Widespread resistance to anticoagulant rodenticides in Mus musculus domesticus in the city of Barcelona

Control of rodent populations is a big challenge because of the rapid evolution of resistance to commonly used roden-ticides and the collateral negative impacts that these products may have on biodiversity. Second-generation anticoag-ulants are very efficient but different single nucleotide polymorphisms (SNPs) in the Vkorc1 gene may confer resistance in rodents. We sequenced exons 1, 2 and 3 of the Vkorc1 gene from 111 mice (Mus musculus domesticus) captured across the city of Barcelona and found SNPs associated with resistance to first-and second-generation anticoagulants in all of them. Although most of the SNPs were associated with resistance to bromadiolone, we also found SNPs associated with resistance to brodifacoum. Out of all the individuals analyzed, 94.59 % carried mutations associated to introgression events with Mus spretus, a sympatric rodent species. Currently most of the chemical products for rodent control com-mercialized in the area are based on bromadiolone, although recent public control campaigns have already shifted to other products. Thus, the widespread occurrence of resistant mice to bromadiolone represents a challenge for rodent control in Barcelona and may increase the risk of secondary poisoning of animals preying on this species. Public health managers, pest control companies and citizens should be aware that the use of bromadiolone based products is ineffec-tive and represents a risk for the environment, including human and animal health.

Automated summary

The rapid evolution of resistance to anticoagulants in rodent populations in Barcelona poses a challenge for controlling them. The study found that most mice carry gene mutations associated with resistance to commonly used anticoagulants, making the current chemical control methods ineffective and potentially harmful to the environment and human health.