Parasitology Practice Questions

Q: Napier's Aldehyde test is done for which of the following?

Kala-azar. **Explanation:** **Napier’s Aldehyde Test** (also known as the Formol-gel test) is a non-specific biochemical test used for the presumptive diagnosis of **Kala-azar (Visceral Leishmaniasis)**. **Why Kala-azar is correct:** The underlying principle of this test is the detection of **hypergammaglobulinemia**. In chronic Kala-azar, there is a massive, polyclonal increase in serum IgG levels. When 1–2 drops of 40% formalin are added to 1 mL of the patient's serum, the excess globulins undergo denaturation. A **positive result** is indicated by the serum turning opaque and solidifying (resembling the white of a boiled egg) within 2–20 minutes. Note that it usually becomes positive only after the disease has persisted for more than 3 months. **Why other options are incorrect:** * **Malaria:** Diagnosis is primarily made via peripheral blood smears (thick and thin) or Rapid Diagnostic Tests (RDTs) detecting PfHRP2 or LDH antigens. * **Acanthamoeba:** Diagnosis involves microscopic examination of corneal scrapings or CSF, and culture on non-nutrient agar seeded with *E. coli*. * **Entamoeba:** Diagnosis of intestinal amoebiasis relies on stool microscopy for cysts/trophozoites or stool antigen detection (EIA). **High-Yield Clinical Pearls for NEET-PG:** * **Chopra’s Antimony Test:** Another non-specific serum test for Kala-azar (uses urea stibamine). * **Specific Test of Choice:** The **rk39 immunochromatographic test** is the rapid gold standard for field diagnosis. * **Definitive Diagnosis:** Demonstration of **LD bodies** (Amastigotes) in bone marrow or splenic aspirates. * **Culture:** Uses **NNN (Novy-MacNeal-Nicolle) medium**, where the Promastigote form is seen.

Q: A 40-year-old male from Bihar complains of pain abdomen and has hepatosplenomegaly. A peripheral smear stain shows findings suggestive of which of the following parasitic infections?

Leishmania. ***Leishmania*** - **Bihar** is highly endemic for **visceral leishmaniasis (Kala-azar)**, and the classic triad of abdominal pain, **hepatosplenomegaly**, and fever strongly suggests this diagnosis. - Peripheral smear shows **LD bodies (amastigotes)** within **monocytes/macrophages**, which are pathognomonic for leishmaniasis. *Plasmodium vivax* - Shows **intra-erythrocytic trophozoites** and **gametocytes** on peripheral smear, not intracellular amastigotes in white blood cells. - Typically presents with **cyclical fever** and **rigors**, without the characteristic hepatosplenomegaly pattern seen in kala-azar. *Microfilaria* - Appears as **extracellular sheathed larvae** circulating freely in blood, not as intracellular parasites. - Clinical presentation includes **lymphatic obstruction**, **elephantiasis**, and **nocturnal periodicity**, not hepatosplenomegaly. *Cryptosporidium parvum* - Primarily causes **intestinal infections** with **watery diarrhea** and is diagnosed through **stool examination**, not peripheral blood smear. - Does **not appear** on peripheral blood smears and does not cause hepatosplenomegaly.

Q: LD bodies are typically found in which stage of the Leishmania parasite lifecycle?

Amastigote forms. **Explanation:** **LD bodies (Leishman-Donovan bodies)** are the diagnostic hallmark of Visceral Leishmaniasis (Kala-azar). They represent the **Amastigote stage** of the *Leishmania* parasite. 1. **Why Option A is correct:** In the human host (vertebrate), the parasite resides within the phagolysosomes of macrophages. Here, it exists in the **amastigote form**—a small, oval, non-flagellated body (2–4 µm). When these are visualized in tissue smears (like splenic or bone marrow aspirates) using Giemsa or Leishman stain, they are referred to as LD bodies. They are characterized by a large nucleus and a rod-shaped kinetoplast. 2. **Why other options are incorrect:** * **Option B:** The **Promastigote form** is the extracellular, motile, flagellated stage found in the midgut of the **Sandfly vector** (*Phlebotomus* spp.) and in artificial culture media (e.g., NNN medium). It is the infective stage for humans but is not referred to as an LD body. * **Options C & D:** These are incorrect because the term "LD body" specifically and exclusively describes the intracellular amastigote stage found in mammalian tissues. **High-Yield Clinical Pearls for NEET-PG:** * **Infective Form:** Promastigote (injected by sandfly bite). * **Diagnostic Form:** Amastigote (LD bodies in macrophages). * **Gold Standard Diagnosis:** Splenic aspirate (highest sensitivity) showing LD bodies. * **Culture Medium:** NNN (Novy-MacNeal-Nicolle) medium, where the parasite converts back to the promastigote form. * **Vector:** *Phlebotomus argentipes* (in the Indian subcontinent).

