Mad cow disease and human health
Variant CJD was a surprising disease, as it acted like CJD, but affected young people more than the typical age group, the elderly. The fact that it crossed the barrier between cows and humans was a sinister warning that it could be more dangerous than scrapie or classical CJD.
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Early warnings that BSE might be transmissible to humans were, in fact, observed by scientists and government officials throughout the period from 1986 (the time of first diagnosis in cattle) to 1995 (when vCJD was first observed in humans). Such observations are noted in, for example, the minutes of a meeting of the National Institute for Biological Standards and Control in May 1988, where the probability of transmission of BSE to humans is assessed as more than remote. The diagnosis in 1990 of a domestic cat with a previously unknown spongiform encephalopathy resembling BSE indicated that the disease could infect a wider range of hosts. Responses to such early warnings of potential dangers to human health were either too weak or came too late. This may have been partly a result of an ‘unwillingness to know’ due to the economic harm this knowledge would cause the UK beef industry. (Cleeland)
"By the end of winter in 1996, more evidence had emerged that a novel subset of CJD was striking young people. The CJD Surveillance Unit counted ten cases since 1994 (including Vicky Rimmer), and eight of the victims had died by early 1996... Another clue that a new disease had emerged lay in the neuropathology. In Stephen Chuchill's brain, neurons had died off and spongy holes had appeared... What was puzzling in Stephen and other young victims were the "floral" plaques around the holes formed in the brain, particuraly within (Yam, 128-129) |
In the early stages patients often present with personality changes and psychiatric symptoms such as depression or withdrawal. Psychiatric symptoms are often the most prominent feature early in vCJD, but dementia develops later. The motor symptoms of vCJD (stumbling, falls and difficulty walking) also tend to appear earlier in vCJD than in classic CJD. The estimated incubation period is 5 to 40 years, and the duration of illness is typically 12-14 months after signs and symptoms appear. vCJD affects people in their 20s, much earlier in age than people with sporadic CJD. One person with variant CJD has been identified in the United States and one in Canada, however, both lived in the UK during the BSE epidemic and contracted their illness from exposure in the UK. (UCSF)
The UK was brought under criticism for not acknowledging the possibility of a threat to humans, but prions as a whole had been undergoing research and redevelopment of their causes for decades. CJD had been known to scientists and doctors much longer than this atypical form, so many were rushing to find whether BSE was the cause of these mysterious deaths.
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Food is not the only source an unlucky few proved. iCJD, iatrogenic form of CJD, passed from human to human via surgery and organ donation, such as through cornea transplants (Yam, 188). Another surprising, but on observation a rather obvious source, was human growth hormones, since human cadavers were needed before synthesizing the molecule took its place.
"To compensate for his under-active pituitary, the patient began daily growth hormones... He began to suffer from dizziness that spring, and by September had progressed to slurred speech and incoordination." (Yam, 189) |