What is the nature of the problem?
In the late 1980s-early 1990s UK faced a unique public health challenge when a previously unknown disease called Bovine Spongiform Encephalopathy (BSE) emerged as an epidemic in British cattle. The disease, more popularly known as Mad Cow Disease, resulted in the infection of 170,000 cattle and the killing of 4.4 million cattle as a preventative measure to stop the spread of infection. The epidemic not only threatened the British cattle but also posed an exceptional threat to human health when the BSE agent jumped species leading to the development of New Variant Creutzfeld-Jacob disease (vCJD) in humans (Prusiner, 1997). This human form of BSE, which resulted from eating infected beef, was fatal with no known cure. Till date, over 100 people have died in Britain due to vCJD. Apart from health hazards, the epidemic of BSE and vCJD also proved to be disastrous for the UK beef trade. The UK government therefore faced multiple challenges - the need to ensure human safety from a novel and fatal disease, the need to contain the spread of BSE epidemic among British cattle and the need to protect the beef industry from huge economic losses. What is the hazard and the likely harm associated with it?
BSE is a neurodegenerative disease that affects cattle. It can be considered as a transmissible spongiform encephalopathy (TSE). The TSEs are a group of diseases caused by an infectious agent called prion. A prion is a specific type of abnormally folded protein which can be transferred from one host to another and can stimulate abnormal folding of other local prion proteins in the brain. This leads to a spongy degeneration of the brain and spinal cord. It takes 30 months to eight years for infected cattle to show signs and symptoms of BSE. The disease is invariably fatal, with no known cure or treatment. Cattle can become infected when they consume cattle feed containing contaminated meat and bone meal. Initially the British government believed that BSE was not transmissible to humans. But later substantial epidemiological evidence became available which indicated that humans can become infected with BSE agent due to consumption of infected beef or due to contact with other nervous tissue derivatives from infected cattle. In humans, the disease is known as vCJD. The hazard for humans was therefore BSE infected beef and the likely harm associated with it was development of vCJD. The hazard for cattle was animal feed prepared from BSE infected meat and bone meal and the likely harm associated with it was development of BSE. However, things were not so well defined at the beginning of the outbreak. Even now, there are various speculations in the scientific community regarding the nature of the disease, the infectious agent and the possible routes of transmission. Therefore, during the epidemic, decisions had to be taken on the basis of presumptions and the observed similarity with Scrapie, a better-understood spongiform encephalopathy of sheep, which is not transmitted to other species. What is the probability of the harm?
Till date there have been over 100 confirmed and probable cases of vCJD in UK. Scientists differ in their opinion about the magnitude of the human epidemic. Some scientists are of the view that the outbreak have already reached its peak and cannot get worse. Whereas, others believe that the epidemic has only started among the exposed population. They argue that owing to long incubation period of the disease thousands may start showing symptoms in the future (Plum, 1997). So, in humans the probability of developing vCJD was and is still high. In cattle the probability of developing BSE was high before the government took containment steps by banning animal protein in animal feed. Since 1986 when BSE was first detected in British cattle, incidence rose steadily till 1992-93 when three out of every 1000 cows had the...