Questions and Answers about Bovine Spongiform Encephalopathy (BSE) or 'Mad Cow'


This morning, France confirmed a single, isolated case of Bovine Spongiform Encephalopathy (BSE), or 'Mad Cow Disease.' The case is being handled properly with preventative measures throughout the region, and the French farm ministry has confirmed there is no threat to human health. But what IS this 'Mad Cow Disease?' Read on to learn more.


What is Bovine Spongiform Encephalopathy (BSE) or "Mad Cow"?

BSE is a rare, chronic degenerative disease affecting the brain and central nervous system of cattle. It is one of several known transmissible spongiform encephalopathies (TSE), which include scrapie (a disease affecting sheep), transmissible mink encephalopathy, chronic wasting disease in elk and deer, and some very rare encephalopathies in other species including humans. BSE is characterized by the progressive degeneration of the nervous system. Cattle with BSE lose their coordination, experience changes in behavior and develop a variety of central nervous system abnormalities. The incubation period in cattle is 2 to 8 years. Once clinical symptoms develop, death occurs in several weeks or months, unless the afflicted animal is destroyed. Bovine Spongiform Encephalopathy (BSE), or "Mad Cow Disease," continues to be in the news worldwide. Surveillance programs are in place to assure consumers that American beef and other food products derived from cattle are safe.

When was BSE first discovered?

BSE first appeared in British cattle in the mid-1980s. There have been numerous cases detected in other countries. A complete list of countries is available from both the U.S. Food and Drug Administration (FDA) and the U.S. Department of Agriculture (USDA).

How is BSE transmitted?

Scientists believe that BSE is transmitted through cattle eating animal feed that has been contaminated with the BSE disease agent. The source of contamination is infected neural tissue such as brain, spinal cord and part of the intestine from BSE-affected cattle. It does not appear that BSE spreads from cattle to cattle or from cattle to other species through physical contact, although there does appear to be an increased risk of BSE in the offspring of BSE-infected cattle. BSE appears to be caused by a prion (pronounced pree-on), a type of rogue protein.

Prion particles contain the same components (amino acid sequence) as normal protein, but they are shaped differently. It is assumed that the prion acts as a template by which normal protein molecules in the brain and central nervous system fashion themselves abnormally, thereby beginning the progression of the disease.

Along with eating beef, is drinking milk and consuming dairy products safe?

Yes. The National Institutes of Health (NIH) researchers and the U.S. Secretary of Agriculture agree that there is no reason to change dietary habits based on news of a single case of BSE in the U.S. BSE has only been detected in the brain, central nervous system and in part of the intestine of affected cattle. No BSE infectivity has been detected in milk or muscle tissue, which is what we eat as beef. In fact, extensive testing has revealed that milk, including milk from cows infected with BSE, does not contain the infective agent. Thus, according to the World Health Organization (WHO), milk and milk products, such as yogurt, ice cream or cheese can be consumed safely, even in countries with high incidence of BSE.

Can humans get BSE?

No, but an extremely rare form of spongiform encephalopathy called Creutzfeld-Jakob Disease (CJD) occurs in humans.

What is CJD and is there a link between BSE and CJD?

CJD (Creutzfeld-Jakob Disease) is an extremely rare, progressive fatal disease of the brain of humans. It affects approximately one in one million persons per year. Most cases of CJD are sporadic and show no relation to regional, ethnic, economic or other factors. CJD has been identified around the world. Most cases of the disease are thought to arise spontaneously and no environmental causative agents have been identified.

Recent diagnoses of a new variant form of CJD (vCJD) in Britain have elevated concerns about the possibility of BSE passing from cattle to humans. vCJD appears to affect a younger population and is distinguishable by a longer duration of illness and a different pathology from that expected for CJD.

Recently released animal studies were conducted to examine the transfer of BSE from cattle to humans. Two studies using different "fingerprinting" techniques offer compelling evidence that there is a link between BSE and vCJD. Although the same "agent" would appear to be responsible for both diseases, there are numerous experiments still underway which promise to offer further evidence and insight into this link. Nevertheless experts have sufficient information and knowledge to assess risks and ensure the public health.

The Centers for Disease Control and Prevention (CDC) conducts surveillance for CJD and vCJD as part of its Emerging Infectious Disease Program.

Are other food products made from cattle products safe?

Yes. For example, gelatin—a clear, jelly-like substance has been used for generations in cooking and for congealed salads and desserts. According to the FDA, most food-grade gelatin in the U.S. comes from the hides of pork, which are not associated with BSE, but can be derived from cattle bones and hides. They are considered low risk tissues for BSE transmission due in part to the manufacturing process. The gelatin manufacturing process of soaking, chemical treatment, purification, filtration, evaporation and drying, produces a very refined and pure product that has been proven to provide a safe gelatin supply for consumption. In addition to food products, gelatin is used in pharmaceuticals, dietary supplements, cosmetics and other industrial applications.

Although not contained in gelatin, refined beef tallow comes from similar sources. It is used in cooking or as a flavoring agent, and also undergoes a highly refined process. Therefore, the World Health Organization (WHO) has stated that all gelatin- or beef tallow-containing food, cosmetic or pharmaceutical products are safe and can be used with confidence. Although research has shown the efficacy of the gelatin manufacturing process to remove or inactivate the BSE-infected agent, the FDA continues to revise its "Guidance for Industry" on the sourcing and processing of gelatin to ensure safety. This document and the actions it calls for are based on a three-tiered risk management scenario. The three tiers—sourcing, processing and use—allow for more flexibility while maintaining a high degree of confidence in the safety of FDA-regulated products for human use.


The federal government, beef industry and food manufacturers are working together to ensure a safe food supply for consumers. They have effective inspection programs and monitoring systems in place to ensure that beef, food and consumer products derived from cattle are safe.

In November 2001 and October 2003, USDA and the Harvard Center for Risk Analysis released studies that investigated the risk of BSE occurring in the United States. USDA commissioned the reports. The authors of the analyses noted that the measures taken by the U.S. government and industry make the U.S. robust against the spread of BSE should it be introduced into this country.

The latest report is available through USDA’s Animal and Plant Health Inspection Service at

Additional Resouces: 
  • USDA Home Page
  • “Commonly Asked Questions About BSE in Products Regulated by FDA’s Center for Food Safety and Applied Nutrition (CFSAN)"
  • European Union “Opinion on the Safety of Gelatine” Adopted at the Scientific Steering Committee at its plenary meeting of 26-27 March 1998. Following a public consideration on the preliminary opinion adopted on 19-20 February 1998