IFT Summarizes Knowledge About TSEs

Media coverage of transmissible spongiform encephalopathies (TSEs), particularly bovine spongiform encephalopathy (BSE), has attempted to oversimplify a complex scientific issue and obscure the fact that Americans enjoy beef. Beef continues to pose an extremely low food safety threat—there are currently no endogenously derived cases of variant Creutzfeldt-Jakob disease in the United States—particularly when compared to other potential, higher-prevalence foodborne maladies.

Stories frequently confuse and obfuscate the importance of managing transmissibility of infectious agents in the cattle herd with controls implemented to provide assurances of food safety. Efforts of the U.S. government and beef industry to (a) control BSE transmissibility and protect animal health and (b) further ensure that food safety threats to public health are negligible should be communicated in a manner that allows consumers to make rational decisions concerning regulatory policy and purchasing. Although the breadth of scientific knowledge is dynamic and ever-improving, regulatory policy founded on science should be the goal of all citizens. The Institute of Food Technologists, which has prepared the Scientific Status Summary, “Understanding BSE and Related Diseases,” published in this issue of Food Technology, should be commended for attempting to communicate the current status of knowledge surrounding TSEs.

Because the prevalence of BSE in the U.S. is so low that it has only been detected in two cows and the risk that BSE infects cattle in the youthful beef cattle population (which constitutes more than 80% of the beef supply available to U.S. consumers) is even lower, consumers can be confident in the safety of U.S. beef. Over the past 15 years, the U.S. Dept. of Agriculture, the Food and Drug Administration, and the cattle industry have built and maintained a series of “firewalls” to protect both cattle and public health.

The U.S. policy regarding BSE is two-fold:
First, “firewalls” have been implemented to prevent transmission of the disease in the U.S. cattle population, including a mandatory mammalian-to-ruminant feed ban that was implemented in 1997 to ensure that the infectious agent is not transmitted from infected cattle to other cattle previously free from BSE. Also, a new surveillance program was implemented—at great cost— in June 2004 to further detect any additional positive animals and to verify that barriers to transmission of the disease are effective. Up to the time of this writing, the expanded program has identified one additional—and potentially atypical—BSE-positive cow out of 394,613 that have been tested in the high-risk population. Previous surveillance activities of USDA since the early 1990s already had demonstrated effectiveness of U.S. efforts to eliminate BSE from the cattle herd.

Second, substantial and additional food safety “firewalls” have been implemented, including regulations requiring removal of specified risk materials (SRMs), such as spinal cord or brain, from beef carcasses that could, should they be from infected cattle, transmit the disease in the food chain. The animal, from Mabton, Wash., that tested positive on December 23, 2003, was imported and from a high-risk group of cows that is the focus of the enhanced surveillance program: those that are older, acting strangely, unable to walk. The cow was old enough to have consumed meat and bone meal from infected cattle before implementation of the mandatory 1997 mammalian- to-ruminant feed ban and probably was originally infected via a small dose of prions since it took a long time for her to manifest clinical signs of the disease.

These are not the type of animals that enter the human food supply, anyway. The vast majority of cattle harvested for food in the U.S. are between 14 and 19 months of age, and research has not suggested that BSE can be routinely detected or transmitted in beef from younger animals. In addition, since January 12, 2004, non-ambulatory cattle (cattle that cannot walk under their own power) are not harvested for food in the U.S., since USDA has banned any cattle that are unable to walk, or that show signs of possible neurological disease, from entering the human food chain.

All of the policies described, combined with those that are not described here, are thought globally to be effective in containing BSE and preventing exposure to other animals or food—risk assessments by Harvard University have supported U.S. policies regarding BSE. Consumers should be confident in the beef products they find at the supermarket and on restaurant menus, and as scientific knowledge continues to evolve, threats to animal and public health will only continue to be further reduced—as long as governments continue to utilize science in regulatory policy development and enforcement activities. Efforts such as the IFT Scientific Status Summary on TSEs can only assist in the efforts of scientists to effectively communicate risks to the general public.

by Keith E. Belk,
Professor,
Program in Meat Science/Center for Red Meat Safety,
Dept. of Animal Sciences,
Colorado State University, Fort Collins, Colo.
[email protected]