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March 26, 2007
Also appeared in print April 2, 2007, p. 11


Pet Food Recall

Aminopterin, a rodent-killing compound, is found in samples of pet food made by Menu Foods

Lois R. Ember

Scientists at the New York State Food Laboratory have identified the rodent-killing compound aminopterin at levels of at least 40 ppm in samples of pet food made by Menu Foods. Menu sells the pet food throughout the U.S. under 95 brand names and has recalled 60 million cans and pouches of wet cat and dog food. To date, Menu says 15 cats and one dog that ate the recalled brands have died of kidney failure.

Aminopterin is not licensed by the U.S. Environmental Protection Agency as a rodenticide, but it is used to kill rodents in other countries. It has been used in the U.S. as a cancer drug, however.

The toxic compound is the 4-amino analog of folic acid, which it inhibits. In the late 1940s it was used as an antitumor agent. Aminopterin stops the growth of cancer cells and suppresses the immune system by inhibiting DNA replication and RNA and protein synthesis. It has now largely been superseded by a less toxic folic acid analog, methotrexate.

Methotrexate at high doses leads to the deposit of 7-hydroxymethotrexate crystals in renal tubules, eventually causing acute kidney failure. Aminopterin's toxicity is believed to be similar to methotrexate's and dose-dependent as well.

The Food & Drug Administration is investigating the animal deaths and is focusing on the wheat gluten used to thicken the gravies in the moist pet foods. By itself, wheat gluten does not cause kidney failure, but it could have been contaminated by aminopterin. Menu Foods imported the wheat gluten from China, where aminopterin is used as a rodent killer.

FDA is not yet saying that aminopterin is the only contaminant in the tainted foods and, therefore, the cause of the animal deaths. Lethargy, vomiting, diarrhea, and lack of appetite are signs of illness in stricken animals. There is no blood test for aminopterin.

Menu Foods is majority-owned by Menu Foods Income Fund of Streetsville, Ontario. Menu Foods also makes food for zoo cats, but that food is not affected by the recall.

Chemical & Engineering News
ISSN 0009-2347
Copyright © 2011 American Chemical Society