Six years after diclofenac ban, vultures struggle for survival….Ananda Banerjee
A two-day symposium on Developing a Regional Response to the Conservation of South Asias Critically Endangered Vulture Species begins today in New Delhi in the backdrop of data that suggests a significant drop in the mortality rate of the big birds, but experts point to more pressing challenges.
The story of conservation efforts aimed at South Asias vultures began with a chance discovery in 2004, when the late American microbiologist J. Lindsay Oaks, who was trying to fathom how hundreds of thousands of vultures were dropping dead all over South-East Asia, accidentally found the catastrophe was actually caused by diclofenac, a veterinary drug that was widely used to treat cattle. Vultures were exposed to diclofenac when they fed on the carcasses of livestock that were put to sleep with the drug. Diclofenac caused renal failure in the vultures and the birds died within days of exposure, with signs of extensive visceral gout. According to experts, just 0.10.8% of carcasses with lethal levels of the drug was enough to wipe out the entire vulture population.
The decline started in the 1990s, when all the three vulture species (oriental white-backed, slender-billed and Indian vultures) appeared to be headed straight for extinction. It was also in 1990 that diclofenac went into mass production after its patent expired. The painkiller, considered a wonder drug for cattle but deadly for vultures, was banned in the subcontinent in 2006. The ban, at that time, seemed to have revived the fortunes of vultures.
Six years since the deadly drug was banned in veterinary usage, however, the population slide continues unabated, bringing the number of vultures down from millions to a few hundred. Today, scientists put the population collapse at 95% and according to the Bombay Natural History Society (BNHS), India currently has 3% of the birds it once did.
The reasons for the unabated decline are many. Even though diclofenac was banned in 2006, the ban took much longer to be implemented. Also, the drug had many cheaper variants that were widely used. The only safe alternative to diclofenac, meloxicam, had just a single manufacturer at that time with limited distribution in the market. Meloxicam had few takers because of slow effectiveness and high costs. Much of that has changed, but an expert points to a disturbing trend.
Human formulations of diclofenac are now being used extensively for animal healthcare in vulture stronghold states like Gujurat, Madhya Pradesh and Rajasthan, said Nita Shah, a scientist with BNHS.
According to Shah, the ban of diclofenac has further complicated the situation as many new drugs, including some that are possibly toxic to vultures, have taken its place. Veterinary drugs such as ketoprofen, which has recently been established as toxic for vultures, and aceclofenac were also in use across the three states. Drugs like nimesulide, phenyl butazone and piroxicam also remain suspects till their toxicity is tested.
There is an urgent need to sensitize chemists and drug associations, pharmacists, veterinary councils and farmers to formulate a way to reduce the spillover of human diclofenac into animal care, she added.
According to a research by conservation scientist Rhys Green from Cambridge University, the ban on diclofenac has worked partially. The level of diclofenac contamination in carcasses has dropped to 5.6 % in 2008 from 10.1% in 2004, which has led to the drop in the annual death rates of vulturesfrom an alarming 80% to 18%. But experts suggest that there is not much hope for the species till the mortality rate comes down to 5%.
The relationship between vultures and people is a unique one. Vultures play an important ecological role in the environment as primary carrion feeders and disposers. They have been relied upon for millennia to scavenge, clean up and remove dead livestock, wild animal carcasses and even human corpses. The loss is felt immensely by the Parsi community, which leaves its dead atop the so-called towers of silence to be consumed by vultures. Vultures have acidic stomachs that are lethal to bacteria, and flocks can strip a body in minutes. Today, the Parsis may have turned to other methods, including solar accelerators to hasten the decomposition of the dead, but none has proved as efficient or as hygienic as vultures.
The vultures virtual absence has also led to a growing population of other scavengers including feral dogs, which spread diseases like rabies. It has necessitated expensive alternative methods of carcass disposal so as to reduce public health risks.
To restore vulture numbers, active conservation breeding programmes are under way in Pinjore (Haryana), Buxa (West Bengal) and Rani (Assam) in collaboration with BNHS and the state governments. But the breeding and release programme is linked to the creation of effective vulture-safe zones free from any diclofenac, and this seems unlikely till a complete ban on all formulations of diclofenac is imposed. Experts say it may not be possible to restore the robust numbers. The species is a slow breeder and pairs can rear only a single chick a year. The revival of large colonies seems unlikely, they say.