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Switching vet drug could save vultures

January 31, 2006 By Michael Hopkin This article courtesy of Nature News.

Alternative livestock drug should be used to avert bird extinctions, say researchers.

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Conservationists battling to save South Asia's vultures have renewed their calls for a regional ban on the widely prescribed livestock drug diclofenac, which is responsible for the fatal poisoning of millions of birds over the past decade.

Their case has been boosted by new research showing that an alternative drug, with the same pain-killing effects as diclofenac, does not harm the vultures; they argue that this should be brought in as an immediate replacement.

Veterinarians identified diclofenac as the cause of a spate of vulture deaths in India and Pakistan several years ago (see ' Vet drug blamed for vulture death'). The drug, an anti-inflammatory prescribed to an estimated five million cattle in the subcontinent every year, causes fatal kidney damage and gout in birds that feed on the cows' corpses.

Tests of another anti-inflammatory, meloxicam, show that it does not cause the same problems in the birds despite having the same action in livestock, say researchers led by Rhys Green of the University of Cambridge, UK. As they report in the journal PLoS Biology1, vultures fed the drug remained healthy, and their blood did not show the uric-acid poisoning characteristic of birds that have ingested diclofenac.

Conservationists will use the discovery as a bargaining chip at a meeting this week with Indian government officials in Delhi to address the vultures' plight. Numbers of white-backed vultures (Gyps) in India and Pakistan have plummeted by more than 95% since the widespread introduction of diclofenac in 1994.

Cheap drugs

Indian officials pledged in March last year to ban diclofenac by September 2005, but still have not done so. More than 50 companies produce it in India alone, and it is estimated that the country has millions of stockpiled doses. Both diclofenac and meloxicam are out of patent, making them cheap to produce. But diclofenac's patent was the first to run out, which explains its predominance, says Green. Changing that now is bound to be a slow and difficult process, he says.

Green now hopes that his research will spur both government and drug companies to ditch diclofenac and switch to meloxicam. "Rather than just saying 'don't prescribe diclofenac', we can now say 'prescribe meloxicam instead and that will be safe for the vultures'," he says.

Green's team tested meloxicam on a sample of 40 African vultures, which are related to the Asian species, so as not to risk harming the endangered Asian birds. They then repeated the test on a small sample of Indian vultures.

It is unclear why the two drugs, both of which quell the same pain and inflammation pathways in livestock, have such different effects on birds, says Green. One possibility is that meloxicam is flushed more quickly from the vultures' bodies, he says.

Last chance

Despite the new work, Indian officials seem unlikely to announce an immediate ban on diclofenac at the Delhi meeting, says British conservationist Chris Bowden, director of the Royal Society for the Protection of Birds' vulture programme. Bowden is currently in India, talking to experts and officials about the issue. He hopes, however, that a ban may be announced when Indian wildlife policy-makers meet again in March, on the anniversary of their original pledge.

In the meantime, Bowden's team is working to establish a network of four vulture-breeding parks in the region, each intended to house around 150 birds. So far, two have been set up: a centre in Haryana state with more than 60 vultures, and a newly established reserve in West Bengal.

Numbers of birds at the centres should swell after nestling collection season, which begins in around six weeks, says Bowden. "But the vultures are still declining at an alarming rate," he says.

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References

  1. Swan G., et al. PLoS Biol., 4 . e66 (2006).

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