Understanding Mouse Resistance In A Mediterranean City: Implications For Rodent Control

Anticoagulant rodenticides are the most commonly used pesticides worldwide that inhibit blood coagulation by
suppressing the activity of the vitamin K epoxide reductase (VKOR). Resistance to these compounds has been reported in multiple rodent populations in different countries, and numerous studies have linked several resistance phenotypes to mutations in the gene Vkorc1, which codifies for the VKOR complex subunit 1. The identification of resistance in rodent populations is key for the efficacy of their control. Here we sequenced exons 1, 2 and 3 of the Vkorc1 gene of 111 mice (Mus musculus domesticus) captured across the city of Barcelona. All the sampled individuals harbored resistant genotypes. Most of the SNPs identified were associated with resistance to first-generation anticoagulants (coumetralyl and chlorophacinone) and second-generation anticoagulants (bromadiolone and difenacoum). We also found one SNP in exon 3 associated with resistance to brodifacoum. Our results show a widespread occurrence of resistant mice in Barcelona, posing a unique challenge for rodent control given the widespread use of bromadiolone based products. Public health managers, pest control companies and citizens should be aware that most currently commercialized products are ineffective for mouse control.