Parasitology Practice Questions

Q: Which of the following is caused by Leishmania?

Leishmania. **Explanation:** The correct answer is **Leishmania**. This question highlights the basic classification of protozoan parasites. **Leishmaniasis** is a vector-borne disease caused by obligate intracellular protozoa of the genus *Leishmania*, transmitted to humans by the bite of infected female **Phlebotomine sandflies**. **Why the other options are incorrect:** * **Trypanosoma:** These are hemoflagellates responsible for **African Sleeping Sickness** (*T. brucei*) transmitted by the Tsetse fly, and **Chagas disease** (*T. cruzi*) transmitted by the Reduviid bug. * **Treponema:** This is a genus of **Spirochetes** (bacteria), not a parasite. The most clinically significant species is *Treponema pallidum*, the causative agent of **Syphilis**. * **Toxoplasma:** *Toxoplasma gondii* is an intracellular coccidian parasite. It causes **Toxoplasmosis**, typically transmitted via ingestion of oocysts from cat feces or undercooked meat, and is a major cause of congenital infections (TORCH complex). **High-Yield Clinical Pearls for NEET-PG:** * **Clinical Forms:** Leishmaniasis presents in three main forms: **Visceral** (Kala-azar), **Cutaneous** (Oriental sore), and **Mucocutaneous**. * **Kala-azar (Visceral Leishmaniasis):** Caused by *L. donovani*. Characterized by the triad of **massive splenomegaly**, irregular fever, and pancytopenia. * **Diagnostic Gold Standard:** Demonstration of **LD bodies** (Amastigotes) in bone marrow or splenic aspirates. * **Culture:** Grown on **NNN (Novy-MacNeal-Nicolle) medium**, where the promastigote stage is seen. * **Drug of Choice:** Liposomal Amphotericin B is currently the preferred treatment for Visceral Leishmaniasis in India.

Q: Which of the following organisms does not cause neurodegeneration?

Iodamoeba. **Explanation:** The core concept tested here is the distinction between **pathogenic free-living amoebae** (which have a predilection for the Central Nervous System) and **intestinal amoebae**. **Why Iodamoeba is the correct answer:** *Iodamoeba bütschlii* is a commensal intestinal amoeba. It is considered **non-pathogenic** to humans and resides in the large intestine. It does not invade the bloodstream or cross the blood-brain barrier; therefore, it cannot cause neurodegeneration or any neurological pathology. **Analysis of Incorrect Options:** * **Naegleria fowleri:** Known as the "brain-eating amoeba," it causes **Primary Amoebic Meningoencephalitis (PAM)**. It enters via the olfactory neuroepithelium, leading to rapid, fulminant brain tissue destruction. * **Balamuthia mandrillaris:** A free-living amoeba that causes **Granulomatous Amoebic Encephalitis (GAE)**, a subacute to chronic necrotizing infection of the CNS, typically in both immunocompetent and immunocompromised hosts. * **Entamoeba histolytica:** While primarily an intestinal pathogen causing dysentery, it can spread hematogenously. **Cerebral amoebiasis** is a rare but recognized extraintestinal complication of *E. histolytica*, presenting as brain abscesses and secondary neurodegeneration. **NEET-PG High-Yield Pearls:** 1. **Free-living amoebae (FLA):** *Naegleria, Acanthamoeba,* and *Balamuthia* are the primary neuro-pathogens. 2. **Naegleria vs. Acanthamoeba:** *Naegleria* causes acute PAM (history of swimming), while *Acanthamoeba* causes chronic GAE (associated with keratitis in contact lens users). 3. **Diagnostic Key:** In *Naegleria* infections, only **trophozoites** are found in CSF; in *Acanthamoeba/Balamuthia*, both **cysts and trophozoites** are present in tissue. 4. **Iodamoeba characteristic:** It is named for its large **iodinophilic vacuole** (glycogen mass) that stains dark brown with iodine.

Q: Cerebral malaria is caused by which Plasmodium species?

