PSYC 415 -- Dr. King The Brain Eater (Nova, PBS, copyright 1998) I. "mad cow disease" - bovine spongiform encephalopathy (BSE) outbreak in England starting in the late 1980s A. symptoms (signs) 1. shaking 2. aggressiveness 3. loss of coordination II. Creutzfeldt-Jakob disease (CJD) A. a similar encephalopathy in humans - very rare B. signs 1. jerking movements 2. hallucinations 3. mutism 4. blindness 5. dementia C. BSE has apparently crossed the species barrier into humans to become a new variant of CJD - at the time this video was made, only a few cases were known; since then the number of cases worldwide has risen to 224 (see http://www.who.int/mediacentre/factsheets/fs180/en/ for the latest updates on this--this figure as of March 2011) 1. first described in the United Kingdom in 1996 2. always fatal with median age at death = 28; no known treatment 3. symptoms include rapidly progressing dementia, memory loss, personality changes, hallucinations, speech impairment, jerky movements, loss of balance and coordination, seizures 4. the chance of getting vCJD, even after eating contaminated meat, is low and you CANNOT get it through contact with an infected person (one possible case of transmission by blood transfusion has been reported) 5. as of June 2016 four cases have been confirmed in the U.S. (see http://www.cdc.gov/prions/vcjd/vcjd-reported.html for the latest updates on this) 6. the only way to confirm the presence of vCJD is at autopsy III. spongiform encephalopathies - [aka transmissible spongiform encephalopathies] A. Kuru - in Papua New Guinea (means "trembles with fear") 1. studied by Carleton Gajdusek - won Nobel Prize for his work (1976) 2. signs: incoordination, loss of balance, fatal within 9 months 3. transmitted by ritual cannibalism (eating of dead relative as ritual feasting) - the Kuru agent (prion) was contained in the brain and spinal cord, which was reserved mostly for women and children B. scrapie (sheep, goats) - a well known spongiform encephalopathy that may be the source of BSE C. BSE due to feeding of protein supplement made from infected cattle and sheep - since banned 1. has a very long incubation period (2-10 years) 2. no one knows to what extent infected beef products entered the food chain [but since there has been no widespread outbreak in the last ten years, apparently the risk is not very great] 3. US banned all British meat products in 1989 4. no evidence has been found of BSE in U.S. downer cows [no longer true - a few have been found in U.S. and Canada since the video] D. mink, bred for fur, are carnivorous; their feed contains remnants from sheep carcasses and downer cattle; they contracted spongiform encephalopathy apparently from this source E. British house cats contracted it from infected beef in pet food - called feline spongiform encephalopathy F. [not mentioned in the video] 1. fatal familial insomnia (in humans) - extremely rare 2. Gerstmann-Straussler-Scheinker Syndrome (a very rare neuro- degenerative disease) 3. chronic wasting disease (in North American deer, elk, and moose) 4. see http://www.cdc.gov/prions/ for more details G. prions 1. all known infectious agents contain nucleic acids (DNA or RNA) and are organisms that replicate via genetic mechanisms a. bacteria b. viruses c. fungi 2. prions do not - prion diseases work not by infection but by conversion 3. prions are proteins 4. they come in two forms: a naturally occurring form that exists in all brains, and an abnormal form 5. the abnormal form is extremely stable 6. when the abnormal form of the protein comes in contact with the normal form, the normal form is "converted" to the abnormal form - this involves a change in the shape of the protein molecule 7. accumulation of abnormal protein in the brain eventually leads to degeneration and spongiform encephalopathy IV. susceptibility may be genetically mediated A. the gene that makes the PrP protein has two alleles, which differ by codon for an amino acid - one codes for valine, the other for methionine 1. heterozygotes (who get one of each allele) are resistant 2. valine homozygotes are more susceptible 3. methionine homozygotes are most susceptible B. nobody knows how much infected material must be eaten to cause a human to get the disease or whether it can accumulate in the body over time V. (not in the video) there is now evidence that all/many degenerative diseases of the brain may be prion or prion-like diseases A. Alzheimer's disease has particularly been researched in this regard 1. https://www.ncbi.nlm.nih.gov/pubmed/15190676 (a 2004 publication) 2. http://www.scientificamerican.com/article/evidence-for-person-to- person-transmission-of-alzheimer-s-pathology/ 3. http://science.sciencemag.org/content/349/6248/1255555 B. these "prions" (if they exist) are not directly transmissible from person to person (i.e., it doesn't spread through contact, like a cold, but there is some concern that it could be spread via surgical instruments)