Those results were reported Monday by Banfield, The Pet Hospital, based upon an analysis of records collected by its more than 615 veterinary clinics.
The analysis suggests that out of every 10,000 cats and dogs seen in Banfield clinics, three developed kidney failure during the time pet food contaminated with melamine, a chemical used to make plastic kitchenware, countertops, fertilizers and flame retardants, was on the market.
The veterinary hospital chain, one of the nation's largest, saw about 1 million dogs and cats during the three months when the more than 100 brands of now-recalled contaminated pet food were sold. It saw 284 extra cases of kidney failure among cats during that period, or a roughly 30 percent increase when compared with background rates. It was not clear whether those animals ate the contaminated food.
"It has meaning when you see a peak like that," said veterinarian Hugh Lewis, who oversees the mining of Banfield's database to do clinical studies. "We see so many pets here, and it coincided with the recall period."
Meanwhile, the chief financial officer of Menu Foods Income Fund, the parent company of the initial pet food maker involved in the recall, says it's just a "horrible coincidence" that he sold nearly half his shares of the company less than three weeks before the massive recall.
The Toronto Globe and Mail reports Mark Wiens sold 14,000 units on Feb. 26 and 27, for $102,000 Canadian (about $82,000 U.S.). Reports of illnesses and deaths related to Menu Foods products came in to the company's toll-free customer relations line in late February. But Wiens says he didn't hear of any possible problems until early March.
In the three weeks since the first pet food was recalled, Banfield vets have examined 1,605 cats and dogs reported to have eaten the recalled food. That is less than 1 percent of pets examined. Just six of those animals — five cats and one dog — have died.
FDA officials previously have said the database compiled by the huge veterinary practice probably would provide the most authoritative picture of the harm done by the tainted cat and dog food.
From its findings, Banfield officials calculated a kidney failure rate during the recall period of .03 percent for pets it examined, although there was no discernible uptick among dogs. That suggests the contamination was more toxic to cats, Lewis said. That is in line with what other experts have said previously.
A simple blood and urine test can determine whether a pet has been affected. If so, the problem can be treated if caught early.
At least six pet food companies have recalled products made with imported Chinese wheat gluten tainted with the chemical. The recall involved about 1 percent of the overall U.S. pet food supply.
Measuring the tainted food's impact on animal health has proved an elusive goal. Previous estimates have ranged from the FDA's admittedly low tally of roughly 16 confirmed deaths to the more than 3,000 unconfirmed cases logged by one Web site.
"On a percentage basis it's not breathtaking, but unfortunately it's a number that, if it was your pet that was affected, it's too high," veterinarian Nancy Zimmerman, Banfield's senior medical adviser, said of the newly estimated incidence rate.
In another estimate Monday, the founder of a veterinary group said 5,000 to 10,000 pets may have fallen ill from eating the contaminated food, and 1,000 to 2,000 may have died.
The estimate was based on a Veterinary Information Network survey of 1,400 veterinarians among its 30,000 members. About one-third reported at least one case, said Paul Pion, the network's founder. He cautioned that a final, definitive tally wasn't possible, and that even his estimate could be halved — or doubled.
Also Monday, the Web site petconnection.com said it had received reports of 3,598 pet deaths, split almost evenly between dogs and cats. The site cautioned that the numbers were unconfirmed.
Banfield's veterinarians treat an estimated 6 percent of the nation's cats and dogs. After the first recall was announced, the chain enhanced its software to allow those veterinarians to plug in extra epidemiological information to help track cases, Zimmerman said.
The new template allowed vets to log what a sick pet had eaten, any symptoms its owner may have noticed, the results of a physical examination, any urine and blood test results and other observations.
Lewis said there is no reason to believe the company's findings — including an apparently heightened vulnerability of kittens to the contaminant — wouldn't hold for other veterinary practices as well.