Creutzfeldt-Jakob disease in Louisiana, 1980-2006.

Transmissible spongiform encephalopathies (TSEs) are diseases thought to be caused by mutant cellular proteins found in mammalian nerve tissues. This family of diseases is known to affect a variety of animals, including: sheep (scrapie), cattle (bovine spongiform encephalopathy), mink (transmissible mink encephalopathy), deer and elk (chronic wasting disease), and humans (GerstmannStraussier-Scheinker syndrome, Fatal Familial Insomnia, kuru, sporadic or familial CreutzfeldtJakob disease, and variant Cruetzfeldt-Jakob disease). In the early 1980s, Stanley Prusiner proved that these diseases could be transmitted by a protein (prion protein or PrP) isolated from nervous tissue of infected animals. No nucleic acid was found to be associated with infectivity, ruling out bacteria, viruses, and fungi as the causative agent of disease. Prusiner won a Nobel Prize in 1997 for his discovery of a new class of disease-causing agents. Also in the 1980s, an epidemic of bovine spongiform encephalopathy (BSE) was described in Great Britain. Over 180,000 BSE cases among cattle have been identified since its discovery in 1986. Current thinking suggests that BSE arose from a change in cattle feeding practices in Great Britain in the late 1970s and 1980s. The BSE epidemic seems to have originated in Great Britain but has been identified in cattle from over 20 countries since it began. A new type of encephalopathy affecting humans was identified in Great Britain in 1994. This disease resembled sporadic or familial CJD (sCJD) and was named new variant CJD, or vCJD. Symptoms of sCJD and vCJD share some commonalities. In most people, illness onset is marked by some sort of neurological abnormality. This can range from blurred vision to slight memory loss to gross hallucinations. Dementia is always present in the disease. Patients suffer memory loss, mood changes, and judgment errors. They may lose interest, become apathetic or irritable, experience sleep disorders, intellectual decline, and disorientation. They may also experience tremors, problems with coordination and gait, and loss of motor control. In some patients, the cerebellar and visual abnormalities predominate. At the end of the disease, patients are mute, stuporous, spastic, and rigid. The disease rapidly progresses with death occurring in six months with sCJD and in 14 months for vCJD. The incidence rate of sCJD varies by geography, but ranges from 0.3 to 1 case per million people per year, with an US average of about 0.9 cases per million people per year. Most cases of sCJD are thought to arise from a spontaneous mutation in the wildtype form of PrP protein found on cell membranes. Mutations favoring sCJD development have been identified and can be inherited or arise spontaneously. Sporadic CJD can also be passed nosocomially and iatrogenically. In the past, patients have been infected through contaminated corneal transplants and through use of contaminated surgical instruments during neurosurgery. In contrast, vCJD cases are believed to result from ingestion or inoculation of BSE infected material. A total of 194 vCJD cases have been identified worldwide to date.