P: Intestinal protozoa Flashcards
If you saw larvae in a faecal specimen (and no eggs), which nematode would this most likely be from?
Strongyloides stercoralis
dx: Rhabidiform larvae
*Eggs not seen in poo bc eggs secreted in intestinal mucosa and hatch
List the four categories of protozoa and their method of movement?
- Aemobas: pseudopodia (small projections)
- Flagellates: flagella
- Ciliates: cilia
- Sporozoa: no organelles or not motile
How could you differentiate between the two human Taenia worms in a clinical laboratory?
By examining the proglottids or scolex.
T.saginata: Tall & skinny uterine tubes in proglottids
T.solium: short & thick uterine tubes in proglottids
a) Generally speaking, what role do trophozoites play in the lifecycle of protozoa compared with cysts?
b) Which organisms do not have a cyst stage?
a) Trophozoites migrate to large intestines
Cysts can survive in external enviro. - the form that gets ingested/infective
b) Dientamoeba fragilis (so need to request fresh stool specimen)
Which protozoan parasites exhibit auto-fluorescence? How could these be differentiated from each other?
- Isospora belli / Cystoisospora belli
- Cyclospora cayetanensis
- Sarcocystosis sp.
*autofluorescence of CWall under UV light
diff by: oocytes
Name the two primary species of Sarcocystis sp. that infect humans? What happens if a human becomes infected with a non-human species?
a) Sarcocystis bovihominis (beef) and S. suihominis (pigs)
b) accidentally ingesting oocyst => Humans can be dead-end intermediate hosts
What is the role of the thick walled and thin walled oocysts in the life cycle of Cryptosporidium sp. & Blastocystis hominis?
Thick walled: protect when excreted from host (poo) - infectious
Thin: involved in autoinfection
Which of the protozoan parasites covered in the lectures can cause dysentery?
-Entamoeba histolytica/dispar
- Balantidium coli (occasionally)
How can Entamoeba histolytica be differentiated from E.coli and E.dispar?
Enzyme immunoassay
- Aby detection (IgG): Sp for E. histolytica
- Ag detection: may diff. b/w E. disapr & E. histolytica
PCR
Which form of H. histolytica invades the GIT wall?
Trophozoites
Which protozoan parasite has been purported to be acquired together with Ascaris and Enterobius?
Dientamoeba fragilis
a) In what animals (other than humans) does Balantidium coli circulate?
b) Which form of this parasite is most likely to be encountered in a faecal specimen?
a) pigs, rodents, non-human primates
b) Trophozoites (cysts less common)
Which protozoan parasite has a strong Hx/association with foodborne Fruit +Veg outbreaks?
Cyclospora cayetanensis
Which group of people are usually at most risk of infection with intestinal protozoa and microsporidia?
Immunocompromised (AIDS, old, young)
Briefly explain what the microsporidia are
- Obligate intracellular spore forming parasites
- like fungi bc CWall contains chitin
