Parasitology Practice Questions

Q: Which of the following eggs does not float on a saturated salt solution?

Unfertilized egg of Ascaris. ### Explanation The ability of parasitic eggs to float in a saturated salt solution (Specific Gravity **1.200**) depends on the principle of **differential density**. Eggs with a specific gravity lower than 1.200 will float, while those that are heavier will sink. **Why Unfertilized Ascaris Eggs do not float:** The **Unfertilized egg of *Ascaris lumbricoides*** is the heaviest among common helminth eggs. It has a specific gravity greater than 1.200 because it is relatively large, elongated, and contains a heavy, disorganized mass of yolk granules. Due to this high density, it settles at the bottom, making the **Salt Flotation Technique** (Willis technique) ineffective for its detection. Sedimentation methods are required instead. **Analysis of Incorrect Options:** * **Fertilized egg of *Ascaris*:** These are rounded, possess a thick shell, and have a specific gravity of approximately **1.050**. Being lighter than the salt solution, they float readily. * **Trichuris trichiura:** Despite their "barrel shape" and polar plugs, these eggs have a specific gravity lower than 1.200 and will float. * **Hymenolepis nana (H. Nana):** These are thin-shelled, lightweight eggs that float easily in saturated salt solutions. **High-Yield Clinical Pearls for NEET-PG:** * **Non-floating eggs (Mnemonic: "OUT"):** **O**perculated eggs (e.g., *Trematodes* like *Fasciola*), **U**nfertilized *Ascaris* eggs, and **T**aenia eggs (variable/heavy). * **Saturated Salt Solution:** The most common reagent used is Sodium Chloride (NaCl). * **Ascaris lumbricoides:** Known as the "Roundworm," it is the most common helminthic infection worldwide. Remember the "Loeffler’s Syndrome" (pulmonary phase) associated with its larval migration.

Q: In occult filariasis, where are microfilariae typically found?

None of the above. ### Explanation **Concept Overview:** Occult filariasis (also known as **Meyers-Kouwenaar syndrome**) is a hypersensitivity reaction to the antigens of microfilariae (*Wuchereria bancrofti* or *Brugia malayi*). Unlike classical filariasis, the hallmark of this condition is the **absence of microfilariae in the peripheral blood**. **Why "None of the above" is correct:** In occult filariasis, the body develops an intense immunological response (Type I and Type IV hypersensitivity). This leads to the rapid destruction and trapping of microfilariae within the **visceral organs**, specifically the **lungs, liver, and spleen**. They are not typically found in the peripheral blood or lymph nodes; instead, they are sequestered in the tissues where they form eosinophilic granulomas known as **Meyers-Kouwenaar bodies**. **Analysis of Incorrect Options:** * **A. Peripheral blood:** This is the most common site for microfilariae in *classical* filariasis (often showing nocturnal periodicity). In occult filariasis, they are characteristically absent from the blood. * **B & C. Lymph nodes:** While adult worms reside in the lymphatic system in classical filariasis causing elephantiasis, in the occult form, the microfilariae are destroyed in the **visceral parenchyma** (lungs/liver) rather than circulating or residing in the peripheral or deep lymph nodes. **NEET-PG High-Yield Pearls:** * **Tropical Pulmonary Eosinophilia (TPE):** The most common clinical manifestation of occult filariasis, presenting with nocturnal cough, wheezing, and massive eosinophilia. * **Diagnostic Marker:** Characterized by significantly elevated **Serum IgE levels** and high titers of antifilarial antibodies. * **Treatment:** Responds dramatically to **Diethylcarbamazine (DEC)**. * **Pathology:** Look for **Meyers-Kouwenaar bodies** (microfilariae surrounded by eosinophilic material) in lung or liver biopsies.

