"We are pretty much convinced where birds are dying of visceral gout or renal failure it is caused by diclofenac," said co-author Rick Watson, international programs director for The Peregrine Fund in Boise, Idaho, which led the international study team.
Ian Newton, an ornithologist with the Centre for Ecology and Hydrology at the Natural Environment Research Council in Cambridgeshire, United Kingdom, said the study is carefully done and clearly shows the link between diclofenac and the vulture deaths.
"Throughout the region, the timing of vulture decline coincides with the period of diclofenac use, and such massive population declines have not been recorded in related vultures in other parts of the world where the drug is mainly restricted for human use," he said.
Oaks and colleagues are currently partnering with the World Wildlife FundPakistan to figure out the economic reasons for why diclofenac has suddenly become widespread throughout the Indian subcontinent, but suspect its growth stems from it being a safe, effective, and cheap pain reliever for animals.
"From a vet's perspective, it is actually a very good drug and there is very little disincentive to use it," said Oaks. "No one thought it would have these ecological impacts."
Like ibuprofen and aspirin, diclofenac can be used to treat ailments such as a sore leg. Although it cannot cure the leg, the drug can alleviate pain enough to allow an ailing buffalo to ferry a load back to the farm from town, said Oaks.
The unintended consequence comes when livestock die shortly after being treated with the drug. Their bodies contain sufficient residues to cause visceral gout in the vultures.
In order to prevent the extinction of these vultures, Oaks and his colleagues are calling for an immediate ban on the veterinary use of the drug. "We know for a fact that diclofenac is really bad, so the first priority is to get that controlled," said Oaks.
Currently, the use of diclofenac to treat livestock appears to be largely restricted to countries in southern Asia. The vulture crisis research community is concerned, however, that if the drug were used in a similar way in Africa, the Middle East, or Europe, it might affect closely related species in these regions too.
Call for Action
To expedite the transfer of this finding to the appropriate authorities, the researchers have organized an international summit next month in Kathmandu, Nepal. "What the outcome will be we can't tell at this stage, but we will provide every bit of opportunity for the governments to respond appropriately," said Watson.
According to Watson, chief among the appropriate responses is an outright ban on the veterinary use of diclofenac. Other options include an aggressive captive breeding program and actively feeding uncontaminated food to the vultures.
"With such an apparently lethal chemical, the most effective solution would be to ban its use altogether in free-ranging livestock, and in my view it is unlikely that vultures could survive where this chemical is in widespread use," said Newton.
While there are several alternatives to diclofenac, the researchers do not know if any of them are safe for the vultures. Further studies may reveal an answer. In the meantime, they recommend a captive breeding program to ensure viable populations for future re-introduction programs.
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