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Mad Cow Disease Undetected Thus Far in Texas Herd

Posted on: Monday, 11 July 2005, 18:00 CDT

Jul. 10--No sign of mad cow disease was detected in 29 cattle from the Texas herd that produced the nation's second case of the fatal brain-wasting disease, the Agriculture Department said Saturday.

Thirty-eight other Texas cattle from the same herd have been killed for testing, and an unknown number of additional livestock are being traced, spokesman Jim Rogers said.

Brain tissue samples from the 38 were sent Friday to the National Veterinary Services Laboratory in Ames, Iowa, for the same Bio-Rad rapid test to determine signs of bovine spongiform encephalopathy, or BSE, Rogers said. Results are pending.

Non-negative results from the rapid test are considered inconclusive because the test frequently yields false positives.

But an inconclusive result will prompt a pair of confirmatory tests -- the Western blot, and immunohistochemistry, or IHC -- both considered more reliable. In the case of an inconclusive result, samples would also be sent to the Veterinary Laboratories Agency in Weybridge, England, for simultaneous confirmatory testing.

Last month, the government added the Western blot as a mandatory test after a routine IHC test on the infected Texas cow at Ames was negative.

The case was confirmed only because researchers used the animal's samples to try a new rapid IHC test, which was positive. The department's inspector general, Phyllis Fong, then ordered the Western blot and further testing in England.

The tests on the first 29 were conducted at the Iowa laboratory, not at Texas A&M University, as the Star-Telegram reported Saturday.

The Agriculture Department has not disclosed the name or location of the herd's ranch, widely believed to be a cattle-breeding operation in East Texas. The infected cow was sold at auction Nov. 11 after it had problems delivering its last calf, Rogers said.

Scientists believe that the fatal disease is spread to livestock by feed contaminated with BSE-laden proteins known as prions, passed from rendered parts of cattle. Such ruminant-to-ruminant feed was banned in 1997. Researchers are trying to determine whether there is a spontaneously occurring strain of the disease.

The department has said that samples from the Texas cow showed BSE more akin to that found in France and unlike what was commonly discovered by the British.

All dead and high-risk livestock, including "downer" animals -- those that are alive but cannot walk -- and those showing neurological problems, are removed before entering the food supply. After the animals are killed, samples are sent for testing.

In the Texas case, the 12-year-old cow was discovered dead on arrival on Nov. 15 at a Waco slaughterhouse, H&B Packing. It was then shipped across town to Champion Pet Food. Samples were sent to A&M for the rapid test. The carcass was later sent to College Station and incinerated.

Champion co-owner Rick Bauer said all dead and downer cattle that reach his dog food plant are tested for BSE.

Humans can contract a version of the disease, known as variant Creutzfeldt-Jakob, by eating BSE-tainted meat. Of the 153 confirmed cases, most were in Europe. The only victim in the United States was a person who lived in Britain when contaminated beef was available.

Variant Creutzfeldt-Jakob disease, or vCJD, reportedly affects about one person per million per year. In the United States this translates to 250 to 300 new cases per year, according to the Creutzfeldt-Jakob Disease Foundation in Akron, Ohio.

The disease is extremely difficult to diagnose. About 85 percent of all cases fall into one of two categories -- classical and sporadic. The remaining 15 percent are familial, or inherited.

The foundation has also reported a few cases of transmission during medical procedures, with contaminated surgical equipment or instruments suspected as the mechanism of transmission. These cases are referred to as iatrogenic or acquired CJD.

Differentiating these types from the variant disease associated with contaminated beef requires testing after death.

ON THE WEB:

--www.usda.gov

--www.cjdfoundation.org/cjdisease.html

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Copyright (c) 2005, Fort Worth Star-Telegram, Texas

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Source: Fort Worth Star-Telegram (Fort Worth, Texas)

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