Cracking the case of the pet food killer

From ANIMAL PEOPLE, May 2007:

PORTLAND, Oregon–As many as 39,000 American dogs and cats
may have been injured or killed by pet foods contaminated by
melamine, a chemical formerly considered safe, during the three
months or longer that the tainted food was in distribution.
Banfield Pet Hospitals, operating 615 veterinary clinics
around the U.S., produced this preliminary estimate from information
on client visits, from December 2006 through mid-March 2007. During
that time the Banfield hospitals handled more than one million animal
visits, and saw a 30% increase in cases of cats suffering from
kidney failure.
The data suggests that three out of every 10,000 cats and
dogs who ate the contaminated pet food developed kidney failure,
Banfield told Associated Press.
Receiving consumer complaints about pet foods allegedly
poisoning healthy dogs and cats, Menu Foods Inc. ordered test
feedings. After 16 cats and dogs died from kidney failure during the
laboratory test feeding, Menu Foods on March 16, 2007 recalled 60
million cans of dog and cat food. A Canadian firm with U.S. plants
in Emporia, Kansas, and New Jersey, Menu Foods supplied products
to at least seven different companies, who sold Menu-made pet food
under more than 100 brands.

Other pet food makers were soon implicated in a nationwide
investigation and series of recalls that swiftly went international.
Pet food contaminated with the same chemical was discovered in South
Africa and Puerto Rico–and the source turned out to be China.
Receiving more than 15,000 calls about pet food believed to
be contaminated during the first 30 days after the initial recall,
the U.S. Food & Drug Administration assigned 400 employees to find
the suspect shipments, respond to callers, and test 430 samples of
potentially contaminated wet and dry food, FDA director of field
investigations Michael Rogers told media. More than twice as many
people called the FDA about the pet food recall, spokespersons said,
than normally call in a year about all issues combined.
The 30,000-member Veterinary Information Network reported
receiving unsolicited reports of more than 500 pet illnesses and 104
While Menu Foods became convinced by the test results that it
had sold tainted product, identifying the contaminant perplexed
toxicologists for weeks.
The New York State Food Labor-atory on March 23 identified
traces of a chemical called aminopterin as the likely culprit, and
began trying to identify which specific component of the recalled pet
food had become contaminated.
But American SPCA senior vice president Steven Hansen, DVM,
was skeptical. Hansen, a veterinary toxicologist, manages the
ASPCA’s Midwest office, including the Animal Poison Control Center.
“Aminopterin,” now used in some nations as a rat poison,
“has been used to treat cancer in people, since it is able to
disrupt rapidly-growing cells,” Hansen explained. “In animals, it
should result in effects that mimic this function, including bloody
diarrhea, bone marrow suppression, abortion, and birth defects.
Renal damage-seen in the affected animals-can occur at high doses.
“However,” Hansen said, “to be consistent with the effects
of aminopterin, we should also see a significant number of affected
pets showing the accompanying signs of severe intestinal damage.
“We have seen reports coming in from all around the country
that animals who ate the contaminated foods are suffering from renal
failure,” Hansen acknowledge. “But the data we’ve been collecting
does not conclusively prove this connection.”
Hansen’s skepticism was affirmed on March 29, when the FDA
and Menu Foods announced that they had discovered another chemical
called melamine in the contaminated food, and that it appeared to be
turning up consistently. Initially detected in the wheat gluten
component of the recalled pet food, melamine has been commonly used
for more than 60 years to make hard plastic dishes, cleaning
products, stain-resistant laminates, flame-retardant foam,
soundproofing, and nitrogen-releasing synthetic fertilizer.
Melamine had apparently never before been found as a food
contaminant–not in pet food and not in people food.
FDA Center for Veterinary Medicine chief Stephen Sundlof told
reporters that the FDA had not found any studies of melamine in cats,
and found the results of only a single 1945 study that tested it on
dogs. That study suggested the chemical increased urine output when
fed to dogs in large amounts.
“We don’t think this is the final conclusion,” said New York
State Department of Agriculture and Markets spokesperson Jessica A.
Chittenden. “Melamine is not a known toxin. There is not enough
data to show that it is toxic to cats. We are confident we found
aminopterin,” Chittenden insisted, “and it makes sense with the
However, the FDA did not find aminopterin in the pet food
samples it tested. The Cornell University College of Veterinary
Medicine also did not find aminopterin, but found melamine both in
recalled pet food and in urine and tissue samples from afflicted cats.
The Iowa State University Veter-inary Diagnostic Laboratory
rushed to confirm the Cornell findings. But the next shocker came
from the California Animal Health & Food Safety Laboratory System at
the University of California’s Davis campus.
Not initially involved in the pet food recall, the Davis lab
eventually offered to test unrecalled foods. The staff expected to
help reassure the public about pet food safety, U.C. Davis professor
of veterinary clinical toxicology Bob Poppenga told Sacramento Bee
staff writer Carrie Peyton Dahlberg.
On April 7, however, U.C. Davis toxicology professor Birgit
Puschner notified the FDA that she had found melamine in six brands
of cat food that were not on the original recall list, and in
several additional varieties of foods sold by some of the recalled
“In light of the new findings, toxicologists at U.C. Davis
are stepping up their offer to test other foods to ensure all
problems are found,” wrote Peyton Dahlberg.
“There aren’t that many labs that are doing this kind of
testing right now. It’s our obligation to follow up,” said Poppenga.
Within days melamine was found in wheat gluten, rice protein
concentrate, and corn gluten pet food components, all imported from
China. As the materials were labeled “food grade,” the FDA
investigated whether any had entered the human food supply.
The investigation spread with the discovery that some pet
food was diverted for use as hog feed after it was deemed unsafe for
pet consumption.
In the first verified case, rice protein concentrate
imported from China by Diamond Pet Food Inc. was sold to American Hog
Farm, in Ceres, California. Similar materials may have been fed
to pigs in New York, North Carolina, South Carolina, Utah, and
Ohio, and at least one poultry farm in an unspecified location, FDA
chief vet Sundlof said.
Melamine was found in the urine of pigs raised in California
and both North and South Carolina, Sundlof confirmed.

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