Parasitology Practice Questions

Q: Schistosomiasis is a disease characterized by granulomatous reactions to the ova or to products of the parasite at the place of oviposition. Clinical manifestations include which one of the following?

Splenomegaly. **Explanation:** The clinical manifestations of Schistosomiasis (Bilharziasis) are primarily driven by the host’s **granulomatous immune response** to eggs trapped in tissues, rather than the adult worms themselves. **Why Splenomegaly is Correct:** In infections caused by *Schistosoma mansoni* and *S. japonicum*, adult worms reside in the mesenteric veins. Eggs are deposited and travel via the portal circulation to the liver, where they trigger periportal (Symmers' pipe-stem) fibrosis. This leads to **portal hypertension**, which subsequently causes congestive **splenomegaly** and esophageal varices. This "hepatosplenic schistosomiasis" is a classic presentation in chronic cases. **Analysis of Incorrect Options:** * **A. Bladder wall hyperplasia:** While *S. haematobium* affects the urinary tract, it typically causes bladder wall **calcification**, ulceration, and squamous cell carcinoma. "Hyperplasia" is not the characteristic pathological description used for these lesions. * **B. Pulmonary embolism:** While eggs can reach the lungs causing pulmonary hypertension (cor pulmonale), they do not typically cause classic thromboembolism. * **D. Cardiac abnormalities:** Heart involvement is rare and usually secondary to pulmonary hypertension (Right heart failure), not a primary manifestation of oviposition. **NEET-PG High-Yield Pearls:** * **Intermediate Host:** Freshwater snails (*Biomphalaria* for *S. mansoni*; *Bulinus* for *S. haematobium*). * **Infective Stage:** Cercaria (penetrates skin during swimming). * **Diagnostic Feature:** Eggs with spines (*S. haematobium*: Terminal spine; *S. mansoni*: Lateral spine). * **Drug of Choice:** Praziquantel. * **Katayama Fever:** An acute serum sickness-like reaction occurring weeks after infection.

Q: Dwarf tapeworm refers to which of the following?

Hymenolepsis nana. **Explanation:** **Hymenolepis nana (H. nana)** is known as the **Dwarf Tapeworm** because it is the smallest intestinal cestode infecting humans, typically measuring only 15–40 mm in length. **Why H. nana is the correct answer:** It is unique among tapeworms because it does not mandatory require an intermediate host; it can complete its entire life cycle in a single host (Man). It is the only cestode capable of **internal autoinfection**, where eggs hatch within the intestine and develop into larvae (cysticercoids) in the villi, leading to heavy parasite loads. **Analysis of Incorrect Options:** * **A. Echinococcus granulosus:** Known as the **Dog Tapeworm**. It causes Hydatid disease and is characterized by the formation of slow-growing cysts in the liver and lungs. * **B. Loa loa:** Known as the **African Eye Worm**. It is a nematode (roundworm) transmitted by the *Chrysops* fly, characterized by Calabar swellings and subconjunctival migration. * **C. Schistosoma mansoni:** Known as a **Blood Fluke**. It is a trematode that resides in the mesenteric veins and causes intestinal schistosomiasis and portal hypertension. **High-Yield Clinical Pearls for NEET-PG:** * **Smallest Cestode:** *H. nana* (Dwarf tapeworm). * **Largest Cestode:** *Diphyllobothrium latum* (Fish tapeworm). * **Infective Stage:** Embryonated eggs (most common) or cysticercoid larvae (via ingestion of infected insects). * **Diagnosis:** Stool microscopy showing characteristic eggs with **polar filaments** (distinguishes it from *H. diminuta*). * **Treatment of Choice:** Praziquantel.

Q: Strawberry cervix is seen in which of the following conditions?

