see also:

• parasites
• the febrile returned traveller

• infection caused by the amoeba Entamoeba histolytica
• usually transmitted by the fecal-oral route
• amoebiasis is estimated to cause 70,000 deaths per year world wide
• it is often endemic in regions of the world with limited modern sanitation systems, including Mexico, Central America, western South America, South Asia, and western and southern Africa.

• 90% are asymptomatic
• can remain latent in an infected person for several years

• 10% develop gastroenteritis after an incubation period usually 2-4 weeks, which ranges from mild diarrhoea to severe dysentery (severe ulceration of the gastrointestinal mucosal surfaces occurs in less than 16% of symptomatic cases)
• it is an uncommon cause of traveller's diarrhoea

• a granulomatous mass (known as an amoeboma) may form in the wall of the ascending colon or rectum due to long-lasting immunological cellular response
• NB. inflammatory caecal area masses in returned travellers may be due to:
  • ameboma
  • helminthoma
  • ascaris - usually pulmonary symptoms in 1st 2 weeks with cough, wheeze, maybe eosinophilia
  • hookworm may cause eosinophilic enteritis
  • strongyloidiasis may rarely cause eosinophilic oophoritis
  • appendiceal abscess
  • Crohn's disease
  • malignancy
  • etc.

• 10% of invasive cases result in spread to almost any organ, but in particular, the liver.
• complications include:
  • subdiaphragmatic abscess
  • perforation of diaphgram to pericardium and pleural cavity
  • perforation to abdominal cavital (amoebic peritonitis)
  • perforation of skin (amoebic cutis)

• can occur at skin around site of colostomy wound, perianal region, region overlying visceral lesion and at the site of drainage of liver abscess

• urogenital tract amoebiasis derived from intestinal lesion can cause amoebic vulvovaginitis (May's disease), rectovesicle fistula and rectovaginal fistula.

• can occur from hepatic lesion by haemotagenous spread and also by perforation of pleural cavity and lung.
• may cause lung abscess, pulmono pleural fistula, empyema lung and broncho pleural fistula.

• amoebic meningoencephalitis
• amoebic intracerebral abcess

• stool microscopy - cysts shed in stool but may need 3 samples to detect as shedding is not constant
• serologic tests are available - positive after 2wks of infection

• infections occur in both the intestine and in the intestinal wall and/or liver.
• Thus, two different classes of drugs are needed to treat the infection, one for each location.