Since the 1996 review in the Department of Animal Sciences Research & Review publication (Ockerman, 1996) entitled "Facts and Speculation About Bovine Spongiform Encephalopathy (BSE)," several things have changed. With the knowledge that has been gained up to this point it appears appropriate to update our information.
The British Government has conducted a two year, 23 million dollar (AMI, 2000) inquiry into the spread of Bovine Spongiform Encephalopathy (BSE). This report was published on October 26, 2000. According to Lynn Candon's (AMI, 2000) evaluation of the government report, he indicated that the report was highly critical of the government's action. He also stated that the report noted lax enforcement of the 1989 ban on brain, spinal cord and other hazardous tissue entering the human food chain, and poor communication between government departments. The sixteen volumes of the full inquiry report can be found on the Internet at http://62.189.42.105/report/contents.htm. In the Executive Summary of this report (http://62.189.42.105/report1/execum2.htm), some sections were critical, and others were complimentary of the government's action. This update is a chronological listing of events, the Committee's interpretation of those events, with no attempt in this update was made to assess blame for this tragic situation.This survey looked at BSE (cattle disease) and variant vCJD (human disease which is a new variant of CJD) and the possibility of a relationship between the two. These two diseases are varieties of a rare group of diseases known as Transmissible Spongiform Encephalophalthy (TSE). The TSE cause the appearance of microscopic holes in the brain giving a sponge-like appearance. They are invariably fatal and affect both humans and animals. The TSE have been identified in animals such as Scrapies in sheep and goats, Chronic Wasting Disease (CWD) in wild deer in North America, and Transmissible Mink Encephalopathy (TME) in the U.S. In humans, the disease has been identified as Creulzfeldt-Jakob disease (CJD), Gerstmann-Staussler Syndrome (GSS), kuru (in the native language known, as trembling with fear), Fatal Familial Insommomnia (FFI), and now, vCJD (new variant of CJD). Scrapies has been identified in sheep in the U.K. for 200 years and this disease has never infected cattle or humans. A single feature of these diseases is that they are transmittable in particular from parent to offspring. There have been occurrences in humans as well as other species. Also, by genetic mutation, they may be inherited or occur spontaneously. Infectious agents, "prions", are extremely difficult to inactivate and are often described as almost immortal. They can withstand treatments [heat (even ashing, did not entirely inactivate), chemical, irradiation, detergents, burying] commonly used to disinfect various contaminating materials. Researchers also have failed to detect an immune response in hosts. Some researchers think this is an unconventional virus but the more common theory is that it is a reaction between proteins. This theory says that the deformation of one of these proteins (prion protein which contains no DNA or RNA) in large numbers in the brain develops a spongy appearance that always fatally damages the brain. The current theory is that this abnormal protein (rogue "prion") combines with a normal protein (normal prion) and changes the normal protein into another rogue prion. The now two rogue prions separate and continue the process of conversion of normal prion proteins into abnormal or rogue prion proteins. This process does not change the chemical composition but does change the physical shape. This deformed protein from an animal suffering from BSE can then be introduced into the body of other animals or humans and may induce similar proteins that are found in the host, to be deformed in the same way. The normal prion protein exists in the natural form in all animals and the chemical composition is not precisely the same in each specie. In fact, there is slight variation in animals from the same specie. The more similar the prion protein, the easier the transmission of a TSE appears to be. Transmission is easier between animals of the same specie. In animals that are of a different specie, the "specie barrier" will sometimes prevent transmission but not always. The obvious way a deformed protein can be transmitted between animals is through food. However, there are other possibilities such as medical products administered by injection, consumption as well as other techniques. Experiments have been shown that it is much easier to transmit TSE by injecting infected tissue directly into the brain than by feeding. In this case only a minute quantity is necessary. Also, CJD has been transmitted by surgical instruments even though they have gone through normal medical sterilization. Cases of CJD in younger people suggests that this is a new variant (vCJD) of the disease (CJD).