By Charles Haviland BBC News, Kathmandu

Conservationists say the birds are threatened with extinction

A company has launched a veterinary drug to replace diclofenac, whose residues accumulate in dead livestock and kill vultures at an alarming rate.

Vultures are a vital part of the ecology in South Asia.

The scavenging birds' rapid and efficient consumption of animal carcasses has traditionally prevented the spread of disease.

But in the past 10 years the numbers of three local vulture species have declined by more than 90%.

Main culprit

They are now threatened with total extinction.

Two years ago, researchers working in Pakistan discovered that diclofenac, an anti-inflammatory drug used in livestock, was poisoning and killing vultures.

Now Nepal's largest veterinary pharmaceutical company has introduced a new drug containing meloxicam, which will treat livestock effectively but also be safe for scavenging birds.

A senior government official said that in due course this new drug, marketed as Melox, would completely replace diclofenac.

The government recently said it would stop the latter production and importation of diclofenac.

Nepalese bird conservation groups are hopeful the safe drug will spread, and are also involved in community-level initiatives to conserve vultures.