When a prion particle infects an animal brain, it causes the normal brain protein (PrPc), which is relatively resistant to protease digestion, to change to an abnormal form of accumulated fibrils. When enough normal protein cells have been altered, disease results as a progressive destruction of brain cells, forming a sponge-like pattern of holes. Among these spongiform diseases are: “mad cow” and Creutzfeldt-Jakob. Kuru is another form of the disease that occurs when the infecting prions are spread through the ritual cannabalism.
SSPE (subacute sclerosing panencephalitis) is a very rare and slow viral infection of the brain, caused by a defective measles virus, taking years to manifest itself. Other members of the group include:
- progressive rubella panencephalitis, caused by the German measles virus;
- kuru, a fatal disease of cannibals in New Guinea;
- Creutzfeld-Jakob disease, a form of the “mad cow disease.”
All have two things in common.
- The disease starts long before the first symptoms appear.
- The infectious agents are defective or unconventional in some way.
SSPE was first described in 1933. US patients were typically rural adolescents from the southeastern states. Because the disease started with emotional and behavioral changes, the teens were thought to be going through adjustment difficulties. But, after several months, such other symptoms as visual disturbances, and walking and memory problems began to appear. Later, they would lapse into a coma and die. Attempts to isolate or culture the causitive agent was not successful until 1969, when the defective form of the measles virus was isolated from the brains of SSPE patients. This mutant microbe is so rare that it occurs in about one out of a million cases.
See this article for a possible cause.