Parasitology Practice Questions

Q: Where does Schistosoma Japonicum reside?

Ileocecal plexus. **Explanation:** *Schistosoma japonicum* is a blood fluke that primarily inhabits the **superior mesenteric veins**, which drain the small intestine and the ascending/transverse colon. The **ileocecal plexus** is the specific anatomical site within this drainage system where the adult worms reside and deposit their eggs. **Why the other options are incorrect:** * **Vesical Plexus:** This is the primary habitat for ***Schistosoma haematobium***. It leads to urinary schistosomiasis, characterized by terminal hematuria and an increased risk of squamous cell carcinoma of the bladder. * **Systemic Circulation:** While cercariae travel through the blood to reach the liver (where they mature), the adult worms do not reside in the general systemic circulation. They live specifically in the portal venous system. * **Gallbladder:** This is a common site for liver flukes like *Clonorchis sinensis* or *Fasciola hepatica*, but not for Schistosomes. **High-Yield NEET-PG Pearls:** 1. **Habitat Mnemonic:** * *S. haematobium*: **H**ematobium = **H**ole (Bladder/Vesical plexus). * *S. mansoni*: **M**ansoni = **M**inferior (Inferior mesenteric veins/Sigmoid-rectal area). * *S. japonicum*: **J**aponicum = **J**uperior (Superior mesenteric veins/Ileocecal area). 2. **Egg Morphology:** *S. japonicum* eggs are unique for being **rounded/oval with a rudimentary lateral knob** (often difficult to see), unlike the prominent terminal spine of *S. haematobium* or the large lateral spine of *S. mansoni*. 3. **Pathology:** *S. japonicum* is associated with "Katayama Fever" and has the highest egg output, often leading to severe hepatic fibrosis and portal hypertension.

Q: Splenic rupture is most commonly associated with infection by which of the following Plasmodium species?

Plasmodium vivax. ### Explanation **Correct Answer: A. Plasmodium vivax** **1. Why Plasmodium vivax is correct:** While *Plasmodium falciparum* is responsible for the highest overall mortality in malaria, **spontaneous splenic rupture** is most frequently associated with **non-falciparum malaria**, specifically ***Plasmodium vivax***. The underlying mechanism involves rapid splenic enlargement (splenomegaly) during the acute phase of infection. In *P. vivax*, the spleen becomes congested, soft, and friable. Sudden increases in intra-abdominal pressure or minor trauma can lead to subcapsular hematoma formation and subsequent rupture. It is a rare but life-threatening complication, typically occurring during the primary infection rather than chronic relapses. **2. Why other options are incorrect:** * **B & C (P. ovale & P. malariae):** While these species cause splenomegaly, they are significantly less common globally and have a lower incidence of splenic complications compared to *P. vivax*. * **D (P. falciparum):** Although *P. falciparum* causes severe systemic disease (cerebral malaria, ARDS, renal failure), it is less commonly associated with acute splenic rupture. In endemic areas, chronic *P. falciparum* exposure leads to "Tropical Splenomegaly Syndrome" (Hyperreactive Malarial Splenomegaly), where the spleen becomes massive but fibrotic (firm), making it more resistant to acute rupture than the "soft" spleen of acute *P. vivax*. **3. High-Yield Clinical Pearls for NEET-PG:** * **Most common cause of Malarial Splenic Rupture:** *P. vivax*. * **Most common cause of Cerebral Malaria:** *P. falciparum*. * **Schüffner’s dots:** Seen in *P. vivax* and *P. ovale*. * **Maurer’s clefts:** Seen in *P. falciparum*. * **Ziemann’s dots:** Seen in *P. malariae*. * **Recurrence vs. Relapse:** Relapse (due to hypnozoites in the liver) is a feature of *P. vivax* and *P. ovale*.

Q: 'rK 39 antigen' is useful for the diagnosis of which condition?

