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Journalism of Courage
A common painkiller used widely by both humans and in livestock may be behind the mysterious plunge in the number of vultures in South Asia, bringing three species to the brink of extinction.
A study carried out on the white-backed vulture (Gyps bengalensis) in the Panjab province of Pakistan by a team of 14 American and Pakistani scientists has identified diclofenac residues as the cause of the bird population decline.
A non-steroidal, anti-inflammatory, anti-pyretic analgesic found as an active ingredient in many commonly used medicines like Voveran, diclofenac is believed to cause renal failure and visceral gout in the birds.
The study has appeared in the latest issue of the prestigious British journal Nature.
This is the first time a pharmaceutical drug is being blamed for the large-scale collapse of a species. However, it has echoes of the controversy in America in the 1960s, when common pesticide DDT was blamed for the decline of eagles. This was poignantly captured in Rachel Carson’s famous book Silent Spring.
Diclofenac is widely used in Pakistan in livestock, and the study shows that even minute doses of the drug are toxic to the white-backed vulture. Almost two-thirds of the 20 captive vultures which were experimentally fed meat laced with diclofenac died.
The team found no other viruses in the vultures, nor any other toxic substances like heavy metals or pesticides to explain the deaths.
Lead author of the study J. Lindsay Oaks of Washington State University, Pullman, Washington, says: ‘‘This discovery is significant in that it is the first known case of a pharmaceutical causing major ecological damage over a huge geographic area.’’ He adds that the most probable source of diclofenac exposure is the consumption of treated livestock.
‘‘Finding that a drug is responsible for the collapse and threatened extinction of these species is helpful yet alarming,’’ adds Dr Rick Watson, International Programs Director of The Peregrine Fund, US, a non-profit organisation that coordinated the research effort. ‘‘Helpful, because now we can do something about it and we may have time to save these species.’’ While some are calling for a ban on the use of diclofenac, most Indian experts believe there is no need for such measures.
Vibhu Prakash, an ornithologist and chief of Vulture Care Centre in Pinjore, Haryana, says: ‘‘Diclofenac definitely kills vultures but it is not clear how the vultures get it.’’ According to him, the livestock given diclofenac rapidly excrete the drug out, and neither does it bio-accumulate to be able to kill vultures on such a large scale. He believes the scientists may be reading ‘‘more than what the evidence provides’’.
A separate study done by their group in India, he adds, found traces of diclofenac in only a fifth of the 40 vulture carcasses studied. He believes that an unknown and as yet unidentified viral disease may be killing the vultures in the subcontinent.
Nagendra Sharma, Director of National Dairy Research Institute, Karnal, also plays down the finding. According to him, diclofenac is very rarely used in animals in India.
Director General of the Indian Council of Agricultural Research (ICAR), New Delhi, Mangla Rai only says: ‘‘There is no doubt that vultures have drastically declined and a concerted national effort has to be made to ensure that the population recovers.’’
Since the 1990s, the entire South Asian region has been witnessing a decline in the population of vultures. Once a highly abundant bird, today the white-backed vulture is listed as ‘‘critically endangered’’ by Bird Life International, UK.
Bombay Natural History Society, Mumbai, was the first institution to raise an alarm over the falling vulture numbers in India. They noticed an over 97 per cent decline in vultures at the Keoladeo National Park, Rajasthan, in 1999.