Q: Rhinosporidium seeberi is a

Aquatic protist. **Explanation:** **Rhinosporidium seeberi** was traditionally classified as a fungus for over a century due to its morphology (production of sporangia and spores) and its staining characteristics (Gomori Methenamine Silver positive). However, modern molecular analysis (18S rRNA sequencing) has reclassified it as an **aquatic protist** belonging to the class **Mesomycetozoea**, a group of fish parasites located at the evolutionary boundary between animals and fungi. * **Why Option B is correct:** Phylogenetic studies show it is not a true fungus but a protist. It is typically found in stagnant water and soil, and infection is usually acquired through contact with contaminated water (e.g., swimming in ponds). * **Why Option A is incorrect:** While it resembles fungi morphologically (producing thick-walled sporangia containing thousands of endospores), it cannot be cultured on fungal media (like SDA) and does not respond to standard antifungal therapy. * **Why Options C & D are incorrect:** Its complex life cycle, large size (sporangia up to 350 µm), and eukaryotic structure rule out bacteria and viruses. **Clinical Pearls for NEET-PG:** * **Clinical Presentation:** Causes **Rhinosporidiosis**, characterized by friable, leafy, **strawberry-like polypoid masses** in the nose (most common) or conjunctiva. * **Epidemiology:** Highly endemic in **South India** (Tamil Nadu, Kerala) and Sri Lanka. * **Diagnosis:** Histopathology shows large, thick-walled **sporangia** filled with hundreds of **endospores**. * **Treatment:** The treatment of choice is **surgical excision** with wide cautery of the base. Dapsone is sometimes used to prevent recurrence.

Q: Which of the following is NOT true about the peripheral blood smear findings in malaria?

Enlarged erythrocytes in Plasmodium falciparum. ### Explanation The correct answer is **D (Enlarged erythrocytes in Plasmodium falciparum)** because *Plasmodium falciparum* typically infects red blood cells (RBCs) of all ages, and the infected cells remain **normal in size**. In contrast, *Plasmodium vivax* and *Plasmodium ovale* have a predilection for young RBCs (reticulocytes), which are naturally larger, and the parasite further causes the host cell to expand and become distorted. #### Analysis of Options: * **Option A (Single ring form in P. vivax):** This is a **true** statement. *P. vivax* usually presents with a single, large, thick ring (trophozoite) within the RBC. * **Option B (Multiple ring forms in P. falciparum):** This is a **true** statement and a classic diagnostic feature. *P. falciparum* often shows multiple rings within a single RBC (polyparasitism) and "accoulee" or "applique" forms (rings at the periphery of the cell). * **Option C (Enlarged erythrocytes in P. vivax):** This is **true**. Infected RBCs in *P. vivax* are significantly enlarged, pale, and often show **Schüffner’s dots**. * **Option D (Enlarged erythrocytes in P. falciparum):** This is **false**, making it the correct choice. RBCs in *P. falciparum* infections are of normal size and may show **Maurer’s clefts** (coarse granulations). #### NEET-PG High-Yield Pearls: * **P. falciparum:** Characterized by banana/crescent-shaped gametocytes, multiple rings per cell, and Maurer’s clefts. It is the most common cause of cerebral malaria. * **P. vivax:** Characterized by Schüffner’s dots, enlarged RBCs, and the presence of all stages (rings, trophozoites, schizonts) in peripheral blood. * **P. malariae:** Characterized by "Band forms" and "Ziemann’s stippling." * **Gold Standard Diagnosis:** Microscopy of **thick smears** (for detection/parasite load) and **thin smears** (for species identification).

Q: A fisherman presents with complaints of chronic diarrhea and fatigue. His physician orders a peripheral smear, which reveals a megaloblastic anemia. What is the most likely cause?

Diphyllobothrium latum. **Explanation:** The clinical presentation of chronic diarrhea, fatigue, and **megaloblastic anemia** in a fisherman is a classic description of **Diphyllobothrium latum** (Fish Tapeworm) infection. **Why Diphyllobothrium latum is correct:** * **Mechanism:** *D. latum* is the largest tapeworm infecting humans. It has a unique affinity for **Vitamin B12 (Cobalamin)**. The parasite competes with the host for B12 absorption in the small intestine, absorbing up to 80-100% of the dietary intake. * **Clinical Consequence:** Long-standing depletion of Vitamin B12 leads to impaired DNA synthesis, resulting in **megaloblastic anemia** (macrocytic anemia with hypersegmented neutrophils) and potential neurological symptoms (Subacute Combined Degeneration of the spinal cord). * **Epidemiology:** It is transmitted via the consumption of undercooked or raw freshwater fish (containing plerocercoid larvae), making it common among fishermen and sushi consumers. **Why other options are incorrect:** * **Clonorchis sinensis (Chinese Liver Fluke):** Primarily causes biliary tract diseases, including cholangitis and **cholangiocarcinoma**. It does not cause megaloblastic anemia. * **Echinococcus granulosus (Dog Tapeworm):** Causes **Hydatid cyst** disease, typically involving the liver or lungs. It presents with space-occupying lesions, not nutritional anemia. * **Taenia saginata (Beef Tapeworm):** Usually asymptomatic or causes mild GI upset. It does not interfere with Vitamin B12 absorption. **NEET-PG High-Yield Pearls:** * **Infective stage:** Plerocercoid larva. * **Diagnostic stage:** Operculated eggs in stool (bile-stained). * **Intermediate hosts:** 1st - Cyclops (Crustacean); 2nd - Freshwater fish. * **Treatment:** Praziquantel is the drug of choice. * **Key Association:** "Fish Tapeworm = Vitamin B12 deficiency."