Trichomonas vaginalis infection. **Explanation:** **Trichomonas vaginalis infection** is the correct answer. The "Strawberry Cervix" (colpitis macularis) is a classic clinical sign characterized by punctate hemorrhages on the cervical epithelium. This occurs because the parasite causes intense local inflammation and capillary dilation, making the cervix appear red and speckled, resembling the surface of a strawberry. While highly specific for Trichomoniasis, it is only visible on physical examination in about 2-5% of cases (more frequently seen via colposcopy). **Analysis of Incorrect Options:** * **A. Gardnerella vaginalis:** This is the primary causative agent of Bacterial Vaginosis (BV). It is characterized by a "thin, homogenous, fishy-smelling discharge" and the presence of **Clue cells** on microscopy, but it does not cause a strawberry cervix. * **C. Candida infection:** Vulvovaginal Candidiasis typically presents with intense pruritus and a thick, white, **"curd-like" or "cottage cheese" discharge**. The vaginal mucosa may be erythematous, but it lacks the punctate hemorrhages of Trichomoniasis. * **D. Mycoplasma pneumoniae:** This is a respiratory pathogen responsible for atypical pneumonia and is not associated with vaginal or cervical infections. **NEET-PG High-Yield Pearls:** * **Trichomoniasis:** Caused by a flagellated protozoan. Look for **"frothy, yellowish-green, foul-smelling discharge"** and a vaginal pH > 4.5. * **Diagnosis:** The gold standard is **NAAT**, but the most common bedside test is **Wet Mount microscopy** showing "jerky/twitching motility." * **Treatment:** Drug of choice is **Metronidazole**. Crucially, the **partner must also be treated** to prevent reinfection (it is an STI). * **Whiff Test:** Positive (fishy odor with KOH) in both Bacterial Vaginosis and Trichomoniasis.

Q: What is the treatment of choice for Echinococcus granulosus?

Albendazole. **Explanation:** **Echinococcus granulosus**, the causative agent of Cystic Echinococcosis (Hydatid cyst), is primarily managed through a combination of surgery, aspiration (PAIR), and chemotherapy. **Why Albendazole is the Correct Choice:** **Albendazole** is the drug of choice because it is a broad-spectrum anthelmintic with superior pharmacokinetic properties compared to other benzimidazoles. It is a prodrug that is converted into **albendazole sulfoxide**, which achieves high concentrations in the hydatid cyst fluid and wall. It works by inhibiting microtubule synthesis, leading to glucose depletion and death of the scolex. In clinical practice, it is used as a primary treatment for small/multiple cysts or as an adjuvant before and after surgery/PAIR to reduce the risk of secondary seeding. **Analysis of Incorrect Options:** * **B. Thiabendazole:** While it is a benzimidazole, it is rarely used now due to significant systemic toxicity and lower efficacy compared to newer agents. * **C. Mebendazole:** It was previously used but is less effective than Albendazole because it is poorly absorbed from the gastrointestinal tract, leading to inconsistent therapeutic levels within the cyst. * **D. Praziquantel:** It is highly effective against adult tapeworms and is often used as an **adjunct** to Albendazole to kill protoscolices more rapidly, but it is not the primary "treatment of choice" for the cyst itself. **High-Yield Clinical Pearls for NEET-PG:** * **PAIR Technique:** Puncture, Aspiration, Injection (of scolicidal agents like hypertonic saline or 95% ethanol), and Re-aspiration. * **Diagnosis:** "Egg-shell calcification" on X-ray; "Water-lily sign" or "Camel-back sign" on USG/CT. * **Casoni’s Test:** An immediate hypersensitivity skin test (now largely replaced by ELISA). * **Surgical Precaution:** Extreme care must be taken to prevent cyst rupture, which can lead to life-threatening **anaphylaxis**.

Q: Which of the following is a flagellated amoeba?

Naegleria fowleri. **Explanation:** The correct answer is **Naegleria fowleri**. This organism is classified as a **Free-Living Amoeba (FLA)** and is unique because it is "amphizoic," meaning it can exist as both a free-living organism and a pathogen. **Why Naegleria fowleri is correct:** *Naegleria fowleri* is known as a **"transformer"** because it exists in three stages: the trophozoite, the cyst, and the **flagellated stage**. When environmental conditions change (such as a decrease in nutrient concentration or exposure to distilled water), the trophozoite develops two long flagella to move quickly to a more favorable environment. This transient flagellated form is a key diagnostic feature. **Why the other options are incorrect:** * **Entamoeba histolytica:** This is an obligate intestinal parasite. It exists only as a trophozoite (moving via pseudopodia) and a cyst. It never develops flagella. * **Acanthamoeba:** While it is a free-living amoeba, it only has two stages: trophozoite and cyst. It lacks a flagellated stage. It is characterized by "acanthopodia" (spine-like projections). * **Balamuthia:** Similar to *Acanthamoeba*, *Balamuthia mandrillaris* exists only in trophozoite and cyst forms and does not possess flagella. **High-Yield Clinical Pearls for NEET-PG:** * **Disease:** *Naegleria fowleri* causes **Primary Amoebic Meningoencephalitis (PAM)**, a rapidly fatal CNS infection typically seen in healthy children/young adults with a history of swimming in warm freshwater. * **Path of Entry:** Through the **cribriform plate** via the olfactory nerves. * **Diagnosis:** Wet mount of CSF shows **actively motile trophozoites**. Note: Only the trophozoite form is found in human tissue; cysts are not seen in brain sections (unlike *Acanthamoeba*). * **Drug of Choice:** Amphotericin B.

