Human Transmissible Spongiform Encephalopathies

Creutzfeldt-Jakob disease (CJD) is a rare and fatal human neurodegenerative condition characterized in most cases by a rapidly progressive dementia, myoclonus, and a periodic electroencephalogram (EEG). It is classified as a transmissible spongiform encephalopathy (TSE) because it causes characteristic spongy degeneration of the brain and can be transmitted to laboratory animals. TSEs also affect a range of animal species including sheep, goats, cows, deer, mink, and cats in nonexperimental conditions. CJD is by far the most common human TSE. It occurs sporadically in about 85% of cases, and is inherited in 10% to 15% of cases; the remaining cases are iatrogenic. The other human prion diseases are Gerstmann-Sträussler-Scheinker disease and fatal familial insomnia, both extremely rare hereditary disorders, and kuru, a disease seen in Papua New Guinea and acquired via ritualistic cannibalism. CJD occurs worldwide, but as systematic surveillance has only been undertaken in very few countries, its incidence in much of the world is currently unknown.