Q: Romana's sign is seen in?

Trypanosoma cruzi. **Explanation:** **Romana’s sign** is a classic clinical hallmark of **acute Chagas disease**, caused by the protozoan parasite ***Trypanosoma cruzi***. It occurs when the parasite (transmitted via the feces of the Reduviid/Triatomine bug) enters through the conjunctiva or the skin near the eye. It is characterized by unilateral, painless periorbital edema, conjunctivitis, and local lymphadenopathy (pre-auricular nodes). **Why the other options are incorrect:** * **Toxoplasma gondii:** Typically presents as asymptomatic infection, lymphadenopathy, or chorioretinitis in immunocompromised patients, but does not cause Romana’s sign. * **Loa loa (African Eye Worm):** Known for **Calabar swellings** (transient subcutaneous angioedema) and the visible migration of the adult worm across the subconjunctiva. * **Wuchereria bancrofti:** The primary cause of Lymphatic Filariasis, leading to hydrocele, lymphedema, and elephantiasis, but not acute periorbital swelling. **High-Yield Clinical Pearls for NEET-PG:** * **Vector:** Reduviid bug (also called Triatomine or "Kissing bug"). * **Chagas Disease Triad (Chronic):** Achalasia cardia (Megaesophagus), Megacolon, and Dilated Cardiomyopathy (most common cause of death). * **Chagoma:** A localized inflammatory swelling at the site of entry on the skin (distinct from Romana's sign, which is specifically ophthalmic). * **Diagnosis:** C-shaped trypomastigotes on peripheral blood smear (acute phase) or Xenodiagnosis. * **Treatment:** Benznidazole or Nifurtimox.

Q: Which of the following parasitic infections is associated with Salmonella?

Schistosoma hematobium. **Explanation:** The association between **Salmonella** and **Schistosomiasis** is a classic example of a pathogen-parasite interaction. The correct answer is **Schistosoma haematobium** (and other species like *S. mansoni*). **Why it is correct:** Salmonella species (particularly *S. typhi* and *S. typhimurium*) have a unique ability to adhere to and colonize the **tegument** (outer surface) of adult Schistosoma worms. The bacteria utilize the parasite as a protected niche, leading to **chronic salmonellosis**. This synergy results in prolonged bacteremia that is often refractory to standard antibiotic therapy until the underlying parasitic infection is treated. While *S. mansoni* is more commonly linked to intestinal salmonellosis, *S. haematobium* is frequently associated with persistent urinary tract colonization and "urinary carriers" of Salmonella. **Why other options are incorrect:** * **Paragonimus (Lung fluke):** Associated with pulmonary symptoms mimicking tuberculosis; it does not have a recognized symbiotic relationship with Salmonella. * **Taenia solium (Pork tapeworm):** Primarily associated with neurocysticercosis or intestinal taeniasis; no specific link to Salmonella bacteremia. * **Hymenolepis nana (Dwarf tapeworm):** The most common cause of all cestode infections, but it does not serve as a reservoir for Salmonella. **High-Yield Clinical Pearls for NEET-PG:** * **Chronic Carrier State:** Always suspect Schistosomiasis in a patient with recurrent enteric fever who fails to respond to antibiotics. * **Mechanism:** Salmonella pili bind to the mannose-resistant receptors on the schistosome surface. * **Other Salmonella Associations:** * **Sickle Cell Anemia:** Predisposes to Salmonella Osteomyelitis. * **Chronic Gallbladder Disease:** Associated with the chronic carrier state of *S. typhi*.

Q: A girl complained of abdominal pain with the passage of foul-smelling stool that does not wash away easily. There is a history of swimming in contaminated water. What is the likely causative organism?

