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Morphology and life cycle of T. cruzi

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The parasite undergoes several morphological changes during its development that involve changes in size, shape and position of the kinetoplast relative to the nucleus. Its life cycle involves three morphologically differentiated stages: amastigote, epimastigote y trypomastigote.

The amastigote is round and does not possess a flagellum. It is intra-cellular and they are able to multiply within the macrophages of the host and develop as flagellate trypomastigotes.

 

 

The epimastigote is extra-cellular in lives in the bug. If a trypomastigote is taken in by a bug during its blood meal, it changes shape to the epimastigote form and multiplies in a high rate in the mid-gut of the infected bug.

Epimastigote forms pass on to the rectum where they stick to the rectal wall and start to divide to form very active metacyclic trypomastigotes.

The metacyclic form can be found in the faeces of the triatomine bug from where it is able to penetrate the subcutaneous tissues of the host.

 

 

The trypomastigote circulates in the blood stream and invades other host cells, especially the ones in the heart and muscles. In this stage it remains extra-cellular, but it is unable to multiply.

It passes through the blood circulation to muscle cells. After penetrating the cells it forms once again into amastigote.

   

How does infection occur?

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The metacyclic trypomastigote is the infectious form of T. cruzi.

After a blood meal the vector defecates and the infectious material embedded in the mid-gut is released in the faeces.

Ilust. of tritomine haciendo caca.

The parasite enters the subcutaneous tissues, multuplies in the endothelial reticular system and is immediately phagocyted by the hosts' macrophages.

When T. cruzi is in he bloodstream it migrates to the vertebrate's cardiac cells and the smooth muscular cells (digestive tube) where it loses its flgellum to enter into the amastigote stage and multiplies itself. This is how it is able to form a pseudocyst.

Ilust. de un corazon chagasico

A certain amount of parasites are transformed into the trypomastigote stage and are able to enter the bloodstream and infect other tissues.

If a vector has a blood meal on an infected person, the trypomastigote form gets to the mid-gut of the bug and transform into epimastigote to multiply. Then an amplified parasite population transforms into metacyclic trypomastigotes in the rectum of the vector awaiting to contaminate a new vertebrate through defecation.