Q: In which type of malarial parasite is the exoerythrocytic stage absent?

P. falciparum. ### Explanation The life cycle of *Plasmodium* in humans consists of two main stages: the **Exoerythrocytic (Hepatic) cycle** and the **Erythrocytic cycle**. The correct answer is **P. falciparum** (and also **P. malariae**). In these species, once the sporozoites enter the liver cells and mature into schizonts, they are released into the bloodstream to begin the erythrocytic phase. There is **no persistent liver stage** (hypnozoite). Once the liver is cleared, it remains clear unless a new mosquito bite occurs. **Analysis of Options:** * **P. vivax & P. ovale (Options A & B):** These species possess a "dormant" exoerythrocytic stage known as **hypnozoites**. These forms can remain latent in the liver for months or years, leading to **relapses** of malaria even after the blood stage has been treated. * **P. malariae (Option D):** Like *P. falciparum*, it lacks a true exoerythrocytic (hypnozoite) stage. However, it is known for **recrudescence** (survival of low-level parasites in the blood), not relapse from the liver. In many competitive exams, if both are options, *P. falciparum* is the classic textbook answer for the absence of a persistent liver phase. **High-Yield NEET-PG Pearls:** 1. **Relapse vs. Recrudescence:** Relapse is due to hypnozoites in the liver (*P. vivax/ovale*). Recrudescence is due to persistent sub-clinical parasites in the blood (*P. falciparum/malariae*). 2. **Drug of Choice for Hypnozoites:** **Primaquine** or **Tafenoquine** must be administered to achieve a "radical cure" in *P. vivax* and *P. ovale* infections. 3. **Primaquine Caution:** Always screen for **G6PD deficiency** before administration to prevent acute hemolysis. 4. **P. falciparum** is the most common cause of cerebral malaria and lacks the Schuffner’s dots seen in *P. vivax*.

Q: A patient with AIDS experienced an acute episode of diarrhea. Stool examination revealed an oval structure, 8 to 9 micrometers in diameter, that was acid-fast and fluoresced blue under ultraviolet light. What is the most likely identification of this organism?

Cyclospora. **Explanation:** The clinical presentation of acute diarrhea in an immunocompromised (AIDS) patient, combined with specific morphologic and staining characteristics, points directly to **Cyclospora cayetanensis**. **Why Cyclospora is correct:** The key diagnostic features provided are: 1. **Size:** Cyclospora oocysts are typically **8–10 μm** in diameter (twice the size of *Cryptosporidium*). 2. **Staining:** They are **variably acid-fast** (some stain pink/red, others remain ghost-like). 3. **Autofluorescence:** This is the pathognomonic "clincher" for NEET-PG. Under UV light (330–365 nm), Cyclospora oocysts exhibit **intense blue/green autofluorescence** due to the presence of phenolic compounds in the oocyst wall. **Why other options are incorrect:** * **Cryptosporidium:** While also acid-fast and common in AIDS, the oocysts are significantly smaller (**4–6 μm**) and **do not** exhibit autofluorescence. * **Enterocytozoon (Microsporidia):** These are much smaller (1–3 μm) and are not acid-fast; they require specialized stains like Modified Trichrome or Calcofluor White. * **Giardia:** These are flagellated protozoa (cysts are 8–12 μm) but are **not acid-fast** and do not fluoresce. They typically present with foul-smelling, fatty stools (steatorrhea). **High-Yield Clinical Pearls for NEET-PG:** * **Size Comparison:** *Cryptosporidium* (4–6 μm) < *Cyclospora* (8–10 μm) < *Isospora/Cystoisospora* (25–30 μm). * **Treatment:** Unlike *Cryptosporidium* (Nitazoxanide), *Cyclospora* is treated with **Trimethoprim-Sulfamethoxazole (TMP-SMX)**. * **Transmission:** Often associated with contaminated imported soft fruits (raspberries, strawberries) and leafy vegetables.

Q: What causes swollen belly syndrome?

