Organism

One of two diseases cause by Trypanosome parasites

Transmission

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

Epidemiology

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

Pathogenesis

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.

  • 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

Acute

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.

Chronic

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.

Complications

  • 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

Diagnosis

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

Treatment

  • 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

Prevention

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

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