Bovine Spongiform Encephalopathy
Bovine spongiform encephalopathy (BSE) is a relatively new disease found
primarily in cattle.
This disease of the bovine breed was first seen in the United
Kingdom in November 1986 by histopathological examination of affected brains
(Kimberlin, 1993) .
From the first discovery in 1986 to 1990 this disease
developed into a large-scale epidemic in most of the United Kingdom, with very
serious economic consequences (Moore, 1996).
BSE primarily occurs in adult cattle of both male and female genders.
most common age at which cows may be affected is between the ages of four and five
Due to the fact that BSE is a neurological disease, it is
characterized by many distinct symptoms: changes in mental state 'mad-cow',
abnormalities of posture, movement, and sensation (Hunter, 1993).
The duration of
the clinical disease varies with each case, but most commonly lasts for several
BSE continues to progress and is usually considered fatal (Blowey, 1991).
After extensive research, the pathology of BSE was finally determined.
Microscopic lesions in the central nervous system that consist of a bilaterally
symmetrical, non-inflammatory vacuolation of neuronal perikarya and grey-matter
neuropil was the scientists' overall conclusion (Stadthalle, 1993).
are consistent with the diseases of the more common scrapie family.
further investigation, the conclusion was made that BSE was a new member of the
scrapie family (Westgarth, 1994).
Transmission of BSE is rather common throughout the cattle industry.
the incubation period of one to two years, experimental transmission was found
possible by the injection of brain homogenates from clinical cases (Swanson, 1990).
This only confirmed that BSE is caused by a scrapie-like infectious agent.
How does the transmission become so readily available among the entire United
Kingdom feedlot population?
Studies showed that the mode of infection was meat and
bone meal that had been incorporated into concentrated feedstuffs as a protein-rich
supplement (Glausiusz, 1996).
is thought that the outbreak was started by a scrapie infection of cattle, but the
subsequent course of the epidemic was driven by the recycling of infected cattle
material within the cattle population (Lyall, 1996).
Although the average rate of
infection is very low, the reason why this led to such a large number of BSE cases
is that much of the United Kingdom dairy cattle population was exposed for many,
continuous years (Kimberlin, 1993).
To help control the outbreak, the British government in 1988 introduced a ban
on the feeding of ruminant protein to other ruminant animals (Lacey, 1995).
knowledge for the pathogenesis of the BSE disease shows precisely the actions that
must be taken in order to control and minimize the risk of infection in healthy
cattle around the world (Darnton, 1996).
The appearance of BSE has made a sizable impact throughout much of the world