Parasitology Practice Questions

Q: What is the vector for Kala-azar?

Sand fly. **Explanation:** **Kala-azar (Visceral Leishmaniasis)** is caused by the protozoan parasite *Leishmania donovani*. The correct answer is the **Sand fly** (specifically *Phlebotomus argentipes* in India). 1. **Why Sand fly is correct:** The sand fly acts as the biological vector. When it bites an infected human, it ingests macrophages containing **amastigotes**. Inside the sand fly’s midgut, these transform into flagellated **promastigotes** (the infective stage), which are then transmitted to a new host during a subsequent blood meal. 2. **Why other options are incorrect:** * **Flea:** Primarily the vector for *Yersinia pestis* (Plague) and *Rickettsia typhi* (Endemic typhus). * **Tsetse fly:** The vector for *Trypanosoma brucei*, causing African Sleeping Sickness. * **Tick:** Vectors for diseases like Rickettsial fever (Rocky Mountain Spotted Fever), Babesiosis, and Lyme disease. **High-Yield Clinical Pearls for NEET-PG:** * **Infective Form:** Promastigote (found in the vector). * **Diagnostic Form:** Amastigote (LD bodies) found in the Reticuloendothelial system (Spleen, Bone marrow, Liver). * **Gold Standard Diagnosis:** Splenic aspiration (highest yield) or Bone marrow biopsy showing LD bodies. * **Drug of Choice:** Liposomal Amphotericin B is currently the preferred treatment. * **Post-Kala-azar Dermal Leishmaniasis (PKDL):** A non-ulcerative cutaneous lesion appearing years after "cured" visceral leishmaniasis, acting as a reservoir for the parasite.

Q: Which virulence factor aids Entamoeba histolytica in adhering to the intestinal mucosa?

Lectin. **Explanation:** *Entamoeba histolytica* utilizes a multi-step process to invade the colonic mucosa, with **adherence** being the critical first step. **1. Why Lectin is Correct:** The primary virulence factor responsible for adherence is the **Gal/GalNAc lectin** (Galactose and N-acetyl-D-galactosamine-binding lectin). This surface protein allows the trophozoite to bind specifically to galactose and galactosamine residues on the colonic mucin and epithelial cell surfaces. Without this attachment, the amoeba cannot initiate tissue destruction or phagocytosis. **2. Why Other Options are Incorrect:** * **Cysteine Protease:** These are enzymes secreted by the parasite to **degrade** host extracellular matrix proteins (like collagen and elastin) and immune mediators (IgA, IgG), facilitating tissue invasion after adherence has occurred. * **Amoebopore:** These are small peptides that form **pores** in the host cell membrane, leading to cytolysis (cell death). They act after the lectin-mediated binding. * **Neuraminidase:** This enzyme is more characteristic of viruses (like Influenza) or certain bacteria (like *Vibrio cholerae*); it is not a primary virulence factor for *E. histolytica*. **Clinical Pearls for NEET-PG:** * **Pathognomonic Sign:** Presence of **ingested RBCs** (Erythrophagocytosis) in trophozoites is the definitive feature of *E. histolytica* (distinguishing it from the non-pathogenic *E. dispar*). * **Flask-shaped ulcers:** The characteristic lesion produced in the colon. * **Anchovy sauce pus:** The classic description of aspirated material from an Amoebic Liver Abscess. * **Treatment:** Metronidazole/Tinidazole for invasive disease, followed by a luminal amoebicide (e.g., Diloxanide furoate or Paromomycin) to eradicate cysts.

Q: Which of the following is a known reservoir for pigs?

