Parasitology Practice Questions

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: What is the most common presenting symptom of Enterobius vermicularis infection?

Abdominal pain. **Explanation:** *Enterobius vermicularis*, commonly known as **Pinworm** or **Seatworm**, is the most common helminthic infection worldwide. **Why Abdominal Pain is the Correct Answer:** While the hallmark symptom of Enterobiasis is nocturnal perianal pruritus (itching), among the options provided, **abdominal pain** is the most frequent clinical presentation. This occurs due to the presence of adult worms in the cecum and appendix, which can cause mild mucosal irritation or, in some cases, symptoms mimicking acute appendicitis. **Analysis of Incorrect Options:** * **Rectal Prolapse:** This is a classic complication associated with heavy infections of ***Trichuris trichiura* (Whipworm)**, not Enterobius. * **Urticaria:** This is more characteristic of helminths that undergo a tissue-migratory phase (e.g., *Ascaris lumbricoides* or *Strongyloides stercoralis*), leading to eosinophilic allergic responses. * **Vaginitis:** While *E. vermicularis* can cause ectopic migration into the female genital tract (leading to vulvovaginitis or salpingitis), it is a **complication** rather than the most common presenting symptom. **High-Yield Clinical Pearls for NEET-PG:** * **Diagnostic Gold Standard:** NIH Swab or **Scotch Tape Test** (Cellophane tape test) performed early in the morning to detect eggs. * **Egg Morphology:** Planoconvex, non-bile stained, with a "D" shape. * **Autoinfection:** Occurs via the fecal-oral route (finger-sucking or nail-biting) due to the intense perianal itching. * **Treatment:** Albendazole or Mebendazole (single dose, repeated after 2 weeks). **Treat the entire family** to prevent reinfection.

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: Cholangiocarcinoma has been associated with infection by which of the following parasites?

Clonorchis sinensis. **Explanation:** The correct answer is **Clonorchis sinensis**. **1. Why Clonorchis sinensis is correct:** *Clonorchis sinensis* (the Chinese Liver Fluke) and *Opisthorchis viverrini* are well-established biological carcinogens. These parasites reside in the **distal biliary passages**. Chronic infection leads to mechanical irritation, production of proline-like substances, and chronic inflammation of the bile duct epithelium. This results in adenomatous hyperplasia, which can progress to **Cholangiocarcinoma** (bile duct cancer). Transmission occurs via the ingestion of undercooked freshwater fish containing metacercariae. **2. Analysis of Incorrect Options:** * **Paragonimus westermani (Lung Fluke):** Associated with pulmonary infections mimicking tuberculosis (hemoptysis, cavitary lesions). It does not involve the biliary tract. * **Loa Loa (African Eye Worm):** A nematode transmitted by the *Chrysops* fly. It causes Calabar swellings and subconjunctival migration; it has no association with malignancy. * **Schistosoma haematobium (Bladder Fluke):** While it is associated with cancer, it causes **Squamous Cell Carcinoma of the Urinary Bladder**, not cholangiocarcinoma. It resides in the vesical venous plexuses. **3. NEET-PG High-Yield Clinical Pearls:** * **Drug of Choice:** Praziquantel is the treatment for all trematodes (flukes) except *Fasciola hepatica* (Triclabendazole). * **Intermediate Hosts:** *C. sinensis* requires two intermediate hosts: 1st - Snail (Parafossarulus), 2nd - Freshwater fish. * **Imaging:** On ultrasound/CT, chronic infection may show "ductal dilatation with eccentric wall thickening." * **Other Parasite-Cancer Link:** Remember *Schistosoma japonicum* is occasionally linked to colorectal cancer.

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 parasites is commonly found in muscles?

