VKORC1 mutations in house mice in the Auckland Region (Aotearoa/New Zealand)

Introduced house mice are widespread in Aotearoa/New Zealand, and they have significant impacts on native wildlife. The most common toxins for controlling rodents are anticoagulant rodenticides (AR). Even though AR are an efficient tool, resistance to these substances in rodent populations has been detected in many countries. This phenomenon represents a major factor in reducing the success of pest management, and it is mostly related to missense mutations in the VKORC1 gene. Despite the crucial importance of effective house mouse management, genetic AR resistance in mice in Aotearoa/New Zealand is poorly understood. In this study, we undertook a genetic survey of six sites across the Auckland region to investigate the presence of VKORC1 mutations potentially involved in AR resistance. We found a total of five different missense mutations across four of the six sites. Three mutations leading to amino acid changes have been recorded in rodents previously while two are novel. Among these, the well-known Tyr139Cys, involved in resistance to some powerful AR like bromadiolone, is found with a high allelic frequency in central Auckland. Our results suggest that even across a moderate geographic region, there can be important genetic diversity and clustering in AR resistance. Anticoagulant rodenticides are a critical tool in introduced rodent management, but their use must be deliberated and genetic screening of rodent populations should increasingly be an important part of AR management operations.