Diclofenac-related vulture death in Spain may point toward a much bigger problem
Should the end times be near, whether through global warming, loss of fish from the oceans, nuclear war, or any of myriad other calamities, vanishing vultures might be among the early harbingers of the apocalypse.
Vultures might be expected to descend on the scene to convert the dead into phosphate fertilizer and spread it over the newly cleansed earth in the form of guano.
But the arrival of “The Rapture” anticipated by many Biblical literalists may not be accompanied by the arrival of those particular raptor species.
The cause of a possible impending “Silent Spring” for vultures is not eco-disaster, nor a pesticide, nor even anything widely recognized as toxic.
Chemically related to Ibuprofen and Motrin
Rather, it is diclofenac, a medicine used to relieve lameness and stiff joints in farmed and working animals, also used by many human arthritis patients. Diclofenac is chemically related to Ibuprofen and Motrin, though different enough to be more strictly regulated.
In most of the world, diclofenac has until very recently been regarded as harmless.
But that belief “has now been shown to be wrong,” Royal Society for the Protection of Birds scientist John Mallord recently alerted Robin McKie of The Guardian.
“A young cinereous vulture in the Boumort National Hunting Reserve in [Catalonia] Spain has been confirmed to have died of diclofenac poisoning,” Mallord explained.
“This is a hugely worrying development. You can have several vultures feeding on a single cattle carcass,” Mallord explained, “and if it is contaminated with the drug, you will kill them all just from a single feeding. This has probably been happening for some time,” Mallord said, “with many other vultures having died.”
Global scope & consequences
In short, what ecologists and regulators had mostly appeared to regard as strictly a regional environmental issue, and an issue largely resolved, might actually be of global scope and consequences.
This issue also might not be as easily dealt with as vulture observers––a rare subspecies of birdwatcher––had hoped.
That diclofenac kills vultures is not, in itself, recent news. What is news is that diclofenac is now known to be killing vultures in places thousands of miles from where it was previously known to be a problem. This suggests that much more diclofenac may be at large in vulture habitat than has been suspected.
Vultures are known to be in steep decline worldwide, but not from ambient exposure to diclofenac, especially not in the developed world. A 42% loss of vultures from West Africa since 1990 has been blamed on deliberate poisoning, by poachers.
Up to 99.9% of some vulture species disappeared
Indeed, there is considerable evidence that poachers have a role in the loss of vultures. But poachers as well as users of working animals may be exposing vultures to diclofenac––and, unlike farmers and carriage drivers, may be doing it deliberately.
Washington State University microbiologist J. Lindsay Oaks, consulting for the Peregrine Fund, an international raptor conservation group, in January 2003 discovered the unusual sensitivity of vultures to diclofenac while investigating a catastrophic loss of vultures from the Asian subcontinent.
Up to 99.9% of some vulture species had abruptly disappeared.
Pakistan, Nepal, & Bangladesh ban diclofenac
Farmers and others who worked with oxen, buffalos, horses, mules, and donkeys turned out to be heavy users of diclofenac to keep the animals on the job pulling carts and plows.
When eventually the animals died, their remains were left for the vultures. This was (and is) an intended kindness, in a part of the world in which Parsis, or followers of the Zoroastrian religion, have historically had their own remains left for vultures in structures called Towers of Silence.
Street dog proliferation was widely attributed to dogs taking over the former scavenging role of vultures, though the major cause was (and remains) simply that Asian subcontinental nations are now raising, slaughtering, and discarding the offal from substantially more sheep, goats, cattle, and poultry than ever before, in a region whose people have historically consumed less meat than people anywhere else.
By Oaks’ death, on January 15, 2011, at age 51, the Asian subcontinental nations of India, Pakistan, Nepal, and Bangladesh had all banned diclofenac.
A decade ago, long-billed, slender-billed, and oriental white-rumped vulture populations all appeared to be recovering.
But that was before the aging human population of the industrialized developed world became a whole new and fast-growing market for diclofenac, to ease some of the most painful, persistent, and ubiquitous consequences of growing older.
Wrote McKie, “Diclofenac was approved in Spain and other European nations because farmers, drug companies, and regulators argued that cattle carcasses were disposed of differently in Europe than in India. This meant vultures would not be able to eat meat tainted with diclofenac.”
Overlooked, apparently, was that the remains of animals treated with diclofenac may be far from the only source of environmental exposure to diclofenac, not only for vultures but also for other animal species whose susceptibility has yet to be discovered.
Medical demand growing at 4% per year
Currently, global medical demand for diclofenac is growing at almost 4% per year, and is expected to reach $5.64 billion by 2025, according to the market research firm IndustryArc.
The underlying problem––as with DDT, the focus of Rachel Carson’s 1962 best-selling book Silent Spring, widely credited with launching the late 20th century environmental movement––may be food chain accumulation of residues.
Food chain accumulation of toxins in top predators, little understood then, is today recognized as the reason why tuna and other large fish who eat lots of little fish gradually acquire enough mercury to make their flesh hazardous to human consumers, to cite just one more of many now well-known examples.
Food chain accumulation has also been observed to occur with residues from other pharmaceuticals, particularly anti-depressant drugs.
State University of New York at Buffalo chemistry professor Diana Aga and colleagues in 2017 reported finding anti-depressant residues in all ten Great Lakes species they sampled in the Niagara River, which links Lake Erie and Lake Ontario via Niagara Falls.
“The continuous release of pharmaceuticals and personal care products into freshwater systems impacts the health of aquatic organisms,” Aga et al concluded, attributing the problem to the current inability of sewage treatment plants to intercept the estimated 70% of pharmaceuticals that humans discharge through urine.
A 2014 study by University of Wisconsin at Milwaukee researcher Rebecca Klaper and associates, published in the journal Aquatic Toxicology, warned that even very small amounts of the anti-depressant fluoxetine, marketed as Prozac, may significantly depress mating behavior in male fish.
The antidepressants Celexa, Paxil, Zoloft, Effexor and Wellbutrin, and the antihistamine diphenhydramine also turned up in Great Lakes fish.
Food chain accumulation of diclofenac
As of the moment, almost nothing is known about possible food chain accumulation of diclofenac––or any other commonly used arthritis treatment or pain reliever.
“The evidence found in Spain sadly confirms what we have been warning about for almost a decade,” BirdLife International head of conservation Iván Ramírez told McKie of The Guardian.
“Vultures are dying from veterinary diclofenac poisoning,” Ramirez said, “and this could already be affecting population trends. It is absurd to keep insisting on licensing a drug that kills threatened species when there are plenty of other safe and cheap alternatives in Europe.”
But non-veterinary use of diclofenac could also be the problem. Any animal exposed to the residues who becomes part of the vulture menu could be a source of lethal accumulation.
Merely banning diclofenac, moreover, may not prevent vulture deaths if lethal accumulation is occurring from the whole range of drugs of similar composition and characteristics, some of which––like Ibuprofen and Motrin––have already long been among the most widely used and most useful pharmaceuticals in the human pharmacopeia.
To recite a cliché notoriously often concluding scientific papers, especially on problematic and controversial topics, much more research is needed.