Make your own free website on Tripod.com

home

 

 

Development of the disease

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The symptoms of the disease develop in two phases, one acute and the other chronic.

Infection of T. cruzi has an incubation period of 4-10 days, generally without symptoms. It then proceeds to an acute phase that lasts 2-4 months, followed by a chronic phase that progresses throughout the patient’s life.

The acute phase begins with the inoculation of the infectious metacyclic forms and is characterized by the presence of T. cruzi in the blood. In this phase of the illness the symptoms are very light and discrete and could be mistaken for a cold or flu. The presence of fever and general malaise are common in this stage. On the other hand, it is also possible that certain typical symptoms like the Romaña’s sign or chagoma appear at this stage that can define a more accurate diagnose.

The last is a sore at the point of entry of the parasite; if this is near the eye, an ocular swelling may result (conjunctivitis with oedema of the eyelid due to inoculation of the mucous). Other symptoms include subcutaneous oedemas (if the bug has bitten the skin), hepatosplenomegaly and sinus tachycardia.

During the chronic phase, T. Cruzi is still present in the blood but in very low concentration. It is mainly installed in the cardiac cells and the smooth muscle cells. The parasites penetrate and multiply in the cells of vital organs causing irreversible tissue damage that will eventually interfere with organ development and function. The heart is the organ most commonly affected, as well as the gastrointestinal tract. Approximately 10 to 30% of those who recover from the acute phase develop chronic cases.

Heart problems include:

  1. biventricular enlargement
  2. thinning of ventricular walls
  3. apical aneurysms
  4. widespread lymphocytic infiltrate

Chronic cases can lead to death from congestive heart failure due to destruction of the heart muscle by the parasite.

Gastrointestinal complications due to parasite infection of nerve cells that regulate peristalsis may lead to dilation of the esophagus (megaesophagus) and/or colon (megacolon).

 

The early part (also called indeterminate form), as well as the later part of the chronic phase may be asymptomatic.
   

¿What harm does the parasite cause to the insect?

 

 

In general, T. cruzi does not cause harm to its invertebrate host. There is evidence for a suppressive effect on the insect vectors’ haemocoelic immune system and its survivorship may be reduced also by starvation and sub-lethal doses of insecticides.