Parasitology Practice Questions

Q: An otherwise healthy person who wears contact lenses develops a small ulceration of the eye. What is the most likely cause?

Acanthamoeba. **Explanation:** The clinical scenario describes a contact lens wearer with a corneal ulcer, which is a classic presentation for **Acanthamoeba keratitis**. **1. Why Acanthamoeba is correct:** Acanthamoeba is a free-living amoeba found in soil and water. In the context of NEET-PG, the strongest risk factor for this infection is **contact lens use** (especially involving poor hygiene, such as using tap water for cleaning or swimming with lenses). The organism exists in two forms: the active trophozoite and the resilient cyst. A hallmark clinical feature is **pain out of proportion to clinical findings** and the presence of a **ring-shaped stromal infiltrate** in later stages. **2. Why the other options are incorrect:** * **Cytomegalovirus (CMV):** Typically causes retinitis (pizza-pie appearance) in immunocompromised patients (e.g., HIV/AIDS). It does not typically cause primary corneal ulcers in healthy individuals. * **Toxocara:** Usually presents as **Ocular Larva Migrans**, characterized by posterior pole granulomas or endophthalmitis, often in children who have contact with puppies. * **Toxoplasma:** The most common cause of posterior uveitis (retinochoroiditis). It presents with a "headlight in the fog" appearance on fundoscopy, not a corneal ulcer. **High-Yield Clinical Pearls for NEET-PG:** * **Stain of choice:** Calcofluor white (binds to cysts) or Periodic acid-Schiff (PAS). * **Culture medium:** Non-nutrient agar enriched with *E. coli*. * **Early sign:** Radial keratoneuritis (infiltration along corneal nerves). * **Treatment:** Topical biguanides (PHMB) or Chlorhexidine.

Q: Unsegmented eggs are seen in which of the following parasites?

Trichuris trichura. **Explanation:** The classification of helminth eggs based on their stage of development at the time of excretion is a high-yield topic for NEET-PG. Eggs are generally categorized as **unsegmented** (single-celled zygote), **segmented** (containing multiple blastomeres), or **embryonated** (containing a fully formed larva). **Correct Answer: A. Trichuris trichiura** *Trichuris trichiura* (Whipworm) eggs are laid in an **unsegmented stage**. They are characterized by a distinct barrel shape with bipolar mucus plugs. These eggs require a period of incubation in the soil (usually 2–3 weeks) to become embryonated and infective. **Analysis of Incorrect Options:** * **B & C. Necator americanus & Ancylostoma duodenale (Hookworms):** Hookworm eggs are **segmented** when passed in fresh feces. They typically contain 4 to 8 blastomeres (cleavage stages) surrounded by a thin, transparent hyaline shell. * **D. Dracunculus medinensis:** This parasite is **viviparous**. It does not lay eggs; instead, the gravid female releases fully formed, active motile larvae (L1) directly into water. **High-Yield Clinical Pearls for NEET-PG:** * **Unsegmented eggs:** *Trichuris trichiura*, *Ascaris lumbricoides* (fertilized), and *Fasciola hepatica*. * **Segmented eggs:** Hookworms (*Ancylostoma* and *Necator*). * **Embryonated eggs (containing larva):** *Enterobius vermicularis*, *Strongyloides stercoralis* (rarely seen in stool as they hatch in the mucosa), and *Hymenolepis nana*. * **Bipolar plugs:** Pathognomonic for *Trichuris trichiura*. * **Bile-stained eggs:** *Ascaris*, *Trichuris*, and *Taenia* (Mnemonic: **ATT**). Hookworm eggs are **non-bile stained**.

Q: A male patient presented with pain and discomfort in the upper abdominal region. His abdomen has enlarged, and he has experienced significant weight loss. The Casoni test is positive. What is the most likely diagnosis?

Echinococcosis. **Explanation:** The clinical presentation and the positive **Casoni test** point directly toward **Echinococcosis** (Hydatid cyst disease), caused by the larval stage of the cestode *Echinococcus granulosus*. 1. **Why Echinococcosis is correct:** The liver is the most common site for hydatid cysts (70% of cases), leading to hepatomegaly (enlarged abdomen) and right upper quadrant pain. Significant weight loss occurs in chronic or advanced cases. The **Casoni test** is an immediate hypersensitivity skin test used to detect *Echinococcus* antigens. While largely replaced by imaging (USG/CT) and serology (ELISA) in modern practice, it remains a classic high-yield diagnostic marker in medical exams. 2. **Why other options are incorrect:** * **Diphtheria:** A respiratory infection caused by *Corynebacterium diphtheriae*, characterized by a pseudomembrane in the throat and bull-neck appearance. The diagnostic test is the **Schick test**. * **Scarlet Fever:** Caused by Group A Streptococcus; presents with a "strawberry tongue" and sandpaper rash. The diagnostic test is the **Dick test**. * **Kala Azar (Visceral Leishmaniasis):** While it causes massive splenomegaly and weight loss, it is diagnosed via bone marrow/splenic aspirate (LD bodies) or the **Montenegro skin test** (which is negative in active disease). **High-Yield Clinical Pearls for NEET-PG:** * **Definitive Host:** Dog; **Intermediate Host:** Sheep (Humans are accidental intermediate hosts/dead-end hosts). * **Microscopy:** "Hydatid sand" (brood capsules and protoscolices) is found in the cyst fluid. * **Imaging:** Look for "Water lily sign" or "Camelot sign" on USG/CT. * **Management:** PAIR (Puncture, Aspiration, Injection, Re-aspiration) technique and Albendazole. Avoid cyst rupture to prevent life-threatening **anaphylaxis**.

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).

Question 1

An otherwise healthy person who wears contact lenses develops a small ulceration of the eye. What is the most likely cause?

Accepted Answer

Acanthamoeba

Answer

Cytomegalovirus

Answer

Toxocara

Answer

Toxoplasma

Question 2

Unsegmented eggs are seen in which of the following parasites?

Accepted Answer

Trichuris trichura

Answer

Necator americanus

Answer

Ankylostoma

Answer

Dracunculus

Question 3

A male patient presented with pain and discomfort in the upper abdominal region. His abdomen has enlarged, and he has experienced significant weight loss. The Casoni test is positive. What is the most likely diagnosis?

Accepted Answer

Echinococcosis

Answer

Diphtheria

Answer

Scarlet fever

Answer

Kala Azar

Question 4

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

Accepted Answer

Kala-azar

Answer

Malaria

Answer

Acanthamoeba

Answer

Entamoeba

Question 5

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 6

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 7

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 8

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 9

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

Accepted Answer

Brucella

Answer

Malaria

Answer

Toxoplasma

Answer

Babesia

Question 10

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

Parasitology — MCQs

Parasitology — MCQs

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