Giardia lamblia. The clinical presentation described is a classic case of **Giardiasis**, caused by the flagellated protozoan **Giardia lamblia**. **Why Giardia lamblia is correct:** The hallmark of Giardiasis is **steatorrhea** (fatty, foul-smelling stools that float and are difficult to flush/wash away). This occurs because the parasite attaches to the duodenal and jejunal mucosa via a ventral sucking disc, causing blunting of villi and malabsorption of fats. The history of **swimming in contaminated water** (lakes, streams, or pools) is a high-yield risk factor, as Giardia cysts are resistant to standard chlorine levels [1]. **Why the other options are incorrect:** * **Naegleria fowleri:** Known as the "brain-eating amoeba," it is also associated with contaminated water but causes Primary Amoebic Meningoencephalitis (PAM), not gastrointestinal symptoms. * **Amoeba (Entamoeba histolytica):** Causes amoebic dysentery characterized by bloody stools (haematochezia) and flask-shaped ulcers. It does not typically cause steatorrhea [2]. * **Shigella:** A bacterial cause of inflammatory diarrhea (dysentery). It presents with high fever, tenesmus, and stools containing blood and mucus, rather than foul-smelling, fatty stools. **High-Yield Clinical Pearls for NEET-PG:** * **Site of infection:** Primarily the **Duodenum** and upper Jejunum (Giardia "likes" the alkaline environment) [1]. * **Diagnosis:** Stool microscopy (cysts or pear-shaped trophozoites with "falling leaf" motility). **Entero-test (String test)** can be used if stool samples are negative. * **Drug of Choice:** **Tinidazole** (preferred over Metronidazole due to single-dose efficacy). * **Common Association:** Increased incidence in patients with **IgA deficiency**.

Question 1

Which of the following eggs does not float on a saturated salt solution?

Accepted Answer

Unfertilized egg of Ascaris

Answer

Fertilized egg of Ascaris

Answer

Trichuris trichura

Answer

H. Nana

Question 2

In occult filariasis, where are microfilariae typically found?

Accepted Answer

None of the above

Answer

Peripheral blood

Answer

Peripheral lymph nodes

Answer

Deep lymph nodes

Question 3

Which of the following statements is true regarding malaria?

Accepted Answer

Red blood cell size is enlarged in Plasmodium vivax infection.

Answer

Red blood cell size is enlarged in Plasmodium falciparum infection.

Answer

Schüffner's dots are seen in Plasmodium malariae infection.

Answer

Relapse occurs in Plasmodium falciparum infection.

Question 4

Rhinosporidium seeberi is a

Accepted Answer

Aquatic protist

Answer

Fungi

Answer

Bacteria

Answer

Virus

Question 5

Which of the following is NOT true about the peripheral blood smear findings in malaria?

Accepted Answer

Enlarged erythrocytes in Plasmodium falciparum

Answer

Single ring form in Plasmodium vivax

Answer

Multiple ring forms in Plasmodium falciparum

Answer

Enlarged erythrocytes in Plasmodium vivax

Question 6

A fisherman presents with complaints of chronic diarrhea and fatigue. His physician orders a peripheral smear, which reveals a megaloblastic anemia. What is the most likely cause?

Accepted Answer

Diphyllobothrium latum

Answer

Clonorchis sinensis

Answer

Echinococcus granulosus

Answer

Taenia saginata

Question 7

Romana's sign is seen in?

Accepted Answer

Trypanosoma cruzi

Answer

Toxoplasma

Answer

Loa loa

Answer

Wuchereria

Question 8

What is true about the peripheral blood smear of Plasmodium vivax?

Accepted Answer

Single ring with cytoplasm condensed around in each erythrocyte.

Answer

Mature or old erythrocytes are affected.

Answer

Parasitized erythrocytes are of the same size as normal erythrocytes.

Answer

Only ring and gametocytes are seen.

Question 9

Which of the following parasitic infections is associated with Salmonella?

Accepted Answer

Schistosoma hematobium

Answer

Paragonimus

Answer

Taenia solium

Answer

Hymenolepis nana

Question 10

A girl complained of abdominal pain with the passage of foul-smelling stool that does not wash away easily. There is a history of swimming in contaminated water. What is the likely causative organism?

Accepted Answer

Giardia lamblia

Answer

Naegleria

Answer

Amoeba

Answer

Shigella

Parasitology — MCQs

Parasitology — MCQs

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