African sleeping sickness takes its name from a disturbance in the normal circadian rhythm (sleep-wake cycle) during the second stage of the infection. When the disease moves from the blood and lymphatic system into the central nervous system, the infected person may experience insomnia during the night and drowsiness during the day. Two different protozoa of the Trypanosoma genus cause this parasitic disease. The National Institutes of Health identifies these subspecies as Trypanosoma brucei rhodesiense and Trypanosoma brucei gambiense.
Trypanosoma Brucei Gambiense
Infection by this parasite causes West African or Gambian sleeping sickness. In most cases, it enters the human body through the bite of a tsetse fly, a grayish-brown insect the size of a honey bee. The fly picks up the parasite through the blood of an infected human or animal. The tsetse fly exists only in rural parts of Africa, and transmission of this strain of the disease occurs where the fly is endemic, in certain areas of central Africa and a smaller number of regions in West Africa. There, tsetse flies live in locations with heavy vegetation near waterholes and along river banks, and they bite during the day. The CDC notes that most reported cases come from seven countries: the Democratic Republic of Congo, Angola, Sudan, Central African Republic, Republic of Congo, Chad and northern Uganda.
Trypanosoma Brucei Rhodesiense
Trypanosoma brucei rhodesiense causes East African or Rhodesian sleeping sickness, which occurs in areas of eastern Africa and in some southeastern parts of the continent. A parasite-carrying tsetse fly also transmits this form of the disease. In the affected areas of eastern and southeastern Africa, tsetse flies live in savanna lands or forested locations. The CDC reports that Uganda, Tanzania, Malawi and Zambia account for at least 95 percent of all reported cases of this variety.
Congenital and Bloodborne Causes
The CDC reports that on rare occasions, a pregnant woman infected with West African sleeping sickness may cause infection in her baby. Infection occurs when the parasite passes from her body to that of the unborn child. A blood donation from a person infected with the parasite may cause infection in the recipient of a blood transfusion. Another rare cause of sleeping sickness, as noted by the Directors of Health Promotion and Education, is an organ transplant from an infected donor.
References
- National Institutes of Health: Sleeping Sickness
- The Centers for Disease Control: West African trypanosomiasis
- University of Southern Carolina School of Medicine: Microbiology and Immunology Online
- The Centers for Disease Control: East African trypanosomiasis
- Directors of Health Promotion and Education: African Trypanosomiasis