Kala azar. **Explanation:** The **rK39 antigen** is a recombinant protein derived from a 39-amino acid repeat unit found in the kinesin-like protein of ***Leishmania donovani***. It is the gold standard for the rapid serological diagnosis of **Visceral Leishmaniasis (Kala-azar)**. 1. **Why Kala-azar is correct:** The rK39 immunochromatographic test (ICT) detects circulating antibodies against this specific antigen. It is highly sensitive (>95%) and specific, especially in the Indian subcontinent. It is a point-of-care test that provides results within minutes, making it ideal for field diagnosis in endemic areas like Bihar and West Bengal. 2. **Why other options are incorrect:** * **Diphtheria:** Diagnosis is primarily clinical, confirmed by **Elek’s gel precipitation test** or culture on Löffler's serum slope/Potassium tellurite agar. * **Tuberculosis:** Diagnosis relies on Sputum microscopy (AFB), **CBNAAT (GeneXpert)**, or culture on LJ medium. Serological tests are not recommended for TB diagnosis. * **Leprosy:** Diagnosis is clinical (skin patches with sensory loss) and confirmed by **Slit-skin smears** (Z-N stain) or histopathology. **High-Yield Clinical Pearls for NEET-PG:** * **rK39 Limitations:** It remains positive for several months even after a successful cure; therefore, it **cannot** be used to diagnose relapse or monitor treatment response. * **PKDL:** rK39 is also positive in cases of Post-Kala-azar Dermal Leishmaniasis. * **Definitive Diagnosis:** The "Gold Standard" for Kala-azar remains the demonstration of **LD bodies** (Amastigotes) in splenic or bone marrow aspirates. * **Drug of Choice:** Liposomal Amphotericin B is currently the preferred treatment for Kala-azar in India.

Q: The most sensitive among the following tests for the diagnosis of malaria is?

Quantitative buffy coat test. The diagnosis of malaria relies on the detection of Plasmodium parasites or their components in the blood. The **Quantitative Buffy Coat (QBC)** test is the most sensitive method among the options provided. [1] **1. Why QBC is the correct answer:** The QBC technique involves staining a specialized capillary tube with acridine orange and centrifuging it. [1] Centrifugation concentrates the parasites (which contain DNA) into a small area just below the white blood cell layer (the buffy coat). Because the parasites are **concentrated** and fluoresce under a microscope, QBC can detect as few as **5 parasites per microliter** of blood, making it significantly more sensitive than standard microscopy. **2. Why other options are incorrect:** * **Thin peripheral blood smear:** While excellent for **speciation** (identifying the species) and quantifying parasite density, it is less sensitive than thick smears or QBC because it uses a smaller volume of blood. * **PfHRP2 (Rapid Diagnostic Test):** This detects the Histidine-Rich Protein 2 of *P. falciparum*. While fast, it can yield false negatives in low parasitemia or "prozone effect" scenarios and false positives due to persistent antigens after treatment. [1] * **Pan plasmodial LDH:** This enzyme-based RDT is less sensitive than QBC and HRP2, particularly at low parasite levels, and is primarily used to monitor treatment response as LDH is only produced by live parasites. [1] **Clinical Pearls for NEET-PG:** * **Gold Standard:** Light microscopy (Thick and Thin smears) remains the "Gold Standard" for routine diagnosis. * **Thick Smear:** Used for **screening** (more sensitive than thin smear). * **Thin Smear:** Used for **species identification**. * **Most Sensitive Overall:** PCR (Polymerase Chain Reaction) is the most sensitive test available, but among the clinical/microscopic options listed, QBC is superior. [1] [2]

Q: How is primary amoebic meningoencephalitis most likely acquired?

