Researchers at the University of Guelph think they are on to something in determining the mechanism by which pets have been sickened and died by pet food:
University of Guelph researcher Perry Martos said animals likely developed crystals in their kidneys because of a reaction between cyanuric acid and melamine — a chemical used to make plastics and fertilizer, and found in the recalled pet food.
"We knew these two compounds had been implicated, but because neither seemed sufficiently toxic on its own, it was unclear how they might have been involved," Martos said in a statement.
Martos said tests on the affected animals have shown the presence of crystal-like substances in the animals' kidneys and urine samples.
Again, though, the scientist concede that neither compound by itself is toxic. The theory goes like this. The food is deliberately spiked with melamine by Chinese food exporters, a non-toxic substance, so that it tests higher for protein. The food is processed and then eaten. The melamine is then metabolized into cyanuric acid by the bacteria inside the digestive system.
So far so good. Melamine, which is non-toxic, is converted into cyanuric acid, which is also non-toxic. At least, not normally toxic as long as it is quickly expelled.
Now comes the key bit. Before the cyanuric acid is expelled or further metabolized, the animal eats again, bringing melamine in contact with cyanuric acid:
Richard Goldstein of the Cornell University College of Veterinary Medicine hypothesized that the crystallization of melamine and cyanuric acid might cause cyanuric acid to remain in the kidneys for longer periods of time than when cyanuric acid in pool water is accidentally swallowed by people, explaining its apparent increased toxicity in this case.
It would be interesting to know if the animals that got particularly sick were heavy eaters, or ate smaller portions but more often.
There are still a lot of questions, and the scientists at Guelph warn people that the findings are preliminary. Indeed, if it weren't for the atmosphere of crisis, I doubt there would have been any announcements at this early stage. But now we have a theory that fits the known facts, including the most puzzling that despite the widespread illnesses reported, the effects were far from universal, either in scope or in severity. A pure poison would have had a broader and more uniform effect, I think. But this theory incorporates a large portion of random chance,
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