PULLMAN, Wash. — Three years of hard work by Washington State University researcher Lindsay Oaks have led to a major discovery linking the decline of three Asian vulture species to a drug commonly used to treat livestock there.

Oaks, a microbiologist with the WSU College of Veterinary Medicine, worked with an international team of scientists on the problem. The findings of their work will be published in the journal Nature (www.Nature.com/nature).

Oaks will join a team of experts to speak at an international summit meeting Feb. 5-6 in Katmandu, Nepal.  The team will reveal additional details of their findings and propose possible solutions to help mitigate the long-term decline of these rare species.

The paper links the veterinary use of the anti-inflammatory drug diclofenac in domestic livestock with the catastrophic crash of three species of raptors. The discovery is the result of a three-year effort by an international team of scientists, assembled and led by The Peregrine Fund, and included members from WSU, the Ornithological Society of Pakistan, Bird Conservation Nepal, the Zoological Society of San Diego, the National Wildlife Health Center, the University of California and University of Idaho.

“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,” said Oaks, the lead diagnostic investigator for The Peregrine Fund’s team.

The oriental white-backed vulture was once one of the most common raptors on the entire Indian sub-continent.  But over the last decade, population losses of more than 95 percent have been reported in many areas.

In conducting the research, the team analyzed the remains of 259 vultures, and found that 85 percent died from the same problem: renal failure. Preliminary research indicated that the kidney disease was due to a toxin, and all of the conventional causes of kidney disease in birds were ruled out.

Based on surveys of veterinarians in the region, it was theorized that the anti-inflammatory drug diclofenac might have been responsible. The drug is commonly used to treat livestock and is known to cause kidney damage in both birds and mammals. Cattle that die are the primary food source for the vultures. Testing soon showed that tissues from all the affected vultures contained residues of diclofenac. When the records were examined, widespread veterinary use of diclofenac in south Asia also coincided with the population decline of the vultures.

Editor’s note: Images and broadcast quality video are available through The Peregrine Fund (http://www.peregrinefund.org/).