Livestock Painkillers are Devastating Vulture Populations

'Gypful' by Pierre Dalous via Wikimedia
Janet Fang 17 Oct 2014, 20:10

Anti-inflammatory drugs for cattle are poisoning vast numbers of vultures. In India, the drug has already devastated scavenger populations, and despite its ban, illicit use continues. What’s more, researchers conducting a forensic examination of a dead vulture in Spain are now worried that European vulture populations are about to suffer the same fate. 

Across the Indian subcontinent in the last two decades, populations of Gyps vulture species have collapsed because of exposure to a non-steroidal anti-inflammatory drug (NSAID) called diclofenac in the livestock carcasses that the vultures feed on. Farmers in India have been using the drug as a painkiller for cattle since 1994. But because of rapidly declining scavenger populations—up to 95 percent for some now critically endangered species—the Indian government banned the drug for veterinary use in 2006, advocating a “vulture-safe” alternative called meloxicam in its place. 

To measure the effectiveness and impacts of the ban, a large international team led by Rhys Green of Cambridge examined drug residue data in liver samples collected from 6,207 mammal carrion (like cattle and water buffalo) in India since 2004. They found that the prevalence of diclofenac in carcasses in 2009 was half of that before the ban, while meloxicam prevalence increased by 44 percent. Also, the team calculated the expected vulture death rate from diclofenac per meal in 2009 and found that it was one-third of that before the ban.

“It looks as if, if one can be successful in persuading people to use meloxicam,” Green tells The Scientist, “then you’re quite probably going to reduce the use of toxic diclofenac.” But their data clearly suggest that unauthorized diclofenac use persists. Their findings were published in Philosophical Transactions of the Royal Society B this week as part of a special issue on pharmaceuticals in the environment.  

And that’s the good news. 

In 2012, the carcass of a wild Eurasian griffon vulture (Gyps fulvus) was discovered on an Andalucian game hunting reserve in Spain. A team led by Mark Taggart from the University of the Highlands and Islands examined the carcass forensically, and they’re now reporting the first case of a wild vulture that’s exposed to— and apparently killed by—an NSAID outside Asia. It’s also the first reported instance of a death in the wild resulting from environmental exposure to an NSAID that’s not diclofenac. 

Like vultures poisoned by diclofenac in Asia, this bird had severe visceral gout. Liver and kidney samples showed elevated levels of another NSAID, called flunixin. These findings were published in Conservation Biology last week. 

“We are now asking the European Union to ban diclofenac as a first step,” José Tavares of Vulture Conservation Foundation tells Nature. And then other potentially harmful drugs like flunixin might also be considered. 

Image: Pierre Dalous via Wikimedia CC BY-SA 3.0

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