MLT GlobeParasitology: Blood & tissue protozoa – page 2
108 Parasitology MCQs on Blood & tissue protozoa with answers and explanations.
Which disease is transmitted by the bite of infected Phlebotomus sandflies?
Phlebotomus (Old World) and Lutzomyia (New World) sandflies transmit Leishmania. Dengue and yellow fever are Aedes-borne; malaria is Anopheles-borne.
Which of these parasites is NOT transmitted by mosquitoes?
Leishmania is transmitted by sandflies. Plasmodium is spread by Anopheles, and W. bancrofti by Culex, Anopheles or Aedes mosquitoes.
A young man develops rapidly progressive meningoencephalitis days after swimming in a warm freshwater pond. Which specimen confirms Naegleria fowleri?
Motile Naegleria trophozoites are seen in fresh CSF wet mounts and can be confirmed by PCR. Blood, skin and stool do not contain the parasite.
Which statement about human toxoplasmosis is FALSE?
Toxoplasma is acquired from cat oocysts, tissue cysts in meat, the placenta or transplants, not from insects. Reactivation causes encephalitis in AIDS.
Where are the oocysts of Toxoplasma gondii produced and shed?
Sexual reproduction occurs only in the feline intestine, producing oocysts shed in cat faeces. Humans harbour tachyzoites and tissue cysts (bradyzoites).
Which statement about human Plasmodium species is accurate?
Female Anopheles transmit sporozoites. Gametocytes form in human RBCs, and hypnozoites are produced by P. vivax and P. ovale, not P. falciparum.
The chills and fever of a malaria paroxysm coincide with which event in the parasite's cycle?
When schizonts rupture, merozoites and pyrogenic parasite material are released, triggering cytokine-driven fever. Liver-stage events are clinically silent.
In the malaria life cycle, what role does the human play?
Sexual reproduction occurs in the Anopheles mosquito, making it the definitive host. Humans harbor only asexual (schizogony) stages and gametocytes, so they are the intermediate host.
Which organism undergoes asexual multiplication (schizogony) inside human hepatocytes?
Sporozoites of Plasmodium enter hepatocytes and undergo exo-erythrocytic schizogony, producing thousands of merozoites. Ascaris larvae only pass through the liver and do not multiply.
Massive intravascular hemolysis with dark urine (blackwater fever) is classically a complication of:
Blackwater fever is linked to P. falciparum, especially with quinine use, and causes hemoglobinuria. Schistosoma haematobium causes hematuria (intact red cells), not hemoglobinuria.
Which Plasmodium stage must a female Anopheles swallow in a blood meal to become infected?
Only sexual-stage gametocytes survive and develop in the mosquito gut. Asexual stages (rings, trophozoites, schizonts) are digested.
Where does sporogony of Plasmodium falciparum take place?
Sporogony, the sexual cycle that produces sporozoites, occurs in the mosquito's gut wall (oocyst). Human red cells and liver cells support schizogony only.
Why can P. vivax and P. ovale cause attacks months after the first episode has cleared?
Hypnozoites are dormant liver forms that later resume development, causing true relapse. Primaquine or tafenoquine is needed to clear them.
A Giemsa-stained smear of a bone marrow or splenic aspirate from a kala-azar patient shows which parasite form?
In humans Leishmania exists as oval amastigotes (Leishman-Donovan bodies) with nucleus and kinetoplast inside macrophages. Promastigotes are found in the sandfly and in culture.
Which is a typical feature of visceral leishmaniasis?
Kala-azar presents with long-lasting fever, hepatosplenomegaly, pancytopenia and weight loss. It is caused mainly by L. donovani and L. infantum and spread by sandflies.
Plasmodium falciparum causes the most severe disease mainly because infected red cells:
Sequestration of infected cells in the microvasculature of the brain, kidney and placenta causes organ damage. Multiple infection and irregular fever are features but not the main reason for severity.
Leishmania donovani amastigotes are found in all of these except:
L. donovani is an intracellular parasite of mononuclear phagocytes, including Kupffer cells and splenic macrophages. It does not infect erythrocytes, unlike Plasmodium or Babesia.
For which parasite is an animal (the domestic cat and other felids) the definitive host?
Sexual reproduction of T. gondii occurs only in the intestine of felids, which shed oocysts. The Entamoeba species and Giardia have direct life cycles in humans.
When a bone marrow aspirate from kala-azar is cultured on NNN medium, which form grows?
At 22 to 26 C in culture, amastigotes transform into flagellated promastigotes, the same form seen in the sandfly. Amastigotes are seen in tissue smears.
The leishmanial (Leishman-Donovan body) form of hemoflagellates is the:
The rounded intracellular form without a free flagellum is the amastigote. The other forms have flagella and occur in vectors, culture or blood.