1.  Foreign Sources of Infection To − Vi Nguyen

2. Foreign Infection  Preventable environmental source of infection  Remove infectious material, epidemic outbreaks disappear  Ex. BSE & Kuru

4. Infectious Forms of Prion Diseases in Humans  Kuru  Iatrogenic CJD  ddVariant CJD

5. Kuru  Fore tribe from Papua New Guinea transmitted kuru through ritualistic cannibalism  Ate dead relatives  Only exposed to infectious agent if they consumed or came in contact with brain tissue or spinal fluid

6. Iatrogenic  Prion tainted human growth hormone and gonadotropin  Dura mater grafts  Transplants of corneas obtained from people who died of CJD  Neurosurgical procedures in which ineffectively sterilized depth electrodes or instruments were used

7. vCJD  Results from prions being transmitted from cattle with BSE to humans through consumption of contaminated beef products  All vCJD individuals were identified to express methionine methionine homozygously at codon 129  Except a single case of vCJD in a patient who was heterozygous at codon 129  Raised possibility of a second wave of BSE related deaths

8. Spread of BSE  Late 1970s, hydrocarbon solvent extraction method used in rendering offal was abandoned  Resulted in meat and bone meal with a much higher fat content  Fed to cattle, sheep, pigs, and chickens  Allowed scrapie prions from sheep or low levels of bovine prions generated sporadically to survive the rendering process  Resulted in widespread infection of cattle

9. CWD  White tailed deer and elk have developed CWD  Only prion disease known in free ranging animals

16. Genetics vs. Environment  1930 High incidence of familial CJD in some families was known  60 more years would pass before significance was appreciated  Once shown to be an infectious disease, little attention was paid to the familial form of the disease  How do you think the course of scientific investigation might have proceeded had transmission studies not been performed until after the molecular genetic lesion was discovered?

17.  If we discovered the molecular genetic lesion before the transmission studies were performed, the prion concept may have been more readily accepted  Prion concept explains how a single disease can have a genetic or infectious etiology  Because the transmissibility was discovered first, there was more skepticism as to whether prions were a whole new infectious agent