Q: Which of the following helminth eggs are typically non-bile stained?

Ancylostoma duodenale. In parasitology, the distinction between **bile-stained** and **non-bile stained** eggs is a high-yield classification for identifying helminths under microscopy. ### 1. Why Ancylostoma duodenale is Correct **Ancylostoma duodenale** (Hookworm) eggs are **non-bile stained**. These eggs are characterized by a thin, transparent hyaline shell membrane. Because they do not absorb bile pigments during their passage through the intestine, they appear colorless or pearly white under the microscope. Other common non-bile stained eggs include *Enterobius vermicularis* (Pinworm) and *Necator americanus*. ### 2. Why the Other Options are Incorrect * **Trichuris trichiura (Whipworm):** These eggs are classic examples of **bile-stained** eggs. They are yellowish-brown, barrel-shaped, and possess characteristic polar plugs. * **Ascaris lumbricoides (Roundworm):** Both fertilized and unfertilized eggs of *Ascaris* are **bile-stained**, giving them a distinct golden-brown color. (Note: Decorticated eggs may appear clear, but the species is fundamentally classified as bile-stained). * **Option D:** Incorrect because only *Ancylostoma* fits the non-bile stained criteria in this list. ### 3. Clinical Pearls for NEET-PG * **Mnemonic for Non-Bile Stained Eggs:** "**NH**E" (**N**ecator americanus, **H**ookworm/Ancylostoma, **E**nterobius vermicularis). *Note: Hymenolepis nana is also non-bile stained.* * **Mnemonic for Bile Stained Eggs:** "**ABC**T" (**A**scaris, **B**ile-stained, **C**lonorchis, **T**richuris/Taenia). * **Hookworm Key Feature:** The egg is typically seen in the "segmented" stage (usually 4–8 blastomeres) with a clear space between the shell and the internal yolk mass.

Q: The image shows the ovum of a helminth. What is true about this helminth?

Produces non-bile stained eggs.. ***Produces non-bile stained eggs.*** - **Enterobius vermicularis** (pinworm) produces characteristic **D-shaped, colorless, non-bile stained eggs** that are easily identifiable under microscopy. - These eggs have a **flattened side** and are typically collected using the **scotch tape test** from the perianal region. *Transmission is through ingestion of infected pork.* - **Enterobius vermicularis** is transmitted through the **fecal-oral route** and **fomites**, not through ingestion of infected pork. - **Taenia solium** (pork tapeworm) is transmitted through infected pork, but has distinctively different egg morphology. *The helminth causes a transient, self-resolving infection in humans.* - **Pinworm infections** are typically **chronic and persistent** due to frequent **auto-reinfection** and **reinfection cycles**. - The infection requires active treatment and does not resolve spontaneously without intervention. *The drug of choice for this condition is albendazole.* - The drugs of choice for **Enterobius vermicularis** are **mebendazole** or **pyrantel pamoate**, not albendazole. - **Albendazole** is primarily used for other helminthic infections like **hydatid cysts** and **neurocysticercosis**.

Q: Which of the following methods is used to diagnose a corneal ulcer caused by Acanthamoeba?

