BSE (bovine spongiforme enzephalopatie) is a deadly disease among cattle without a cure. It is not only an economical danger for many people in the live-stock industry but is also under suspicion to cause a deadly disease for humans called Creutzfeld-Jakob disease.
The disease attacks the brain and central nervous system of cattle. An infected brain has a consistence like a sponge because brain cells (neurons) alter their form and stick together forming holes between them. An examination of brain tissue is necessary for a definite diagnosis. BSE does not affect an immune response and thereby can not discovered with a blood test. Infected cattle become aggressive, loose coordination of movement and finally die. Up to now 160.000 cattle died on BSE. The disease carrying agent is unknown. It could be a virus but the popular thesis says prions could be the cause of BSE. The theory of prions (proteinaceus infectious particles) was developed 1982 at the University of California. The prion is a little protein molecule without nucleic acid (containing the genotype) but with the ability to transform protein molecules in brain to an useless form. It is not known how this is done and how prions replicate.The disease was first spotted 1985 in Great Britain. Because of a shortness in pastures for so many cattle and to lower production costs a substitute fodder is in use. It is made out the remains of cattle and sheep from slaughterhouses and cadavers, reduced to pieces and heated. After privatization of the companies making such fodder, the process of manufacture was changed due economical reasons. The process was shortened and the temperature was lowered. Therefore a disease carrying agent for a sheep disease called scrapie survived the process. This agent has managed to cross the border between the species and caused BSE among cattle. Infected cattle has been exported to Ireland, Denmark, France, Germany and Portugal. BSE also appeared in Switzerland, where the substitute fodder was used. The BSE agent is very resistant against normal heating and chemicals. Meanwhile there is evidence that the BSE agent can cross the border to some other species (cats, mink, mice).
British government announced March 1996 that it may be possible that humans can get infected by BSE. The Creutzfeld-Jacob disease by humans has similar symptoms as BSE in cattle. The brain of infected people has the same sponge-like appearance with transformed protein, there is no immune response, the agent is unknown and there is no cure. In Great Britain there has been cases of Creutzfeld-Jakob in the last months with patients younger than the usual average from 50 to 60 years. An infection with Creutzfeld-Jacob can be caused by transmission (inherited disease, 1-2 in a million) but can also occur by transplantation of infected body tissue (for example cornea). There are Creutzfeld-Jacob patients who worked closely with cattle (butchers, sellers). The incubation time, from infection to appearing of the first symptoms, is long. For BSE it is something between 6 months and 15 years, for Creutzfeld-Jakob between 22 months and 35 years.
The uncertainty how dangerous it is to eat meat or gelatin products from infected cattle will remain for a while.
There are statistical hints that BSE can be transferred from cow to calf with cow's milk. Calves from infected mother cows have a three times higher likelihood to get BSE then calves from mother cows without symptoms. It is known from sheep that a similar disease called scrapie is transmitted from mother to lamb.
There are also further hints that BSE is transferable to humans. A new protein test has shown that BSE particles from infected cows, mice and apes resemble more the appearance of the new variant of the human Creutzfeld-Jakob disease (vCJD) than the classical Creutzfeld-Jakob disease (CJD). This new variant (vCJD) occurs not only by older people but also by people around twenty and the appearance of the disease like losing balance control in an early stage reminds one on the behaviour of BSE infected cattle. The statistical burst of vCJD cases in Great Britain in the last years has brought BSE under heavy suspicion to be the cause of the disease. The new test is a further step in the evidence to link BSE to vCJD.
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