Parasitology Practice Questions

Q: A patient diagnosed with malaria has a peripheral blood smear showing all stages of schizonts with 14-20 merozoites and yellowish-brown pigment. What is the most likely type of malaria?

Plasmodium vivax. ### Explanation The correct answer is **Plasmodium vivax**. The diagnosis of malaria species via peripheral blood smear relies on specific morphological characteristics of the parasite and the infected Red Blood Cells (RBCs). **Why Plasmodium vivax is correct:** * **Schizont Morphology:** *P. vivax* schizonts are large and typically contain **12–24 merozoites** (matching the 14–20 range in the question). * **Pigment:** It characteristically shows **yellowish-brown (golden-brown)** hemozoin pigment. * **RBC Appearance:** *P. vivax* infects young RBCs (reticulocytes), causing the cells to become **enlarged/hypertrophied** and often showing Schüffner’s dots. * **Stages Present:** Unlike *P. falciparum*, all stages (trophozoites, schizonts, and gametocytes) are commonly seen in the peripheral blood. **Why the other options are incorrect:** * **P. falciparum:** Typically, only ring forms and crescent-shaped gametocytes are seen in peripheral blood. Schizonts are rarely seen as they are sequestered in deep capillaries. When present, they contain 8–36 merozoites and dark black pigment. * **P. malariae:** Schizonts typically show a **"Rosette appearance"** with only **6–12 merozoites**. The pigment is usually dark brown/black. It infects older RBCs, so the cells are not enlarged. * **P. ovale:** While it also shows Schüffner’s dots and 6–12 merozoites, the infected RBCs are typically **oval-shaped with fimbriated (tufted) edges**. **High-Yield NEET-PG Pearls:** * **P. vivax & P. ovale:** Associated with **Hypnozoites** (latent liver stages) causing relapses; treated with Primaquine. * **P. falciparum:** Associated with **Maurer’s dots** and multiple rings per RBC (Accole/Applique forms). * **P. malariae:** Associated with **Ziemann’s dots** and "Band forms." * **P. knowlesi:** A zoonotic malaria showing a 24-hour erythrocytic cycle (quotidian fever).

Q: Which of the following will give Medusa head colony on x-ray?

Round worm infestation. **Explanation:** The "Medusa head" appearance on an X-ray (specifically on a Barium meal follow-through) is a classic radiological sign of **Ascariasis (Roundworm infestation)** caused by *Ascaris lumbricoides*. **Why Roundworm is correct:** *Ascaris lumbricoides* are large nematodes (20–35 cm) that reside in the small intestine. When a large number of worms are present, they tend to intertwine or clump together. On a contrast X-ray, the barium outlines the external surfaces of these tangled worms, while some barium may be ingested by the worms themselves (appearing as central longitudinal streaks). This mass of intertwined, elongated shadows resembles the snake-like hair of the mythical figure Medusa, hence the term **"Medusa head appearance."** **Why other options are incorrect:** * **Hookworm (Ancylostoma/Necator):** These are much smaller (approx. 1 cm). They do not form large visible masses on X-rays; their clinical hallmark is iron deficiency anemia due to blood-sucking. * **Taenia solium:** While these are long tapeworms, they usually present as single infestations and do not form the characteristic tangled "Medusa head" mass. Radiological findings are more common in *Cysticercosis* (calcified cysts in muscles/brain). **High-Yield Clinical Pearls for NEET-PG:** * **Whirlpool Sign:** Seen on Ultrasonography in cases of intestinal ascariasis. * **Loeffler’s Syndrome:** Transient pulmonary infiltrates with eosinophilia caused by the larval migration of *Ascaris* through the lungs. * **Bolus Obstruction:** *Ascaris* is the most common helminthic cause of mechanical bowel obstruction in children. * **Biliary Ascariasis:** Can lead to cholecystitis, pancreatitis, or cholangitis.

Q: A fully embryonated egg of Trichuris trichiura contains which of the following?

