Widespread anticoagulant rodenticide exposure in hedgehogs and their prey in Belgium: prevalence, distribution and hedgehogs' health implications.

The impact of commonly used anticoagulant rodenticides (ARs) on non-target wild animals is poorly understood. This study contributes to a better understanding of European hedgehog (Erinaceus europaeus) exposure to ARs, associated sublethal health effects, and the role of slugs (Deroceras and Lehmannia, important prey items) in AR transmission. Ultra-Performance Liquid Chromatography-Tandem Mass Spectrometry (UPLC-MS/MS) was used to determine exposure levels to first- and second-generation anticoagulant rodenticides (FGARs and SGARs) in 128 free-ranging European hedgehogs and 120 slugs. Short-term health effects of AR exposure were examined by administering an oral subclinical brodifacoum dose (0.019 mg/kg) to domestic African pygmy hedgehogs (Atelerix albiventris) once a week for six consecutive weeks. All livers of wild hedgehogs tested positive for at least one AR compound, with a maximum concentration for brodifacoum reaching 6743 ng/g wet weight (ww). AR prevalence was significantly higher in slugs from residential areas (30 %), compared to agricultural (7 %; p = 0.0353), forest (3 %; p = 0.0211) and park (3 %, p = 0.0211) areas. This coincides with significantly higher AR concentrations in hedgehogs from areas with higher human population densities (p = 0.047). No direct positive correlation was found between AR levels and the occurrence of hedgehog diphtheric disease (HDD), an often fatal ulcerative bacterial infection in hedgehogs, likely driven by multiple factors. Histopathological examination revealed hemorrhages in the renal medulla in two out of nine laboratory-exposed hedgehogs, suggesting sublethal effects after short-term AR exposure. The omnipresence of subclinical AR concentrations in wild hedgehogs and notably higher AR prevalence in slugs in densely populated areas, urge to explore long-term and ecosystem effects of widespread AR use.