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American trypanosomiasis

T.cruzi occurs widely in both reduviid bugs and a broad spectrum of reservoir animals in North, Central, and South America.


Trypanosoma cruzi is a pleomorphic trypanosome that includes an additional form of amastigote in its life cycle. The vector for transmission are reduviid bugs.

Pathogenesis

During the acute phase, the organism occurs in blood as a typical trypomastigote and in the reticuloendothelial cells as a typical amastigote. The amastigotes can kill cells and cause inflammation, consisting mainly of mononuclear cells. Cardiac muscle is the most frequently and severely affected tissue. In addition, neuronal damage leads to cardiac arrhythmias and loss of tone in the colon (megacolon) and esophagus (megaesophagus). In the chronic phase, the organism persists in the amastigote form.

Epidemiology

T.cruzi occurs widely in both reduviid bugs and a broad spectrum of reservoir animals in North, Central, and South America. Human disease is found most often among children in South and Central America, where there is direct correlationbetween infected wild animal reservoir hosts and the presence of infected bugs whose nests are found in human dwellings.

Clinical features

Chagas’ disease may be asymptomatic acute or chronic disease. One of the earliest signs is development at the site of the bug bite of an erythematous and indurated area called a chagoma. This is often followed by a rash and edema around the eyes and face; in young children frequently an acute process with CNS involvement may occur. Acute infection is also characterized by fever, chills, malaise, myalgia, and fatigue. 
The chronic Chagas’ disease is characterized by hepatosplenomegaly, myocarditis, and enlargement of the esophagus and colon as a result of the destruction of nerve cells (E.g. Auerbach’s plexus) and other tissues that control the growth of these organs. Involvement of the CNS may produce granulomas in the brain with cyst formation and a meningoencephalitis. Death from chronic Chagas’ disease results from tissue destruction in the many areas invaded by the organisms, and sudden death results from complete heart block and brain damage.

Laboratory diagnosis

Examine thin or thick stained preparations for trypomastigotes. Wet preparations should also be examined to look for motile organisms that leave the blood stream and become difficult to find. Biopsy of lymph nodes, liver, spleen, or bone marrow may demonstrate organisms in amastigote stage.

Immunity




Unlike African trypanosomiasis, the antigenic variation is less common in T.cruzi infection. Therefore, the humoral and cellular immune responses function in the immune system.

Treatment

The drug of choice is nifurtimox. Alternative agents include allopurinol and benzimidazole.

Prevention

• Bug control, eradication of nests
• Treating infected person & exclusion of donors by screening blood.
• Development of vaccine.


American trypanosomiasis American trypanosomiasis Reviewed by gafacom on November 27, 2019 Rating: 5

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