Parasitology Practice Questions

Q: Which of the following are NOT seen in the peripheral smear in Plasmodium falciparum infection?

Maurer's dots and Schizonts. In *Plasmodium falciparum* infection, the peripheral blood smear typically shows only **early trophozoites (ring forms)** and **gametocytes**. ### Why the Correct Answer is Right **Maurer’s dots and Schizonts** are generally absent from the peripheral circulation in *P. falciparum*: 1. **Schizonts:** *P. falciparum* exhibits a phenomenon called **sequestration**. Mature stages (late trophozoites and schizonts) express PfEMP-1 proteins on the RBC surface, causing them to adhere to the endothelial lining of deep capillary beds (brain, kidneys, etc.). Therefore, they are rarely seen in peripheral blood unless the infection is extremely heavy or terminal. 2. **Maurer’s dots:** These are coarse granulations seen in the cytoplasm of infected RBCs. While they are characteristic of *P. falciparum*, they are usually only visible in the mature stages that have been sequestered, making them an uncommon finding in a standard peripheral smear. ### Analysis of Other Options * **Accolé (Appliqué) forms:** These are early ring forms found at the very edge of the RBC. They are a hallmark of *P. falciparum* and are **frequently seen** in peripheral smears. * **Schuffner’s dots:** These are characteristic of *P. vivax* and *P. ovale*, not *P. falciparum*. ### NEET-PG High-Yield Pearls * **Multiple rings per RBC** and **Accolé forms** are diagnostic of *P. falciparum*. * **Gametocytes:** *P. falciparum* gametocytes are uniquely **crescent or banana-shaped**. * **Sequestration** is the primary reason why *P. falciparum* causes **Cerebral Malaria** (cytoadherence in brain capillaries). * **Ziemann’s dots** are associated with *P. malariae*.

Q: Auto infection occurs in which of the following organisms?

All of the above. **Explanation:** **Autoinfection** is a process where an individual serves as both the reservoir and the host, becoming reinfected by a pathogen already present in their body without the need for an external environment or intermediate host. * **Hymenolepis nana (Dwarf Tapeworm):** This is the most common cause of autoinfection. Eggs released in the intestine can hatch immediately into oncospheres, which penetrate the villi and develop into cysticercoid larvae, eventually maturing into adult worms within the same host (**Internal Autoinfection**). * **Enterobius vermicularis (Pinworm):** Eggs deposited on the perianal skin can hatch into larvae that migrate back into the anus (**Retroinfection**) or be transferred to the mouth via contaminated fingers (**External Autoinfection/Fecal-oral**). * **Taenia solium (Pork Tapeworm):** If a person harboring the adult worm ingests eggs (via contaminated food or reverse peristalsis), the eggs hatch into larvae that migrate to tissues, causing **Cysticercosis**. This is a critical clinical distinction from T. saginata, which does not cause autoinfection. **High-Yield NEET-PG Pearls:** 1. **Other organisms causing autoinfection:** *Strongyloides stercoralis* (Internal autoinfection via filariform larvae) and *Cryptosporidium parvum*. 2. **H. nana** is unique because it is the only cestode that does not mandatory require an intermediate host. 3. **Hyperinfection syndrome:** Seen in *Strongyloides* in immunocompromised patients (e.g., those on steroids) due to massive internal autoinfection. 4. **Diagnosis:** *Enterobius* is best diagnosed via the **NIH Swab/Scotch Tape test**, not routine stool microscopy.

Q: Chaga's disease is transmitted by which of the following vectors?

Reduvid bug. **Explanation:** **Chagas disease** (also known as American Trypanosomiasis) is caused by the protozoan parasite *Trypanosoma cruzi*. The primary mode of transmission is through the infected feces of the **Reduvid bug** (Option D), also commonly known as the "kissing bug," "assassin bug," or "triatomine bug." The transmission occurs when the bug bites a human (usually on the face) and defecates near the wound; the parasite enters the body when the person inadvertently rubs the feces into the bite site or mucous membranes. **Analysis of Incorrect Options:** * **Hard Tick (Ixodidae):** These are vectors for diseases such as Kyasanur Forest Disease (KFD), Indian Tick Typhus, and Lyme disease. * **Soft Tick (Argasidae):** These are primarily responsible for transmitting Relapsing fever (endemic). * **Sandfly (Phlebotomus):** This is the vector for Kala-azar (Visceral Leishmaniasis) and Oriental sore (Cutaneous Leishmaniasis). **High-Yield Clinical Pearls for NEET-PG:** * **Romaña’s sign:** Unilateral painless periorbital edema is a classic early clinical sign of Chagas disease. * **Chronic Complications:** Long-term infection can lead to **Mega-viscera** (Megaesophagus and Megacolon) and **Dilated Cardiomyopathy** (the most common cause of death). * **C-shaped Trypomastigote:** On a peripheral blood smear, *T. cruzi* typically appears in a characteristic "C" or "U" shape. * **Chagas vs. Sleeping Sickness:** While Chagas is American Trypanosomiasis (Reduvid bug), African Sleeping Sickness is caused by *T. brucei* and transmitted by the **Tsetse fly**.

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.

Question 1

Which of the following are NOT seen in the peripheral smear in Plasmodium falciparum infection?

Accepted Answer

Maurer's dots and Schizonts

Answer

Schizonts and Acccolé

Answer

Maurer's dots and Acccolé

Answer

Acccolé and Shuffner's dots

Question 2

Auto infection occurs in which of the following organisms?

Accepted Answer

All of the above

Answer

Hymenolepis nana

Answer

Enterobius vermicularis

Answer

Taenia solium

Question 3

Chaga's disease is transmitted by which of the following vectors?

Accepted Answer

Reduvid bug

Answer

Hard tick

Answer

Soft tick

Answer

Sandfly

Question 4

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 5

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

Accepted Answer

Ascaris lumbricoides

Answer

Strongyloides

Answer

Ancylostoma duodenale

Answer

Necator americanus

Question 6

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 7

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 8

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 9

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 10

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.

Parasitology — MCQs

Parasitology — MCQs

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