Parasitology Practice Questions

Q: DEC Provocation test is used for which condition?

Filariasis. **Explanation:** **Diethylcarbamazine (DEC) Provocation Test** is a diagnostic technique used for **Lymphatic Filariasis**, specifically caused by *Wuchereria bancrofti* and *Brugia malayi*. **Why it is the correct answer:** In many endemic areas, microfilariae exhibit **nocturnal periodicity**, meaning they circulate in the peripheral blood only at night (usually between 10 PM and 2 AM). To avoid collecting blood samples at night, a "DEC Provocation Test" is performed. A small dose of DEC (2 mg/kg) is administered to the patient. This drug stimulates the microfilariae to emerge from the deep pulmonary capillaries into the peripheral circulation within 30–60 minutes, allowing for daytime blood collection and diagnosis. **Why other options are incorrect:** * **Malaria:** Diagnosis is primarily via thick and thin peripheral blood smears (Gold Standard) or Rapid Diagnostic Tests (RDTs) detecting PfHRP2 or LDH antigens. * **Guinea Worm (*Dracunculus medinensis*):** Diagnosis is clinical, based on the visualization of the adult worm emerging from a skin ulcer, usually on the lower distal limbs. * **Yellow Fever:** This is a viral hemorrhagic fever diagnosed via Serology (ELISA for IgM) or PCR; it has no relation to microfilariae. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice:** DEC is the treatment of choice for Filariasis (except in cases of co-infection with Onchocerciasis or Loiasis due to the risk of Mazzotti reaction). * **Contraindication:** DEC provocation should be avoided in patients suspected of having **Loiasis** (*Loa loa*), as it can trigger fatal encephalopathy. * **Tropical Pulmonary Eosinophilia (TPE):** A hypersensitivity reaction to filarial antigens; DEC is used here both for diagnosis and treatment.

Q: A 6-year-old girl presents with intense perianal itching, especially at night. Physical examination reveals perianal excoriation. An adhesive tape test is positive for worms. Which of the following is the most likely parasite in this patient?

Enterobius vermicularis. **Explanation** The clinical presentation described is a classic case of **Enterobiasis**, caused by **Enterobius vermicularis** (Pinworm or Seatworm). **Why Option C is Correct:** * **Nocturnal Pruritus Ani:** The hallmark symptom is intense perianal itching at night. This occurs because the gravid female worm migrates out of the anus to deposit eggs on the perianal skin folds. * **Adhesive Tape Test (Scotch Tape Test):** This is the gold standard for diagnosis. Since eggs are rarely found in feces, a transparent adhesive tape is applied to the perianal area in the morning to collect and visualize the characteristic **planoconvex (D-shaped)** eggs under a microscope. * **Transmission:** It is common in children due to the feco-oral route and autoinoculation (finger-to-mouth after scratching). **Why Other Options are Incorrect:** * **Options A & D (Hookworms):** *Ancylostoma duodenale* and *Necator americanus* primarily cause iron-deficiency anemia and ground itch at the site of larval penetration (usually the feet). They do not cause perianal itching. * **Option B (Ascaris lumbricoides):** The giant roundworm typically presents with intestinal obstruction, Loeffler’s syndrome (pulmonary phase), or biliary colic. Diagnosis is made by finding eggs in the stool, not via the tape test. **High-Yield Clinical Pearls for NEET-PG:** * **Morphology:** Eggs are non-bile stained and D-shaped. * **Treatment:** **Albendazole** or Mebendazole (single dose, repeated after 2 weeks). It is crucial to **treat the entire family** to prevent reinfection. * **Ectopic Migration:** In females, the worm can migrate into the vagina, leading to vulvovaginitis or pelvic inflammatory disease (PID).

Q: Sleeping sickness is transmitted by which vector?

Tsetse fly. **Explanation:** **Correct Answer: A. Tsetse fly** Sleeping sickness, also known as **African Trypanosomiasis**, is caused by protozoan parasites of the genus *Trypanosoma brucei* (*T.b. gambiense* and *T.b. rhodesiense*). The definitive vector for this disease is the **Tsetse fly** (genus *Glossina*). When an infected fly takes a blood meal, it injects metacyclic trypomastigotes into the host's skin, leading to a systemic infection characterized by fever, lymphadenopathy (Winterbottom’s sign), and eventually CNS involvement (meningoencephalitis). **Why the other options are incorrect:** * **B. House fly (*Musca domestica*):** These are mechanical vectors. They do not support the biological life cycle of parasites but transmit pathogens like *E. coli*, *Shigella*, and various helminth eggs via contaminated feet and mouthparts. * **C. Sand fly (*Phlebotomus*):** This is the vector for **Leishmaniasis** (Kala-azar) and Sandfly fever. It transmits *Leishmania* promastigotes. * **D. Simulium fly (Black fly):** This is the vector for **Onchocerciasis** (River Blindness), transmitting the filarial nematode *Onchocerca volvulus*. **High-Yield Clinical Pearls for NEET-PG:** * **Winterbottom’s Sign:** Posterior cervical lymphadenopathy; a classic clinical sign of African Trypanosomiasis. * **Antigenic Variation:** *Trypanosoma brucei* undergoes **Variant Surface Glycoprotein (VSG)** switching, allowing it to evade the host immune system. * **Drug of Choice:** **Suramin** or **Pentamidine** for early stages; **Melarsoprol** or **Eflornithine** for late-stage CNS involvement. * **Chagas Disease:** Do not confuse with American Trypanosomiasis, which is caused by *T. cruzi* and transmitted by the **Reduviid (Triatomine) bug**.

