Parasitology Practice Questions

Q: USG guided aspiration of a hepatic cyst shows anchovy sauce appearance of the aspirate. The patient is most probably infected with which of the following?

Entamoeba histolytica. **Explanation:** The correct answer is **Entamoeba histolytica**. **1. Why Entamoeba histolytica is correct:** The "anchovy sauce" appearance is a classic pathognomonic description of the aspirate from an **Amoebic Liver Abscess (ALA)**. This occurs when *E. histolytica* trophozoites travel from the colon to the liver via the portal circulation. The abscess does not contain true pus; instead, it consists of **liquefactive necrosis** of hepatocytes. The characteristic reddish-brown, thick, non-foul-smelling fluid resembles anchovy sauce due to the mixture of necrotic liver tissue and blood. **2. Why the other options are incorrect:** * **Balantidium coli:** While it causes dysentery similar to amoebiasis, it rarely spreads extra-intestinally and does not cause liver abscesses. * **Giardia lamblia:** This parasite inhabits the duodenum and upper jejunum. It causes malabsorption and steatorrhea but does not invade tissues or cause hepatic cysts. * **Toxoplasma gondii:** This is an intracellular parasite that typically presents with lymphadenopathy, encephalitis (in immunocompromised), or congenital infections. It does not produce large necrotic hepatic cysts. **3. High-Yield Clinical Pearls for NEET-PG:** * **Location:** ALA is most commonly found in the **Right Lobe** of the liver (due to the bulk of portal drainage). * **Microscopy:** The "anchovy sauce" aspirate usually contains **no trophozoites in the center**; they are found in the peripheral abscess wall. * **Diagnosis:** Indirect Hemagglutination (IHA) is the most sensitive serological test. * **Treatment:** Drug of choice is **Metronidazole**, followed by a luminal amoebicide (e.g., Paromomycin) to eradicate the intestinal colonization. * **Differential:** Do not confuse with **Hydatid cyst** (*Echinococcus granulosus*), which shows "clear spring water" fluid and "hydatid sand."

Q: Which of the following is a causative agent of Visceral Leishmaniasis?

Leishmania donovani. **Explanation:** **Leishmania donovani** is the primary causative agent of **Visceral Leishmaniasis (VL)**, also known as **Kala-azar**. In the Indian subcontinent, it is the sole species responsible for the disease. The parasite targets the reticuloendothelial system (liver, spleen, and bone marrow), leading to the classic triad of prolonged fever, massive splenomegaly, and pancytopenia. **Analysis of Options:** * **Leishmania donovani (Correct):** It causes the visceral form of the disease. In India, it is transmitted by the sandfly *Phlebotomus argentipes*. * **Leishmania braziliensis & L. panamensis (Incorrect):** These species belong to the *Viannia* subgenus and are primarily responsible for **Mucocutaneous Leishmaniasis (Espundia)** and Cutaneous Leishmaniasis in Central and South America. * **Leishmania major (Incorrect):** This species is a common cause of **Old World Cutaneous Leishmaniasis** (Oriental Sore), typically presenting as self-healing skin ulcers. **High-Yield Clinical Pearls for NEET-PG:** * **Vector:** Female Sandfly (*Phlebotomus* species). * **Infective Stage:** Promastigote (flagellated form found in the sandfly). * **Diagnostic Stage:** Amastigote (LD bodies) found within macrophages in bone marrow or splenic aspirates. * **Gold Standard Diagnosis:** Splenic aspiration (highest sensitivity, but risky); Bone marrow aspiration is the most common clinical practice. * **RK-39 Immunochromatographic test:** Best rapid screening test for field use. * **Drug of Choice:** Liposomal Amphotericin B is currently the preferred treatment. * **Post-Kala-azar Dermal Leishmaniasis (PKDL):** A non-ulcerative skin condition that develops in some patients after the apparent cure of VL, acting as a reservoir for the parasite.

Q: All of the following statements about the Sabin-Feldman Dye test are true, except:

Bluish staining of trophozoites indicates a positive test.. The **Sabin-Feldman Dye Test** is the gold standard serological reference test for diagnosing **Toxoplasmosis**. Understanding its mechanism is crucial for NEET-PG. ### Why Option D is the Correct Answer (The "Except" Statement) The test is based on the principle that specific antibodies against *Toxoplasma gondii*, in the presence of a complement-like "accessory factor," will neutralize the parasite. * **Negative Test:** In the absence of antibodies, the cell membrane of the live trophozoites remains intact, allowing **Methylene blue** to enter and stain the cytoplasm **blue**. * **Positive Test:** When specific antibodies are present, they damage the parasite's membrane. Consequently, the trophozoites lose their affinity for the dye and remain **unstained/colorless**. Therefore, **bluish staining indicates a negative result**, making Option D the false statement. ### Analysis of Other Options * **Option A:** It is indeed the classic serological test for *Toxoplasma gondii*, measuring IgG antibodies. * **Option B:** Alkaline Methylene blue is the specific dye used to visualize the trophozoites. * **Option C:** IgG antibodies against Toxoplasma typically appear 1–2 weeks after infection and can persist at detectable levels for many years, or even life. ### High-Yield Clinical Pearls * **Gold Standard:** While rarely performed now due to the need for live tachyzoites (biohazard risk), it remains the reference standard. * **Accessory Factor:** The test requires a heat-labile serum component (complement-like) obtained from Toxoplasma-negative individuals. * **Alternative Tests:** In modern practice, ELISA (for IgM/IgG) and PCR are more commonly used. * **Congenital Toxoplasmosis Triad:** Chorioretinitis, Hydrocephalus, and Intracranial calcifications.

Q: Which of the following is TRUE about Acute Primary Amoebic Meningoencephalitis?

Diagnosis is by demonstration of trophozoite in CSF. **Explanation:** **Primary Amoebic Meningoencephalitis (PAM)** is a rapidly fatal central nervous system infection caused by the free-living amoeba, ***Naegleria fowleri***. **Why Option B is Correct:** The definitive diagnosis of PAM is made by the **microscopic demonstration of motile trophozoites** in a fresh sample of **Cerebrospinal Fluid (CSF)**. Unlike other amoebae, *Naegleria fowleri* exists in the brain and CSF only as trophozoites (never as cysts). On a wet mount, these trophozoites exhibit characteristic "slug-like" pseudopodial movement. **Analysis of Incorrect Options:** * **Option A:** *Acanthamoeba* species cause **Granulomatous Amoebic Encephalitis (GAE)**, which is a **chronic**, subacute infection typically seen in immunocompromised individuals. PAM (caused by *Naegleria*) is the one that is acute and fulminant. * **Option C:** Transmission is **not fecal-oral**. Infection occurs when contaminated water is forcefully inhaled or splashed into the nose (e.g., during diving or swimming), allowing the amoeba to penetrate the **cribriform plate** and migrate along the olfactory nerves to the brain. * **Option D:** While it can occur in the tropics, it is specifically associated with **warm freshwater** (lakes, hot springs, or poorly chlorinated pools) during hot summer months in temperate regions as well. The key risk factor is the temperature of the water, not just the climate zone. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice:** Amphotericin B (often used in combination with Miltefosine). * **CSF Findings:** Resembles pyogenic meningitis (high neutrophils, low sugar, high protein), but the presence of RBCs (hemorrhagic) and the absence of bacteria on Gram stain should raise suspicion for PAM. * **Morphology:** *Naegleria fowleri* is the only free-living amoeba with a flagellated stage (biflagellate) in its life cycle.

Q: Which one of the following tests is used for the diagnosis of Giardia lamblia infection?

Enterotest. **Explanation:** **Giardia lamblia** is a flagellated protozoan that primarily inhabits the duodenum and upper jejunum. While stool microscopy for cysts and trophozoites is the standard initial investigation, the **Enterotest (String Test)** is a specialized diagnostic tool used when stool examinations are repeatedly negative but clinical suspicion remains high. 1. **Why Enterotest is Correct:** In this procedure, the patient swallows a gelatin capsule containing a weighted nylon string. The capsule dissolves in the stomach, and the string moves into the duodenum. After 4–6 hours, the string is withdrawn. The bile-stained mucus adhering to the string is scraped and examined microscopically for motile trophozoites. This is highly effective because *Giardia* colonizes the exact area the string samples. 2. **Why Other Options are Incorrect:** * **Casoni’s Test:** An immediate hypersensitivity skin test used for diagnosing **Hydatid disease** (*Echinococcus granulosus*). It has largely been replaced by serology (ELISA). * **Parasite F Test:** This is not a standard diagnostic term in parasitology. It may be a distractor or a confusion with the "Fecal Occult Blood Test." * **Napier’s Test (Aldehyde Test):** Used for the presumptive diagnosis of **Visceral Leishmaniasis (Kala-azar)**. It depends on the increase in serum gamma globulins. **High-Yield Clinical Pearls for NEET-PG:** * **Morphology:** *Giardia* trophozoites have a characteristic "falling leaf" motility and a "monkey face" appearance (two nuclei and four pairs of flagella). * **Pathogenesis:** It causes malabsorption (steatorrhea) by "carpeting" the duodenal mucosa, leading to the blunting of villi. It does **not** invade the bloodstream. * **Drug of Choice:** Metronidazole or Tinidazole. * **Stool Findings:** Look for "foul-smelling, bulky, greasy stools" in the clinical stem.

Q: Which of the following statements is NOT true about Rhinosporidiosis?

