Protozoa

Question 1

Three groups of protozoa

Answer 1

Amoeba
Flagellates
Coccidia

Question 2

What is the most common infective amoeba species and where is it found?

Answer 2

Entamoeba histolytica
Common in large intestine of humans, usually transmitted fecal-oral route via contaminated food/water, or by personal contact.

Question 3

What is the life cycle of Entamoeba histolytica

Answer 3

• Ingested cysts ex-cyst in small intestine → multiply by binary fission
• Attach to colonic mucosa via Gal/GalNAc lectin → produce cysteine proteases that cause tissue damage
• 2-6 wks: flask-shaped ulcers in colon
• Can disseminate to liver (abscess) or amebiasis

Question 4

What infections does Entamoeba histolytica cause?

Answer 4

Amebiasis
- 3rd most common cause of death from parasite

Amebic Dysentery, which can disseminate

Liver abscess (usu develops within 5 mos; responds to metronidazole, without resection)

Question 5

How is Entamoeba histolytica infection treated?

Answer 5

Colitis or Abscess: Tinidazole or Metronidazole

Luminal Infection: Paromomycin, Iodoquinol

Question 6

What are the four flagellates that commonly cause infections?

Answer 6

Giardia lambia
Trichomonas
Trypanosoma
Leishmania