Sleeping sickness is 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, T. brucei rhodesiense and T. brucei gambiense. The more severe form of the illness is caused by rhodesiense.
After a person is bitten by an infected fly, a red, painful swelling develops at the site of the fly bite, similar to that seen in Chagas disease. From this site, the parasite invades the blood stream, causing episodes of fever, headache, sweating, and generalized enlargement of the 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.
Ultimately the parasites invade the brain, first causing behavioral changes such as fear and mood swings, followed by headache, fever, and weakness. Simultaneously, the patient may develop myocarditis.
Without treatment, death may occur within 6 months from cardiac failure, or from rhodesiense infection itself. 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.
Risk factors include living in those parts of Africa where the disease is found and being bitten by tsetse flies. The incidence is extremely low in the U.S. -- it is only found in travelers who have visited or lived in those African areas.
Signs and tests: A physical examination may show signs of meningoencephalitis (inflammation of the brain and meninges).
Tests include the following:
- Blood smear (demonstrates motile trypanosomes in blood)
- Lymph node aspiration (demonstrates motile trypanosomes in node material)
- CSF (demonstrates motile trypanosomes in cerebrospinal fluid)
- Low red blood cell count in blood
- Elevated globulin levels
- Low albumin levels
- Elevated ESR
- Antibody and antigen test are not very helpful
Expectations (prognosis): Untreated rhodesiense infection is almost universally fatal. Gambiense infection causes the classic "sleeping sickness" disease. Both diseases should be treated immediately upon diagnosis. The diseases are easier to treat during the blood-borne stage and more difficult to treat once meningoencephalitis develops.
Prevention: Pentamidine injections protect against gambiense, but have not yet been demonstrated as effective against rhodesiense. Insect control measures can help prevent the spread of sleeping sickness in areas where the disease is endemic.