Diving or swimming in contaminated water. **Explanation:** **Primary Amoebic Meningoencephalitis (PAM)** is caused by ***Naegleria fowleri***, often referred to as the "brain-eating amoeba." This free-living amoeba thrives in warm, stagnant freshwater (lakes, ponds, and poorly chlorinated swimming pools). 1. **Why Option A is correct:** The infection is acquired when water containing the amoebae is forcefully pushed into the nasal cavity, typically during **diving or swimming**. The amoebae penetrate the **nasal mucosa**, cross the **cribriform plate**, and migrate along the **olfactory nerves** to reach the brain. This leads to rapid, fulminant destruction of brain tissue and meningeal inflammation. 2. **Why other options are incorrect:** * **Option B:** IV drug abuse is associated with infections like HIV, Hepatitis B/C, or fungal endocarditis, but not PAM. * **Option C:** Using human excrement (night soil) as fertilizer is a common transmission route for soil-transmitted helminths (e.g., *Ascaris*) or feco-oral protozoa (e.g., *Entamoeba histolytica*), which cause intestinal or liver abscesses, not PAM. * **Option D:** Raw fish/seafood consumption is linked to parasites like *Diphyllobothrium latum* (fish tapeworm) or *Anisakis*, not *Naegleria*. **High-Yield Clinical Pearls for NEET-PG:** * **Pathogen:** *Naegleria fowleri* is a thermophilic amoeba (grows at temperatures up to 45°C). * **Diagnosis:** Look for **motile trophozoites** in a fresh wet mount of **CSF**. * **CSF Findings:** Resembles bacterial meningitis (high neutrophils, low glucose, high protein) but with RBCs (hemorrhagic). * **Treatment:** Drug of choice is **Amphotericin B**. * **Note:** Do not confuse PAM with **Granulomatous Amoebic Encephalitis (GAE)**, which is caused by *Acanthamoeba* or *Balamuthia* and typically occurs in immunocompromised patients via skin or respiratory routes.

Q: Which nematode resides in the caecum and appendix?

Enterobius vermicularis. **Explanation:** The correct answer is **Enterobius vermicularis** (Pinworm or Seatworm). **1. Why Enterobius vermicularis is correct:** The adult worms of *Enterobius vermicularis* primarily inhabit the **caecum, appendix, and adjacent portions of the ascending colon**. They attach to the mucosa using their mouth parts. A unique feature of their life cycle is that the gravid females migrate nocturnally through the anal canal to deposit eggs on the perianal skin, leading to the classic symptom of **pruritus ani**. **2. Why the other options are incorrect:** * **Ascaris lumbricoides (Roundworm):** The adult worms reside in the **lumen of the small intestine** (jejunum). While they can occasionally migrate into the appendix causing appendicitis, their primary habitat is not the caecum. * **Mansonella ozzardi:** This is a filarial nematode. The adult worms reside in the **mesentery, subperitoneal tissues, or thoracic cavity**, while the microfilariae circulate in the blood. They do not inhabit the intestinal lumen. **3. NEET-PG Clinical Pearls:** * **Diagnosis:** The "Gold Standard" is the **NIH Swab** or **Scotch Tape technique** performed early in the morning. Stool examination for eggs is usually negative (only 5% sensitivity) because eggs are laid on perianal skin, not in feces. * **Transmission:** Autoinfection and retroinfection are common. It is often a "familial infection." * **Drug of Choice:** Albendazole or Mebendazole (single dose, repeated after 2 weeks to kill newly hatched larvae). * **Ectopic sites:** In females, the worm can migrate into the vulva and vagina, causing vulvovaginitis or salpingitis.

Q: What is the natural habitat of Schistosoma (blood flukes)?

All of the above. **Explanation:** The correct answer is **D. All of the above**. Schistosomes, unlike other trematodes (flukes), are unique because they reside in the **venous system** of their definitive host (humans) rather than the intestine or liver. They are dioecious (separate sexes) and live in permanent copulation within the veins. 1. **Why the answer is correct:** The term "Schistosoma" refers to a genus that includes several species with specific anatomical preferences. * ***S. haematobium*** primarily inhabits the **vesical and pelvic venous plexuses** (surrounding the urinary bladder). * ***S. mansoni*** and ***S. japonicum*** reside in the **portal venous system** and mesenteric veins. Since the question asks for the habitat of "Schistosoma" (the genus) generally, all listed venous sites are correct. 2. **Analysis of Options:** * **Option A & C:** These are the specific habitats for *S. haematobium*. Eggs are deposited in the bladder wall, leading to terminal hematuria. * **Option B:** The portal vein is the site where schistosomes mature, and the pelvic/mesenteric veins are where they reside as adults. **High-Yield NEET-PG Pearls:** * **Infective stage:** Cercaria (enters via skin penetration, often during swimming). * **Diagnostic stage:** Non-operculated eggs with characteristic spines (*S. haematobium*: Terminal spine; *S. mansoni*: Lateral spine; *S. japonicum*: Rudimentary spine). * **Intermediate host:** Freshwater snails (*Biomphalaria*, *Bulinus*, *Oncomelania*). * **Clinical Association:** *S. haematobium* is a known risk factor for **Squamous Cell Carcinoma of the bladder**. * **Treatment of choice:** Praziquantel.

