BSE Fact Sheet
Date: January 2, 1997
FACT SHEET
Contacts:
HHS Press Office - (202) 690-6343
FDA Press Office - (301) 443-3285
USDA APHIS - (301) 734-7799
USDA FSIS - (202) 720-9113
OVERVIEW: On March 20, 1996, the British government announced a possible link between bovine spongiform encephalopathy (BSE), a chronic disease affecting the central nervous system of cattle, and ten cases of a variant form of Creutzfeldt-Jakob disease (CJD), a related disease among humans. At a World Health Organization consultation in April, a group of international experts concluded that there is no definite link between BSE and the new variant CJD, but that epidemiological evidence suggests exposure to BSE may be the most likely explanation for the ten cases of variant CJD in the United Kingdom.
In October 1996, John Collinge, one of the foremost British authorities on CJD, and his colleagues published results of their research on various strains of prions, which are thought to transmit BSE. Their results suggest that the new variant CJD resembles BSE rather than other forms of CJD.
No case of BSE has ever been reported among cattle in the United States, and, since 1989, no cattle have been imported from countries with confirmed cases of naturally occurring BSE. In addition, no beef has been imported from foreign countries with native cattle cases of BSE since 1985.
Although BSE remains a disease among cattle in some foreign countries, the U.S. government is taking steps to even further reduce the risk of BSE and enhance surveillance and study of CJD among humans. This fact sheet provides some background about CJD and BSE and summarizes U.S. efforts concerning the two diseases.
BSE (sometimes referred to as "mad cow disease") and CJD belong to the unusual group of progressively degenerative neurological diseases known as transmissible spongiform encephalopathies (TSEs). These diseases are characterized by an incubation period of several months (among mink) to several years, during which there is no visible indication of the disease. The incubation period for BSE among cattle ranges from three to eight years; for CJD among humans, it is approximately 13 years.
Following a relatively short clinical course of neurological signs, the disease is characterized by 100-percent mortality of its victims. There is no known treatment or cure.
BSE among cattle was first described in the U.K. in November 1986. Epidemiological evidence established that it was an extended, common-source outbreak, one that occurred in many places at nearly the same time and was traced to the same source. It is believed that rendered feed ingredients contaminated with a TSE agent served as the common source of infection. The epidemic expanded when carcasses of BSE-infected cattle were rendered and used as feed ingredients, thereby further spreading the TSE agent.
Through November 15, 1996, about 165,000 head of cattle in over 33,000 herds were diagnosed with BSE in the U.K. The disease has also been confirmed in domestic cattle in the Republic of Ireland, France, Portugal, Oman, and Switzerland. The epidemic peaked in January 1993 at nearly 1,000 new cases per week; currently, fewer than 200 suspect cases are diagnosed every week.
U.S. ACTIONS: Steps to Minimize any Possible Risk
The United States Department of Agriculture (USDA) is responsible for the health of U.S. livestock. USDA's Food Safety and Inspection Service operates a substantial program for inspecting animals intended for human consumption. The USDA's Animal and Plant Health Inspection Service enforces explicit import regulations covering animals and animal products offered for import into the U.S., to prevent the importation of foreign exotic diseases such as foot-and-mouth disease, rinderpest, and African swine fever. USDA examines all cattle before they can be approved for use as human food. Cattle with undiagnosed diseases of the central nervous system are not allowed for human food. USDA examines over 33 million head of cattle each year.
In 1989, the USDA issued restrictive import prohibitions designed to prevent the entry of BSE into U.S. livestock herds. Its aggressive BSE monitoring program has examined more than 5,100 brains of U.S. cattle exhibiting various abnormal behaviors, including neurological symptoms.
USDA veterinary pathologists have performed histopathological examinations of brain tissue, as well as immunohistochemistry to detect possible spongiform encephalopathy. No evidence of BSE has ever been found in these U.S. cattle specimens.
Agencies of the U.S. Public Health Service have a long-standing commitment to research, epidemiological studies, and consumer protection involving BSE and CJD.
