Mad cow epidemic

Baeten, V. and Dardenne, P. (2001) The contribution of near infrared spectroscopy to the fight against the mad cow epidemic. NIRS News 12(6), 12-13. 

The human population has been seeded to an unknown extent with latent infectious prion protein from the mad cow epidemic (Enserink, 2005) and possibly also from the CWD epidemic now underway in deer and elk. 

Because of the economically catastrophic mad cow epidemic and the ensuing risk to humans, intense research has been brought to focus on prions and the corresponding TSEs. Likewise, basic research on the normal prion protein has accelerated. 

The central issue in the progression of disease is how PrP = propagates itself from the source of exposure (food) to the brain. In the examples provided by kuru, the recent mad cow epidemic in the United Kingdom, and the resultant transmission of vCJD to humans, the common link is that infectious prions in contaminated food reached the brain by some mechanism, and once in the brain, seeded the conversion of native host PrP to an infective PrP conformation. 

Let us review. Escape from restriction is the commonest causes of epidemics by really new epidemics encountered so far in prehistorical and historical time. It might typically involve a mutation which, for example, overrides the immune system of a new host or permits entry into the cell of the new host. There are some 60 well-known zoonotic examples, if not exactly running from A to Z, certainly from Acinetobacter pneumonia to Yersiniosis that infect humans. The Z disease if it comes, may be aptly named the analogous Greek letter omega has been used in many science fiction stories for the ultimate bacterial or viral disease The Omega Man was a film in which Charlton Heston played the last uninfected man on Earth. Recent real-life examples include the recent outbreak in Toronto of bird flu (from Asian water birds), SARS (from the civet, etc.), anthrax (sheep), ebola (from rodents), and acquired CJD (sheep, mad cow). 

Human TSEs are rare but include the Creutzfeldt-Jacob disease (CJD), Gertstmann-Straussler-Scheinker (GSS) disease, and famihal fatal insomnia. All three human diseases appear to have both familial and sporadic occurrence, and appear to be different manifestations of pathology of the same prion protein. Kuru is the human disease caused by ritual cannibalism of brain. Similarly, human vCJD appears to have originated in the mad cow BSE epidemic in the United Kingdom. The hypothesis... 

All evidence points to TSEs as a family of related diseases caused by the same homologous prion protein in all species (see reviews by Brown, 2005 Soto, 2006 Watts et al., 2006). Some comfort can be taken that the sporadic occurrences of TSEs are rare in all species and in human populations however, it is equally clear from recent events that a persistent threat of epidemics of TSEs exists. Such epidemics have potentially enormous consequences, such as the economically catastrophic epidemic of mad cow disease in the United Kingdom. Thus far, there is no early diagnosis during the long period of latency, although current research is demonstrating the possible presence of infectious prion protein in tissues at some time before clinical symptoms appear. 

The epidemic of mad cow disease that resulted in the loss of upwards of 200,000 cattle apparently arose due to feeding cattle a meal that contained contaminated neural tissue. Animal feed containing nervous tissue is considered to be the source of prion diseases occurring in sheep and goats. There also appears to be cross-infectivity between species, as scores of humans have contracted a variant form of Creutzfeld-Jakob disease (vCJD) from eating contaminated beef " ... 

Not listed in Box 25.2 is the zoonosis arising from bovine spongiform encephalopathy (BSE), or mad cow disease . There is no conclusive evidence that the transmissible spongiform encephalopathies of man are acquired from animals, but the occmrence of so-called new variant Creutzfeld Jakob disease in man that has coincided with an epidemic of mad cow disease in cattle and related species has led to the... 

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