Rhabditiform larva. **Explanation:** The correct answer is **C. Rhabditiform larva.** *Trichuris trichiura* (Whipworm) follows a direct life cycle. When eggs are passed in the feces, they are unsegmented and non-infective. For these eggs to become infective, they must undergo development in the soil (embryonation). During this process, the zygote matures into a **first-stage rhabditiform larva** within the eggshell. Therefore, a **fully embryonated egg** is the infective stage and contains a mature larva. **Analysis of Incorrect Options:** * **A. Eight blastomeres:** This represents an early stage of cleavage. While some helminths (like *Ancylostoma duodenale*) are passed in the 4-to-8 cell stage, *Trichuris* eggs are passed unsegmented. * **B. Unsegmented ova:** This is the state of the egg when it is **freshly passed** in the feces. It is not yet embryonated and is not infective to humans. * **D. Ciliated embryo:** This refers to a **Miracidium**, which is the larval stage found in the eggs of Trematodes (flukes), not Nematodes like *Trichuris*. **High-Yield NEET-PG Pearls:** * **Morphology:** *Trichuris* eggs are characteristically **barrel-shaped** (bile-stained) with **bipolar mucus plugs**. * **Infective Stage:** Embryonated egg containing rhabditiform larva (ingested via contaminated food/water). * **Clinical Presentation:** Heavy infections in children can lead to **rectal prolapse** due to increased peristalsis and mucosal edema. * **Diagnosis:** Stool microscopy for characteristic eggs; "Whip-like" adult worms may be seen on colonoscopy.

Q: Diphyllobothrium latum causes anemia by:

Competition with the host for vitamin B12. ### Explanation **Correct Answer: C. Competition with the host for vitamin B12** *Diphyllobothrium latum* (the Fish Tapeworm) is the largest tapeworm infecting humans. The primary mechanism for anemia is **nutritional competition**. The adult worm has a high affinity for Vitamin B12 and can absorb up to 80-100% of the host’s dietary intake. This leads to a Vitamin B12 deficiency, resulting in **Megaloblastic Anemia** (also known as Bothriocephalus anemia), which is clinically indistinguishable from Pernicious Anemia. **Why the other options are incorrect:** * **A. Blood-sucking activities:** This is the mechanism for *Ancylostoma duodenale* and *Necator americanus* (Hookworms), which cause Iron Deficiency Anemia. * **B. Production of a toxin:** While some parasites cause pathology via metabolic byproducts, *D. latum* does not produce a specific hematopoiesis-inhibiting toxin. * **D. Occlusion of the common bile duct:** This is a classic complication of *Ascaris lumbricoides* (migration) or *Clonorchis sinensis* (liver fluke), but it is not a feature of *D. latum* or a cause of its associated anemia. **High-Yield Clinical Pearls for NEET-PG:** * **Infective Stage:** Plerocercoid larva (found in undercooked freshwater fish). * **Diagnostic Stage:** Operculated eggs in stool (unembryonated). * **Morphology:** Scolex has two slit-like sucking grooves called **Bothria**. * **Key Association:** It is the only parasite classically associated with **Vitamin B12 deficiency** and megaloblastic changes. * **Treatment:** Praziquantel is the drug of choice.

Q: Which of the following diseases worldwide is transmitted by the mosquito genera Culex, Anopheles, and Aedes?

Filariasis. ### Explanation **Correct Answer: C. Filariasis** **Why Filariasis is Correct:** Lymphatic Filariasis (caused primarily by *Wuchereria bancrofti* and *Brugia malayi*) is unique because it can be transmitted by multiple genera of mosquitoes depending on the geographical location and the species of the parasite. * **Culex:** The most common vector worldwide (especially *Culex quinquefasciatus* in urban/semi-urban areas). * **Anopheles:** A major vector in rural areas, particularly in Africa. * **Aedes:** Transmits the sub-periodic form in the Pacific islands. * **Mansonia:** The primary vector for *Brugia malayi* (often found near water plants like *Pistia*). **Why Other Options are Incorrect:** * **A. Malaria:** Exclusively transmitted by the female **Anopheles** mosquito. * **B. Dengue:** Transmitted primarily by **Aedes aegypti** and occasionally *Aedes albopictus*. * **D. Yellow Fever:** Also transmitted by the **Aedes** genus (specifically *Aedes aegypti* in urban cycles and *Haemagogus* in jungle cycles). **NEET-PG High-Yield Pearls:** 1. **Vector for Brugia malayi:** Specifically **Mansonia** mosquitoes. Control involves the removal of aquatic plants (*Pistia stratiotes*). 2. **Nocturnal Periodicity:** Microfilariae of *W. bancrofti* appear in peripheral blood between **10 PM and 2 AM**, coinciding with the biting habits of the Culex vector. 3. **Drug of Choice:** **Diethylcarbamazine (DEC)** is the standard treatment; however, it is contraindicated in Onchocerciasis (due to Mazzotti reaction). 4. **National Health Goal:** India aims for the **Elimination of Lymphatic Filariasis (ELF)** using Mass Drug Administration (MDA) with DEC + Albendazole (and recently, Ivermectin/IDA triple therapy).

