Parasitology Practice Questions

Q: Black malarial pigment is seen in which Plasmodium species?

P. falciparum. **Explanation:** Malarial pigments, known as **hemozoin**, are insoluble crystals created by the parasite through the detoxification of heme, a byproduct of hemoglobin digestion. The color and morphology of these pigments vary across *Plasmodium* species and serve as a key diagnostic feature under light microscopy. **Why P. falciparum is correct:** In *Plasmodium falciparum* infections, the hemozoin pigment appears as **solid black or dark brown** granules. These are typically seen as a single, dense mass in the gametocyte stage (crescent-shaped) or as coarse, dark clumps in the schizont stage. The intensity of the black color is a hallmark of *P. falciparum*. **Why the other options are incorrect:** * **P. vivax:** Produces **yellowish-brown** or golden-brown pigment granules that are fine and scattered throughout the cytoplasm. * **P. malariae:** Characterized by **dark brown** pigment, often described as coarser than *P. vivax* but lacking the distinct jet-black appearance of *P. falciparum*. It often forms a central mass in the "rosette" schizont. * **P. ovale:** Similar to *P. vivax*, it produces **dark brown** granules, but they are generally fewer in number. **High-Yield Clinical Pearls for NEET-PG:** * **Maurer’s Clefts:** Coarse granulations seen in RBCs infected with *P. falciparum*. * **Schüffner’s Dots:** Fine stippling seen in *P. vivax* and *P. ovale*. * **Ziemann’s Dots:** Fine dust-like dots seen in *P. malariae*. * **Recrudescence:** Seen in *P. falciparum* and *P. malariae* due to sub-lethal parasitemia. * **Relapse:** Seen in *P. vivax* and *P. ovale* due to **hypnozoites** (latent liver stages).

Q: Which of the following may cause biliary obstruction?

Clonorchis. **Explanation:** The correct answer is **Clonorchis sinensis** (the Chinese Liver Fluke). **Why Clonorchis is correct:** *Clonorchis sinensis* is a trematode that primarily inhabits the **distal bile ducts**. The adult worms cause mechanical obstruction, chronic inflammation, and hyperplasia of the biliary epithelium. Long-term infection leads to biliary stasis, stone formation (pigment stones), and recurrent pyogenic cholangitis. Crucially for NEET-PG, chronic irritation by *Clonorchis* is a major risk factor for **Cholangiocarcinoma** (bile duct cancer). **Why the other options are incorrect:** * **Ancylostoma duodenale (Hookworm):** These reside in the small intestine (jejunum) and attach to the mucosa to suck blood, leading to iron deficiency anemia. They do not migrate into the biliary tree. * **Enterobius vermicularis (Pinworm):** These primarily inhabit the cecum and appendix. Their main clinical manifestation is perianal pruritus; they do not cause biliary pathology. * **Strongyloides stercoralis:** These reside in the mucosal tunnels of the duodenum and upper jejunum. While they can cause severe autoinfection in immunocompromised hosts (Hyperinfection syndrome), they are not a cause of biliary obstruction. **NEET-PG High-Yield Pearls:** 1. **Biliary Parasites:** Apart from *Clonorchis*, the other major parasite causing biliary obstruction is ***Ascaris lumbricoides*** (due to its tendency to migrate into the Ampulla of Vater) and ***Fasciola hepatica***. 2. **Intermediate Hosts:** *Clonorchis* requires two intermediate hosts: 1st - Snail (Parafossarulus); 2nd - Freshwater fish (Cyprinidae family). 3. **Infective Stage:** Metacercariae found in undercooked fish. 4. **Drug of Choice:** Praziquantel is the gold standard treatment for *Clonorchis* and most trematodes.

Q: Loeffler's syndrome is seen with all of the following except:

Giardiasis. **Explanation:** **Loeffler’s Syndrome** (Simple Pulmonary Eosinophilia) is a clinical condition characterized by transient respiratory symptoms (cough, wheezing, dyspnea), migratory pulmonary infiltrates on X-ray, and peripheral blood eosinophilia. It occurs during the **pulmonary phase** of certain helminthic life cycles when larvae migrate through the lungs. **Why Giardiasis is the Correct Answer:** * **Giardiasis** is caused by *Giardia lamblia*, a protozoan that inhabits the duodenum and upper jejunum. It does **not** have a tissue-migratory phase and does not pass through the lungs. Therefore, it cannot cause Loeffler’s syndrome. **Why the other options are incorrect:** * **Ascaris lumbricoides:** This is the most common cause of Loeffler’s syndrome. Larvae hatch in the intestine, enter the portal circulation, and migrate through the alveolar walls to be coughed up and swallowed. * **Strongyloides stercoralis:** This nematode follows a similar migratory path (skin → lungs → intestine). It is a classic cause of pulmonary eosinophilia. * **Toxocara (Visceral Larva Migrans):** *Toxocara canis/cati* larvae migrate through various organs, including the lungs, triggering a significant eosinophilic response. **High-Yield NEET-PG Pearls:** 1. **Mnemonic for Loeffler’s Syndrome (NASA):** **N**ecator americanus, **A**scaris lumbricoides, **S**trongyloides stercoralis, **A**ncylostoma duodenale. 2. **Diagnosis:** Look for **Charcot-Leyden crystals** in the sputum (formed from eosinophil breakdown). 3. **Stool Examination:** During the pulmonary phase of *Ascaris*, stool samples are usually **negative** for eggs because the adult worms have not yet matured in the intestine. 4. **Tropical Pulmonary Eosinophilia (TPE):** Unlike Loeffler’s, TPE is a severe, chronic hypersensitivity reaction to microfilariae (*W. bancrofti*).

