A common veterinary drug has likely exterminated almost all of Asia’s once-abundant vultures over the past few years, say the members of a prominent team of investigators.
Scientists from around the world have been scurrying to determine why Asia’s vultures are disappearing. Much of the research has been conducted by the Royal Society for the Protection of Birds (RSPB) in Britain and the Peregrine Fund in the United States, in collaboration with partners in Nepal, Pakistan and India.
The ornithologists found hundreds of vulture carcasses. Post-mortem examinations showed that most of the birds had visceral gout, caused by kidney dysfunction. Kidney failure results in an accumulation of uric acid crystals in the blood, which then precipitate out in the heart, liver and other organs.
But what was causing kidney failure in Asian vultures?
Politics thwarted much of the researchers’ work, particularly in India, where bureaucrats made it difficult to export vulture blood and tissue samples to overseas laboratories.
‘The renal failure could be caused by many factors, both infectious, such as a virus or bacteria, and non-infectious, such as a toxin or metabolic disease,” says Lindsay Oaks, the professor of virology at Washington State University responsible for the Peregrine Fund’s post-mortem analyses.
Researchers from the Zoological Society of London (ZSL) and RSPB were convinced that the disease was caused by an infection, particularly because the mortalities seemed to be confined to the Gyps genus. An adenovirus was isolated from vulture faeces by the ZSL’s Andrew Cunningham.
Sugapurath Satheesan, a knowledgeable Indian vulture biologist, insisted the deaths were caused by a variety of factors, including food shortages, human persecution, indiscriminate poisoning and pesticides.
Even vulture biologists and conservationists in Africa were concerned about the deaths: if an infectious disease was responsible for the mortalities, it would likely spread to Africa. Eurasian griffon vultures migrate to and from Africa’s northern areas. They could introduce the disease to the continent, which could then be transmitted by the over-lapping populations of other Gyps vulture species as far as the most southerly Cape vulture colony at Potberg in the Western Cape.
This would be an ecological disaster, considering the vitally important ecological role of vultures in Africa. Could the Serengeti and Kruger ecosystems even function without vultures?
Workshops have been held in Uganda, Kenya and South Africa since 2001 to start monitoring programmes, create an awareness about the problem and even prepare Africa for the possible arrival of an infectious disease. Munir Virani, a Kenyan raptor biologist, says an infectious disease would not be immediately detected if it arrived in Africa because of inadequate monitoring of breeding colonies in North and East Africa.
The Endangered Wildlife Trust’s vulture study group has been at the forefront of the African initiatives, proposing actions to combat the imminent arrival of an infectious disease in Africa — if this was the cause of the Asian vulture mortalities.
Vibhu Prakash of the Bombay Natural History Society raised the alarm when he found that the number of breeding pairs of oriental white-backed vultures in Keoladeo National Park in India had declined by 96%, from 363 in 1987/88 to 20 in 1998/99. Other surveys found similar decreases throughout India, in neighbouring Pakistan and in Nepal.
The situation for the tree-nesting slender-billed vulture was even more dire, with possibly only a few hundred pairs remaining.
The once-common oriental white-backed vulture, probably numbering well more than 100 000 birds in the late 1980s, fulfilled a valuable role in the subcontinent. For thousands of years they cleaned up carcasses and prevented the spread of diseases in a region where Hindus do not eat cattle, and where Muslims regard livestock that die of natural causes to be unfit for human consumption.
Some communities, such as Zoroastrians in India and Buddhists in Tibet, use vultures to dispose of human corpses. But these bodies have not been consumed in places like the Towers of Silence at Malabar Hill in Mumbai since the vultures disappeared. Now crows and kites fulfil their function far less efficiently. Local Parsees are urgently seeking solutions to the problem and have even suggested building a giant aviary over this important burial site.
Other scavengers have proliferated since the vultures disappeared and packs of more than 1 000 feral dogs are seen at carcass dumping sites. This may have severe consequences, such as the spread of rabies. A young boy was recently attacked and killed by a pack of dogs when he walked past one site.
Oaks surprised the ornithological world recently when he announced a startling finding at the World Working Group of Birds of Prey and Owls conference in Budapest, much to the relief of Africa’s vulture biologists and conservationists. He and his colleagues presented a paper on their diagnostic work that showed vultures were extremely susceptible to residues of the non-steroidal anti-inflammatory drug diclofenac. Tissue from 23 vultures that had died with clinical signs of gout all contained diclofenac.
In both Pakistan and India veterinarians use diclofenac to treat cattle and buffalo. A survey conducted by the Peregrine Fund and the Ornithological Society of Pakistan found the drug to be cheap and widely available.
‘There has been an exponential increase in the use of this drug in southern Asia during the past few years,” says Martin Gilbert, a Scottish veterinarian who works for the fund in Pakistan.
Diclofenac is essentially Voltaren, which is commonly used by humans to relieve pain, tenderness and inflammation caused by rheumatoid arthritis and gout. Fortunately, diclofenac is not registered for veterinary purposes in South Africa, though similar drugs such as vedaprofen, phenylbutazone, eltenac, flunixin and ramifenazone are, and might also cause kidney failure after chronic exposure. They will have to be tested to determine if they are a risk to vultures.
Veterinarians now recommend that carcasses of animals treated with any non-steroidal anti-inflammatory drugs be disposed of to prevent access by vultures.
Much work needs to be done even if diclofenac is found to be the main cause of the vulture mortalities in southern Asia. Scientists must conduct further research on its toxicity to other scavenging raptors, provide alternative veterinary products to replace diclofenac and establish a captive breeding population that can be reintroduced to the wild.
Without these urgent interventions, the extinction of these species of vulture in the Indian subcontinent within the next three to five years is not unlikely. —