Q: Hookworm thrives on what component of blood?

Plasma. ### Explanation The correct answer is **Plasma**. **Underlying Medical Concept:** Hookworms (*Ancylostoma duodenale* and *Necator americanus*) are hematophagous nematodes that attach to the mucosal villi of the small intestine using their buccal capsules. While it is a common misconception that they consume whole blood for nutrition, they primarily ingest blood to extract **plasma proteins and glucose**. The hookworm’s digestive tract is inefficient at processing solid cellular components. Once the worm draws blood, it rapidly passes the red blood cells (RBCs) through its intestine relatively intact and unutilized. The worm primarily utilizes the liquid portion—**plasma**—as its main source of nourishment. The iron deficiency anemia associated with hookworm infestation is actually a result of the **accidental loss of RBCs** (hemorrhage) caused by the worm's anticoagulant (ancylostomin) and its inability to digest the iron-rich hemoglobin it ingests. **Analysis of Incorrect Options:** * **A. Whole blood:** Although the worm ingests whole blood, it does not "thrive" on it entirely; it selectively utilizes plasma components and discards the rest. * **C. Serum:** Serum is plasma minus clotting factors. Since the worm ingests circulating blood (which contains fibrinogen), it is consuming plasma, not serum. * **D. Red blood cells:** Hookworms cannot effectively digest the hemoglobin within RBCs. The RBCs are excreted in the host's feces, leading to the characteristic occult blood loss. **NEET-PG High-Yield Pearls:** * **Daily blood loss:** *A. duodenale* (0.15–0.2 ml/day) causes more blood loss than *N. americanus* (0.03 ml/day). * **Clinical Presentation:** Microcytic hypochromic anemia (Iron deficiency) and Ground itch (at the site of larval entry). * **Infective Stage:** Filariform larva (L3). * **Diagnostic Feature:** Non-bile stained, segmented eggs with a clear space between the shell and the embryo.

Q: Apart from Plasmodium, which of the following can infect red blood cells in ring forms?

Babesia microti. **Explanation:** The correct answer is **Babesia microti**. This is a high-yield concept in parasitology because *Babesia* is the primary differential diagnosis for *Plasmodium falciparum* on a peripheral blood smear. **1. Why Babesia microti is correct:** *Babesia* is an intraerythrocytic protozoan. Like *Plasmodium*, it infects red blood cells (RBCs) and presents as small, pleomorphic **ring forms** (trophozoites). * **Key Diagnostic Feature:** Unlike Malaria, *Babesia* does not produce pigment (hemozoin) or have a gametocyte stage. It classically forms a **"Maltese Cross"** appearance (tetrads) during asexual reproduction (budding), which is pathognomonic. **2. Why other options are incorrect:** * **Trypanosoma:** These are extracellular hemoflagellates found in the **plasma**, not inside the RBCs. They appear as C-shaped or U-shaped organisms with a flagellum and undulating membrane. * **Schistosoma:** These are trematodes (flukes). The adult worms reside in the **venous plexus** (mesenteric or vesical), and their eggs are found in stool or urine. They do not infect RBCs. * **Microfilaria:** These are the larval stages of nematodes (like *Wuchereria bancrofti*). They are found in the **lymphatics or blood plasma**, appearing as large, multi-nucleated worm-like structures, never as intraerythrocytic rings. **NEET-PG High-Yield Pearls:** * **Vector:** *Babesia* is transmitted by the **Ixodes tick** (the same vector for Lyme disease). * **Clinical Presentation:** Often causes a malaria-like illness (fever, hemolytic anemia). It is particularly severe or fatal in **asplenic patients**. * **Morphology:** Look for "Maltese Cross" and the absence of Schüffner’s dots or malarial pigment.

Q: Night blood survey is done in which of the following conditions?

