PARIS, Jan 28: Scientists believe they have figured out the baffling decline of vultures in Pakistan and India, declaring that the phenomenon is due to toxic residues from a veterinary drug.

Vultures which feed on the carcasses of livestock recently given diclofenac, an anti-inflammatory widely used in the sub-continent, build up such levels of the drug that they suffer kidney failure, they report in Thursday's issue of Nature, the British science weekly.

Experts have been struggling for years to explain a decline of more than 95 per cent in the past decade of many populations of the Oriental white-backed vulture (Gyps bengalensis), a bird that pays a vital role in the food chain.

Once one of the commonest raptors on the Indian continent, the creature is now listed as critically endangered. The researchers led by Lindsay Oaks, a veterinary microbiologist at Washington State University, linked high levels of diclofenac with death from visceral gout, a degenerative kidney disease, among 259 vultures they autopsied in Pakistan.

The team tested their theory by feeding captive vultures the drug either directly or indirectly, using meat from the carcasses of buffaloes or goats that had been treated with it.

In both India and Pakistan, diclofenac is sold over the counter as a non-steroid painkiller for farm animals, and farmers in those countries often leave the carcasses of animals that die of disease or injury for scavengers to remove.

Two other South Asian raptors that have been threatened by drastic declines are the long-billed vulture and the slender-billed vulture. The birds' decline had opened up dozens of speculative paths, such as a bacterial, a novel virus or perhaps a parasite as the cause.

"This discovery is significant in that it is the first known case of a pharmaceutical causing major ecological damage over a huge geographic area and threatening three species with extinction," Oaks was quoted as saying by the Peregrine Fund, a US wildlife agency for birds of prey that sponsored the research.

A meeting will be held in Kathmandu on February 5 and 6 to discuss diclofenac's role in the vultures' decline and outline potential solutions to the threat, the statement said.

"Vultures have an important ecological role in the Asian environment, where they have been relied upon for millennia to clean up and remove dead livestock and even human corpses," said Peregrine Fund biologist Munir Virani.

"Their loss has important economic, cultural and human health consequences."India's Parsees depend on vultures for disposal of their corpses, considering burial or burning of human remains to defile the elements.-AFP