Taenia solium. **Explanation:** The correct answer is **Taenia solium**. In the life cycle of *Taenia solium* (the pork tapeworm), humans serve as the definitive host, while **pigs serve as the intermediate host (reservoir)**. Pigs become infected by ingesting eggs or gravid proglottids from human feces. The larvae then develop into *Cysticercus cellulosae* within the pig's muscle tissue. Humans acquire the infection by consuming undercooked "measly pork" containing these larvae. **Analysis of Incorrect Options:** * **Taenia saginata (Beef Tapeworm):** The intermediate host/reservoir is **cattle**, not pigs. Humans are the only definitive host. * **Trichinella spiralis:** While pigs are a major source of human infection, *Trichinella* is unique because the **same individual animal** acts as both the definitive and intermediate host. It does not follow the classic reservoir-to-human transmission pattern of *T. solium*. * **Ancylostoma (Hookworm):** These are soil-transmitted helminths. Their life cycle involves eggs being passed in human feces and larvae developing in the **soil**; they do not require a pig as a reservoir. **High-Yield NEET-PG Pearls:** * **Infective Stage for Humans:** For intestinal taeniasis, it is the *Cysticercus cellulosae* (larva). For **Cysticercosis** (neurocysticercosis), it is the **ingestion of eggs** (via feco-oral route), where humans act as accidental intermediate hosts. * **Diagnostic Feature:** *T. solium* has a scolex with four suckers and a rostellum with hooks ("armed" scolex), whereas *T. saginata* lacks hooks ("unarmed"). * **Drug of Choice:** Praziquantel for intestinal infection; Albendazole + Steroids for Neurocysticercosis.

Q: Calabar swelling is due to which of the following?

Hypersensitivity to adult worm of Loa-Loa. **Explanation:** **Calabar swellings** (also known as fugitive swellings) are the clinical hallmark of **Loiasis**, caused by the African eye worm, *Loa loa*. These are transient, localized subcutaneous edematous areas, typically found on the extremities (wrists or ankles). **1. Why Option A is Correct:** The underlying pathophysiology of Calabar swelling is a **Type I hypersensitivity reaction** (IgE-mediated) to the metabolic products or antigens released by the **migrating adult worm** in the subcutaneous tissues. These swellings are non-pitting, itchy, and can last for several days before disappearing and reappearing at a different site. **2. Why the Other Options are Incorrect:** * **Option B:** While microfilariae (larvae) circulate in the blood (diurnal periodicity), the localized subcutaneous swellings are specifically triggered by the movement and antigens of the adult worms, not the larvae. * **Options C & D:** *Onchocerca volvulus* causes **Onchocerciasis** (River Blindness). Its clinical manifestations include subcutaneous nodules (Onchocercomata), "hanging groin," and "leopard skin." The severe inflammatory response in Onchocerciasis is primarily due to the death of **microfilariae** (larvae), not adult worms, often exacerbated by the release of *Wolbachia* endosymbionts. **High-Yield Clinical Pearls for NEET-PG:** * **Vector:** *Chrysops* (Deer fly or Mango fly). * **Diagnosis:** Detection of microfilariae in peripheral blood (collected between **10 AM – 2 PM** due to diurnal periodicity) or visualization of the adult worm crossing the **subconjunctiva** of the eye. * **Drug of Choice:** Diethylcarbamazine (DEC). Note: Use with caution if microfilarial load is high to avoid encephalopathy. * **Eosinophilia:** Loiasis typically presents with very high peripheral blood eosinophil counts.

Q: Which of the following statements regarding Giardia is true?

Both A and B are true.. **Explanation:** *Giardia lamblia* (also known as *G. duodenalis* or *G. intestinalis*) is a flagellated protozoan that causes giardiasis. Understanding its life cycle and morphology is crucial for NEET-PG. **Why the correct answer is D (Both A and B are true):** * **Statement A is true:** The **cyst** is the infective stage. It is hardy, acid-resistant, and can survive in the environment (especially water) for months. Infection occurs via the fecal-oral route through contaminated food or water. * **Statement B is true:** Once ingested, excystation occurs in the stomach and duodenum. The resulting trophozoites primarily inhabit the **duodenum and upper jejunum**. They attach to the mucosal surface using a ventral sucking disc, leading to malabsorption (steatorrhea). **Why Option C is incorrect:** * The trophozoite form of *Giardia* possesses **four pairs of flagella (total of 8)**, not two. It is characteristically pear-shaped (pyriform) and contains two nuclei, giving it a "monkey-face" or "owl-eye" appearance under the microscope. **High-Yield Clinical Pearls for NEET-PG:** * **Morphology:** The cyst is oval with 4 nuclei (quadrinucleate), while the trophozoite is pear-shaped with 2 nuclei. * **Clinical Presentation:** Characterized by foul-smelling, greasy stools (**steatorrhea**) that float, flatulence, and abdominal cramps. It does **not** cause bloody diarrhea (non-invasive). * **Diagnosis:** Stool microscopy (cysts/trophozoites) or the **String Test (Entero-test)** to sample duodenal contents. * **Treatment:** Drug of choice is **Metronidazole** or Tinidazole. * **Association:** Increased incidence is seen in patients with **Selective IgA deficiency**.

