BSE to CJD?
Few animal diseases have caught public attention more than what came to be known as Mad Cow Disease. Bovine Spongiform Encephalopathy, or BSE for short and for those who struggle with the full scientific description, was first seen in the United Kingdom in 1986. TV footage of cattle staggering and collapsing in pens and yards fed media and public horror and concern for what was, at first, an unexplained yet spreading condition in the UK national herd. The epidemic lasted six years with over 180,000 cases confirmed in the UK between November 1986 and November 2002.
Although by far the most cases have been diagnosed in the UK, BSE is
undoubtedly present in many countries around the world and, says Andrew Speedy
of FAO's Animal Production and Health Division, the fact that BSE has not been
confirmed in a country may well be because of a failure to look for and dentify
the disease rather than because it is absent. Since 1989, when the first case
was reported outside ithe UK, BSE has been confirmed in much of western and
eastern Europe, and in Canada, Israel, Japan and Oman, with the greatest
concentration, outside of UK, in France, Germany, Ireland, Spain and
Switzerland.
The disease affects the brain and spinal cord of cattle, and the causal agent is thought to be a self-replicating protein, known as a prion. This is highly stable and capable of surviving freezing, drying and heating to temperatures used for pasteurising and sterilizing animal products. It was the feeding to cattle of offal from affected animals, rendered into meat and bone meal, that spread the infection. Although the disease has a long incubation of four to five years, it usually proves fatal within weeks of the typical symptoms manifesting themselves.
High and low risk countries
The countries at greatest risk from BSE are those where cattle are fed
intensively with supplementary protein feeds and where animal protein, derived
from slaughtered livestock has been used. However, BSE has also been introduced
to countries, including Canada and Oman, though the importation of animals
already infected. African, Asian and Latin American countries are also at risk,
albeit at lower risk, either because there have been imports of infected feed
or cattle. And the potential for BSE to develop in these countries is greater
because, for the most part, it is these countries where there is little or no
monitoring or testing for the disease. "In Africa, Asia and Latin America
slaughter arrangements are very varied but it is important that they comply
with and implement basic requirements for good practices and hygiene. This is
particularly the case for meat that is intended for export from Africa to
Europe", urges Andrew Speedy. Among the requirements of good practice are
that materials from the brain and spinal cord of animals should not enter the
human food chain and neither should such material be used in any way for animal
feeds.
A further concern related to BSE has been the diagnosis of what has been termed 'the human form of BSE', Creutzfeldt-Jacob disease (CJD), which may arise as a result of consuming BSE infected meat. Hence, the categorisation of BSE as a zoonosis. There appears to be a genetic predisposition in some humans to CJD. Additionally, a small number of cases may have developed as a result of surgical contamination or cornea transplants. A variant form of CJD, vCJD, appears to affect younger people. The symptoms and mortality resulting from both forms of CJD are extremely distressing.
BSE is a disease that should not have been permitted to develop and spread since, with hindsight, the feeding of animal offals to ruminants was inappropriate. Now that the disease and its modes of transmission are understood, it remains for all governments to institute the appropriate procedures for monitoring and testing for the disease, and to implement improved slaughter, inspection and processing for meat, particularly meat for export. And, of course, to prohibit the sale of body parts and processed produce, originating as brain or spinal tissues, for animal feed or human food.