Q: Which of the following is caused by Leishmania?

Leishmania. **Explanation:** The correct answer is **Leishmania**. This question highlights the basic classification of protozoan parasites. **Leishmaniasis** is a vector-borne disease caused by obligate intracellular protozoa of the genus *Leishmania*, transmitted to humans by the bite of infected female **Phlebotomine sandflies**. **Why the other options are incorrect:** * **Trypanosoma:** These are hemoflagellates responsible for **African Sleeping Sickness** (*T. brucei*) transmitted by the Tsetse fly, and **Chagas disease** (*T. cruzi*) transmitted by the Reduviid bug. * **Treponema:** This is a genus of **Spirochetes** (bacteria), not a parasite. The most clinically significant species is *Treponema pallidum*, the causative agent of **Syphilis**. * **Toxoplasma:** *Toxoplasma gondii* is an intracellular coccidian parasite. It causes **Toxoplasmosis**, typically transmitted via ingestion of oocysts from cat feces or undercooked meat, and is a major cause of congenital infections (TORCH complex). **High-Yield Clinical Pearls for NEET-PG:** * **Clinical Forms:** Leishmaniasis presents in three main forms: **Visceral** (Kala-azar), **Cutaneous** (Oriental sore), and **Mucocutaneous**. * **Kala-azar (Visceral Leishmaniasis):** Caused by *L. donovani*. Characterized by the triad of **massive splenomegaly**, irregular fever, and pancytopenia. * **Diagnostic Gold Standard:** Demonstration of **LD bodies** (Amastigotes) in bone marrow or splenic aspirates. * **Culture:** Grown on **NNN (Novy-MacNeal-Nicolle) medium**, where the promastigote stage is seen. * **Drug of Choice:** Liposomal Amphotericin B is currently the preferred treatment for Visceral Leishmaniasis in India.

Q: Which of the following organisms does not cause neurodegeneration?

Iodamoeba. **Explanation:** The core concept tested here is the distinction between **pathogenic free-living amoebae** (which have a predilection for the Central Nervous System) and **intestinal amoebae**. **Why Iodamoeba is the correct answer:** *Iodamoeba bütschlii* is a commensal intestinal amoeba. It is considered **non-pathogenic** to humans and resides in the large intestine. It does not invade the bloodstream or cross the blood-brain barrier; therefore, it cannot cause neurodegeneration or any neurological pathology. **Analysis of Incorrect Options:** * **Naegleria fowleri:** Known as the "brain-eating amoeba," it causes **Primary Amoebic Meningoencephalitis (PAM)**. It enters via the olfactory neuroepithelium, leading to rapid, fulminant brain tissue destruction. * **Balamuthia mandrillaris:** A free-living amoeba that causes **Granulomatous Amoebic Encephalitis (GAE)**, a subacute to chronic necrotizing infection of the CNS, typically in both immunocompetent and immunocompromised hosts. * **Entamoeba histolytica:** While primarily an intestinal pathogen causing dysentery, it can spread hematogenously. **Cerebral amoebiasis** is a rare but recognized extraintestinal complication of *E. histolytica*, presenting as brain abscesses and secondary neurodegeneration. **NEET-PG High-Yield Pearls:** 1. **Free-living amoebae (FLA):** *Naegleria, Acanthamoeba,* and *Balamuthia* are the primary neuro-pathogens. 2. **Naegleria vs. Acanthamoeba:** *Naegleria* causes acute PAM (history of swimming), while *Acanthamoeba* causes chronic GAE (associated with keratitis in contact lens users). 3. **Diagnostic Key:** In *Naegleria* infections, only **trophozoites** are found in CSF; in *Acanthamoeba/Balamuthia*, both **cysts and trophozoites** are present in tissue. 4. **Iodamoeba characteristic:** It is named for its large **iodinophilic vacuole** (glycogen mass) that stains dark brown with iodine.

