Oops. The drug ketoprofen, which conservationists once hoped might aid South Asia’s collapsing vulture populations, has turned out to be yet another poison for the birds.
A medical cousin of ibuprofen, ketoprofen reduces inflammation and pain, and some of India’s farmers treat their cattle and other livestock with it. Researchers started testing ketoprofen in hopes of finding livestock drugs that don’t leave residues in carcasses that vultures eat, says zoologist Richard Cuthbert of the Royal Society for the Protection of Birds in Sandy, England.
Since the early 1990s, residues of a widely popular anti-inflammatory, diclofenac, have inadvertently poisoned so many vultures in the genus Gyps that three species now totter on the brink of extinction. The one known bird-friendly alternative, meloxicam, costs somewhat more than the main vulture menace and has not replaced it in practice.
In an effort to increase the number of safe drugs, Cuthbert and an international team of researchers tested ketoprofen on two related vulture species in Africa that are not considered to be endangered. Direct doses of ketoprofen killed vultures, as did meals of carcasses from recently dosed cattle, the researchers report online December 8 in Biology Letters. The researchers note that a recently published survey of carcasses in southern India did find ketoprofen residues at these lethal concentrations.
Losing vultures has deprived farmers of their traditional way of disposing of carcasses, Cuthbert says. Dozens of the birds could clean up a dead animal in 20 minutes. “Now you’ve got a rancid cow sitting there for weeks,” he says.
Packs of wild dogs are taking over some of the clean-up, and a 2008 analysis raised concerns that the growing numbers of dogs could increase people’s exposure to rabies.
Farmers don’t use ketoprofen as widely as they used the first identified vulture killer, Cuthbert says. But he warns that ketoprofen use is growing.
A drug that produces even a relatively small number of lethal carcasses warrants attention, comments Lindsay Oaks, of Washington State University in Pullman. He’s one of the veterinarians who in 2004 first linked diclofenac to the vulture decline. Based on mathematical models of deaths of older, breeding birds from the first toxic drug, he says, “A shockingly small percentage could drive a huge decline.”
Since that first link, India, Pakistan and Nepal have banned the manufacture of diclofenac for animals in their countries. But now, Cuthbert says, farmers just buy the drug as it’s packaged for humans and use it for animals.
The new tests showing ketoprofen’s toxicity also raise worries about using the drug directly on captive birds for reducing inflammation and pain, the researchers say. The Gyps vultures died at exposures of 1.5 to 5 milligrams per kilogram of body weight, dosages within the range of veterinary use.
In North America at least, the vulture-friendly drug meloxicam has largely replaced ketoprofen for treating birds, says veterinarian Scott Ford of Bremerton, Washington, who chairs the conservation committee of the Association of Avian Veterinarians.
Vultures in the Americas are more like cousin species than close siblings to the endangered South Asian birds. One of the few species tested, North America’s turkey vulture, tolerates diclofenac residues, according to a 2008 analysis.
Even if farmers don’t need vultures to clean up rancid cows, Cuthbert puts in a plea for vulture conservation. “With their heads in a carcass, they may not be that attractive, but they’re doing their job,” he says. And they do have their own kind of beauty. “They’re mind-blowing flyers.”