Mass Die-off of Vultures Solved

[Guest guest]

"In the past 10 years, population losses of more than 95% have been reported in

three raptor species across many areas of the Indian sub-continent."

 

The World's No.1 Science & Technology News Service

Mysterious mass die-off of vultures solved

18:00 28 January 04

 

Vet drug 'killing Asian vultures'

NewScientist.com news service

 

The catastrophic decline of griffon vultures in south Asia is being

caused not by a mysterious disease, as had been thought, but a

common painkiller given to sick cattle.

 

If the treated animal dies and is eaten by vultures, a single meal

can be enough to kill the bird. The scientists who made the

discovery now want the drug banned from veterinary use and are

holding a meeting next week with officials from Nepal, India and

Pakistan.

 

Griffon vultures are huge scavengers and used to be ubiquitous in

south Asia. But their population has declined drastically since the

mid-1990s, and one species is near extinction.

 

As a result, animal carcasses rot outside villages, attracting

rabies-ridden packs of dogs. The Parsee religious community in India

is also in crisis, as it disposes of its dead by feeding them to

vultures.

 

 

Acid crystals

 

 

Lindsay Oaks, a veterinary microbiologist at Washington State

University in Pullman, and colleagues looked for pathogens or toxins

in freshly dead vultures from breeding colonies in Pakistan and

Nepal by sending tissues back to US laboratories for analysis.

 

Efforts by Andrew Cunningham of the Zoological Society of London,

UK, and colleagues to establish the cause of the vultures' decline

in India were hindered by that county's laws banning the export of

genetic material.

 

Vultures that have died in the decline have kidney damage and uric

acid crystals throughout their bodies, but Oaks's group could find

no disease germs or environmental toxins. Vultures that died

following pesticide poisoning or collisions had no uric acid.

 

"We started wondering if they could be exposed to any veterinary

drugs in the dead livestock they eat," says Oaks. They discovered

that diclofenac, which can cause kidney damage, is very heavily

prescribed by local vets, and its use increased over the same time

period as the vulture decline. The cheap drug is used to treat

lameness and injury - common conditions before a buffalo or cow dies.

 

 

Tiny dose

 

 

Analysis of the kidneys of dead vultures with uric acid symptoms

revealed diclofenac residues, while no residues were found in other

birds.

 

 

The researchers also gave diclofenac, and meat from animals treated

with diclofenac, to 20 non-releasable vultures rescued from nesting

colonies. "We hated to do it," says Oaks. The diclofenac killed

these vultures in very small doses, with the same symptoms as the

dead, wild vultures. Furthermore, the higher the dose of the drug,

the more likely the vultures were to die.

 

Vultures come from miles around to feed on a carcass, so each gets a

small bit of many animals. Rhys Green of the UK's Royal Society of

the Protection for Birds calculates that only one in 250 dead cattle

needs to have been recently treated with diclofenac to cause a

decline in vultures of 30 per cent per year - about what has been

observed.

 

Cunningham is now trying to find out whether diclofenac is also

responsible for the decline in India. "This may be a breakthrough",

he told New Scientist. "We hope so, as this would greatly improve

the chances for an eventual recovery of the species."

 

Journal reference: Nature (DOI: 10.1038/nature02317)

 

Vet drug 'killing Asian vultures'

 

http://news.bbc.co.uk/2/hi/science/nature/3437583.stm

G. bengalensis is now critically endangered (Photo: rspb-images.com)

Scientists believe they have identified the main cause behind the catastrophic

decline seen in Asian vulture numbers.

In the past 10 years, population losses of more than 95% have been reported in

three raptor species across many areas of the Indian sub-continent.

 

Lindsay Oaks' research team has now shown the birds are dying after eating the

carcasses of livestock treated with the common veterinary drug diclofenac.

 

Dr Oaks, backed by The Peregrine Fund, reports his work in Nature magazine.

 

"This discovery is significant in that it is the first known case of a

pharmaceutical causing major ecological damage over a huge geographic area and

threatening three species with extinction," the US researcher from Washington

State University said.

 

The three species are the Oriental white-backed vulture (Gyps bengalensis), the

long-billed vulture (Gyps indicus) and the slender-billed vulture (Gyps

tenuirostris).

 

All three are now classed as critically endangered.

 

Experimental work

 

The birds succumb to kidney failure and visceral gout. Early signs that the

raptors are affected can be seen from the way they hang their heads down to

their feet for long periods.

 

Such has been the alarming decline in bird numbers that international

organisations have pumped hundreds of thousands of pounds into research to track

down the cause of all the deaths.

 

Now, Dr Oaks and colleagues have found high residues diclofenac in dead vultures

in the field.

 

They have also been able produce similar patterns of disease in experimental

vulture colonies fed the drug either directly or via carcasses of buffalo or

goat that had been treated with diclofenac.

 

Other possible causes of death, such as poisoning by mercury or arsenic or

infection by viruses, have been investigated and ruled out.

 

Diclofenac is a non-steroidal anti-inflammatory drug that has been in human use

for pain and inflammation for decades. The veterinary use of diclofenac on

livestock in South Asia has grown in the past decade.

 

Pivotal role

 

The Nature report has led ornithological and other conservation groups to call

for the immediate withdrawal of diclofenac from use.

 

"Vultures have an important ecological role in the Asian environment, where they

have been relied upon for millennia to clean up and remove dead livestock and

even human corpses," said Dr Munir Virani, a biologist for US-based Peregrine

Fund, and who coordinated the massive field investigations across Nepal, India,

and Pakistan.

 

"Their loss has important economic, cultural, and human health consequences."

 

One immediate impact has been the explosion in feral dog populations which have

moved into areas no longer scavenged by vultures.

 

Britain has invested significant research time and money on the vulture problem

through its Darwin Initiative for the Survival of Species.

 

Dr Debbie Pain, a research scientist at the Royal Society for the Protection of

Birds, said: "In the 1980s, [Gyps bengalensis] was thought to be the most

abundant large bird of prey in the world, but in little over a decade, the

population has crashed by more than 99%, with the loss of tens of millions of

birds.

 

"The decline of Asian vultures is one of the steepest declines experienced by

any bird species, and is certainly faster than that suffered by the dodo before

its extinction. If nothing is done these vulture species will become extinct."