Q: A patient from a tribal area of Jharkhand presents with fever for the last 3 days. Peripheral blood is collected and stained with Giemsa. A diagnosis of malaria is made. The smear is shown in the figure. What is the likely causative species?

Plasmodium falciparum. ***Plasmodium falciparum*** - **Multiple ring forms** per RBC and **double chromatin dots** are characteristic features seen on Giemsa-stained smears, along with **appliqué position** (rings attached to RBC membrane). - **No RBC enlargement** is observed, and **crescent-shaped gametocytes** are pathognomonic when present; high prevalence in **tribal areas of Jharkhand**. *Plasmodium vivax* - Shows **enlarged RBCs** with **Schüffner's dots** and typically **single ring forms** per infected cell. - **Oval-shaped gametocytes** and **amoeboid trophozoites** are characteristic, unlike the multiple rings seen in P. falciparum. *Plasmodium malariae* - Produces **band-form trophozoites** that span across the RBC diameter and **rosette-pattern schizonts**. - **72-hour fever cycle** and **no RBC enlargement**, but lacks the multiple ring forms typical of P. falciparum. *Plasmodium ovale* - Shows **oval-shaped RBCs** with **fimbriated edges** and **Schüffner's dots** similar to P. vivax. - **Single ring forms** per RBC and **compact trophozoites**, not the multiple rings characteristic of P. falciparum infections.

Question 1

Where does Schistosoma Japonicum reside?

Accepted Answer

Ileocecal plexus

Answer

Vesical Plexus

Answer

Systemic Circulation

Answer

Gallbladder

Question 2

Splenic rupture is most commonly associated with infection by which of the following Plasmodium species?

Accepted Answer

Plasmodium vivax

Answer

Plasmodium ovale

Answer

Plasmodium malariae

Answer

Plasmodium falciparum

Question 3

'rK 39 antigen' is useful for the diagnosis of which condition?

Accepted Answer

Kala azar

Answer

Diphtheria

Answer

Tuberculosis

Answer

Leprosy

Question 4

The most sensitive among the following tests for the diagnosis of malaria is?

Accepted Answer

Quantitative buffy coat test

Answer

Thin peripheral blood smear

Answer

PfHRP2 antigen test

Answer

Pan plasmodial LDH test

Question 5

How is primary amoebic meningoencephalitis most likely acquired?

Accepted Answer

Diving or swimming in contaminated water

Answer

Intravenous drug abuse

Answer

Using human excrement as vegetable fertilizer

Answer

Eating raw fish or seafood

Question 6

Which nematode resides in the caecum and appendix?

Accepted Answer

Enterobius vermicularis

Answer

Ascaris lumbricoides

Answer

Mansonella ozzardi

Answer

All of these

Question 7

A man working in a construction company presented with watery, foul-smelling diarrhea since 3 weeks. There is no blood in the stools. If giardiasis is suspected, what is the best diagnostic method?

Accepted Answer

Presence of both cysts and trophozoites in stools

Answer

Complement fixation test (CFT)

Answer

Presence of cysts only

Answer

Haemagglutination

Question 8

Which parasite commonly causes pulmonary eosinophilia syndrome?

Accepted Answer

Strongyloides

Answer

Enterobiasis

Answer

Hookworm

Answer

Trichinella

Question 9

What is the natural habitat of Schistosoma (blood flukes)?

Accepted Answer

All of the above

Answer

Veins of the urinary bladder

Answer

Portal and pelvic veins

Answer

Vesical plexuses

Question 10

A patient from a tribal area of Jharkhand presents with fever for the last 3 days. Peripheral blood is collected and stained with Giemsa. A diagnosis of malaria is made. The smear is shown in the figure. What is the likely causative species?

Accepted Answer

Plasmodium falciparum

Answer

Plasmodium vivax

Answer

Plasmodium malariae

Answer

Plasmodium ovale

Parasitology — MCQs

Parasitology — MCQs

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