Protozoa - Amoebae Flashcards
What species causes intestinal Amoebae?
Entamoeba histolytica, E.dispar
What are the stages of intestinal Amoebae?
- Trophozoites - motile feeding stage
- Cysts - infective stage
What does non-invasive Amoebiasis cause?
ON MUCOSA SURFACE:
Asymptomatic cyst passer (90% of cases), non-dysenteric diarrhoea, cramps, abdominal discomfort
What does invasive amoebiasis cause?
- Necrosis of mucosa (ulcer) - dysentery, haematophagous trophozoites
- Ulcer enlargement - colitis, peritonitis, occasional amoeboma
- Metastasis - extraintestinal amoebiasis
How is extraintestinal amoebiasis disseminated? What does extraintestinal amoebiasis cause?
- Dissemination primarily via blood stream (e.g. portal vein)
- Predominantly liver (abscess)
- Amoeba-free stools common
- Other sites infrequent (brain, cutaneous, pulmonary)
How to diagnose intestinal amoebiasis?
- Stool examination for trophozoites/cysts
- Sigmoidoscopy
What is the differential diagnosis for intestinal amoebiasis?
Inflammatory bowel disease
How to treat intestinal Amoebiasis?
Metronidazole 500-750mg tid x 10 days
What are the clinical presentations of hepatic amoebiasis?
- Fever
- Liver enlargement, tenderness (upper right quadrant), abscess
How to diagnose hepatic amoebiasis?
Stool examination, serology, imaging, abscess aspiration (reddish brown liquids trophozoites at abscess wall)
How to treat hepatic amoebiasis?
Metronidazole 750mg tid x 7-10 days
What is immunodetection?
- Mostly enzyme immunoassays
- Many cartridge-based
- Increasingly adopted in diagnostic labs
What are the 2 free-living pathogenic amoebae and what diseases do they cause?
- Naegleria fowleri - primary amoebic meningoencephalitis
- Acanthamoeba spp. - Granulomatous amoebic encephalitis, amoebic keratitis, skin or lung lesions
What are the predisposing factors for Amoebic Keratitis?
Ocular trauma, contact lens (contaminated cleaning solutions)
What are the symptoms of Amoebic Keratitis?
Severe ocular pain, corneal lesions (refractory to usual treatments)
