Second U.S. Case of Mad Cow Disease Confirmed

Infected Cow Was Pulled From Food Supply Last Year

By Daniel DeNoon
WebMD Medical News Reviewed By Brunilda Nazario, MD
on Friday, June 24, 2005

June 24, 2005 -- A U.S. cow -- pulled from the food supply last November -- really did have mad cow disease.mad cow disease.

Agriculture Secretary Mike Johanns today announced that tests confirm the animal had bovine spongiform encephalopathy -- BSE, commonly known as mad cow disease.

Humans who eat infected nerve tissue from beef infected with BSE can contract a human version of the mad cow disease called variant Creutzfeldt-Jakob disease (vCJD). However, the U.S. cow was never used as meat. The animal was a "downer" cow --- that is, it was unable to stand when it arrived at the processor. An "interim" USDA rule in effect since January 2004 prohibits the use of downer cows for meat.

Conflicting Results in Early Tests

An initial quick test showed that the animal had mad cow disease. But a more sophisticated test came up negative. When yet another quick test was positive, tissues from the cow were sent to the U.K. for further tests. These tests finally confirmed that the cow had BSE.

"This animal was blocked from entering the food supply because of the firewalls we have in place," Johanns says, in a news release. "Americans have every reason to continue to be confident in the safety of our beef."

Currently, the USDA tests some 1,000 animals a day for mad cow disease. That, of course, is a small fraction of the animals slaughtered each day.

In 1989 the federal government prohibited the importation of certain types of live animals from countries where mad cow disease is known to exist. This ban also includes meat products used in human, animal, and pet foods.

The cow is the second U.S. animal to have tested positive for BSE. The USDA is investigating the animal's herd of origin.

Cows get the disease after eating feed made from an infected cow. Cattle feed made from processed cattle has been banned in the U.S. since 1997. Both U.S. cows with BSE were born before the ban was in place.

Critics of the U.S. ban have said that it is not uniformly enforced.

SOURCES: News release, U.S. Department of Agriculture. International Society for Infectious Diseases, ProMed Newswire, June 14, 2005. WebMD: "Mad Cow Disease: Know the Basics."