Primary and secondary poisoning by anticoagulant rodenticides of non-target animals in Spain

Anticoagulant rodenticide (AR) levels were studied in liver of 401 wild and domestic animals found dead in Spain with evidences of AR poisoning, including 2 species of reptiles (n = 2), 42 species of birds (n = 271) and 18 species of mammals (n = 128). Baits (n = 32) were also analyzed to detect the potential use of ARs in their intentional preparation to kill predators. AR residues were detected in 155 (38.7%) of the studied animals and 140 (34.9%) may have died by AR poisoning according to the clinical information, necropsy findings, residue levels and results of other toxicological analysis. Animals considered with sublethal AR exposure had total AR residues (geometric mean with 95% CI) in liver of 0.005 (0.003–0.007) μg/g wet weight (w.w.) and animals diagnosed as dead by AR poisoning had 0.706 (0.473–1.054) μg/g w.w. ARs were detected in 19% of baits illegally prepared to kill predators. In terms of the total incidents studied in our laboratory between 2005 and 2010 (n = 1792 animals), confirmed poisonings represented 40.9% of the cases, and 21.1% of these were due to ARs (8.6% of the total sample). Nocturnal raptors (62%) and carnivorous mammals (38%) were amongst the secondary consumers with highest prevalence of AR exposure, especially to second generation ARs (SGARs). On the other hand, granivorous birds showed the highest prevalence of AR exposure (51%), especially to chlorophacinone in a region treated against a vole population peak in 2007. The presence of hemorrhages was significantly associated with AR levels in liver, but some animals (7.2%) with elevated residue levels (> 0.2 μg/g w.w.) showed no evidence of macroscopic bleeding. The use of accumulative SGARs and the application of baits on surface (i.e. treated grain by spreader machines) should be discontinued in future EU regulations on the use of rodenticides to prevent the poisoning of non-target wildlife species.

► Anticoagulant rodenticides were involved in 21.1% of confirmed poisonings. ► Granivorous birds showed the highest prevalences of primary AR exposure (51%). ► Secondary exposure was high in nocturnal raptors (62%) and carnivore mammals (38%). ► Highest prevalence was found during the chemical control of a population outbreak of common vole. ► 7.2% animals with high residues levels (> 0.2 μg/g) had no macroscopic hemorrhages.