Parasitology Practice Questions

Q: Coconut cake appearance of the rectum is seen in which parasitic infection?

Trichuris trichura. **Explanation:** The "coconut cake" appearance of the rectum is a classic clinical sign of heavy infection with **Trichuris trichiura** (Whipworm). **Why Trichuris trichiura is correct:** In cases of massive infestation, particularly in children, thousands of adult worms attach to the mucosa of the large intestine and rectum. The worms embed their thin, whip-like anterior ends into the mucosa, while their thicker posterior ends hang into the lumen. On proctoscopy, these numerous white, glistening bodies of the worms against the backdrop of an inflamed, edematous, and prolapsed rectal mucosa resemble a **"coconut cake."** This heavy burden often leads to **rectal prolapse**, a high-yield clinical association for this parasite. **Why the other options are incorrect:** * **Enterobius vermicularis (Pinworm):** Primarily causes perianal pruritus (itching) at night. While it inhabits the cecum, it does not cause the mucosal changes or heavy clustering associated with the coconut cake appearance. * **Ancylostoma duodenale & Necator americanus (Hookworms):** These parasites reside in the small intestine (jejunum) and suck blood, leading to microcytic hypochromic anemia. They do not typically affect the rectum or cause rectal prolapse. **High-Yield Clinical Pearls for NEET-PG:** * **Morphology:** Adult worm is whip-shaped (thin anterior, thick posterior). * **Egg:** Characteristic **barrel-shaped** (lemon-shaped) with **bipolar mucus plugs**. * **Clinical Triad:** Chronic diarrhea, iron deficiency anemia, and rectal prolapse (in children). * **Treatment:** Albendazole or Mebendazole.

Q: Calabar swellings are characteristic of infection with which parasite?

Loa Loa. **Explanation:** **Loa loa** (the African Eye Worm) is the correct answer. **Calabar swellings** are transient, localized, subcutaneous edematous areas that typically appear on the extremities. They represent a **Type I hypersensitivity reaction** to the metabolic products of the migrating adult worms or the worms themselves as they move through the subcutaneous connective tissue. **Analysis of Options:** * **Loa loa (Correct):** Transmitted by the **Chrysops fly** (deer fly/mango fly). It is characterized by Calabar swellings and the visible migration of the adult worm across the subconjunctiva of the eye. * **Ascaris lumbricoides:** Primarily causes intestinal obstruction or Loeffler’s syndrome (eosinophilic pneumonia) during its pulmonary phase, but does not cause migratory subcutaneous swellings. * **Hymenolepis nana:** The dwarf tapeworm. It resides in the small intestine and typically causes vague abdominal symptoms or is asymptomatic; it has no migratory tissue phase involving the skin. * **Strongyloides stercoralis:** Known for causing **Larva Currens**, a rapidly moving serpiginous cutaneous eruption (creeping eruption) caused by migrating larvae, distinct from the localized, puffy Calabar swellings. **High-Yield Clinical Pearls for NEET-PG:** * **Vector:** *Chrysops* fly (day-biting). * **Microfilariae:** Exhibit **diurnal periodicity** (found in peripheral blood during the day, usually 10 AM – 4 PM). * **Diagnosis:** Identification of microfilariae in a peripheral blood smear or visualization of the adult worm in the eye. * **Treatment:** **Diethylcarbamazine (DEC)** is the drug of choice, but caution is required if microfilarial load is high due to the risk of encephalopathy.

Q: Which of the following is FALSE regarding Giardia lamblia?

The trophozoite has an axostyle for adherence to surfaces.. **Explanation:** The correct answer is **C** because it contains a factual error regarding the morphology of *Giardia lamblia*. While the trophozoite does possess an **axostyle** (a central supporting rod), it is **not** used for adherence. Adherence to the intestinal mucosa is mediated by a specialized **ventral sucking disc** (adhesive disc). The axostyle functions as a structural cytoskeleton. **Analysis of Options:** * **Option A (True):** The **quadrinucleate cyst** is indeed the infective stage. It is resistant to environmental stressors and gastric acid. * **Option B (True):** Cysts are highly resilient and can survive in cold water for approximately **3 months**, making waterborne transmission common. * **Option D (True):** Under a microscope, the trophozoite exhibits a characteristic **"falling leaf" motility**, which is a classic diagnostic feature in stool wet mounts. **Clinical Pearls for NEET-PG:** * **Morphology:** The trophozoite is pear-shaped (pyriform) and described as having a **"Monkey face"** or **"Old man with glasses"** appearance due to its two nuclei. * **Pathogenesis:** It causes **malabsorption** (especially of fats) by coating the duodenal and jejunal mucosa, leading to **steatorrhea** (foul-smelling, greasy stools). It does not invade the bloodstream. * **Diagnosis:** The **String Test (Entero-test)** can be used to sample duodenal contents. Antigen detection (ELISA) is now the preferred method. * **Treatment:** Drug of choice is **Tinidazole** or Metronidazole. Nitazoxanide is an alternative.

Q: Which of the following parasite's life cycle is shown below?

