Chagas Disease
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One of two diseases cause by Trypanosome parasites


Via the triotimine bugs (bite at night) – blood sucking reduvids –transmit when faeces come into contact with blood/mucosal surfaces.


Caused by Trypanosome cruzi (latin America)
Occurs in humans and large numbers of wild/domesticated animals
Congenital infection occurs in 10% seropositive women.

Chagas Disease geographical distribution
Chagas Disease geographical distribution. This file is taken from wikimedia commons and is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license.


In the host, trypamastigotes multiply at the bite site, enter the bloodstream

  • Within the bugs  intestine, T cruzi undergoes a number of developmental stages, finially ending with a flagellated form living in the rectum
  • The vector defecates when ingesting the blood meal
  • Faeces containing infectious trypomastigotes are dumped onto the victim’s skin(close to the bite wound)
  • On waking  the bite victim will rub the (itching) bite, pushing the faeces into the wound, or into the eyes.
Trypanosoma cruzi crithidia
Trypanosoma cruzi crithidia
  • Trypomastigotes enter the victim’s bloodstream through the bite wound/musous membranes
  • Then invades macrophage cells and transforms into intracellular amastigotes
  • These multiply by binary fission and are released as trypomastigotes into the bloodstream and tissues
  • These infect new cells of wide variety of tissues with preference to neuroglia and muscle cells (cycle repeats multiple times)
  • Induces inflammatory response enhanced by high parasitaemiaàdirect destruction of infected cell and cell necrosis mediated by inflammatory factors in target tissues
  • Finally, clinical manifestations of the disease occur


Clinical features


Occurs shortly after an initial infection and lasts for few weeks or months resolving spontaneously in approximately 90% of infected individuals.
Usually symptom-free/exhibits only mild, generalised signs or symptoms: (unless immune-compromised)

  • Fever
  • Fatigue
  • Body aches
  • Headache
  • Rash
  • Loss of appetite
  • Diarrhea, and vomiting.
  •  Mild hepatosplenomegaly
  • Lymphadenopathy
  • Romaña’s sign- swelling of the eyelid on the side of the face near the bite wound

*Although symptoms resolve,even with treatment the infection persists and enters a chronic phase.


Usually develops over many years latency. (10% of individuals progress directly from the acute form to symptomatic chronic disease)
Two subtypes

  • Determinate (20-40%) – become symptomatic
  • Indeterminate  (60-80%) – never develop symptoms

Features of chronic disease

  • Chronic stage affects the nerves, digestive system and heart.
  • 2/3 have cardiac damage due to destruction of the conduction system, myocytes, and parasympathetic cardiac nerves leading to dilated cardiomyopathy and its complications.
  • 1/3 have GI tract damage due to irregular parasympathetic intramural denervation mainly affecting the oesophagus and the colon leading to  functional peristaltic disturbance, and consequences such as megaoesophagus or megacolon.


  • Volvulus of the sigmoid colon is a rare complication appearing in advanced cases, and is associated with a high risk of intestinal necrosis
  • Left untreated, can be fatal
  • Most deaths are due to heart muscle damage


  • Acute disease- microscopy/culture parasites in blood, CSF or lymph node aspirate
  • Chronic disease- serology (Chaga’s IgG ELISA)


  • Nifurtimox
  • Benznidazole

These suppress parasitaemia, shorten course of acute illness and prevent. Can lead to acute neuro and cardio complications.
Treatment for chronic disease is symptom
atic only


  • Mosquito net and insecticides
  • Vector control
  • No vaccination currently available


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Dr Tom Leach

Dr Tom Leach MBChB DCH EMCert(ACEM) FRACGP currently works as a GP and an Emergency Department CMO in Australia. He is also a Clinical Associate Lecturer at the Australian National University, and is studying for a Masters of Sports Medicine at the University of Queensland. After graduating from his medical degree at the University of Manchester in 2011, Tom completed his Foundation Training at Bolton Royal Hospital, before moving to Australia in 2013. He started almostadoctor whilst a third year medical student in 2009. Read full bio

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