Contents
Organism
- Protozoan- Entamoeba histolytica
- Incubation: days-years
Transmission
Faecal-oral (usually contaminated water): infection by ingestion of 4-nucleated cysts.
Epidemiology
Humans are the only reservoir
10% world population are infected (rare in temperate climates)
Pathogenesis
Cyst is digested in gut releasing trophozoites (active parasites) which can colonise and invade colonic mucosa and cause cell lysis and ulcerations. Trophozoites may remain in the bowel or invade extra-intestinal tissues leaving ‘flask-shaped ulcers’. Cysts pass in the stools of carriers indefinitely and are viable for up to 2 months.
[image from wikipedia]
Clinical features
Leads to bloody diarrhoea, abdo pains and pyrexia (over period of 3 weeks)
Presentation may vary between:
- asymptomatic (90%)
- mild diarhoea
- severe amoebic dysentery
Complications
Fulminant colitis (in immunosuppressed, elderly or pregnant)
Amoeboma- inflammatory mass, usually ileocaecal
Amoebic liver abscess
Chronic amoebiasis – intermittent non-bloody mucoid diarrhoea
Diagnosis
Motile amoeba seen in fresh stool
Faecal antigen detection
US/CT = aspiration may confirm amoebic liver abscess
Positive serology
Treatment
Metronidazole
Diloxanide furoate (after metronidazole to destroy gut cysts)
Prevention
Sanitation and good personal hygiene
