Is diazinon used as antiparasitic in sheep a threat for bearded vultures?

Abstract

Wildlife poisoning can occur under different circumstances, including the misuse, abuse or illegal use of biocides and pesticides. In Spain, poisoning of predatory and scavenger species has been commonly associated with the illegal use of pesticides to kill predators, especially wolf by farmers and fox by game-keepers. However, accidental exposures could be underscored if the investigation schemes are focused on the identification of illegal poisonings. Here we present data regarding the exposure of bearded vulture (Gypaetus barbatus) to external antiparasitics in Spain, as a case of potential threat by accidental exposure and poisoning of the endangered European population of this species. We have studied 24 suspected poisonings of bearded vultures and the breeding failure of one pair in Aragon (NE Spain) between 2006 and 2013. This study is part of a larger monitoring of wildlife poisonings (n=462) performed in the provinces of the Pyrenees in Spain. As evidences were found that external antiparasitics used on livestock were a probable cause of some of these poisonings, 24 feet of pork and 116 feet of lamb were analysed by GC-MS. Brain acetylcholinesterase (AchE) activity was measured in the brain when this sample was available. Poisoning was diagnosed in 16.7% of bearded vultures, mainly by diazinon related to lamb feet consumption, and in several cases with a significant inhibition of brain AChE. Other species of scavengers, like Egyptian vulture (Neophron percnopterus), showed much higher frequencies of poisoning (76.7%), especially by intentional poisonings. Pork feet had no residues of external antiparasitics, but lamb feet showed residues of diazinon, pirimiphos-methyl, chlorpyrifos, fenthion, permethrin or cypermethrin, with occurrences varying among slaughterhouses (up to 100%). Washing the feet with water significantly reduced the levels of external antiparasitics, so this measure was regularly adopted to reduce the risk of exposure in the managed feeding sites. In some cases, lamb feet contained up to 618 ng/g of diazinon, which can give a toxicity-exposure ratio below 5. Moreover, mean concentrations of diazinon in lamb feet were above the levels that can affect thermoregulation in sub-acutely exposed birds, especially nestlings.