Parasitology Practice Questions

Q: A biology graduate student who recently visited a tropical region of Africa presents with new visual impairment and the sensation that something is moving in her eye. She is concerned because she was warned about an eye disease transmitted by black flies. While in Africa, she was in a river area and received numerous black fly bites. She also has some subcutaneous nodules. If her infection was acquired by black fly bite, what is the most likely causative agent?

Onchocerca volvulus. **Explanation** The correct answer is **D. Onchocerca volvulus**. The clinical presentation describes **Onchocerciasis (River Blindness)**. The diagnosis is confirmed by the classic triad: history of exposure in an endemic region (Africa), transmission via the **Black fly (*Simulium* species)**, and clinical features including subcutaneous nodules (**Onchocercomas**) and visual impairment. The "moving sensation" in the eye refers to the migration of microfilariae into the ocular tissues, leading to sclerosing keratitis—the second leading infectious cause of blindness worldwide. **Why other options are incorrect:** * **A. Ancylostoma braziliense:** Causes Cutaneous Larva Migrans (creeping eruption). It is transmitted by direct skin contact with soil contaminated by hookworm larvae from cats/dogs, not by black flies. * **B. Trichinella spiralis:** Acquired by consuming undercooked meat (pork) containing encysted larvae. It presents with periorbital edema, myalgia, and eosinophilia, but does not involve black fly transmission. * **C. Dracunculus medinensis:** Causes Guinea worm disease. It is transmitted by drinking water containing infected *Cyclops* (copepods). It presents with a painful skin blister, usually on the lower limb, through which the adult worm emerges. **High-Yield NEET-PG Pearls:** * **Vector:** *Simulium* (Black fly) breeds in fast-flowing rivers (hence "River Blindness"). * **Infective stage:** Third-stage larvae (L3). * **Diagnosis:** **Skin snip preparation** to demonstrate microfilariae (they do not have a periodic presence in the blood). * **Treatment:** **Ivermectin** is the drug of choice (kills microfilariae). Doxycycline is used to target *Wolbachia*, an endosymbiont essential for the worm's survival. * **Mazzotti Reaction:** A severe inflammatory response (fever, rash, hypotension) that can occur after treating Onchocerciasis with diethylcarbamazine (DEC).

Q: All of the following are true about Trichinella spiralis EXCEPT?

Fairey's test is the intradermal test done.. **Explanation:** *Trichinella spiralis* is a tissue nematode that causes Trichinellosis. Understanding its unique life cycle and diagnostic tests is crucial for NEET-PG. **Why Option D is the Correct Answer (The "Except" statement):** The intradermal test used for the diagnosis of Trichinellosis is the **Bachman intradermal test**, not Fairey’s test. **Fairey’s test** is an intradermal test historically associated with **Schistosomiasis**. Therefore, statement D is factually incorrect regarding *Trichinella*. **Analysis of Other Options:** * **Option A:** Humans are indeed **accidental hosts**. While both the adult and larval stages occur in the same host, humans act as a **dead-end** because the larvae encysted in human muscle are unlikely to be consumed by another host. * **Option B:** The primary mode of transmission is the **ingestion of raw or undercooked meat** (most commonly pork) containing the infective encysted larvae. * **Option C:** Larvae have a predilection for highly active muscles with high oxygen content. The **extraocular muscles** are the most frequently involved, followed by the tongue, diaphragm, and intercostal muscles. **Clinical Pearls for NEET-PG:** * **Clinical Triad:** Look for a history of pork ingestion followed by **fever, periorbital edema, and myalgia**. * **Lab Findings:** Marked **Eosinophilia** and elevated **Creatine Phosphokinase (CPK)** due to muscle damage. * **Diagnosis:** Muscle biopsy (showing coiled larvae) is the gold standard. * **Treatment:** Albendazole or Mebendazole are the drugs of choice.

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.

Question 1

A biology graduate student who recently visited a tropical region of Africa presents with new visual impairment and the sensation that something is moving in her eye. She is concerned because she was warned about an eye disease transmitted by black flies. While in Africa, she was in a river area and received numerous black fly bites. She also has some subcutaneous nodules. If her infection was acquired by black fly bite, what is the most likely causative agent?

Accepted Answer

Onchocerca volvulus

Answer

Ancylostoma braziliense

Answer

Trichinella spiralis

Answer

Dracunculus medinensis

Question 2

A 30-year-old farmer, treated initially with chloroquine for uncomplicated malaria, now has an episode of relapse. What could be the reason for relapse?

Accepted Answer

P. vivax has a persistent exoerythrocytic stage (hypnozoite).

Answer

P. vivax has a significant level of chloroquine resistance.

Answer

P. vivax has a persistent erythrocytic stage.

Answer

Chloroquine is not one of the drugs of choice.

Question 3

All of the following are true about Trichinella spiralis EXCEPT?

Accepted Answer

Fairey's test is the intradermal test done.

Answer

Man is an accidental host and acts as a dead-end.

Answer

Transmitted by ingestion of raw or undercooked pork.

Answer

Most common muscle involved is extraocular muscles.

Question 4

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 5

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 6

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 7

Rhinosporidium seeberi is a

Accepted Answer

Aquatic protist

Answer

Fungi

Answer

Bacteria

Answer

Virus

Question 8

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 9

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 10

Romana's sign is seen in?

Accepted Answer

Trypanosoma cruzi

Answer

Toxoplasma

Answer

Loa loa

Answer

Wuchereria

Parasitology — MCQs

Parasitology — MCQs

On this page

Practice by Chapter

Want unlimited practice?