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Trypanosoma Cruzi
Laboratory Diagnosis
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peripheral blood smear, stained with Giemsa stain or Microhematocrit containing acridine orange as a stain
Novy, MacNeal and nicolle(NNN) medium or its modifications are used for growing T. cruzi
Animal inoculation: Guinea pig or mice inoculation may be done with blood, CSF, lymph node aspirate
Xenodiagnosis: The reduviid bugs are reared in a trypanosome-free laboratory and s tarved for 2 weeks. They are then fed on patient's blood. If trypomastigotes a re ingested, they will multiply and develop into epimastigotes and trypomastigotes, which can be found in the feces of the bug 2 weeks later.
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Molecular diagnosis: Electrocardiography (ECG), PCR and Endoscopy
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History and Distribution
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Carlos Chagas, investigating malaria in Brazil in 1909, accidentally found this trypanosome in the intestine of a triatomine bug and then in the blood of a monkey bitten by the infected bugs.
Chagas named the parasite T cruzi after his mentor Oswaldo Cruz and the disease was named as Chagas disease in his honor.
Habitat
In humans, T cruzi exists in both amastigote and trypomastigote forms
In reduviid bugs, epimastigote forms are found in the midgut and metacyclic trypomastigote forms are present in hindgut and feces.
Amastigotes are the intracellular parasites. They are found in muscular tissue, nervous tissues and reticuloendothelial tissues.
Morphology
Amastigote
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Morphologically, it resembles the amastigote of Leishmania spp., hence, it is frequently called as Leishmania form
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This form is found in muscles, nerve cells and reticuloenodothelial systems.
Trypomastigote
In stained blood smears, they are shaped like alphabet "C'';" U'';o r "S'; having a free flagellum.
These forms do not multiply in humans and are taken up by the insect vectors.
In the blood, they appear either as long, thin flagellate about (20 mcm long) or short stumpy form (15 μm long).
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Epimastigote form
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Found in the insect vector, the reduvid bug
Life Cycle
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Infective form
The vectors important in human infection are the reduviid bugs adapted to living in human habitations, mainly Triatoma infestans
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found in feces of reduviid bugs. The metacyclic trypomastigotes introduced in human body by bite of reduviid bugs invade the reticuloendothelial system and spread to other tissues
After passing through promastigote and epimastigote forms, they again become trypomastigotes, which are released into the bloodstream and are the infective stage for triatomine bug.
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