All of the above. **Explanation:** Acanthamoeba keratitis is a sight-threatening infection often associated with contact lens wear or exposure to contaminated water. Diagnosing it requires identifying the characteristic double-walled cysts or trophozoites in corneal scrapings. **Why "All of the above" is correct:** While Acanthamoeba is a protozoan, its cell wall contains chitin and cellulose, making it susceptible to stains and methods typically used for fungi: * **KOH Mount (10%):** This is a rapid bedside technique. KOH dissolves cellular debris, allowing the highly resistant, double-walled Acanthamoeba cysts to be visualized under a light microscope. * **Calcofluor White:** This is a fluorescent stain that binds to cellulose and chitin. It is considered highly sensitive for identifying Acanthamoeba cysts, which appear as bright apple-green or blue-white structures under a fluorescence microscope. * **Lactophenol Cotton Blue (LPCB):** Though primarily a fungal stain, LPCB can be used to stain the cysts, providing contrast to visualize their morphology. **High-Yield Clinical Pearls for NEET-PG:** * **Gold Standard Culture:** Non-nutrient agar (NNA) enriched with **Escherichia coli** (look for "trailing" or "tracks" made by amoeba). * **Classic Clinical Sign:** **Ring Infiltrate** (advanced stage) and **Radial Keratoneuritis** (early stage, pathognomonic). * **Symptoms vs. Signs:** Characterized by **pain out of proportion** to the clinical findings. * **Other Stains:** Periodic Acid-Schiff (PAS) and Giemsa stain can also be used. * **Treatment of Choice:** Topical biguanides (PHMB 0.02%) or Diamidines (Propamidine isethionate/Brolene).

Q: Which of the following are NOT seen in the peripheral smear in Plasmodium falciparum infection?

Maurer's dots and Schizonts. In *Plasmodium falciparum* infection, the peripheral blood smear typically shows only **early trophozoites (ring forms)** and **gametocytes**. ### Why the Correct Answer is Right **Maurer’s dots and Schizonts** are generally absent from the peripheral circulation in *P. falciparum*: 1. **Schizonts:** *P. falciparum* exhibits a phenomenon called **sequestration**. Mature stages (late trophozoites and schizonts) express PfEMP-1 proteins on the RBC surface, causing them to adhere to the endothelial lining of deep capillary beds (brain, kidneys, etc.). Therefore, they are rarely seen in peripheral blood unless the infection is extremely heavy or terminal. 2. **Maurer’s dots:** These are coarse granulations seen in the cytoplasm of infected RBCs. While they are characteristic of *P. falciparum*, they are usually only visible in the mature stages that have been sequestered, making them an uncommon finding in a standard peripheral smear. ### Analysis of Other Options * **Accolé (Appliqué) forms:** These are early ring forms found at the very edge of the RBC. They are a hallmark of *P. falciparum* and are **frequently seen** in peripheral smears. * **Schuffner’s dots:** These are characteristic of *P. vivax* and *P. ovale*, not *P. falciparum*. ### NEET-PG High-Yield Pearls * **Multiple rings per RBC** and **Accolé forms** are diagnostic of *P. falciparum*. * **Gametocytes:** *P. falciparum* gametocytes are uniquely **crescent or banana-shaped**. * **Sequestration** is the primary reason why *P. falciparum* causes **Cerebral Malaria** (cytoadherence in brain capillaries). * **Ziemann’s dots** are associated with *P. malariae*.

Q: Auto infection occurs in which of the following organisms?

All of the above. **Explanation:** **Autoinfection** is a process where an individual serves as both the reservoir and the host, becoming reinfected by a pathogen already present in their body without the need for an external environment or intermediate host. * **Hymenolepis nana (Dwarf Tapeworm):** This is the most common cause of autoinfection. Eggs released in the intestine can hatch immediately into oncospheres, which penetrate the villi and develop into cysticercoid larvae, eventually maturing into adult worms within the same host (**Internal Autoinfection**). * **Enterobius vermicularis (Pinworm):** Eggs deposited on the perianal skin can hatch into larvae that migrate back into the anus (**Retroinfection**) or be transferred to the mouth via contaminated fingers (**External Autoinfection/Fecal-oral**). * **Taenia solium (Pork Tapeworm):** If a person harboring the adult worm ingests eggs (via contaminated food or reverse peristalsis), the eggs hatch into larvae that migrate to tissues, causing **Cysticercosis**. This is a critical clinical distinction from T. saginata, which does not cause autoinfection. **High-Yield NEET-PG Pearls:** 1. **Other organisms causing autoinfection:** *Strongyloides stercoralis* (Internal autoinfection via filariform larvae) and *Cryptosporidium parvum*. 2. **H. nana** is unique because it is the only cestode that does not mandatory require an intermediate host. 3. **Hyperinfection syndrome:** Seen in *Strongyloides* in immunocompromised patients (e.g., those on steroids) due to massive internal autoinfection. 4. **Diagnosis:** *Enterobius* is best diagnosed via the **NIH Swab/Scotch Tape test**, not routine stool microscopy.

