wales and Northern Ireland.

“We can only manage the spread of resistance when we know where it is,” he says. “Right now, pest control technicians, farmers and gamekeepers in some parts of the country could be using products that are ineffective.

“And where resistance genes are still absent, others may be using resistance-breaking products unnecessarily. Only a resumption of testing can address this.”