Exposure of domestic cats (Felis catus) to rodenticidal compounds

Anticoagulant rodenticides (ARs) are highly effective, but can be of environmental concern due to primary and secondary non-target exposure, with the latter possible being relevant to domestic cats. Therefore, liver residues of ARs and an alternative rodenticide, α-chloralose, were systematically monitored in domestic cats for the first time in the current study. In 2021 and 2022, the carcasses of 99 cats were collected in Slovenia and liver residues were measured by using solid supported liquid–liquid extraction and LC-MS/MS. The results show that 65% of cats carried at least one rodenticide. The second-generation ARs brodifacoum and bromadiolone were most prevalent and found in 53.5 and 25.3% of the samples, respectively. Of first-generation ARs, coumatetralyl was the most prevalent (21.2% of cats). More compounds were detected at high human population density, low farm density and in rural versus intermediate landscapes, but no effect was found for livestock density. Similar trends were found for the presence of brodifacoum, bromadiolone and all rodenticides combined. Farm density was negatively correlated with brodifacoum liver concentration. Individual factors (cat age, sex, outdoor activity) did not matter. The results indicate that a reasonably populated rural landscape, and not the rural or intermediate environment as such, is the main driver of cat exposure to ARs. The risk quotient (RQ) of worst-case acute brodifacoum poisoning was 1506. In summary, a potential environmental problem is globally highlighted for cats that is probably related to secondary exposure to ARs, with a pattern different to that seen in wild predators. Cats are an appropriate sentinel species for assessing rodenticide exposure and endangerment in the environment.