Sleeping sickness

Alternative names:

African trypanosomiasis

Definition:

An infectious parasitic disease carried by tsetse flies and characterized by inflammation of the brain and the covering of the brain (meninges).

Causes, incidence, and risk factors:

Sleeping sickness is caused by two organisms, Trypanosoma bruceri rhodesiense and Trypanosoma bruceri gambiense. Rhodesiense produces the most severe form of the illness.

After a person is bitten by an infected fly, the parasites multiply in the blood and lymph nodes. Parasites then invade the central nervous system (early with rhodesiense and later with gambiense) where they produce the symptoms typical of sleeping sickness.

A red painful swelling develops at the site of the fly bite, similar to that seen in Chagas disease. From this site of inoculation, the parasite invades the blood stream causing episodes of fever, headache, sweating, and generalized enlargement of the lymph nodes.

Ultimately the parasites invade the brain, causing first behavioral changes such as fear and mood swings followed by headache, fever, and weakness. Simultaneously the patient may develop myocarditis. Death may occur within 6 months from cardiac failure or infection if the person is infected with rhodesiense. Gambiense infection may require up to 2 years before symptoms of infection in the central nervous system appear. Gambiense-infected people develop drowsiness during the day but insomnia at night. Sleep becomes uncontrollable as the disease progresses until the patient becomes comatose.