ON A TRIP to India I took yoga lessons on the roof of a 19th-century shooting lodge. The monkeys watched intently, peacocks cried from the lawns, and in case my teacher overdid the exercises, vultures gathered in a tree.

In many parts of India vultures are disappearing; the Parsee towers in Bombay can no longer fulfil their traditional role of providing the last resting place for bodies before the birds carry them away.

The mystery of the vanishing vultures has now been solved, and the answer carries a human as well as avian warning. The vultures survive on dead animals. In many parts of India cattle are revered and when they become old, hobbling painfully, farmers treat them with non-steroidal anti-inflammatory drugs (NSAIDS). These are used to treat arthritic and inflammatory conditions in human beings too, and include such well-known preparations as Ponstan, Indocid (indomethacin), Naproxen and ibuprofen. Apparently Indian farmers often choose diclofenac (Voltarol) for their cattle.

These drugs can occasionally cause kidney damage in human beings. It is not common, but if large doses of NSAIDs are to be prescribed, kidney function must be borne in mind.

Unlike humans, vulture kidneys are sensitive to NSAIDs and it is thought that the shortage of the scavenging vultures is the result of them dying from kidney failure triggered by diclofenac. The diclofenac prescribed for the cattle, but not yet metabolised, is eaten by the vulture as it picks the cattle’s bones clean and the overdose of NSAIDs absorbed causes acute renal papillary necrosis. There have been reports of renal papillary necrosis and nephrotic syndrome in humans caused by diclofenac, but this is rare. In humans the greater danger is perforation of the gut or intestinal haemorrhage.