Fasciola hepatica. ***Fasciola hepatica*** - The life cycle involves **Lymnaea snails** as intermediate hosts and **metacercariae** encysted on aquatic vegetation like watercress. - Adult flukes migrate through **liver parenchyma** before settling in **bile ducts**, causing hepatic damage and biliary obstruction. *Paragonimus westermani* - Uses **freshwater crabs** or **crayfish** as second intermediate hosts, not aquatic vegetation. - Adults reside in **lung cysts**, not bile ducts, causing pulmonary symptoms and hemoptysis. *Clonorchis sinensis* - Requires **freshwater fish** as second intermediate hosts where metacercariae encyst in muscle tissue. - Adults migrate directly to **bile ducts** without liver parenchyma migration phase seen in Fasciola. *Fasciolopsis buski* - Metacercariae encyst on **aquatic plants** similar to Fasciola but adults remain in the **small intestine**. - Does not involve **liver migration** or bile duct colonization, causing primarily intestinal symptoms.

Q: Which of the following is a true mode of transmission of Toxoplasma?

All of the above. **Explanation:** *Toxoplasma gondii* is an obligate intracellular protozoan with a complex life cycle involving multiple modes of transmission to humans (the intermediate hosts). The correct answer is **All of the above** because *Toxoplasma* can be transmitted through several distinct routes: 1. **Ingestion of Oocysts/Tissue Cysts:** This is the most common route. Humans can ingest **sporulated oocysts** from soil or water contaminated by feline feces (definitive host) or **tissue cysts (bradyzoites)** found in undercooked meat (e.g., pork or lamb). 2. **Vertical Transmission:** Tachyzoites can cross the placenta if a woman acquires a primary infection during pregnancy, leading to **Congenital Toxoplasmosis**. 3. **Organ Transplantation & Blood Transfusion:** Though less common, the parasite can be transmitted via infected donor organs (containing tissue cysts) or through blood transfusions (containing tachyzoites). **Why other options are included:** Options A, B, and C are all scientifically accurate modes of transmission. In NEET-PG multiple-choice formats, when three distinct, valid mechanisms are listed, "All of the above" is the definitive choice. **High-Yield Clinical Pearls for NEET-PG:** * **Definitive Host:** Domestic cat (where the sexual cycle occurs). * **Infective Stages:** Oocysts (feces), Tissue cysts (meat), and Tachyzoites (transplacental). * **Congenital Triad:** Chorioretinitis, Hydrocephalus, and Intracranial calcifications. * **Diagnosis:** Sabin-Feldman Dye Test (Gold Standard) and PCR for amniotic fluid. * **Treatment:** Pyrimethamine and Sulfadiazine (Spiramycin is used in pregnancy to prevent transmission).

Q: Which of the following parasite eggs consists of polar filaments arising from either end of the ambryophore?

Hymenolepis nana. **Explanation:** The correct answer is **Hymenolepis nana** (Dwarf Tapeworm). **Why H. nana is correct:** The morphology of *Hymenolepis nana* eggs is a high-yield topic in parasitology. These eggs are characterized by an oval shape with a double membrane. The inner membrane (embryophore) encloses the oncosphere (hexacanth embryo) and possesses two distinct **polar thickenings**. From these thickenings, **4 to 8 polar filaments** arise and spread into the space between the inner and outer shells. This is a pathognomonic feature used to differentiate *H. nana* from *H. diminuta* (which lacks polar filaments). **Why other options are incorrect:** * **Taenia saginata & Taenia solium:** The eggs of both *Taenia* species are morphologically identical. They are spherical, brown, and have a thick, radially striated wall (embryophore) resembling a "wagon wheel." They do **not** possess polar filaments. * **Echinococcus granulosus:** The eggs of *Echinococcus* are morphologically indistinguishable from *Taenia* species (radially striated embryophore). Diagnosis is usually made via imaging or serology, as eggs are not typically found in human feces (humans are intermediate hosts). **NEET-PG High-Yield Pearls:** * **Smallest Cestode:** *H. nana* is the smallest intestinal cestode infecting humans. * **Direct Life Cycle:** It is unique among tapeworms because it does not require an intermediate host (though insects can act as optional ones). * **Autoinfection:** It is the only cestode capable of completing its entire life cycle in a single host, leading to internal autoinfection and heavy worm burdens. * **Treatment:** Praziquantel is the drug of choice.

Q: What is true about Plasmodium falciparum?