Q: Cerebral malaria is caused by which Plasmodium species?

Falciparum. **Explanation:** **Plasmodium falciparum** is the most virulent species of malaria and is the primary cause of **Cerebral Malaria**. The underlying pathophysiology involves **cytoadherence** and **sequestration**. *P. falciparum* expresses a protein called **PfEMP-1** (Plasmodium falciparum erythrocyte membrane protein 1) on the surface of infected Red Blood Cells (RBCs). This protein acts as a ligand for receptors like **ICAM-1** and **CD36** on the vascular endothelium. This causes infected RBCs to stick to the walls of small capillaries (sequestration) and to each other (rosetting), leading to microvascular obstruction, tissue hypoxia, and localized inflammatory responses in the brain. **Analysis of Incorrect Options:** * **P. vivax & P. ovale:** These species primarily cause "Benign Tertian Malaria." They prefer infecting young RBCs (reticulocytes), leading to lower parasite loads. While *P. vivax* can occasionally cause severe complications, it does not typically cause the classic sequestration-driven cerebral malaria. Both are known for forming **hypnozoites** in the liver, leading to relapses. * **P. malariae:** This species causes "Quartan Malaria" (72-hour cycle). It typically results in a milder clinical course but is uniquely associated with **nephrotic syndrome** (quartan malarial nephropathy) due to immune complex deposition. **High-Yield Clinical Pearls for NEET-PG:** * **Blackwater Fever:** Severe intravascular hemolysis leading to hemoglobinuria, specifically associated with *P. falciparum*. * **Maurer’s Clefts:** Seen in RBCs infected with *P. falciparum*; whereas **Schüffner’s dots** are seen in *P. vivax/ovale*. * **Multiple Rings & Accole forms:** Characteristic peripheral smear findings for *P. falciparum*. * **Drug of Choice:** For severe/cerebral malaria, **Intravenous Artesunate** is the gold standard.

Q: Which of the following is false regarding Trichomonas vaginalis?

Mature cysts are passed in feces.. **Explanation:** The correct answer is **C (Mature cysts are passed in feces)** because *Trichomonas vaginalis* is unique among pathogenic protozoa as it **does not have a cyst stage**. It exists only as a trophozoite. Furthermore, it is a urogenital parasite, not an intestinal one; therefore, it is not passed in feces but is transmitted primarily through sexual contact. **Analysis of Options:** * **A. Trophozoites have 5 anterior flagella:** This is a common point of confusion. *T. vaginalis* actually possesses **4 anterior flagella** and a **5th flagellum** that forms the outer edge of the undulating membrane. (Note: Some texts refer to the total flagellar count, but the classic description is 4 free anterior flagella). * **B. Exhibits twitching motility:** This is a classic diagnostic feature. In a wet mount of vaginal or urethral discharge, the trophozoites exhibit a characteristic jerky, **twitching motility**, which is a high-yield fact for identification. * **D. Drug of choice is metronidazole:** Metronidazole (or Tinidazole) is the gold standard treatment. It is crucial to treat both the patient and the **sexual partner** simultaneously to prevent "ping-pong" reinfection. **Clinical Pearls for NEET-PG:** * **Habitat:** Female vagina and male urethra/prostate. * **Clinical Presentation:** Causes "Strawberry Cervix" (colpitis macularis) due to punctate hemorrhages. * **Diagnosis:** Gold standard is **Whiff Test** (amine odor with KOH) and **Diamond’s Medium** for culture. * **pH:** It thrives in an alkaline vaginal pH (>4.5), unlike the normal acidic environment.

Q: L.D. bodies are seen in which of the following conditions?

Kala-azar. **Explanation:** **L.D. Bodies (Leishman-Donovan bodies)** are the **amastigote stage** of the protozoan parasite *Leishmania donovani*. This stage is found intracellularly within the reticuloendothelial system (macrophages, liver, spleen, and bone marrow) of the human host. 1. **Why Kala-azar is correct:** Kala-azar, also known as Visceral Leishmaniasis, is caused by *L. donovani*. In the human host, the parasite exists as an ovoid, non-flagellated amastigote (L.D. body) measuring 2–4 µm. Demonstration of these bodies in splenic or bone marrow aspirates remains the **gold standard for diagnosis**. 2. **Why other options are incorrect:** * **Toxoplasmosis:** Caused by *Toxoplasma gondii*. It presents as tachyzoites (active infection) or bradyzoites (tissue cysts), not L.D. bodies. * **Malaria:** Caused by *Plasmodium* species. Diagnostic stages include ring forms, trophozoites, schizonts, and gametocytes within RBCs. * **Sleeping sickness (African Trypanosomiasis):** Caused by *Trypanosoma brucei*. It exists only in the **trypomastigote** stage (extracellular flagellates) in human blood and CSF; it does not have an amastigote stage. **High-Yield Clinical Pearls for NEET-PG:** * **Vector:** Sandfly (*Phlebotomus argentipes*). * **Infective stage:** Promastigote (found in the sandfly). * **Diagnostic stage:** Amastigote (L.D. body). * **Morphology of L.D. Body:** Contains a nucleus and a rod-shaped **kinetoplast**. * **Culture:** NNN (Novy-MacNeal-Nicolle) medium. * **Drug of Choice:** Liposomal Amphotericin B.