Cattle Feed Restrictions: As recommended by the World Health Organization consultation in April, the Food and Drug Administration and the livestock industry are moving to ban the use of ruminant protein in all ruminant feeds.
While national livestock organizations and professional animal health groups have announced a voluntary ban on the use of ruminant and mink protein in feeds, the Food and Drug Administration is expediting regulations to codify the prohibition. This month, FDA proposed a regulation that would prohibit the use of nearly all protein sources of ruminant and mink protein in feed intended for ruminants. In addition to prohibiting tissues with the potential to spread TSEs, the proposed rule would establish a flexible system of controls to ensure that ruminant feed does not contain animal protein derived from ruminant and mink tissues. FDA's proposal also points out that the agency is considering alternatives to this ruminant-to-ruminant prohibition and that it is seeking comments on any such alternatives.
For many years, FDA has carefully reviewed pharmaceutical products marketed in the U.S. for possible or potential contamination with conventional microorganisms (bacteria, yeast and mold) during their manufacture.
In 1990, FDA intensified its microbiological review of new drug applications for human drug products derived from bovine sources. Manufacturers are required to document that: animal tissues used in the manufacture of these drug products did not originate in a country where native cattle have been diagnosed with BSE; the animals had been inspected by the source country's veterinary authorities, both before and after slaughter; and that the animals are suitable for food use.
As a condition of approval, drug manufacturers of bovine-derived pharmaceuticals are required to report outbreaks of BSE in countries where the bovine materials originate.
Beginning in 1992 and most recently in May 1996, FDA also issued a series of letters advising all manufacturers of FDA-regulated products derived from bovine tissue materials that source materials should not come from cattle that ever resided in a BSE country.
Research: The National Institutes of Health has long been actively researching CJD and kuru, a related disease among humans, and BSE in animals. NIH research has independently confirmed findings to date from the Department of Agriculture and the Centers for Disease Control and Prevention (CDC).
In the 1960s and 1970s, the Nobel Prize-winning team at the NIH Laboratory of Central Nervous System Studies conducted experiments on the oral transmission of CJD, kuru, and scrapie, a similar disease that affects sheep and goats.
In the 1970s, scientists at the University of California in San Francisco used extracts of scrapie-infected brains to postulate that the infectious agent was a single protein, PrP. Naming this class of infectious proteins as "prions," scientists showed that prions were a variant of normal proteins. Further research in the 1990s linked three outbreaks of CJD in Europe and Israel to a genetic mutation in the victims. It is now known that about 10 percent of CJD can be inherited, although it is not known if the genetic defect causes the disease or if another agent, such as a prion, is required.
Today, researchers in the United States and around the world are collaborating in the search for methods to detect, prevent and treat prion-linked diseases. NIH scientists are providing input to the current investigation of the ten cases in the U.K. and have developed a diagnostic test that can be performed before death. This collaboration between NIH and international experts fuels the ongoing search for clues that one day might lead to a treatment for this group of diseases.
Disease Surveillance: The Centers for Disease Control and Prevention in Atlanta conduct surveillance for CJD through examination of death certificate data for U.S. residents. Based on this surveillance, during the period 1979 to 1993, the annual incidence of CJD remained stable at approximately one case per million persons.
In light of concern about the new variant CJD cases in the United Kingdom, CDC is working with the Council of State and Territorial Epidemiologists to expand current CJD surveillance. CDC is piloting enhanced surveillance efforts, including an active search for variant CJD as described in the United Kingdom. This enhanced surveillance is coordinated through CDC's Emerging Infections Disease Programs in Minnesota, Oregon, Connecticut, and California.
The Department of Agriculture is the lead agency for animal health, animal products and food safety. For further information about BSE as it relates to animal health and meat and poultry products, contact the Animal and Plant Health Inspection Service at (301)-734-7799. For information about BSE as it relates to food safety issues, contact the Food Safety and Inspection Service at (202) 720-9113.
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