Crescentic macrogametocyte. **Explanation:** *Plasmodium falciparum* is the most virulent species of malaria, characterized by unique morphological features and a high parasite load. **Why Option C is Correct:** The hallmark of *P. falciparum* is the presence of **crescentic (banana-shaped) gametocytes**. These appear in the peripheral blood about 7–10 days after the initial asexual cycle. The macrogametocyte (female) is typically longer and more slender with central, compact chromatin, while the microgametocyte (male) is broader with diffuse chromatin. **Analysis of Incorrect Options:** * **A. Preferentially infects old erythrocytes:** This is incorrect. *P. falciparum* is unique because it **infects RBCs of all ages** (young and old), leading to very high levels of parasitemia. In contrast, *P. vivax* prefers reticulocytes (young RBCs), and *P. malariae* prefers senescent (old) RBCs. * **B. Schuffner's dots:** These are characteristic of *P. vivax* and *P. ovale*. In *P. falciparum*, the dots seen are called **Maurer’s clefts** (coarse granulations). * **D. Large schizonts:** While *P. falciparum* does form schizonts, they are **rarely seen in peripheral blood** because they sequester in deep capillaries (leading to cerebral malaria). When seen, they are smaller than those of *P. vivax*. **High-Yield Clinical Pearls for NEET-PG:** * **Multiple rings per RBC** and **Appole forms** (rings at the margin) are diagnostic of *P. falciparum*. * **Sequestration:** Mediated by **PfEMP-1** protein, causing cytoadherence to vascular endothelium (CD36/ICAM-1). * **Recrudescence** is seen in *P. falciparum* (due to sub-optimal treatment), whereas **Relapse** (hypnozoites) is seen in *P. vivax/ovale*.

Q: What condition is characterized by the occurrence of tetrads in red blood cells?

Babesiosis. **Explanation:** The correct answer is **Babesiosis**. This condition is caused by the protozoan parasite *Babesia microti*, which infects red blood cells (RBCs). The hallmark diagnostic feature on a Giemsa-stained peripheral blood smear is the presence of **merozoites arranged in a cross-like formation**, known as the **"Maltese Cross"** or **tetrad**. This occurs due to the parasite budding in pairs without producing pigment or gametocytes. **Analysis of Options:** * **Malaria:** While *Plasmodium falciparum* also infects RBCs and can show multiple ring forms, it typically presents with **crescent-shaped gametocytes** or Schüffner’s dots. It never forms tetrads. * **Lyme disease:** Caused by the spirochete *Borrelia burgdorferi*, it is a bacterial infection. While it shares the same vector (*Ixodes* tick) as Babesiosis, it is an extracellular pathogen and does not infect RBCs. * **Plague:** Caused by *Yersinia pestis*, it is a gram-negative coccobacillus. On microscopy, it shows a characteristic **"safety-pin" appearance** (bipolar staining) but does not involve intra-erythrocytic tetrads. **High-Yield Clinical Pearls for NEET-PG:** * **Vector:** *Ixodes scapularis* (deer tick). Co-infection with Lyme disease is common. * **Clinical Presentation:** Fever, hemolytic anemia, and hemoglobinuria. It is particularly severe or fatal in **asplenic patients**. * **Diagnosis:** Peripheral smear (Maltese cross) is the gold standard; PCR is more sensitive. * **Treatment:** Combination of **Atovaquone + Azithromycin** (preferred) or Quinine + Clindamycin.

Question 1

Coconut cake appearance of the rectum is seen in which parasitic infection?

Accepted Answer

Trichuris trichura

Answer

Enterobius vermicularis

Answer

Ancylostoma duodenale

Answer

Necator americanus

Question 2

Calabar swellings are characteristic of infection with which parasite?

Accepted Answer

Loa Loa

Answer

Ascaris

Answer

Hymenolepis

Answer

Strongyloides

Question 3

Cholangiocarcinoma has been associated with infection by which of the following organisms?

Accepted Answer

Clonorchis sinensis

Answer

Paragonimus westermani

Answer

Loa Loa

Answer

Schistosoma haematobium

Question 4

Which of the following is FALSE regarding Giardia lamblia?

Accepted Answer

The trophozoite has an axostyle for adherence to surfaces.

Answer

The quadrinucleate cyst is the infective form.

Answer

Cysts can survive in water for up to 3 months.

Answer

It exhibits falling leaf motility.

Question 5

Which of the following parasite's life cycle is shown below?

Accepted Answer

Fasciola hepatica

Answer

Paragonimus westermani

Answer

Clonorchis sinensis

Answer

Fasciolopsis buski

Question 6

Malaria recrudescence is defined as:

Accepted Answer

Reappearance of parasitemia after a period of subpatent parasitemia during treatment

Answer

Parasitemia resistant to treatment

Answer

Relapse of infection from dormant liver forms

Answer

Relapse specifically in Plasmodium vivax and ovale infections

Question 7

Which of the following is a true mode of transmission of Toxoplasma?

Accepted Answer

All of the above

Answer

Vertical transmission

Answer

Ingestion of uncooked cysts

Answer

Organ transplantation

Question 8

Which of the following parasite eggs consists of polar filaments arising from either end of the ambryophore?

Accepted Answer

Hymenolepis nana

Answer

Taenia saginata

Answer

Taenia solium

Answer

Echinococcus granulosus

Question 9

What is true about Plasmodium falciparum?

Accepted Answer

Crescentic macrogametocyte

Answer

Preferentially infects old erythrocytes only

Answer

Schuffner's dots are characteristic

Answer

Large schizonts

Question 10

What condition is characterized by the occurrence of tetrads in red blood cells?

Accepted Answer

Babesiosis

Answer

Malaria

Answer

Lyme disease

Answer

Plague

Parasitology — MCQs

Parasitology — MCQs

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