Health

A CONSERVATION catastrophe has become a human tragedy. The mass poisoning that has killed millions of India's vultures may have indirectly claimed the lives of almost 50,000 people, according to an analysis of the wider impacts of the bird die-off.

Since the 1990s, numbers of long-billed, slender-billed and oriental white-backed vultures have declined at an unprecedented rate. All three species could be driven toward extinction within a decade. The cause is a veterinary drug called diclofenac, which was routinely given to cattle. When the cattle died, vultures that fed on their carcasses were poisoned by the drug. Although now banned in India, diclofenac is stlll used to some extent.

It seems the drug has also had an unforeseen knock-on impact. As vulture numbers crashed, the population of feral dogs across India surged, feasting upon cattle carcasses that would otherwise have been stripped bare by birds. Many of these dogs carry rabies, and now scientists in the UK and India, led by Anil Markandya of the University of Bath, UK, have put a figure on how many people have died from rabies after being bitten by such dogs.

They calculate that the decline of vultures made way for at least 5.5 million extra feral dogs in India between 1992 and 2006. During this period, these extra dogs would have been responsible for at least 38.5 million bites. National surveys show that in India 123 people die of rabies per 100,000 dog bites, suggesting that a minimum of 47,300 people have died as a result of the vulture die-off (Ecological Economics, DOI: 10.1016/j.ecolecon.2008.04.020). Taking account of the cost of treating bite victims and dealing with the extra deaths, the researchers calculate that the use of diclofenac has indirectly cost India $34 billion.

Despite the scale of the disaster, "it is unfair to blame anyone, as the impacts of diclofenac were unforeseen", says Markandya. "The lesson is to check the consequences of drugs before using them for animals that are part of an ecological system such as this."

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