Q: What is the intermediate host of the organism shown here?

Cyclops. ***Cyclops*** - **Cyclops** (a copepod crustacean) is the sole intermediate host for **Dracunculus medinensis** (Guinea worm), shown in the image. - Humans become infected by drinking water containing **infected Cyclops**, which release larvae when digested in the stomach. *Snail* - **Snails** serve as intermediate hosts for **schistosomes** (blood flukes) and **liver flukes**, not Guinea worm. - The **miracidium** stage of these parasites penetrates snails to develop into **cercariae**. *Pig* - **Pigs** act as intermediate hosts for **Taenia solium** (pork tapeworm) and **Trichinella spiralis**. - Guinea worm does not require **mammalian intermediate hosts** for its life cycle completion. *Mosquito* - **Mosquitoes** are vectors for **filarial worms** like **Wuchereria bancrofti** and **Brugia malayi**. - They also transmit **malaria parasites** but have no role in **Guinea worm transmission**.

Q: A patient presents with itching, rashes, and inguinal lymphadenopathy. Skin snips reveal non-sheathed microfilariae. What is the most probable causative organism?

Mansonella streptocerca. ### Explanation The correct answer is **Mansonella streptocerca**. The diagnosis is based on two key clinical and laboratory findings: the **specimen type (skin snips)** and the **morphology of the microfilariae (non-sheathed)**. **1. Why Mansonella streptocerca is correct:** * **Habitat:** Unlike most filarial worms that reside in the blood or lymphatics, *M. streptocerca* (along with *Onchocerca volvulus*) resides in the **dermis**. Therefore, the diagnostic procedure of choice is a **skin snip**, not a blood film. * **Morphology:** The microfilariae are **unsheathed** and possess a characteristic "walking stick" or "shepherd’s crook" shaped tail. * **Clinical Presentation:** It typically causes dermatological symptoms like pruritic rashes, hypopigmented macules, and inguinal lymphadenopathy (often referred to as "hanging groin" in chronic filarial infections). **2. Why other options are incorrect:** * **Wuchereria bancrofti:** These microfilariae are **sheathed** and are found in the **blood** (showing nocturnal periodicity), not in skin snips. They primarily cause lymphatic filariasis (elephantiasis). * **Brugia malayi & Brugia timori:** Both species produce **sheathed** microfilariae found in the **peripheral blood**. They are characterized by two distinct terminal nuclei at the tip of the tail, which are absent in *Mansonella*. **3. High-Yield Clinical Pearls for NEET-PG:** * **Skin Snip Positive Filariae:** Remember the duo—*Onchocerca volvulus* and *Mansonella streptocerca*. * **Sheath vs. No Sheath:** * *Sheathed:* *W. bancrofti, B. malayi, Loa loa.* * *Unsheathed:* *Onchocerca volvulus, Mansonella* species. * **Vector:** *Mansonella streptocerca* is transmitted by **Culicoides** biting midges. * **Treatment:** Diethylcarbamazine (DEC) is effective against *M. streptocerca*, unlike *Onchocerca* where Ivermectin is preferred.

Question 1

Black malarial pigment is seen in which Plasmodium species?

Accepted Answer

P. falciparum

Answer

P. vivax

Answer

P. malariae

Answer

P. ovale

Question 2

Which of the following may cause biliary obstruction?

Accepted Answer

Clonorchis

Answer

Ancylostoma

Answer

Enterobius

Answer

Strongyloides

Question 3

Loeffler's syndrome is seen with all of the following except:

Accepted Answer

Giardiasis

Answer

Toxocara

Answer

Strongyloides stercoralis

Answer

Ascaris lumbricoides

Question 4

What is the intermediate host of the organism shown here?

Accepted Answer

Cyclops

Answer

Snail

Answer

Pig

Answer

Mosquito

Question 5

A patient presents with itching, rashes, and inguinal lymphadenopathy. Skin snips reveal non-sheathed microfilariae. What is the most probable causative organism?

Accepted Answer

Mansonella streptocerca

Answer

Wuchereria bancrofti

Answer

Brugia malayi

Answer

Brugia timori

Parasitology — MCQs

Parasitology — MCQs

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