Q: A 32-year-old man presented with various signs and symptoms after consuming crab from a local restaurant. Which parasite can be transmitted through consuming crab?

Paragonimus westermanii. **Explanation:** The correct answer is **Paragonimus westermanii**, also known as the **Oriental Lung Fluke**. **1. Why Paragonimus westermanii is correct:** The life cycle of *Paragonimus westermanii* involves two intermediate hosts. The first is a snail, and the second is a **crustacean (crab or crayfish)**. Humans become infected by ingesting raw or undercooked crabs containing the infective stage, the **metacercariae**. Once ingested, the larvae excyst in the duodenum, penetrate the intestinal wall, migrate through the diaphragm, and eventually mature in the lungs, leading to symptoms like hemoptysis (mimicking tuberculosis). **2. Why other options are incorrect:** * **A. Diphyllobothrium latum:** This is the fish tapeworm. Infection occurs via the consumption of undercooked **freshwater fish** containing plerocercoid larvae. * **B. Clonorchis sinensis:** Known as the Chinese Liver Fluke. While it also uses a snail as the first intermediate host, the second intermediate host is **freshwater fish**, not crabs. * **C. Enterobius vermicularis:** This is the pinworm. Transmission is primarily via the **fecal-oral route** (ingestion of embryonated eggs) or autoinfection; it does not involve an aquatic intermediate host. **Clinical Pearls for NEET-PG:** * **Classic Presentation:** A patient with a history of crab consumption presenting with chronic cough and "rusty-brown" sputum (containing eggs). * **Radiology:** May show ring-shadows or "cotton-wool" opacities in the lungs, often confused with TB. * **Diagnosis:** Identification of operculated eggs in sputum or feces. * **Drug of Choice:** Praziquantel.

Question 1

DEC Provocation test is used for which condition?

Accepted Answer

Filariasis

Answer

Malaria

Answer

Guinea worm

Answer

Yellow fever

Question 2

A 6-year-old girl presents with intense perianal itching, especially at night. Physical examination reveals perianal excoriation. An adhesive tape test is positive for worms. Which of the following is the most likely parasite in this patient?

Accepted Answer

Enterobius vermicularis

Answer

Ancylostoma duodenale

Answer

Ascaris lumbricoides

Answer

Necator americanus

Question 3

Sleeping sickness is transmitted by which vector?

Accepted Answer

Tsetse fly

Answer

House fly

Answer

Sand fly

Answer

Simulium fly

Question 4

Which of the following is caused by Leishmania?

Accepted Answer

Leishmania

Answer

Trypanosoma

Answer

Treponema

Answer

Toxoplasma

Question 5

A Pap smear from a 30-year-old woman demonstrates protozoal parasites. What are these organisms most likely to be?

Accepted Answer

Trichomonas vaginalis

Answer

Cryptosporidium parvum

Answer

Entamoeba histolytica

Answer

Giardia lamblia

Question 6

Which of the following organisms does not cause neurodegeneration?

Accepted Answer

Iodamoeba

Answer

Balamuthia

Answer

Naegleria

Answer

Entamoeba

Question 7

Cerebral malaria is caused by which Plasmodium species?

Accepted Answer

Falciparum

Answer

Ovale

Answer

Vivax

Answer

Malariae

Question 8

Which of the following is false regarding Trichomonas vaginalis?

Accepted Answer

Mature cysts are passed in feces.

Answer

Trophozoites have 5 anterior flagella.

Answer

Exhibits twitching motility.

Answer

Drug of choice is metronidazole.

Question 9

L.D. bodies are seen in which of the following conditions?

Accepted Answer

Kala-azar

Answer

Toxoplasmosis

Answer

Malaria

Answer

Sleeping sickness

Question 10

A 32-year-old man presented with various signs and symptoms after consuming crab from a local restaurant. Which parasite can be transmitted through consuming crab?

Accepted Answer

Paragonimus westermanii

Answer

Diphyllobothrium

Answer

Clonorchis sinensis

Answer

Enterobius

Parasitology — MCQs

Parasitology — MCQs

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