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Biology

Causal Agent:

The protozoan parasite, Trypanosoma cruzi, causes Chagas disease, a zoonotic disease that can be transmitted to humans by blood-sucking triatomine bugs.

Life Cycle:

Life cycle of Trypanosma cruzi

An infected triatomine insect vector (or "kissing" bug) takes a blood meal and releases trypomastigotes in its feces near the site of the bite wound. Trypomastigotes enter the host through the wound or through intact mucosal membranes, such as the conjunctiva The number 1. Common triatomine vector species for trypanosomiasis belong to the genera Triatoma, Rhodnius, and Panstrongylus. Inside the host, the trypomastigotes invade cells near the site of inoculation, where they differentiate into intracellular amastigotes The number 2. The amastigotes multiply by binary fission The number 3 and differentiate into trypomastigotes, and then are released into the circulation as bloodstream trypomastigotes The number 4. Trypomastigotes infect cells from a variety of tissues and transform into intracellular amastigotes in new infection sites. Clinical manifestations can result from this infective cycle. The bloodstream trypomastigotes do not replicate (different from the African trypanosomes). Replication resumes only when the parasites enter another cell or are ingested by another vector. The “kissing” bug becomes infected by feeding on human or animal blood that contains circulating parasites The number 5. The ingested trypomastigotes transform into epimastigotes in the vector’s midgut The number 6. The parasites multiply and differentiate in the midgut The number 7 and differentiate into infective metacyclic trypomastigotes in the hindgut The number 8.

Trypanosoma cruzi can also be transmitted through blood transfusions, organ transplantation, transplacentally, and in laboratory accidents.

Life cycle image and information courtesy of  DPDx .

 

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