NEW YORK (Reuters) -- Sausages from the U.K. may carry small traces of the agent thought to transmit mad cow disease.
According to a study from the College of Veterinary Medicine at Texas A&M University, bovine brain tissue can be found in the lungs of up to 5% of slaughtered cattle.
In a letter to the British journal, The Lancet, the U.S. researchers report that the size of the brain tissue found in major lung arteries of slaughtered cows range from very small to almost six inches in length.
The brain tissue gets to the lungs, according to the report, due to use of "The Knocker," a pneumatic bolt used to stun cattle. The large shock delivered to the animal's head appears to propel brain particles into the lungs.
Cow brain tissue has been banned as a food ingredient since fears arose over bovine spongiform encephalopathy (BSE) or 'mad cow disease'.
But cow lungs are "designated as edible tissue in the U.K. and are usually minced to put into sausages because they are not part of the specified offal ban," write the researchers.
American slaughter practices are also under review. "Right now, the U.S. Department of Agriculture has put the stunning process under consideration," said Dr. Murl Bailey, Jr., professor at the Texas A&M School of Veterinary Medicine, and a co-author of the study.
Bovine brain tissue is thought to harbor prion proteins -- the agents suspected of transmitting BSE. There are reports from Britain of cases where it appears the disease was transmitted from cows to humans.
And according to the study, the cooking temperatures used in sausage manufacture are too low to inactivate prion proteins.
While the exact means of transmission remains a mystery, the discovery of brain tissue in the lungs of slaughtered cows raises questions about the safety of other cattle parts for human consumption.
"It is likely that prion proteins are found throughout the bodies of animals stunned for slaughter," write the Texas researchers.
A second letter in The Lancet this week reports that another British farmer has died of Creutzfeldt-Jacob disease (CJD), a rare disease found in humans that closely resembles 'mad cow disease'.
This brings the total number of cases of CJD in British farmers who have been exposed to 'mad cow disease' to four.
The most recent case was a 59-year-old man who was admitted to a hospital in September 1995 for problems with his vision. Within a week of admission, he became increasingly forgetful, and after three weeks, he was bed-bound and barely responsive. He died three months after symptom onset.
He had been exposed to a cow with BSE on his farm in 1991.
"The apparent excess of recent cases of CJD in the U.K. occurring in people exposed to cattle affected with BSE has increased speculation that CJD may result from the transmission of BSE to human beings," write the authors of the letter, CJD researchers in Liverpool and Edinburgh.
Source: The Lancet (1996;348:610-611)
