Bovine spongiform encephalopathy: a review

Transmissible Spongiform Encephalopathies are a group of chronic, always fatal diseases affecting the central nervous system of humans and animals. They occur in all species and are probably caused by agents called prions. In this minireview, a first part provides an overview of the various disease forms, a second part is devoted to the molecular biology of transmissible spongiform encephalopathies, and a last part deals with the specific problems of the Bovine Spongiform Encephalopathy.     

Bovine spongiform encephalopathy: epidemiological studies

This study, initiated in June 1987, describes the epidemiology of bovine spongiform encephalopathy (BSE), a recently described novel neurological disease of domestic cattle first identified in Great Britain in November 1986. Records suggested that the earliest suspected cases occurred in April 1985. There was variability in the presenting signs and the disease course, but the majority of cases developed behavioural disorders, gait ataxia, paresis and loss of bodyweight; pruritus was not a predominant sign. The form of the epidemic was typical of an extended common source in which all affected animals were index cases. The use of therapeutic or agricultural chemicals on affected farms presented no common factors. Specific genetic analyses eliminated BSE from being exclusively determined by simple mendelian inheritance. Neither was there any evidence that it was introduced into Great Britain by imported cattle or semen. The study supports previous evidence of aetiological similarities between BSE and scrapie of sheep. The findings were consistent with exposure of cattle to a scrapie-like agent, via cattle feedstuffs containing ruminant-derived protein. It is suggested that exposure began in 1981/82 and that the majority of affected animals became infected in calfhood.     

Bovine spongiform encephalopathy and human health

Because bovine spongiform encephalopathy (BSE) has probably been caused by accidental transmission of the transmissible agent of sheep scrapie there is concern that humans may be at risk from BSE. Epidemiological and experimental evidence is examined which suggests that this is unlikely.     

Bovine spongiform encephalopathy: epidemiological studies on the origin.

The results of further epidemiological studies of bovine spongiform encephalopathy (BSE) support the previous findings that the onset of exposure of the cattle population to a scrapie-like agent, sufficient to result in clinical disease, occurred in 1981/82. The onset of this exposure was related to the cessation, in all but two rendering plants, of the hydrocarbon solvent extraction of fat from meat and bone meal. A further possible explanation, related to the geographical variation in the reprocessing of greaves to produce meat and bone meal, was identified for the geographical variation in the incidence of BSE.     

Bovine spongiform encephalopathy (BSE) safety measures in Japan

Since the first identification of bovine spongiform encephalopathy (BSE) in Japan in September 2001, a series of safety measures was introduced by the Ministry of Agriculture, Forestry and Fisheries, the Ministry of Health, Labour and Welfare and the Food Safety Commission of the Cabinet Office. These measures included blanket BSE testing and removal of specified risk materials at slaughterhouses, surveillance of risk animals and a ban on the use of meat-and-bone meals and traceability on all farms. The Japanese experience over the past five years has shed light on several issues in countries that have a low BSE incidence.     

A case of spongiform encephalopathy ("cattle madness") in a cow in Switzerland

Spongiform encephalopathies occur in humans and several domestic animal species. Among them, the bovine spongiform encephalopathy (BSE) has aroused considerable interest because of a massive outbreak of this disease in Great Britain, which is thought to result from feeding meat and bone meal contaminated with the spongiform encephalopathy agent. We observed the first case of BSE in Switzerland, which is also the first case on the European continent. A 6 year old cow suffered from progressive neurological disease. On neuropathological examination typical spongiform changes and neuronal vacuolation were found. The origin of the infection remains unknown. It cannot be excluded that the animal was exposed to cattle feed derived from Great Britain. It is possible that additional sporadic cases may occur in Switzerland, an outbreak such as in England is unlikely to happen.