Contents
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 symptomatic only
Prevention
- Mosquito net and insecticides
- Vector control
- No vaccination currently available