The ban on a veterinary drug which caused an unprecedented decline in Asian vulture populations has shown the first signs of progress, according to scientists. However, the recovery of the wild vulture populations requires efforts to see the drug completely removed from the birds' food supply.
In a new study, published today (11 May 2011) in science journal, PLoS ONE, researchers report measurements of the prevalence and concentration of diclofenac in carcasses of domesticated cattle in India, made before and after the implementation of a ban on its veterinary use.
The governments of India, Nepal and Pakistan banned veterinary use of the painkiller, diclofenac, in 2006 because of its lethal effects on vultures that feed on the carcasses of cattle and buffaloes that had been treated with the drug shortly before they died.
The study shows that the proportion of cattle carcasses in India contaminated with the drug declined by over 40% between 2006 and 2008. The concentration of the drug in contaminated animals also fell.
Combining the effects of these two changes, the expected rate of annual population decline of the vultures is expected to slow by approximately 60%. However, the resulting decline rate is still expected to be around 18% per year for the most susceptible species, the oriental white-backed vulture, down from about 40% per year before the ban, meaning that vultures will not recover unless efforts to eradicate the drug becomes still more successful.
Although the legal action has started to show encouraging results, much remains to be done, because diclofenac manufactured for human use is still being used illegally to treat cattle in India.
One of the study's authors, Dr Devendra Swarup, former Research Director of the Indian Veterinary Research Institute, commented: "Because of the difficulty in ensuring that human diclofenac is not being used illegally and in secret, testing the vulture food (cattle carcasses) directly is the only way to find out how safe the vultures really are."
Lead author, Dr Richard Cutbert of RSPB, said: "This shows how much progress has been made, but there is still a job to do to make sure that safe alternative drugs are used. Unfortunately some of the alternatives have not been tested for their safety to vultures and one drug in increasing use, ketoprofen, is already known to be toxic to vultures".
In fact, the only safe alternative used in Indiaknown so far is meloxicam, which is becoming more widely used now that its cost is falling and approaching that of diclofenac. However, other drugs known to be toxic or with unknown effects remain legal and are still being used by vets.
Dr Asad Rahmani, Director of the Bombay Natural History Society said: "Complete removal of diclofenac from vulture food is the single most important action needed to save vultures. Human formulations are still being sold by some irresponsible companies in large veterinary-sized vials (30ml) and these bigger bottles must also be outlawed to make illegal diclofenac use on cattle more difficult and expensive."
Citation: Cuthbert R, Taggart MA, Prakash V, Saini M, Swarup D, et al. (2011) Effectiveness of Action in India to Reduce Exposure of Gyps Vultures to the Toxic Veterinary Drug Diclofenac. PLoS ONE 6(5): e19069. doi:10.1371/journal.pone.0019069
Funding: This project was funded by the Darwin Initiative of the United Kingdom government http://darwin.
Competing Interests: The authors have declared that no competing interests exist.
Notes to editors:
- A study published in 2007, led by Dr Vibhu Prakash from the BNHS, showed that the population of oriental white-backed vultures in India had dropped by an average of more than 40 per cent every year between 2000 and 2007. This species' numbers have dropped by 99.9 per cent since 1992 to about 11,000 from tens of millions. Populations of long-billed and slender-billed vultures together, have fallen by almost 97 per cent over the same period. Long-billed vultures are now thought to number about 45,000 and slender-billed vultures just 1,000. The research was published in the Journal of the Bombay Natural History Society and is here http://www.
rspb. org. uk/ Images/ IndianVultureDeclines_tcm9-188415.
- The International Union for the Conservation of Nature (IUCN) classifies all three species as critically endangered, the highest risk category short of extinct in the wild.
- Previous studies in 2004 - 2007 found that diclofenac was the main, if not the only, cause of vulture declines. The birds die of kidney failure after eating the carcasses of animals that have died within a few days of being treated with diclofenac to ease pain and swelling. Details of these studies can be found at http://www.
- Carcass dumps used to attract thousands of vultures, which could clean a carcass within minutes. Now, packs of up to 200 feral dogs roam these sites, substantially increasing the risk of attack, and diseases like rabies.
- A meeting of the Indian National Board for Wildlife in 2005, chaired by the Prime Minister of India, prompted the withdrawal of licences for the manufacture of veterinary diclofenac.
- The Oriental white-backed (or white-rumped) vulture Gyps bengalensis is up to 85cm long, with a wing span of between 205 and 220cm. Adults are black with a white head and neck and short bill. The bird is sociable and used to breed in very large colonies. Now, they nest in trees in small colonies.
- The Indian long-billed vulture, Gyps indicus, is robust in appearance, more than 90cm long with buff back, white neck and yellowish bill. It is found near cultivated areas, often with white-backed vultures. It now nests in small colonies on steep cliffs and ruins. In the early 1990s, there were colonies of up to 1,000 birds.
- The slender-billed vulture, Gyps tenuirostris, is between 80 and 95cm long, a thinner vulture, mostly brown and scruffy looking. It nests in large trees and is the rarest of the three Asian vulture species.
- The Parsi community is having to find other means of body disposal. In the past, they placed the bodies of their dead on Towers of Silence for vultures to consume.
- In Nepal, efforts are underway to protect wild populations by combining encouragement to observe the diclofenac ban with the provision of safe food. Nepalese authorities halted the domestic manufacture and import of diclofenac in August 2006.
- Three captive breeding centres have been built so far in India, where 250 vultures are housed in total and successful breeding of all three species has now occurred. They are in Haryana, West Bengal and in Assam. Two additional centres are operational in Nepal and Pakistan, and five Indian zoos are also developing captive breeding facilities with support of the Central Zoo Authority.
- The UK Government's Darwin Initiative has helped to fund research and is contributing funds to the captive breeding programme. More details here http://darwin.
defra. gov. uk
- The captive breeding programme in India is run by Bombay Natural History Society and funded by the RSPB, Critical Ecosystem Partnership Fund, Rufford Foundation and the Darwin Initiative, with technical support from the International Centre for Birds of Prey (UK), the Zoological Society of London, the RSPB and the Indian Central Zoo Authority, State Governments of Haryana, West Bengal and Assam. There are additional smaller vulture breeding facilities in Nepal and Pakistan.