Another group of diseases caused by a protozoan are the African sleeping sickness and Chagas’ disease.The protozoa identified in these diseases fall under the genus Trypanosoma. Trypanosoma brucei variety gambiense and rhodesiense produce African sleeping sickness, the Gambian and Rhodesian trypanosomiasis, while the Trypanosoma cruzi causes Chagas’ disease, responsible for South American trypanosomiasis, seen in South and Central America.

The African forms of trypanosomiasis are spread by the bite of the tsetse fly, genus Glossina. Chagas’ disease is transmitted by contamination of the bite wound of the assassin or kissing reduviid bugs, Triatoma and related reduviidae, with infected feces of the insect.

Symptoms, signs, and course- African trypanosomiasis is characterized by irregular fever, generalized lymphadenopathy, particularly the posterior cervical chain, cutaneous eruptions, and areas of painful localized edema. Central nervous system symptoms, such as tremors, headache, apathy, and convulsions, later predominate, and progress to coma and death. The Rhodesian trypanosomiasis is more severe and more often fatal than the Gambian type.

Acute Chagas’ disease occurs predominantly in young children and is characterized in the early stages by fever, lymphadenopathy, hepatosplenomegaly and facial edema. Rarely meningoencephalitis or convulsive seizures may occur, sometimes causing permanent mental or physical defects or death. Acute myocarditis is common and may be fatal. Chronic Chagas’ disease may be mild or even asymptomatic, or may be accompanied by myocardiopathy, megaesophagus, and megacolon, with fatal outcome. These late manifestations probably result from lymphocyte-mediated destruction of muscle tissue and nerve ganglions during the acute stage of the disease. In Brazil and Argentina the disease is often severe, while in Chile it is usually mild.

Diagnosis- the recognition of African trypanosomiasis depends on the demonstration of the trypanosomes. Early in the disease, they may be found in the smears of peripheral blood or in fluid aspirated from an enlarged lymph node. In the advanced stages, they may be found only in the cerebrospinal fluid. Chagas’ disease is identified by demonstration of trypanosomes in the peripheral blood or leishmanial forms in the lymph node biopsy, or by animal inoculation or culture, xenodiagnosis, or CF tests.

Prophylaxis against African trypanosomiasis includes protection against the vector tsetse flies, avoidance of endemic areas, or chemoprophylaxis. Pentamidine 4 mg/kg IM every 3 to 6 months confers a high degree of protection against the Gambian form of disease, but its use in the Rhodesian variety is controversial. Pentamidine may produce cryptic infections and causes diabetes. Residual spraying with benzene hexachloride 5% is most effective in controlling the vector.

Treatment- there is no satisfactory treatment of Chagas’ disease. Prolonged treatment with nifurtimox may result in parasitologic cure, however the organs damaged appears irreversible. Suramin is the drug of choice for both early Rhodesian and Gambian trypanosomiasis. Patients with severe neurologic involvement may develop a reactive encephalopathy when given melarsoprol.