40 Amoebic Infections

Paul Pottinger 21/09/18

We’re now in the sarcodinia

Remember that MOST GI protozoa are harmless

40.1 Entameba histolyctica

Transmission fecal to oral. Go from cyst (passive shape) to trophozoite (active shape)

Cyst survives outside the body, trophozoite can’t

There are other entameba, entameba dispar (are harmless, look like histolytica)

They crawl along

40.1.1 Epi

Found world wide. Less common than other GI. 50,000 deaths/year

More prevalent in tropics and crowded areas.

Up to 4% incdience in asymptomatic urban children in Bangladesh. Found in 8% of kids w diarrhoea. Found in 1% or asymptomatic rural children.

40.1.2 Transmission

Foecal oral.

Pass cysts into environment. Hardy cysts.

Consumed cysts and turn into trophozoite.

40.1.3 Entamoeba

Eat on colon wall, can cause bloody diarrhoea by that.

Can cause ulcers, can spread extra intestinal

They turn from trophs to cysts when the stool dehydrates

40.1.4 Intestinal Ameobiasis*

  • Asymptomatic colonisation OR
  • Non dysenteric infection (intermittent diarrhoea) OR
  • Dystentary (bad bloody diarrhoea, loads of ulcers, febrile response)

Complications:

  • Stricture
  • Haemorrhage
  • Perforation
  • Fistula (entero-cutaneous)
  • Persistent Colitis (sticks around after successful treatment)

It acts v similar to UC!

40.1.4.1 Diagnosis

Gold standard:

Microscopy of phagocytosed red cells in stool.

Watery stool - more likely to find trophs Dry stool - you’ll just see cysts

You want to see trophs rather than cysts, as they are easier to tell apart from dispar

Other:

  • Stool antigen test (useful for histolytica)
  • Molecular PCR (not useful in tropics as the reagents are so expensive)
  • Colon biopsy (flask shaped ulcers seen)

40.1.5 Extraintestinal Amebiasis

Parasites have got into portal blood supply and get off to liver

They get there and form an “amoebic liver abscess”, not really a true abscess as you don’t get pus.

From there they can go other places, off to lung, off to brain if they get to systemic circulation

USUALLY LIVER, sometimes brain, lung, spine, pericardium

You often miss it, because they often do not have dystentry.

40.1.5.1 Case

Man moves to Nigeria (abuja), one month of fever, weight loss (2 stone), cough, chest pain, leukocytosis.

Was treated for malaria 3 times without success. Sent to HTD

CXR shows dense infiltrate right side. Was treated for pneumonia

Started coughing brown disgusting looking sputum. Smells fine though. That’s how you distinguish from bacterial superinfection. Also, amoebic liver abscess gunk shouldn’t have any white cells. It’s chewed up liver! If you see white cells, it’s bacterial superinfection

His “lung liver abscess” has started to drain. Think anchovy paste.

On CT you can see it doesn’t look like hydatids as it has a messy edge

40.1.5.2 Diagnosis

You shouldn’t need to drain these dry.

You should be doing serology for these.

You should be thinking of other pyogenic abscesses.

CAP

IFAT

Latex Agglutination

Stool

40.1.5.3 Epi of Amoebic Liver Abscess

Adults more than kids

Men more than women

Few have colitis

Majority have amoeba in stool

~2% mortality rate

40.1.5.4 Treat

You can treat with metronidazole for Trophs

If don’t get better, consider draining.

Try to avoid draining if you can. Usually unneccesary. They almost always resolve with antibiotics.

You can treat with parmomycin/iodoquinol/diloxanidine (dilo used in london) for cysts

Check in 2 months for repeat infection.

Try to not retest with PCR in patients who seem well! The DNA sticks about!