MLT GlobeParasitology: Intestinal protozoa – page 2
69 Parasitology MCQs on Intestinal protozoa with answers and explanations.
Which statement about Trichomonas vaginalis is FALSE?
T. vaginalis is a urogenital parasite causing vaginitis and urethritis, not dysentery. The other statements are correct.
Which intestinal protozoan can spread through the portal blood to cause disease outside the gut?
Invasive E. histolytica trophozoites enter mesenteric venules and reach the liver, occasionally lung or brain. The other organisms remain in the intestine.
Which part of the gut does Giardia duodenalis mainly colonise?
Giardia trophozoites attach by their ventral disc to the duodenal and jejunal mucosa, explaining malabsorption rather than dysentery.
Colonoscopy shows discrete ulcers with undermined edges that are narrow at the mucosa and wide below (flask-shaped). The likely cause is:
Invasive E. histolytica spreads laterally in the submucosa, producing flask-shaped ulcers. Giardia does not invade, and the free-living amoebae affect the eye or CNS.
In a wet mount of vaginal discharge, the jerky, twitching movement of Trichomonas vaginalis is produced by:
T. vaginalis has four anterior flagella and a short undulating membrane with a recurrent flagellum. Cilia belong to Balantidium and pseudopodia to amoebae.
Which statement about giardiasis is FALSE?
Trophozoites are fragile and destroyed by gastric acid; the cyst is the infective stage. The other statements are true.
A pig farmer has dysentery; a wet mount shows very large oval trophozoites covered in cilia with a kidney-shaped macronucleus. Which protozoan is responsible?
B. coli is the only ciliate pathogen of humans and can cause dysentery with colonic ulcers. E. histolytica is amoeboid, E. coli is non-pathogenic, and Giardia causes non-bloody diarrhoea.
In an infected man, Trichomonas vaginalis is most likely to be found in which site?
T. vaginalis is a urogenital flagellate; in males it colonizes the urethra and prostate. It does not live in the gut, unlike intestinal flagellates such as Giardia.
Which of these infections is acquired without any arthropod vector?
Giardia cysts are swallowed in contaminated water or food (fecal-oral route). Malaria, leishmaniasis and yellow fever all need an insect vector.
Which of the following parasites typically causes bloody diarrhea with mucus (dysentery)?
E. histolytica invades the colonic mucosa, producing flask-shaped ulcers and dysentery with blood and mucus. P. falciparum is a blood parasite, D. latum causes vitamin B12 deficiency and Onchocerca affects skin and eyes.
Which parasite can be seen as motile flagellates in a wet mount of vaginal or urethral discharge?
Jerky motile pear-shaped trophozoites with an undulating membrane in saline mounts are diagnostic of T. vaginalis. The others are intestinal parasites found in stool.
The only ciliate that commonly causes human disease, and the largest protozoan of the human colon, is:
Balantidium coli (Neobalantidium coli) is a large ciliate acquired from pigs that can cause dysentery. Entamoeba species are amoebae and Giardia is a flagellate.
Which intestinal protozoan can spread to cause liver and brain abscesses?
Invasive E. histolytica can reach the liver through the portal vein and occasionally the brain or lungs. Balantidium rarely spreads beyond the colon.
A non-pathogenic amoeba found in the human mouth, especially in gum disease, is:
E. gingivalis lives in the oral cavity and has no cyst stage. E. coli and E. hartmanni are non-pathogenic intestinal amoebae.
The most common form of extraintestinal amoebiasis is:
Trophozoites reach the liver through the portal vein, often forming a right-lobe abscess with anchovy-sauce pus. Lung and brain involvement is much less common.
Protozoa formerly grouped as Rhizopoda (Sarcodina), such as Entamoeba, move by:
Amoebae extend cytoplasmic pseudopodia for movement and feeding. Flagella and undulating membranes are found in flagellates.
Trichomonas vaginalis is best described as a:
T. vaginalis has four anterior flagella and an undulating membrane. It has no cyst stage.
Which statement about Giardia duodenalis is incorrect?
Giardia attaches to the duodenal mucosa and causes malabsorption and fatty diarrhea, not hemolysis. The string test samples duodenal contents for trophozoites.
Which statement about Trichomonas vaginalis is FALSE?
T. vaginalis is a urogenital flagellate with no cyst stage; it causes vaginitis or urethritis, not dysentery. Diagnosis by wet mount or NAAT and metronidazole treatment are standard.
Pear-shaped trophozoites with two nuclei and 'falling leaf' motility in a stool sample are:
Giardia trophozoites look like a face with two nuclei and have a sucking disc and four pairs of flagella. The cysts are oval with four nuclei.