Vultures, voltaren and visceral gout

The recent solving of an ornithological mystery has raised several interesting questions of a vaguely rheumatological nature, such as whether chickens get gout, and which anti-inflammatory to give a cow should you be consulted.
A recent article in the Smithsonian recounts the investigation into the disappearance of thousands of vultures in India and the subcontinent. Vulture populations crashed in the nineties and pathologists were able to show that they died of renal failure with secondary visceral gout. Surprisingly, the usual suspects, disease and human encroachment on habitat, were not involved directly. It turns out that the vultures were being poisoned by voltaren, which they ingested while feasting on deceased, voltaren-treated cattle. After their initial investigations, biologists undertook carefully contolled studies and were able to confirm the toxicity of voltaren to these birds, the high prevalence of voltaren in cattle, and that birds feeding on such cattle can easily ingest a lethal dose. They then tested other nsaids and determined that meloxicam was safe for the birds and cattle. I believe it is now being marketed as moobicox. It's an interesting story about the first proven environmental disaster caused by a pharmaceutical product, it's rather speedy resolution and hopefully a happy ending. (For the vultures at least).

Aside from the environmental aspect, this story also raises some other interesting questions.

1) What the heck is visceral gout?
It turns out that birds, like humans, and unlike non-primate mammals do not have a uricase system of eliminating uric acid and therefore also excrete it via the kidneys. With renal failure,uric acid accumulates quickly throughout the viscera of the bird and likely contributes to their demise. Do they develop articular gout? Not often but it does happen and there are actually chicken models of gout. For a rather disturbing close- up picture of chicken feet with tophi, you can go here. Actually it's not that bad but I guess any close-up of chicken feet is a little disturbing. Do humans get visceral gout? Not that I know of, except for the renal deposits during tumor lysis and the occasional report of unusually located tophi.

2) How much NSAIDS are cows given?
I don't know about here but the study in India showed that 10% were getting the stuff. Apparently, like humans, animals work better when they are not hurting. I find it interesting that the molecule was still in large enough quantity to kill scavengers though. It makes you wonder if an allergic human would be affected if they ate the beef. Would cooking make a difference?

3) Why do voltaren and meloxicam have such different toxicity profiles for birds?
We generally treat the NSAIDs as a class, except for the newer division into cox-1 and cox-2. It is hard to explain why one would have such a dramatically different effect here, but it does remind us of the possibility of drug specific, and species specific, rather than class specific effects of anti-inflammatories.

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[Sadhan Kumar Maity]

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