Veterinary Drug Linked to Asian Vulture Population Crash

BOISE, Idaho, January 29, 2004 (ENS) - Widespread veterinary use of a pharmaceutical called diclofenac is responsible for an alarming decline of three species of Asian vultures, according to an international team of scientists. The researchers say their finding offers a "canary in the coal miner's cage" warning of a dangerous environmental health hazard.

The study, published in the latest issue of the journal "Nature," is the product of a three year effort by an international team of scientists, trying to solve the mystery of unexplained vulture deaths since the mid-1990s. The team was assembled and led by The Peregrine Fund, a conservation group based in Boise.

Stark evidence of the vulture crisis. (Photo by Pat Benson courtesy The Peregrine Fund)

The three species documented by the team are the Oriental white-backed vulture, the long-billed vulture, and the slender-billed vulture. These three endangered species have suffered population declines of more than 95 percent over the past decade in many areas of south Asia, the researchers report.

Declines of this magnitude in once very common species "have not been seen since the extinction of the great auk, or the passenger pigeon in the 19th century," said Dr. Martin Gilbert, veterinarian for The Peregrine Fund.

Gilbert conducted and supervised ecological field studies, and vulture necropsy and tissue collection in Pakistan.

The research team determined that the birds are feeding on animal carcasses full of diclofenac, which for decades has been used in humans as a non-steroidal anti-inflammatory pain reliever.

The veterinary use of diclofenac to relieve pain in livestock has increased in South Asia over the past decade and is now widespread.

Livestock that die shortly after being treated with diclofenac contain sufficient residues to cause kidney failure and death in vultures that consume livestock carcasses, the researchers explained.

A single meal from an animal treated with diclofenac contains enough of the drug to kill a vulture.

A mathematical model developed by the UK branch of the international conservation group BirdLife indicates that the observed rate of vulture population decline - a fall of 30 percent annually - can be induced even if less than one in 200 of the carcasses available to vultures contain lethal amounts of diclofenac.

The team says they have ruled out other causes of the population decline of the three vulture species - a decline that is without precedence among vertebrate species

"Finding that a drug is responsible for the collapse and threatened extinction of these species is helpful yet alarming," said Dr. Rick Watson, international programs director for The Peregrine Fund. "Helpful, because now we can do something about it and we may have time to save these species. Alarming, because this may not be the only pharmaceutical impacting wildlife."

White-backed vulture populations have crashed 99 percent since the late 1980s, with the loss of tens of millions of birds. (Photo by Guy Shorrock courtesy BirdLife International)

"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 Virani, who coordinated the field investigations across Nepal, India, and Pakistan. "Their loss has important economic, cultural, and human health consequences."

To expedite the transfer of knowledge and responsibility to the countries inhabited by vultures, The Peregrine Fund and partners have organized an international vulture summit meeting February 5-6 in Katmandu, Nepal.

The summit will include senior government officials from the affected countries and carries the endorsement of the U.S. State Department. In a letter to invitees, John Turner, U.S. assistant secretary of state for oceans and international environmental and scientific affairs urged national governments of the region to participate.

The summit will include a briefing on the scientific evidence of the role diclofenac has in the catastrophic population collapse of these species, potential solutions to mitigate the effects of diclofenac, and a forum to develop a strategic response to this new environmental threat and to begin the effort to restore these species.

Members of the BirdLife network, including the Bombay Natural History Society in India and the Royal Society for the Protection of Birds (RSPB) in the UK, have joined other conservation organizations to urge governments of countries with vulture populations to ban the use of this drug in livestock.

"The Asian vulture crisis is one of the world’s most important conservation priorities," said the RSPB's Dr. Mark Avery. The society is committing "significant resources to a program to ensure that these birds have a future," he said.

"The speed of the decline is eerily similar to the decline of the peregrine falcon in the 1960s," said Dr. Tom Cade, founder of the Peregrine Fund. "We are in another race against time to save these species."