Filaria. **Explanation:** The correct answer is **Filaria (Option A)**. This is because the most common causative agent of lymphatic filariasis, *Wuchereria bancrofti*, exhibits a unique biological phenomenon known as **Nocturnal Periodicity**. 1. **Why Filaria is correct:** The microfilariae (larval forms) of *W. bancrofti* and *Brugia malayi* circulate in the peripheral blood primarily at night (usually between **10 PM and 2 AM**). During the day, they sequester in the deep capillaries of the lungs. This timing coincides with the peak biting activity of the vector, the *Culex* mosquito. Therefore, a "Night Blood Survey" is essential to achieve maximum sensitivity for diagnosis via peripheral smear. 2. **Why other options are incorrect:** * **Typhoid (B):** Diagnosis is based on the **BASU** rule (Blood culture in 1st week, Antibody/Widal in 2nd, Stool in 3rd, Urine in 4th). There is no diurnal variation in bacteremia. * **Malaria (C):** While malarial paroxysms have cycles, the parasites are generally present in the blood throughout the day. Thick and thin smears are best taken during or immediately after a febrile peak, regardless of the clock time. * **Kala-azar (D):** Caused by *Leishmania donovani*, this is diagnosed via bone marrow or splenic aspiration to find LD bodies; the parasite does not show nocturnal peripheral periodicity. **High-Yield Clinical Pearls for NEET-PG:** * **DEC Provocative Test:** If a night survey is not possible, a small dose of Diethylcarbamazine (2mg/kg) can be given; it brings microfilariae into the peripheral blood within 30–60 minutes even during the day. * **Exceptions:** *Loa loa* (African eye worm) exhibits **Diurnal periodicity** (daytime), while *W. bancrofti* var. *pacifica* is **non-periodic**. * **Stain of choice:** Giemsa or Leishman stain is used to visualize the sheath and nuclei of microfilariae.

Question 1

A patient diagnosed with malaria has a peripheral blood smear showing all stages of schizonts with 14-20 merozoites and yellowish-brown pigment. What is the most likely type of malaria?

Accepted Answer

Plasmodium vivax

Answer

Plasmodium falciparum

Answer

Plasmodium malariae

Answer

Plasmodium ovale

Question 2

Which of the following will give Medusa head colony on x-ray?

Accepted Answer

Round worm infestation

Answer

Hook worm infestation

Answer

Tenia solium infestation

Answer

Hook worm and Round worm infestation

Question 3

Which one of the following is characteristic of microfilaria of W. bancrofti?

Accepted Answer

Caudal end uniformly tapering to a delicate point, and no terminal nuclei present

Answer

Cephalic space twice as long as broad

Answer

Excretory pore prominent

Answer

Nuclear column smudged

Question 4

A fully embryonated egg of Trichuris trichiura contains which of the following?

Accepted Answer

Rhabditiform larva

Answer

Eight blastomeres

Answer

Unsegmented ova

Answer

Ciliated embryo

Question 5

A 20-year-old man presents with swelling of the left lower limb and hydrocele. Which of the following is NOT a causative agent for these symptoms?

Accepted Answer

Onchocerca volvulus

Answer

Brugia malayi

Answer

Brugia timori

Answer

Wuchereria bancrofti

Question 6

Diphyllobothrium latum causes anemia by:

Accepted Answer

Competition with the host for vitamin B12

Answer

Its blood-sucking activities

Answer

The production of a toxin that affects hematopoiesis

Answer

Occlusion of the common bile duct

Question 7

Which of the following diseases worldwide is transmitted by the mosquito genera Culex, Anopheles, and Aedes?

Accepted Answer

Filariasis

Answer

Malaria

Answer

Dengue

Answer

Yellow Fever

Question 8

Hookworm thrives on what component of blood?

Accepted Answer

Plasma

Answer

Whole blood

Answer

Serum

Answer

Red blood cells

Question 9

Apart from Plasmodium, which of the following can infect red blood cells in ring forms?

Accepted Answer

Babesia microti

Answer

Trypanosoma

Answer

Schistosoma

Answer

Microfilaria

Question 10

Night blood survey is done in which of the following conditions?

Accepted Answer

Filaria

Answer

Typhoid

Answer

Malaria

Answer

Kala-azar

Parasitology — MCQs

Parasitology — MCQs

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