It can be cultured on Sabouraud's dextrose Agar.. **Explanation:** Rhinosporidiosis is a chronic granulomatous infection caused by ***Rhinosporidium seeberi***. Despite its name and fungal-like appearance, it is currently classified as an aquatic protistan parasite (Mesomycetozoea). **1. Why Option A is the Correct Answer (The False Statement):** The hallmark characteristic of *Rhinosporidium seeberi* is that it **cannot be cultured** on any artificial microbiological media, including Sabouraud’s Dextrose Agar (SDA). It has never been successfully grown *in vitro*. Diagnosis relies entirely on clinical presentation and histopathology. **2. Analysis of Other Options:** * **Option B (Fungal spherules):** Histopathology is diagnostic. It reveals large, thick-walled **sporangia (spherules)** measuring up to 350 µm, filled with thousands of tiny **endospores**. This is a classic "high-yield" pathology finding. * **Option C (Bleeds to touch):** Clinically, it presents as friable, leafy, or strawberry-like polypoid masses. Due to high vascularity, these lesions **bleed profusely** upon minor trauma or touch. * **Option D (Most common site):** The **nasal mucosa** (nasal septum and floor) is the most common site of involvement (approx. 70%), followed by the nasopharynx and conjunctiva. **Clinical Pearls for NEET-PG:** * **Epidemiology:** Highly prevalent in South India (Tamil Nadu, Kerala) and Sri Lanka; associated with bathing in stagnant pond water. * **Transmission:** Traumatic inoculation of spores from contaminated water. * **Treatment:** Wide surgical excision with **electrocautery** of the base to prevent recurrence. Dapsone is sometimes used as an adjunct. * **Staining:** Sporangia can be visualized with H&E, GMS, and PAS stains.

Q: Which organism serves as an intermediate host for the Guinea worm?

Guinea worm. **Explanation:** The correct answer is **Guinea worm** (*Dracunculus medinensis*). In the context of the question, the organism that serves as the essential intermediate host for the transmission of Dracunculiasis is the **Cyclops** (water flea). *Note: The options provided in the prompt appear to list the diseases/pathogens themselves rather than the hosts. In NEET-PG, the specific intermediate host for Guinea worm is always identified as **Cyclops**.* **Why the correct answer is right:** The life cycle of *Dracunculus medinensis* requires a crustacean of the genus **Cyclops**. When a person drinks stagnant water containing Cyclops infected with L3 larvae, the larvae are released in the stomach, penetrate the intestinal wall, and mature into adults. The female worm eventually migrates to the subcutaneous tissue (usually the lower limbs) to release larvae into the water, completing the cycle. **Why the other options are wrong:** * **Malaria:** This is caused by *Plasmodium* species. The definitive host is the female *Anopheles* mosquito, and the intermediate host is the human. * **Rabies:** This is a viral zoonosis. It does not have an "intermediate host" in the parasitological sense; it is transmitted via the saliva of infected mammals (dogs, bats). * **Salmonella:** This is a bacterium causing enteric fever or gastroenteritis. It is transmitted via the fecal-oral route and does not require an intermediate host. **High-Yield Clinical Pearls for NEET-PG:** * **Intermediate Host:** Cyclops (Water flea). * **Infective Form:** L3 larvae inside the Cyclops. * **Diagnosis:** Step-ladder appearance of the worm under the skin or the "string test" (visualizing the worm upon water contact). * **Prevention:** Filtering water through a fine cloth or boiling. * **Eradication:** India was declared Guinea worm-free by the WHO in **2000**. The last case in India was reported in 1996 (Rajasthan).

Q: Endemic hemoptysis is caused by which parasite?

Paragonimus westermanii. **Explanation:** **Paragonimus westermani**, also known as the **Oriental Lung Fluke**, is the causative agent of **Endemic Hemoptysis**. The term refers to the characteristic clinical presentation of chronic cough and blood-stained sputum (hemoptysis) seen in endemic regions (primarily East Asia and parts of India like Manipur). * **Pathogenesis:** Humans are infected by ingesting metacercariae in undercooked **crabs or crayfish** (second intermediate hosts). The larvae migrate from the intestines, through the diaphragm, into the lungs. Here, they induce a granulomatous reaction, forming cystic cavities. When these cysts rupture into the bronchioles, the patient expectorates eggs, blood, and inflammatory debris, mimicking pulmonary tuberculosis. **Analysis of Incorrect Options:** * **Hymenolepis nana (Dwarf Tapeworm):** The smallest intestinal cestode. It causes abdominal pain and diarrhea but does not involve the lungs. It is unique for its "internal autoinfection" cycle. * **Diphyllobothrium latum (Fish Tapeworm):** Acquired by eating raw freshwater fish. It is clinically significant for causing **Vitamin B12 deficiency** and megaloblastic anemia. * **Clonorchis sinensis (Chinese Liver Fluke):** Inhabits the biliary tract. It is associated with cholangitis, biliary stones, and is a known risk factor for **cholangiocarcinoma**. **NEET-PG High-Yield Pearls:** * **Intermediate Hosts:** 1st – Snail (*Melania* spp.); 2nd – Crab/Crayfish. * **Diagnosis:** Presence of golden-brown, operculated eggs in sputum or stool. * **Radiology:** May show "ring shadows" or "cotton-wool" opacities, often confused with TB. * **Drug of Choice:** Praziquantel.