Trichinella spiralis. **Explanation:** The correct answer is **Trichinella spiralis**. This parasite is the causative agent of **Trichinellosis**. Its unique life cycle involves the same animal acting as both the definitive and intermediate host. After ingestion of undercooked meat (usually pork) containing encysted larvae, the larvae mature in the small intestine. The newborn larvae then migrate via the bloodstream to **striated muscles**, where they encyst. These "nurse cells" are most commonly found in highly active muscles such as the diaphragm, extraocular muscles, and deltoids. **Why the other options are incorrect:** * **Trichuris trichiura (Whipworm):** This is a soil-transmitted helminth that resides in the **large intestine (caecum)**. It does not have a tissue migration phase involving muscles. * **Schistosomiasis (Blood Flukes):** These trematodes reside in the **venous plexuses** (e.g., vesical plexus for *S. haematobium* and mesenteric veins for *S. mansoni*). They do not encyst in muscles. * **Ancylostoma duodenale (Hookworm):** These parasites reside in the **small intestine**, where they attach to the mucosa to suck blood. While they migrate through the lungs (Loeffler’s syndrome), they do not settle in muscle tissue. **NEET-PG High-Yield Pearls:** * **Clinical Triad of Trichinellosis:** Myalgia, periorbital edema, and eosinophilia. * **Diagnosis:** Muscle biopsy (showing coiled larvae) or the **Bachman intradermal test**. * **Other parasites in muscle:** *Taenia solium* (Cysticercosis) also forms cysts in muscles and the brain. * **Key Lab Finding:** Elevated **Creatine Phosphokinase (CPK)** due to muscle damage.

Q: Romana's sign occurs in which condition?

Trypanosomiasis. **Explanation:** **Romana’s sign** is a classic clinical hallmark of **American Trypanosomiasis (Chagas disease)**, caused by the protozoan parasite *Trypanosoma cruzi*. It refers to the painless, unilateral periorbital edema and conjunctivitis that occurs when the parasite (transmitted via the feces of the **Reduviid/Triatomine bug**) enters through the conjunctiva or a nearby bite wound. **Why the other options are incorrect:** * **Babesiosis:** Caused by *Babesia microti* (transmitted by *Ixodes* ticks), it typically presents with a malaria-like illness (fever, hemolytic anemia) and is characterized by "Maltese cross" appearances in RBCs, not localized facial swelling. * **Leishmaniasis:** While Cutaneous Leishmaniasis causes skin ulcers and Visceral Leishmaniasis (Kala-azar) causes hepatosplenomegaly, they do not present with Romana’s sign. A similar-sounding sign, the "Chagoma," is the skin equivalent of Romana’s sign in Chagas disease. * **Schistosomiasis:** This helminthic infection is associated with "Swimmer’s itch" (cercarial dermatitis) and Katayama fever, but not periorbital edema. **High-Yield Clinical Pearls for NEET-PG:** * **Vector:** Reduviid bug (also known as the Kissing bug or Assassin bug). * **Transmission:** Occurs via the **feces** of the bug being rubbed into a wound or mucous membrane (Stercorarian transmission). * **Chronic Chagas Disease:** Look for "Mega" syndromes—**Megaesophagus, Megacolon**, and **Dilated Cardiomyopathy** (the leading cause of death in these patients). * **Diagnosis:** C-shaped trypomastigotes in peripheral blood (acute) or Amastigotes in tissue (Leishmanial stage).

Question 1

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 2

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 3

What is the most common presenting symptom of Enterobius vermicularis infection?

Accepted Answer

Abdominal pain

Answer

Rectal prolapse

Answer

Urticaria

Answer

Vaginitis

Question 4

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 5

Cholangiocarcinoma has been associated with infection by which of the following parasites?

Accepted Answer

Clonorchis sinensis

Answer

Paragonimus westermani

Answer

Loa Loa

Answer

Schistosoma haematobium

Question 6

Romana's sign is seen in?

Accepted Answer

Trypanosoma cruzi

Answer

Toxoplasma

Answer

Loa loa

Answer

Wuchereria

Question 7

Which of the following is true about the mature cyst of E. histolytica?

Accepted Answer

Nuclear structure retains characteristics of the trophozoite.

Answer

Endoplasm and ectoplasm are clearly defined.

Answer

Contains eight chromatid bodies.

Answer

Shows chromatid bodies and glycogen mass.

Question 8

Which of the following parasites is commonly found in muscles?

Accepted Answer

Trichinella spiralis

Answer

Trichuris trichiura

Answer

Schistosomiasis

Answer

Ancylostoma duodenale

Question 9

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 10

Romana's sign occurs in which condition?

Accepted Answer

Trypanosomiasis

Answer

Babesiosis

Answer

Leishmaniasis

Answer

Schistosomiasis

Parasitology — MCQs

Parasitology — MCQs

On this page

Practice by Chapter

Want unlimited practice?