BSE and vCJD: Their biology and management
BSE and vCJD: Their biology and management

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BSE and vCJD: Their biology and management

1.2 BSE

In December 1984, it was noticed that a cow on a Sussex farm was displaying head tremors and loss of coordination. The animal died in February 1985. The vet regarded this case as sufficiently serious for a post-mortem examination to be necessary. In September 1985, a government pathologist confirmed that the cause of its death was a type of disease known as a spongiform encephalopathy. Spongiform encephalopathies (i.e. 'spongy brain diseases') are so called because, on post-mortem examination, brain cells can be seen under the light microscope to contain fluid-filled cavities giving them a spongy appearance (see Figure 4). Other cattle showed similar symptoms and, in a paper published in the peer reviewed scientific journal The Veterinary Record in 1987, bovine spongiform encephalopathy (BSE) was formally recognised as a new disease in cattle. [C]

Because BSE is invariably fatal, cattle displaying its symptoms are usually killed without delay. Affected animals lose weight and the milk yield declines in dairy cattle. However, the most conspicuous and distinctive symptoms of the disease are walking extremely awkwardly, increased nervousness and altered behaviour or temperament (such as kicking during milking). BSE therefore soon became known in the news media and elsewhere as 'mad cow disease'.

(By the way, did you note down the letter E when you read the above paragraph? Although cattle displaying symptoms of BSE are usually killed immediately, this is not a policy applied to humans who contract fatal diseases. This could therefore be described as an ethical issue.)

Question 1

Why might journalists and others choose to refer to BSE as 'mad cow disease' rather than use the disease's proper scientific name? Suggest some advantages and disadvantages of this approach to communication. [C]

Answer

The expression 'bovine spongiform encephalopathy' doesn't exactly trip off the tongue! Furthermore, it includes neither of the keywords - 'cow' and 'disease' - that would aid effective communication with non-specialists because of shared understanding of the terms. In the early days of the disease, the abbreviation 'BSE' would have been relatively unfamiliar and so could not normally have been used without explanation. The phrase 'mad cow disease' is dramatic, memorable and clearly indicates that a cattle disease is being discussed. Within a short while, it had gained such currency that reports tended to explain that mad cow disease was also known as BSE rather than the other way around. The ensuing loss of scientific precision probably didn't matter too much - at least until we started to read of 'the human form of mad cow disease'.

During the late 1980s and early 1990s, BSE developed to epidemic proportions and considerable economic significance in the UK. The number of cases per annum grew quite rapidly for several years before steadily declining (Figure 1) as increasingly severe precautionary measures were taken to control the disease. (Later in this course we will examine some of these control measures and their effectiveness.) By 2004, a total of over 180 000 BSE cases had been reported.

Figure 1
Figure 1 The number of cases of BSE reported in the UK to 2004

Question 2

In which year did the number of BSE cases reported in the UK peak?

Answer

1992.

Question 3

Approximately how many BSE cases were reported in that year?

Answer

37 000.

In due course, BSE also appeared - and occasionally still continues to appear - in other countries. By mid-2004, 24 countries (Figure 2) had reported cases. Moreover, scientists working for the European Commission (EC) believed that BSE is 'highly likely' in eight more countries and 'cannot be excluded' from seven others. Many other countries have not allowed the EC scientists to assess the likelihood that they too have BSE. Nevertheless, BSE is unlikely to flare up again as a major problem in cattle anywhere in the world where vigilance is maintained.

Figure 2
Figure 2 Countries that had at least one reported case of BSE by mid-2004

Spongiform encephalopathies are often referred to as transmissible spongiform encephalopathy (TSE) diseases. Transmissible means that they can cause disease only if they gain access into a new host (e.g. through injection or by being ingested). In contrast, contagious diseases require physical contact between animals and, strictly speaking, infectious diseases can be transferred only by the airborne route.

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