Q: What is the required water host for Schistosoma species?

Snails. **Explanation:** **Schistosoma species** (Blood Flukes) are unique trematodes that require a specific **intermediate host** to complete their life cycle. The correct answer is **Snails** because the life cycle involves the release of *miracidia* from eggs (excreted in stool or urine), which must infect specific freshwater snails. Inside the snail, the parasite undergoes asexual reproduction to transform into *cercariae*, the infective stage for humans. * **Schistosoma haematobium:** Uses *Bulinus* snails. * **Schistosoma mansoni:** Uses *Biomphalaria* snails. * **Schistosoma japonicum:** Uses *Oncomelania* snails. **Why other options are incorrect:** * **Fish:** Serve as the second intermediate host for *Clonorchis sinensis* and *Opisthorchis*, but not for Schistosomes. * **Cyclops:** These are the intermediate hosts for *Dracunculus medinensis* (Guinea worm) and *Diphyllobothrium latum* (Fish tapeworm). * **Crabs/Crayfish:** These serve as the second intermediate host for *Paragonimus westermani* (Lung fluke). **High-Yield Clinical Pearls for NEET-PG:** * **Mode of Infection:** Unlike most trematodes (which are ingested), Schistosomes infect humans via **direct skin penetration** by cercariae in contaminated water. * **Morphology:** They are **non-hermaphroditic** (dioecious); the male has a **gynecophoric canal** where the female resides. * **Pathology:** *S. haematobium* is strongly associated with **Squamous Cell Carcinoma of the bladder** and terminal hematuria. * **Diagnostic Stage:** Detection of characteristic eggs with spines (e.g., Terminal spine in *S. haematobium*; Lateral spine in *S. mansoni*).

Question 1

What is the vector for Kala-azar?

Accepted Answer

Sand fly

Answer

Flea

Answer

Tsetse fly

Answer

Tick

Question 2

Autoinfection is NOT seen in which of the following?

Accepted Answer

Hymenolepis diminuta

Answer

Hymenolepis nana

Answer

Strongyloidosis

Answer

Taenia solium

Question 3

Which virulence factor aids Entamoeba histolytica in adhering to the intestinal mucosa?

Accepted Answer

Lectin

Answer

Cysteine protease

Answer

Amoebopore

Answer

Neuraminidase

Question 4

Which of the following is a known reservoir for pigs?

Accepted Answer

Taenia solium

Answer

Taenia saginata

Answer

Trichinella spiralis

Answer

Ancyclostoma

Question 5

Calabar swelling is due to which of the following?

Accepted Answer

Hypersensitivity to adult worm of Loa-Loa

Answer

Hypersensitivity to larva of Loa-Loa

Answer

Hypersensitivity to adult worm of Onchocerca

Answer

Hypersensitivity to larva of Onchocerca

Question 6

Which of the following is NOT true of kala azar?

Accepted Answer

Complete treatment prevents post-kala-azar dermal leishmaniasis (PKDL)

Answer

Persistent hypergammaglobulinemia

Answer

Pancytopenia

Answer

Cancrum oris can occur

Question 7

Which of the following statements regarding Giardia is true?

Accepted Answer

Both A and B are true.

Answer

The cyst form is infective to humans.

Answer

It primarily inhabits the duodenum and upper jejunum.

Answer

The trophozoite form possesses two flagella.

Question 8

Which of the following is true regarding Giardia lamblia?

Accepted Answer

The trophozoite form is binucleate.

Answer

Malabsorption is commonly seen.

Answer

Diarrhea is seen.

Answer

Jejunal wash fluid is diagnostic.

Question 9

What is the required water host for Schistosoma species?

Accepted Answer

Snails

Answer

Fish

Answer

Cyclops

Answer

Crabs

Question 10

Which of the following is NOT responsible for pulmonary eosinophilia?

Accepted Answer

Babesia microti

Answer

Ascaris lumbricoides

Answer

Paragonimus westermanii

Answer

Wuchereria bancrofti

Parasitology — MCQs

Parasitology — MCQs

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