MLT GlobeDOH exam preparation (Abu Dhabi) – page 27
700 practice MCQs for the DOH medical laboratory exam. Level: Basic to intermediate.
A patient who eats undercooked beef passes motile proglottids; India-ink injection shows 15–30 lateral uterine branches per side. Identify the tapeworm.
T. saginata (beef tapeworm) gravid proglottids have more than 12 lateral uterine branches per side. T. solium has 7–13, and the other two have different proglottid structure.
After swimming in a lake frequented by birds, a person develops an itchy papular rash that resolves without systemic illness. Cause?
Swimmer's itch (cercarial dermatitis) is due to non-human schistosome cercariae that penetrate but die in human skin. Hookworm causes ground itch from soil, not water.
Which intestinal amoeba is a non-pathogenic commensal that resembles a small E. histolytica?
E. hartmanni looks like E. histolytica but is smaller (cysts under 10 µm) and non-pathogenic, so micrometry is used to separate them.
Coarse, irregular red-staining clefts (Maurer's clefts) in red cells containing mature trophozoites are associated with:
Maurer's clefts are membrane structures made by P. falciparum. Vivax and ovale show fine Schüffner's dots, and malariae shows Ziemann's dots.
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.
After a Giardia cyst is swallowed, excystation is triggered by gastric acid and completed so that trophozoites emerge in the:
Excystation starts in the acid stomach and finishes in the duodenum, where each cyst yields two trophozoites that attach to the mucosa. Encystation later occurs lower down.
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.
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.
The stage of W. bancrofti infective to humans is the third-stage (filariform) larva found in the mosquito's:
Microfilariae develop to L3 in the thoracic muscles, then move to the proboscis and enter the skin when the mosquito feeds. Larvae in the thorax are not yet infective.
Which parasite is not a cause of visceral larva migrans?
Visceral larva migrans is caused by nematode larvae of animals (Toxocara, Baylisascaris) that wander through human organs. T. saginata is an intestinal tapeworm with no migrating larva in humans.
Leishmania donovani survives the host's immune response mainly by:
Amastigotes live inside macrophage phagolysosomes, inhibiting oxidative burst and antigen presentation. This lets them multiply in the cells meant to destroy them.
Human cysticercosis (larvae in brain or muscle) is acquired by swallowing:
Ingested T. solium eggs hatch and larvae spread to tissues to form cysticerci. Eating cysticerci in pork causes only intestinal taeniasis.
In the Old World, the sandfly genus that transmits kala-azar is:
Phlebotomus species transmit Leishmania in Asia, Africa and Europe, and Lutzomyia in the Americas. Simulium transmits onchocerciasis and Glossina transmits sleeping sickness.
A gardener gets a nodule after a thorn prick, followed by a chain of nodules along the lymphatics of the arm. The most likely cause is:
Sporothrix schenckii enters via minor trauma and spreads along lymphatics (lymphocutaneous sporotrichosis). Tinea capitis affects the scalp and cryptococcosis is mainly acquired by inhalation.
To identify a Taenia saginata proglottid, it is pressed between two slides after injecting its uterus with:
India ink fills the uterine branches; T. saginata has about 15 to 20 lateral branches per side, compared with 7 to 13 for T. solium.
Standard flotation concentration of stool is least suitable for detecting:
Operculated fluke eggs and schistosome eggs are heavy or collapse in high-density solutions, so sedimentation is preferred. Protozoan cysts and hookworm eggs float well.