Rabid dogs and garbage men stay out in the Indian sun: The Dead Vulture problem

India’s vultures are under attack. Their enemy is Diclofenac. Although always depicted as dirty and nasty, vultures and other carrion-consuming Raptors are one of the most important parts of any ecosystem. They are often said to be nature’s refuse collectors; they prevent areas being covered in carcasses or being smothered by packs of feral dogs or rats. By doing this they halt the spread of disease from the decaying animal or the abundance of mammals that would benefit from the free lunch had the vultures not got there first.

With over 99% of the Indian vulture population being poisoned since 1990, a public health disaster is brewing in the world’s second-most populous country. The cause of this catastrophic decline: a pain-killer and anti-inflammatory often prescribed to cattle that is toxic to vultures, even in tiny quantities. The decline in the vulture population has led to a literally immeasurable surge in feral dog breeding due to the surplus of carrion, not picked up by the vultures. Rapid breeding of feral dogs means more rabies, a frightening thought for a country where 20,000 (of a global 55,000) rabies deaths occurred per year before the vulture die-off began (now an estimated 40-60,000 people die from rabies each year). Although India is likely to have large rabies counts anyway (due to too high a ratio of patients to doctors and a huge degree of poverty) the lack of vultures and increase in feral dogs has exacerbated the issue. Unfortunately, it is not just Rabies that has increased in prevalence in India due to the feral dogs; canine distemper is being spread rapidly to the wildest parts of India causing a threat to the Bengal Tiger and therefore human populations particularly in settlements in and around national parks.

Diclofenac, the active ingredient of the back pain treatment Voltarol, is commonly used by farmers in India to lengthen the lives of their beloved beasts of burden and milk machines. The cause of death from Diclofenac poisoning is thought to be renal failure but may be due to inhibition of uric acid secretion (Diclofenac is known to be an Antiuricosuric) the equivalent of uremic syndrome in mammals. New-world Vultures (Vultures of the Americas) can tolerate up to 100 times more Diclofenac than the Asian Gyps vulture species (such as the White-rumped, long-billed and the Slender-billed Vultures) allowing vulture populations in the United States and Mexico to not be as troubled as those in Asia. To date Diclofenac is banned for veterinary use in Pakistan, Nepal, Iran, and India. However, (as many conservationists have discovered) the application of law to their cause may cause more harm than good as the trade continues illegally, becoming untraceable and impossible to control; in the case of Diclofenac it is sold “for human use only” but in agricultural sized containers in farmers’ markets. A general lack of awareness of the issue (and inability to afford the safer alternative Meloxicam) for most Indians means that the illegal use of Diclofenac in cattle continues.

Vultures will out compete feral dogs for carrion having the advantage of being able to detect and arrive at carcasses much faster, keeping the dog population low and stable.

So with the boom of the feral dog population from the sudden abundance of food, the individual dog populations’ territories become closer and so diseases are both more likely to be spread and spread faster. Although the spread of canine distemper is a huge concern for conservationists serving to protect Tigers, public health officials are more concerned about the increased spread of rabies. The effect of the feral dog population increase has led to over 35% of global Rabies deaths occurring in India, with other West Asian countries also having large death counts due to rabies each year. Although the rabies vaccine has a very high efficacy rate, it is often not received soon enough by bite victims.

Tigers sound like an unlikely animal to be affected be canine distemper virus (CDV) but the pathogen causes severe neurological effects that cause more and more tigers to become aggressive and predatory towards humans. Although capital punishment or simply being shot on site is the penalty for tiger hunting in India, individual tigers that attack humans are caught and destroyed as humans increasingly encroach into tiger habitat. Tigers have never been known to attack humans unprovoked before this. The increase in predation on humans has led to an increasing number of tigers being destroyed, proving to be yet another blow to an already uphill battle to save the big cats in India.

Although more and more is being done to try and protect vultures in India with better legislation and breeding programs throughout being set up, it may have been a blow too far for the slow breeding raptor. The huge genetic bottleneck this population reduction has caused may lead to a significant lack of genetic diversity that will leave the remaining population incredibly vulnerable to infectious disease. Although there is currently no good news and little hope, there is some hope. By raising awareness and better publicizing for the under-loved birds, the global community may yet be able to save these birds – and prevent what is happening in India, spreading to Africa – and be rewarded with a safer, cleaner world.

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