A 12-year-old, Brahma-cross cow from a commercial operation in Texas is the first domestic case of BSE in the U.S., USDA said June 24. The downer cow spent its whole life in Texas and was discovered at a pet food plant in Waco. USDA won't name the source herd or its location in Texas. John Clifford, Chief Veterinarian for USDA, stressed the animal didn't enter either the human or animal food chain.

The Houston Chronicle reported the positive animal was from Southeast Texas. That's what USDA told Benjy Bauer, owner of Waco-based Champion Pet Foods, which took delivery of the animal, Bauer said.

“That's all they would say, and believe me, I've asked them several times. I want to know, too,” Bauer told the Chronicle. He said a livestock hauler brought in the cow, which was dead on arrival at Champion and no part of the animal made it into the company's products.

The now-confirmed, BSE-positive animal is among more than 400,000 animals tested for BSE since USDA initiated its enhanced surveillance program. Tissue from the cow and two other animals tested “inconclusive” in a quick test performed last November and were later cleared using USDA's “gold standard” immunohistochemistry (IHC) test.

Early in June, however, USDA's Office of Inspector General ordered a retest of the animal's tissue without the knowledge of USDA Secretary Mike Johanns. The sample was hand-carried to a Weybridge, England, lab recognized by the World Animal Health Organization, or OIE, as a world reference lab for BSE.

The development was an embarrassment for USDA, which has trumpeted the accuracy and tightness of its BSE testing procedures. In response, USDA changed its testing protocol. If another BSE rapid screening test results in inconclusive findings, USDA will run both an IHC and Western blot confirmatory test. If results from either confirmatory test are positive, the sample will be considered positive for BSE.

“By adding the second confirmatory test, we boost that confidence and bring our testing in line with the evolving worldwide trend to use both IHC and Western blot together as confirmatory tests for BSE,” Johanns said.

A “hold” order was placed on the source herd of the positive animal, identified via DNA testing. At press time, 67 herdmates had tested negative and the quarantine was removed.

Clifford said it's highly unusual to find BSE in more than one animal in a herd or in an affected animal's offspring. APHIS is working with the Food and Drug Administration to determine the herd's feed history. Given the animal's age, he said the cow likely was infected by consuming feed prior to U.S. implementation of its feed ban in 1997.