MLT GlobeParasitology: Blood & tissue protozoa – page 6
108 Parasitology MCQs on Blood & tissue protozoa with answers and explanations.
Plasmodium vivax preferentially invades which red cells?
P. vivax and P. ovale prefer reticulocytes, which limits their parasitaemia; P. falciparum invades red cells of all ages.
People who lack the Duffy blood group antigen on their red cells are largely resistant to infection by:
P. vivax uses the Duffy antigen as its receptor to enter red cells, so Duffy-negative people are largely protected.
Ring forms in which the chromatin dot sits inside the ring, giving a 'bird's-eye' appearance, are described for:
The bird's-eye ring is a described feature of P. malariae, which also shows band-form trophozoites and rosette schizonts.
Parasite products released at schizont rupture trigger fever mainly by stimulating which host cytokine?
Glycosylphosphatidylinositol and hemozoin activate macrophages to release TNF-alpha and IL-1, which act as endogenous pyrogens. IL-4, IL-10 and TGF-beta are mainly anti-inflammatory or Th2 cytokines.
A leishmanin (Montenegro) skin test is typically negative in:
Active kala-azar suppresses cell-mediated immunity, so the delayed-hypersensitivity test is negative; it becomes positive after cure. Cutaneous forms usually give a positive test.
Which Babesia species is known for causing severe, often fatal infection in splenectomized people in Europe?
B. divergens, a cattle parasite, causes fulminant hemolytic disease mainly in asplenic patients in Europe. B. microti causes milder disease in the USA.
In a patient with Plasmodium falciparum infection, finding mature schizonts in the peripheral blood is significant because it usually indicates:
Mature P. falciparum stages normally sequester in deep capillaries, so peripheral schizonts suggest heavy infection and a worse prognosis.
A pregnant woman has positive Toxoplasma IgG and IgM. Which test best helps show the infection occurred more than 4 months ago?
High IgG avidity indicates infection at least 3–5 months earlier, because IgM can persist for months or years. Low avidity supports recent infection.