MLT GlobeParasitology: Blood & tissue protozoa – page 4
108 Parasitology MCQs on Blood & tissue protozoa with answers and explanations.
On a thin film, infected red cells are oval with fimbriated (ragged) edges and show James's dots. Which species is this?
P. ovale makes about a third of infected red cells oval with fimbriated margins. P. vivax enlarges cells but usually keeps them round.
Destructive mucocutaneous lesions of the nose and palate (espundia) in South America are caused by:
Espundia follows metastatic spread of L. (Viannia) braziliensis to mucosae. L. donovani is visceral and L. tropica cutaneous.
Napier's aldehyde test, a historic screening test for kala-azar, gels the serum because of a marked rise in:
Kala-azar causes polyclonal hypergammaglobulinaemia, which the aldehyde and antimony tests detected non-specifically. They are now replaced by rK39 rapid tests and microscopy/PCR.
A traveller to an area with chloroquine-resistant falciparum malaria asks about prevention. Which option is appropriate chemoprophylaxis?
Atovaquone–proguanil (or doxycycline, mefloquine) is recommended where chloroquine resistance is widespread. Mebendazole and metronidazole treat worms and anaerobes/protozoa, not malaria.
Which statement about kala-azar is FALSE?
Most kala-azar cases occur in South Asia and East Africa (L. donovani); Latin American visceral leishmaniasis (L. infantum) is less common. The other statements are true.
Premunition (concomitant immunity), in which resistance to reinfection persists only while low-level infection remains, is classically seen in:
In malaria-endemic areas, persistent low-grade parasitaemia maintains partial immunity; it wanes when parasites are cleared.
A soft contact lens wearer who rinses lenses in tap water develops a painful ring-shaped corneal infiltrate. Which organism is most likely?
Acanthamoeba causes sight-threatening keratitis in contact lens users; corneal scrapings show double-walled cysts. Naegleria causes acute meningoencephalitis, not keratitis.
The rapidly dividing tachyzoite of Toxoplasma gondii is best described as:
Tachyzoites multiply only inside nucleated host cells during acute infection. Bradyzoites in tissue cysts represent chronic infection, and oocysts are shed by cats.
Malaria can follow a mosquito bite or a blood transfusion. Which stages start infection in each case, respectively?
Mosquitoes inject sporozoites, which pass through the liver. Transfused blood contains infected red cells, so merozoites begin the blood cycle directly, with no liver stage or relapse.
Fertilization of Plasmodium gametes to form a zygote (ookinete) takes place in which location?
Gametocytes taken up in a blood meal mature into gametes that fuse in the mosquito midgut. Sporozoites later reach the salivary glands, but no fertilization occurs there.
A patient treated only with a blood schizonticide has a fresh malaria attack months later from dormant liver forms. Which species is most likely?
P. vivax (and P. ovale) form hypnozoites that can reactivate and cause true relapse. P. falciparum, P. malariae and P. knowlesi do not form hypnozoites.
Chronic infection with which Plasmodium species is most associated with nephrotic syndrome, especially in children?
Quartan malarial nephropathy is caused by immune-complex glomerulonephritis in P. malariae infection. P. falciparum more often causes acute kidney injury, not nephrotic syndrome.
Which mechanism contributes to anemia in malaria?
Anemia results from rupture of parasitized cells, complement and antibody-mediated removal of infected and uninfected cells, increased splenic clearance, and TNF-driven marrow suppression. The other options describe the opposite.
Which statement about Plasmodium falciparum is correct?
P. falciparum causes malignant tertian malaria with a roughly 48-hour cycle. A 72-hour cycle is P. malariae; hypnozoites belong to P. vivax/ovale; reticulocyte preference is P. vivax.
Which statement about cutaneous leishmaniasis is incorrect?
Cutaneous leishmaniasis is spread by phlebotomine sandflies, not mosquitoes. Lesion smears show amastigotes, L. major causes Old World disease, and L. mexicana/braziliensis complexes occur in the Americas.
Recrudescence in falciparum malaria is best explained by:
Recrudescence is a renewed attack from surviving erythrocytic parasites, often after incomplete treatment. Relapse from hypnozoites applies to P. vivax and P. ovale; a new bite is reinfection.
Cytoadherence of P. falciparum-infected red cells to the endothelium of brain vessels leads mainly to:
Knobs with PfEMP1 make infected cells stick to cerebral endothelium, blocking microcirculation and causing coma. Blackwater fever is due to massive hemolysis.
The nephrotic syndrome of Plasmodium malariae infection is caused by:
Antigen-antibody complexes deposit in the glomeruli, causing membranoproliferative injury and proteinuria. Hypoproteinemia is a result, not a cause.
Which malaria parasite mainly infects older (senescent) red cells?
P. malariae prefers aged red cells, which keeps parasitemia low. P. vivax and P. ovale prefer reticulocytes, while P. falciparum invades red cells of all ages.
Which finding is not a typical feature of severe falciparum malaria?
WHO criteria for severe malaria include impaired consciousness, seizures, hypoglycemia and shock. Generalized lymph node enlargement is not a feature.