The human trypanosomiases are vector‐borne tropical diseases that occur in tropical Africa and South America and are caused by parasitic protozoa. Human African trypanosomiasis (or sleeping sickness) is caused by two subspecies of Trypanosoma brucei and is transmitted by the bite of the bloodsucking tsetse fly. Chagas disease occurs in Latin America and is caused by Trypanosoma cruzi. This parasite is transmitted by triatomine bugs, which acquire infection by feeding on infected blood, but pass the parasites on to the next host via their infected faeces. The human trypanosomiases are zoonoses and a range of wild and domestic mammals can act as reservoir hosts for the parasites. There are no vaccines for these diseases and control relies on case treatment and limiting opportunities for transmission.

Key Concepts:

  • African human trypanosomiasis or sleeping sickness and Chagas disease in Latin America are caused by insect‐borne, parasitic trypanosomes, but the diseases and the parasite life cycles are completely different.

  • Control of the trypanosomiases relies on treatment of human patients and reduction of transmission, largely achieved through killing the insect vectors.

  • The human trypanosomiases are zoonotic diseases and a range of wild and domestic mammals act as reservoir hosts for the parasites.

  • Vector borne diseases with animal reservoirs have complex epidemiology and are difficult to control.

  • Eradication of human African trypanosomiasis in West Africa seems likely if current treatment, surveillance and tsetse control measures are maintained.

  • Animal reservoir hosts are more important in maintaining human trypanosomiasis in East Africa than West and Central Africa.

  • Eradication of Chagas disease is thwarted by the longevity of infection in humans and circulation of the parasite in a wide range of animal reservoir hosts.

Keywords: parasite; tsetse fly; antigenic variation; sleeping sickness; Chagas disease

Figure 1.

(a) Two morphological forms (long slender and short stumpy) of Trypanosoma brucei in a thin blood smear stained with Giemsa. (b) The essential features of the trypanosome cell. The length of long slender trypanosome from posterior to tip of free flagellum is approximately 35 μm.

Figure 2.

The tsetse fly, Glossina morsitans, feeding on a crocodile. The needle‐like proboscis, here piercing through the skin, is usually held in the protective sheath pointing forward from the head. At rest, the wings are crossed over the back of the fly. Length of fly from head to tip of abdomen is 8–10 mm. Magnification ×55. Reproduced with permission from Dr Joseph McNamara; photographer Mr John Conibear, University of Bristol.

Figure 3.

The life cycle of (a) Trypanosoma brucei and (b) Trypanosoma cruzi.



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Nash TAM (1969) The Tsetse Fly: Africa's Bane. London: Collins.

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Gibson, Wendy(Aug 2011) Trypanosomiases. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1002/9780470015902.a0001957.pub3]