Study of Sensitivity to Warfarin, Chlorophacinone and Bromadiolone of Four Raptors Species
Anticoagulants are widely used to limit rodent infestations but non-target animals, as birds of prey, can poison themselves by primary or secondary routes.1 Raptors seem to be more sensitive to anticoagulants, but no objective data exist.2
The aim of our study was to establish the inhibition constant Ki of the enzyme targeted by anticoagulants, the vitamin K epoxide reductase (VKOR), for several birds of prey. Liver microsomes were extracted from dead raptors originated from a French wildlife rescue center. On necropsy, those animals did not show any sign of poisoning. VKOR activity was tested to include only birds with a real enzymatic activity. Two common buzzards (Buteo buteo), four tawny owls (Strix aluco), one common kestrel (Falco tinnunculus) and one Eurasian sparrowhawk (Accipiter nisus) were eligible for this study. Derivative Michaëlis-Menten formulas were used to determine the inhibition constants. The Ki were compared between the different species with Mann-Whitney-Wilcoxon tests.
Inhibition constants ranged from 948 to 14431 nmol/L for warfarin, 15.66 to 342.3 nmol/L for chlorophacinone and 13.36 to 73.27 nmol/L for bromadiolone. There was no significant difference between the species and between diurnal and nocturnal birds of prey (p>0.05). A higher sensitivity to bromadiolone was suspected in comparison to rats. Further studies with an increased number of raptors are warranted to assess intraspecific variability.
The authors would like to thank the whole USC1233 team for their assistance during experiments.
1. Evans J.A, Ward A.L. Secondary poisoning associated with anticoagulant-killed nutria. J. Am.Vet. Med. Assoc. 1967;151:856–861.
2. Hughes J., Sharp E., Taylor M.J., Melton L., Hartley G. Monitoring agricultural rodenticide use and secondary exposure of raptors in Scotland. Ecotoxicology 2013; 22:974–984.