Second vulture-safe drug offers hope to South Asia’s scavengers

Scientists have confirmed that tolfenamic acid is not harmful to vultures, offering a second alternative to diclofenac and other veterinary drugs which continue to threaten South Asia’s last surviving populations
<p>Critically endangered white-rumped vultures in India. The use of veterinary drugs that are toxic to these birds has led to a collapse in populations across South Asia in the past 30 years. (Image: Ronald Messemaker / Alamy) </p>

Critically endangered white-rumped vultures in India. The use of veterinary drugs that are toxic to these birds has led to a collapse in populations across South Asia in the past 30 years. (Image: Ronald Messemaker / Alamy)

A second vulture-safe alternative to the veterinary drug diclofenac could help South Asia’s great avian scavengers.

Scientists have been working to identify vulture-safe alternatives to the non-steroidal anti-inflammatory drug (NSAID) diclofenac ever since the discovery in 2003 that the drug was the principal cause of a catastrophic collapse in vulture populations across South Asia. The birds ingest the drug, which is used to treat pain and inflammation in livestock and humans, when scavenging the carcasses of animals treated with it.

Four species of South Asian vulture ­– white-rumped (or white-backed), slender-billed, Indian and red-headed – are now listed as Critically Endangered by the International Union for Conservation of Nature (IUCN) after their numbers crashed in the 1990s. Estimated to number 40 million in 1991-92, the population of white-rumped vulture in India fell by 99.9% between 1992 and 2007, the fastest population crash ever recorded for any bird species.


of India’s white-rumped vultures disappeared between 1992 and 2007

Following this discovery, in 2006 diclofenac was banned for use in livestock in India, Pakistan and Nepal, and in 2010 in Bangladesh. However, enforcement of the ban has been a persistent problem. In addition, other NSAIDs still legally in use have been shown to be similarly deadly to vultures.

The first vulture-safe alternative to diclofenac, meloxicam, was identified in 2006.

The finding that the NSAID tolfenamic acid is also safe for vultures is the result of a systematic safety testing study led by the Indian Veterinary Research Institute (IVRI), with the Bombay Natural History Society (BNHS) and the Royal Society for the Protection of Birds (RSPB). Details of the study were published in a preprint paper in August 2021.

How will a second vulture-safe drug make a difference?

It is “hugely significant” that tolfenamic acid has been confirmed as vulture-safe, said Saving Asia’s Vultures from Extinction (SAVE), a consortium of 24 organisations working on vulture conservation, in a report on its website. 

Chris Bowden, SAVE’s programme manager and co-chair of the IUCN Vulture Specialist Group, explained to The Third Pole: “Vets often complain that they like to choose between drugs for different situations. Each NSAID has slightly differing properties.”

Hem Baral, a prominent ornithologist from Nepal who has been researching Asia’s vulture crisis for more than two decades, said that the increase in choice of vulture-safe drugs in South Asia offers “a great hope” for more effective vulture conservation.

“Previously, meloxicam has done an excellent job in saving vultures by replacing diclofenac and other harmful NSAIDs,” Baral told The Third Pole. But, he added, meloxicam never became the drug of choice among veterinarians in the same way diclofenac was. “This could be a combination of supply chains, effectivity and results, combined with awareness and price,” he said.

As diclofenac is legally being used for human consumption, it is getting misused. If little gaps are left in rules, people find it easy to exploit them
MK Ranjitsinh, conservationist

Meloxicam accounted for only 32% of NSAIDs offered for sale in pharmacies surveyed in India in 2017. Bowden said: “Vets were familiar with diclofenac and liked it, so any switch is a challenge. Some say meloxicam works more slowly – although it lasts longer, and has fewer side-effects. Tolfenamic acid does have better antipyretic (fever reducing) properties than meloxicam, so in this is more similar to diclofenac.” He added that the price of tolfenamic acid “should be competitive” with meloxicam and diclofenac, especially if production ramps up, and that it is also available in large vials – no longer the case for diclofenac – further helping the price comparison.

A key question in the take-up of tolfenamic acid by vets and farmers will be awareness and marketing. “We rely on vets and others (including the press) to help this process,” said Bowden. “It needs a big push. Vets are planning webinars, but it needs much more.”

Drug ban and loopholes

Both Bowden and Baral identified weaknesses in the ban on diclofenac as a major problem for vulture conservation efforts. Diclofenac is still legal for use in humans. Its illicit use for veterinary purposes continues, and it is also being produced illegally.

Following reports of companies selling large bottles of diclofenac meant for cattle, but with labels changed to state they were for human use, the Indian government banned the sale of diclofenac in large vials in 2015.

“The vial size restriction was a major loophole, but this has been addressed. The human drug is the same thing, and is available (in small vials only), but this is hard to stop or control. Stricter enforcement and punishment with prosecutions is needed to set an example,” said Bowden. 

MK Ranjitsinh, a leading Indian conservationist, said that gaps in implementing the ban on diclofenac for animal consumption are still being exploited. “As diclofenac is legally being used for human consumption, it is getting misused. If little gaps are left in rules, people find it easy to exploit them,” Ranjitsinh told The Third Pole

Another issue is the legal use of other drugs that are toxic to vultures for veterinary purposes. Bowden said that safety testing by the Indian Veterinary Research Institute is too slow. “This is a serious problem… Aceclofenac [another NSAID] metabolises into diclofenac and yet is legally in use. No ban has been forthcoming despite requests for more than five years. This is a serious loophole and very disappointing.”

Other NSAIDs that are deadly to vultures, including nimesulide and ketoprofen, “are our immediate priorities as all are legally in use [for veterinary purposes]”, said Bowden. Bangladesh banned the production, sale and use of ketoprofen earlier this year, but India is yet to do so.

Regional cooperation key to vulture recovery

The decline in vulture numbers has slowed down in recent years, but the process of recovery is slow and still full of threats, said Baral.

“South Asian countries that harbour vulture populations can learn from one another to improve knowledge for vulture conservation,” Baral said, adding that capacity building, knowledge exchange and transboundary cooperation will be key to success. “As we know, vultures know no political boundaries.”

Losing vultures entirely could have immense environmental, cultural and public health implications for South Asia. When a vulture population declines, other scavengers (such as rats or dogs) can move in. The disappearance of vultures across India in the 1990s coincided with an increase in feral dog numbers, which in turn has been pointed to as driver of a rabies outbreak. The increase in dog numbers alone has been calculated to have resulted in the deaths of almost 50,000 people between 1992 and 2006.

Culturally, the loss of vultures has had huge impacts. Without vultures to consume corpses, many Parsis have had to amend traditional ‘sky burials’.

The Indian government’s Action Plan for Vulture Conservation in India 2020-2025 lays out an ambitious conservation strategy to establish new captive breeding centres and vulture ‘hubs’ in each state. But Bowden notes that stopping all veterinary use of diclofenac and other toxic drugs will be crucial to make the environment sufficiently safe for released vultures to survive.

“India was the first to declare a veterinary diclofenac ban in 2006, and other countries followed. This was hugely significant and probably saved these species from total extinction,” said Bowden. Nepal, Bowden said, has been the most successful so far and has reversed the vulture population decline by effectively eradicating diclofenac. “Releases are going ahead there and going well. All of this is far more successful than India so far.”

“We know what to do. But we risk losing vultures because things are not happening soon enough,” said Bowden.