Microbes and Diseases Chapter 02

CREUTZFELDT-JAKOB DISEASE Prion

Spongiform Encephalopathies Implicated in chronic, persistent disease in humans and animals Brain tissue removed from affected animals resembles a sponge

Etiology Caused by prions –Distinct protein fibrils deposited in brain tissue of affected animals – Protein composition of prions has revolutionized ideas of what can constitute an infectious agent Several animals are victims of similar diseases: – Scrapies: Sheep, mink elk – Bovine spongiform encephalopathy: cows (which is strongly shown to be related to variant CJD in humans)

Epidemiology 1 to 2 cases per 1 million people in US Exact mode of infection is unknown Scientists still do not know how prions replicate given that they have no nucleic acid Transmissible by an unknown mechanism for classic CJD or by ingesting infected meats for variant CJD – Variant form most linked with BSE

Risk Factors for Travelers From 1995 – August, 2006: – UK had the highest incidence – 162 cases – France – 20 cases – Ireland – 4 cases – US – 2 cases – Canada, Italy, Japan, Netherlands, Portugal, Saudi Arabia, Spain – 1 case each

Symptoms & Severity Affects the central nervous system of humans Causes gradual degeneration leading to dementia and, eventually, death – Illness normally progresses to death within 4 -5 months for classic CJD and 13 – 14 months for variant CJD

Prevention Surveillance, culling of sick herds, and banning of high risk materials have been very effective in countries at risk for BSE and CJD Avoid beef or beef products altogether when visiting countries with history of BSE or CJD

Treatment Supportive care only – No known treatments have shown any effectiveness