Validation of a prothrombin time (PT) assay for assessment of brodifacoum exposure in Japanese quail and barn owls

Brodifacoum is an anticoagulant rodenticide which has been linked to secondary poisoning of wild birds. The prothrombin time (PT) and activated clotting time (ACT) tests measure the response of the extrinsic and intrinsic coagulation pathways, respectively. The ACT, hemoglobin, hematocrit and PT measured in Japanese quail (Coturnix japonica) were exposed to brodifacoum at 0, 0.8, 1.4, 1.9, and 2.5 mg/kg and sampled 1, 3, 5 and 7 days post-exposure. Free-living barn owl (Tyto alba) PTs were also measured. The ACT increased with exposure, but showed no clear dose-response relationship. Hemoglobin and hematocrit decreased dose- and time-dependently at doses ≥1.4 mg/kg with no significant change at 0.8 mg/kg. PTs were significantly prolonged in a dose- and time-dependent manner at all doses. Although the ACT test requires further evaluation, PTs appear to be a useful indicator of avian anticoagulant rodenticide exposure suggesting that the barn owls sampled were not significantly exposed.