Q: Chaga's disease is transmitted by which of the following vectors?

Reduvid bug. **Explanation:** **Chagas disease** (also known as American Trypanosomiasis) is caused by the protozoan parasite *Trypanosoma cruzi*. The primary mode of transmission is through the infected feces of the **Reduvid bug** (Option D), also commonly known as the "kissing bug," "assassin bug," or "triatomine bug." The transmission occurs when the bug bites a human (usually on the face) and defecates near the wound; the parasite enters the body when the person inadvertently rubs the feces into the bite site or mucous membranes. **Analysis of Incorrect Options:** * **Hard Tick (Ixodidae):** These are vectors for diseases such as Kyasanur Forest Disease (KFD), Indian Tick Typhus, and Lyme disease. * **Soft Tick (Argasidae):** These are primarily responsible for transmitting Relapsing fever (endemic). * **Sandfly (Phlebotomus):** This is the vector for Kala-azar (Visceral Leishmaniasis) and Oriental sore (Cutaneous Leishmaniasis). **High-Yield Clinical Pearls for NEET-PG:** * **Romaña’s sign:** Unilateral painless periorbital edema is a classic early clinical sign of Chagas disease. * **Chronic Complications:** Long-term infection can lead to **Mega-viscera** (Megaesophagus and Megacolon) and **Dilated Cardiomyopathy** (the most common cause of death). * **C-shaped Trypomastigote:** On a peripheral blood smear, *T. cruzi* typically appears in a characteristic "C" or "U" shape. * **Chagas vs. Sleeping Sickness:** While Chagas is American Trypanosomiasis (Reduvid bug), African Sleeping Sickness is caused by *T. brucei* and transmitted by the **Tsetse fly**.

Question 1

Napier's Aldehyde test is done for which of the following?

Accepted Answer

Kala-azar

Answer

Malaria

Answer

Acanthamoeba

Answer

Entamoeba

Question 2

A 40-year-old male from Bihar complains of pain abdomen and has hepatosplenomegaly. A peripheral smear stain shows findings suggestive of which of the following parasitic infections?

Accepted Answer

Leishmania

Answer

Plasmodium vivax

Answer

Microfilaria

Answer

Cryptosporidium parvum

Question 3

LD bodies are typically found in which stage of the Leishmania parasite lifecycle?

Accepted Answer

Amastigote forms

Answer

Promastigote forms

Answer

Both amastigote and promastigote forms

Answer

Neither amastigote nor promastigote forms

Question 4

Which of the following helminth eggs are typically non-bile stained?

Accepted Answer

Ancylostoma duodenale

Answer

Trichuris trichura

Answer

Ascaris lumbricoides

Answer

All of the above

Question 5

The image shows the ovum of a helminth. What is true about this helminth?

Accepted Answer

Produces non-bile stained eggs.

Answer

Transmission is through ingestion of infected pork.

Answer

The helminth causes a transient, self-resolving infection in humans.

Answer

The drug of choice for this condition is albendazole.

Question 6

Which of the following parasites can be detected in a peripheral blood smear?

Accepted Answer

Brucella

Answer

Malaria

Answer

Toxoplasma

Answer

Babesia

Question 7

Which of the following methods is used to diagnose a corneal ulcer caused by Acanthamoeba?

Accepted Answer

All of the above

Answer

KOH mount

Answer

Calcofluor white stain

Answer

Lactophenol cotton blue stain

Question 8

Which of the following are NOT seen in the peripheral smear in Plasmodium falciparum infection?

Accepted Answer

Maurer's dots and Schizonts

Answer

Schizonts and Acccolé

Answer

Maurer's dots and Acccolé

Answer

Acccolé and Shuffner's dots

Question 9

Auto infection occurs in which of the following organisms?

Accepted Answer

All of the above

Answer

Hymenolepis nana

Answer

Enterobius vermicularis

Answer

Taenia solium

Question 10

Chaga's disease is transmitted by which of the following vectors?

Accepted Answer

Reduvid bug

Answer

Hard tick

Answer

Soft tick

Answer

Sandfly

Parasitology — MCQs

Parasitology — MCQs

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