Sleeping sickness (trypanosomiasis). Sleeping sickness is also known astrypanosomiasis because the etiologic agent is a protozoan belonging to the genusTrypanosoma. The species responsible for African sleeping sickness is T. brucei , which is transmitted by tsetse flies and infects the blood of patients. Headache, lassitude, tremors, and uncoordinated movements characterize infection of the nervous system. Blood smears reveal the trypanosomes, and drug therapy is available with pentamidine and suramin.
The South American form of sleeping sickness is also known as Chagas' disease.The etiologic agent is T. cruzi. This trypanosome is transmitted by triatomid bugs. The organisms affect the nervous system of patients as well as the heart tissue. Often they destroy the nerve ganglia of the heart and cause severe heart disease.
Slow-developing diseases. Other diseases of the nervous system are believed due to viruses that have not yet been isolated. An example is kuru, a slow-developing disease observed in South Pacific peoples. Kuru is called a “slow virus disease” because the symptoms, which include nervous tremors, take over a year to appear. Similar diseases are Creutzfeldt-Jakob disease, scrapie (in goats and sheep), bovine spongiform encephalopathy (the “mad cow disease”), and a number of other diseases possibly caused by prions. Prions are protein particles that do not appear to have nucleic acid associated with them.