The contamination of pet foods with chemically tainted grain from China sickened and killed thousands of dogs and cats across the United States last year. As it turns out, that was not the first incident of widespread pet food contamination leading to mass pet deaths from kidney failure.

The blog Pet Connection recently reported that pet food contaminated with industrial chemicals sickened more than 6,000 dogs and a smaller number of cats across Asia in 2004. The report was based on a paper by Georgia scientists that was published last fall in the Journal of Veterinary Diagnostic Investigation. The Asian poisonings were initially blamed on mold contamination.

After reportedly learning about the Asian incident from a Korean graduate student, Cathy Brown, a renal pathologist at Georgia's Athens Veterinary Diagnostic Laboratory, and colleagues tracked down tissue samples from affected pets that had been stored at a South Korean university. They discovered the same type of insoluble crystals observed in U.S. pets during the 2007 outbreak.

The tainted ingredients in the Asian incident came from a Mars plant in Thailand that manufactured Pedigree dog foods and Whiskas cat food. The culprit in the U.S. poisonings was Chinese grain that had been adulterated with the industrial chemicals melamine and cyanuric acid to make it appear higher in protein. The same contaminants were also found in feed for hogs, chicken and fish that had entered the U.S. food supply.

Mars researchers had linked the incidents even earlier -- in March 2007 -- after scientists figured out that melamine was involved in the U.S. contamination. Mars shared the information with the U.S. Food and Drug Administration, but major veterinary groups including the American Veterinary Medical Association say no one informed them of the link.

The Georgia researchers' findings have worrisome long-term implications for both pets and people:

...[S]ublethal MARF [melamine-associated renal failure] could represent an important, previously unrecognized cause of chronic kidney disease in dogs and cats. Interestingly, the contaminated wheat gluten in the 2007 outbreak was a human food-grade product. The potential effects of ingestion of similarly contaminated material by people are unknown.