Strongyloides fuelleborni. **Explanation:** **Strongyloides fuelleborni** is the causative agent of **Swollen Belly Syndrome (SBS)**, a specific clinical entity primarily reported in infants in Papua New Guinea and parts of Africa. **Why it is the correct answer:** *S. fuelleborni* is a parasite of non-human primates that can infect humans. In infants, heavy infection leads to a severe protein-losing enteropathy. This results in profound **hypoalbuminemia**, which causes generalized edema and massive ascites, giving the characteristic "swollen belly" appearance. It is often associated with respiratory distress and high mortality if untreated. **Analysis of Incorrect Options:** * **A. *Ascaris lumbricoides*:** While heavy Ascaris infections can cause abdominal distension due to a large bolus of worms (intestinal obstruction), it does not cause the specific clinical triad of SBS (ascites/hypoalbuminemia). * **B. *Strongyloides stercoralis*:** This is the common human threadworm. It causes "Hyperinfection Syndrome" in immunocompromised hosts but is not the specific cause of the SBS clinical entity. * **D. *Wuchereria bancrofti*:** This filarial nematode causes lymphatic filariasis. While it can cause "Chylous ascites" in rare cases, its hallmark is elephantiasis of the limbs and scrotum, not Swollen Belly Syndrome. **High-Yield Clinical Pearls for NEET-PG:** * **Transmission:** *S. fuelleborni* is unique because it can be transmitted via **breast milk** (transmammary transmission), which explains why it affects very young infants. * **Diagnosis:** Identification of eggs in the stool (unlike *S. stercoralis*, where larvae are usually found). * **Treatment:** Albendazole or Ivermectin. * **Key Association:** Always link "Swollen Belly Syndrome" + "Infant" + "Papua New Guinea" to *Strongyloides fuelleborni*.

Question 1

Schistosomiasis is a disease characterized by granulomatous reactions to the ova or to products of the parasite at the place of oviposition. Clinical manifestations include which one of the following?

Accepted Answer

Splenomegaly

Answer

Bladder wall hyperplasia

Answer

Pulmonary embolism

Answer

Cardiac abnormalities

Question 2

Dwarf tapeworm refers to which of the following?

Accepted Answer

Hymenolepsis nana

Answer

Echinococcus

Answer

Loa Loa

Answer

Schistosoma mansoni

Question 3

Strawberry cervix is seen in which of the following conditions?

Accepted Answer

Trichomonas vaginalis infection

Answer

Gardenella vaginalis infection

Answer

Candida infection

Answer

Mycoplasma pneumoniae infection

Question 4

What is the treatment of choice for Echinococcus granulosus?

Accepted Answer

Albendazole

Answer

Thio-bendazole

Answer

Mebendazole

Answer

Praziquantel

Question 5

Which of the following is a flagellated amoeba?

Accepted Answer

Naegleria fowleri

Answer

Entamoeba histolytica

Answer

Acanthamoeba

Answer

Balamuthia

Question 6

In which type of malarial parasite is the exoerythrocytic stage absent?

Accepted Answer

P. falciparum

Answer

P. ovale

Answer

P. vivax

Answer

P. malariae

Question 7

What is the correct sequence of the malaria parasite life cycle?

Accepted Answer

Exoerythrocytic stage, Erythrocytic stage, Gametocytic stage, Sporogony

Answer

Exoerythrocytic stage, Gametocytic stage, Erythrocytic stage, Sporogony

Answer

Exoerythrocytic stage, Sporogony, Gametocytic stage, Erythrocytic stage

Answer

Exoerythrocytic stage, Sporogony, Erythrocytic stage, Gametocytic stage

Question 8

A patient with AIDS experienced an acute episode of diarrhea. Stool examination revealed an oval structure, 8 to 9 micrometers in diameter, that was acid-fast and fluoresced blue under ultraviolet light. What is the most likely identification of this organism?

Accepted Answer

Cyclospora

Answer

Cryptosporidium

Answer

Enterocytozoon

Answer

Giardia

Question 9

What causes swollen belly syndrome?

Accepted Answer

Strongyloides fuelleborni

Answer

Ascaris lumricoides

Answer

Strongyloides stercoralis

Answer

Wucheraria bancrofti

Question 10

A 50-year-old male presented with various subcutaneous nodules over the right iliac crest, measuring approximately 1 cm in diameter. Adult worms and microfilariae were detected within the excised nodules. Which of the following organisms is likely the causative agent?

Accepted Answer

Loa Loa

Answer

Onchocerca volvulus

Answer

Mansonella

Answer

Brugia malayi

Parasitology — MCQs

Parasitology — MCQs

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