Tracing Veterinary Pharmaceuticals through Regurgitated Pellets: A Noninvasive Monitoring Approach to Assess Exposure...

Threatened avian scavengers can become highly exposed to pharmaceuticals when they feed on carcasses of medicated livestock. In this study, we assess the use of regurgitated pellets as a potential noninvasive method to monitor vulture exposure to pharmaceuticals. We analyzed pellets (n = 292) from Eurasian griffon vultures (Gyps fulvus) for 48 compounds commonly used in veterinary medicine in Spain as well as their persistence in such a matrix for up to one month in quasi-natural conditions. Samples were analyzed using liquid chromatography with electrospray ionization mass spectrometry (LC-ESI-MS/MS). We observed a high stability of most of the pharmaceuticals in the pellets. We detected veterinary pharmaceuticals in 44.2% of pellets, specifically 43.5% with antibiotics and 2% with NSAIDs (1.4% with both). Pellets containing only domestic livestock remains showed pharmaceuticals more frequently (48.2%, 91/189) than those containing wild ungulate remains (20.0%, 5/25). Pig was the main prey and remained associated with the presence of pharmaceuticals in pellets. The pellet monitoring of a supplementary feeding station supplied by a single farm revealed a temporal shift in the use of specific antibiotics. We highlight that the disposal of livestock carcasses to feed scavengers must be closely controlled because of potential risks posed by veterinary pharmaceutical residues, notably NSAIDs.