Protozoa Flashcards
What are the two forms of entamoeba histolytica?
trophozoite - fragile, can’t live outside host, 1 nucleus
cyst - 4 nuclei, infective
What are the clinical syndromes associated with entameoba histolytica?
intestinal dz
hepatic - liver abscess
rarely pleura, pericardium, brain involved
What are the signs and symptoms of amebic colitis?
pain, diarrhea, bloody stools
fever uncommon
weight loss and volume depletion
How is amebic liver abscess different than amebic colitis?
fever, no colitis
How is entamoeba histolytica transmitted?
fecal-oral transmission of cysts
What is the pathogenesis of entamoeba histolytica?
excystation in small intestine - trophozoites released, migrate to large intestine and adhere to mucosa using lectin-binding receptors
most remain in lumen as commensals
multiply by binary fission and produce cysts, passed in feces
If entamoeba histolytica trophozoites don’t just live as commensal organisms, what can they do?
invade mucosa using cytotoxins that lyse epithelial cells and PMNs
cysteine proteinase degrades collagen and elastin - trophozoites feed on host materials –> non-specific colitis, flask shaped ulcers
How is entamoeba histolytica diagnosed?
ova and parasite exam - LM doesn’t differentiate from lumen dwelling E. dispar
can see trophozoites on trichrome - w ingested RBCs distinguises e. histolytica
What is the treatment for e. histolytica?
anti-motility agents not recommended
metronidazole or tinidazole plus luminal ameobicide
What is the role of e. histolytica inf in the liver?
trophozoites can invade bloodstream w persistent colonization - resistant to complement mediated lysis and ascend portal venous structures
irreversibly damage hepatocytes - BAD
What are the two forms of giardia?
trophozoite - pear shaped, flat surface with sucking disk, four pairs of flagella, two nuclei, live freely in upper small bowel lumen
cyst - infective, resistant to low pH, four nuclei
How is giardia transmitted?
lots of human asymptomatic carriers
wild animals are habitats
fecally contaminated water
hand to mouth transfer in day care centers
What is the pathogenesis of giardia?
same as e. histolytica except for how the trophozoites attach
use ventral disk, flagella mediated forces, and receptor ligand interxn mediated by lectin proteins
trophozoites flattening villi –> pathology
1 cyst –> 2 trophozoites
What is the response to giardia inf?
antigen uptake into macrophages in peyer’s patches –> antibody and cell response
IgA can prevent adherence - giardia produces IgA protease
T lymphocytes can cause crypt hyperplasia
How is giardia diagnosed?
cysts and trophozoites can be found in feces
duodenal fluid or biopsy can show trophozoites
stool antigen test