Q: Which of the following is the infective form of Plasmodium falciparum for humans?

Sporozoites. **Explanation:** The life cycle of *Plasmodium falciparum* involves two hosts: the female *Anopheles* mosquito (definitive host) and the human (intermediate host). **Why Sporozoites is the correct answer:** The **Sporozoite** is the infective stage for humans. When an infected female *Anopheles* mosquito takes a blood meal, it inoculates sporozoites from its salivary glands into the human dermis. These sporozoites enter the bloodstream and reach the liver within 30–60 minutes to initiate the **pre-erythrocytic (exo-erythrocytic) schizogony**. **Analysis of Incorrect Options:** * **Merozoites:** These are released when hepatic or red blood cell schizonts rupture. They are responsible for infecting new erythrocytes but are not the form introduced by the mosquito. * **Hypnozoites:** These are dormant hepatic stages found **only** in *P. vivax* and *P. ovale*. They are responsible for clinical relapses. *P. falciparum* does not have a hypnozoite stage. * **Trophozoites:** This is the intracellular feeding stage within the red blood cells (e.g., the "ring form"). It is a diagnostic stage, not the infective stage. **High-Yield Clinical Pearls for NEET-PG:** * **Infective form for Mosquito:** Gametocytes (taken up during a blood meal). * **Exo-erythrocytic cycle:** Absent in *P. falciparum* (once the liver stage is over, it does not recur from the liver). * **Recrudescence:** Seen in *P. falciparum* due to sub-optimal treatment or drug resistance (not to be confused with "Relapse" caused by hypnozoites). * **Gold Standard Diagnosis:** Peripheral blood smear (Giemsa stain) showing multiple ring forms per RBC and crescent-shaped (banana-shaped) gametocytes.

Question 1

USG guided aspiration of a hepatic cyst shows anchovy sauce appearance of the aspirate. The patient is most probably infected with which of the following?

Accepted Answer

Entamoeba histolytica

Answer

Balantidium coli

Answer

Giardia lamblia

Answer

Toxoplasma gondii

Question 2

Which of the following helminths show their larval form in stool?

Accepted Answer

Ascaris lumbricoides

Answer

Strongyloides

Answer

Ancylostoma duodenale

Answer

Necator americanus

Question 3

Which of the following is a causative agent of Visceral Leishmaniasis?

Accepted Answer

Leishmania donovani

Answer

Leishmania braziliensis

Answer

Leishmania panamensis

Answer

Leishmania major

Question 4

All of the following statements about the Sabin-Feldman Dye test are true, except:

Accepted Answer

Bluish staining of trophozoites indicates a positive test.

Answer

It is a serological test for Toxoplasma.

Answer

It uses Methylene blue dye.

Answer

It may remain positive for years.

Question 5

Which of the following is TRUE about Acute Primary Amoebic Meningoencephalitis?

Accepted Answer

Diagnosis is by demonstration of trophozoite in CSF

Answer

Meningitis caused by Acanthamoeba species is acute in nature

Answer

Caused by fecal-oral transmission

Answer

More common in tropical climates

Question 6

Which one of the following tests is used for the diagnosis of Giardia lamblia infection?

Accepted Answer

Enterotest

Answer

Casoni's test

Answer

Parasite F test

Answer

Napier's test

Question 7

Which of the following statements is NOT true about Rhinosporidiosis?

Accepted Answer

It can be cultured on Sabouraud's dextrose Agar.

Answer

Fungal spherules are seen in biopsy.

Answer

It bleeds to touch.

Answer

The most common site is the nose.

Question 8

Which organism serves as an intermediate host for the Guinea worm?

Accepted Answer

Guinea worm

Answer

Malaria

Answer

Rabies

Answer

Salmonella

Question 9

Endemic hemoptysis is caused by which parasite?

Accepted Answer

Paragonimus westermanii

Answer

Hymenolepis nana

Answer

Diphyllobothrium latum

Answer

Clonorchis sinensis

Question 10

Which of the following is the infective form of Plasmodium falciparum for humans?

Accepted Answer

Sporozoites

Answer

Merozoites

Answer

Hypnozoite

Answer

Trophozoites

Parasitology — MCQs

Parasitology — MCQs

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