Falciparum. **Explanation:** **Plasmodium falciparum** is the most virulent species of malaria and is the primary cause of **Cerebral Malaria**. The underlying pathophysiology involves **cytoadherence** and **sequestration**. *P. falciparum* expresses a protein called **PfEMP-1** (Plasmodium falciparum erythrocyte membrane protein 1) on the surface of infected Red Blood Cells (RBCs). This protein acts as a ligand for receptors like **ICAM-1** and **CD36** on the vascular endothelium. This causes infected RBCs to stick to the walls of small capillaries (sequestration) and to each other (rosetting), leading to microvascular obstruction, tissue hypoxia, and localized inflammatory responses in the brain. **Analysis of Incorrect Options:** * **P. vivax & P. ovale:** These species primarily cause "Benign Tertian Malaria." They prefer infecting young RBCs (reticulocytes), leading to lower parasite loads. While *P. vivax* can occasionally cause severe complications, it does not typically cause the classic sequestration-driven cerebral malaria. Both are known for forming **hypnozoites** in the liver, leading to relapses. * **P. malariae:** This species causes "Quartan Malaria" (72-hour cycle). It typically results in a milder clinical course but is uniquely associated with **nephrotic syndrome** (quartan malarial nephropathy) due to immune complex deposition. **High-Yield Clinical Pearls for NEET-PG:** * **Blackwater Fever:** Severe intravascular hemolysis leading to hemoglobinuria, specifically associated with *P. falciparum*. * **Maurer’s Clefts:** Seen in RBCs infected with *P. falciparum*; whereas **Schüffner’s dots** are seen in *P. vivax/ovale*. * **Multiple Rings & Accole forms:** Characteristic peripheral smear findings for *P. falciparum*. * **Drug of Choice:** For severe/cerebral malaria, **Intravenous Artesunate** is the gold standard.

Q: Which of the following is false regarding Trichomonas vaginalis?

Mature cysts are passed in feces.. **Explanation:** The correct answer is **C (Mature cysts are passed in feces)** because *Trichomonas vaginalis* is unique among pathogenic protozoa as it **does not have a cyst stage**. It exists only as a trophozoite. Furthermore, it is a urogenital parasite, not an intestinal one; therefore, it is not passed in feces but is transmitted primarily through sexual contact. **Analysis of Options:** * **A. Trophozoites have 5 anterior flagella:** This is a common point of confusion. *T. vaginalis* actually possesses **4 anterior flagella** and a **5th flagellum** that forms the outer edge of the undulating membrane. (Note: Some texts refer to the total flagellar count, but the classic description is 4 free anterior flagella). * **B. Exhibits twitching motility:** This is a classic diagnostic feature. In a wet mount of vaginal or urethral discharge, the trophozoites exhibit a characteristic jerky, **twitching motility**, which is a high-yield fact for identification. * **D. Drug of choice is metronidazole:** Metronidazole (or Tinidazole) is the gold standard treatment. It is crucial to treat both the patient and the **sexual partner** simultaneously to prevent "ping-pong" reinfection. **Clinical Pearls for NEET-PG:** * **Habitat:** Female vagina and male urethra/prostate. * **Clinical Presentation:** Causes "Strawberry Cervix" (colpitis macularis) due to punctate hemorrhages. * **Diagnosis:** Gold standard is **Whiff Test** (amine odor with KOH) and **Diamond’s Medium** for culture. * **pH:** It thrives in an alkaline vaginal pH (>4.5), unlike the normal acidic environment.

Q: L.D. bodies are seen in which of the following conditions?

Kala-azar. **Explanation:** **L.D. Bodies (Leishman-Donovan bodies)** are the **amastigote stage** of the protozoan parasite *Leishmania donovani*. This stage is found intracellularly within the reticuloendothelial system (macrophages, liver, spleen, and bone marrow) of the human host. 1. **Why Kala-azar is correct:** Kala-azar, also known as Visceral Leishmaniasis, is caused by *L. donovani*. In the human host, the parasite exists as an ovoid, non-flagellated amastigote (L.D. body) measuring 2–4 µm. Demonstration of these bodies in splenic or bone marrow aspirates remains the **gold standard for diagnosis**. 2. **Why other options are incorrect:** * **Toxoplasmosis:** Caused by *Toxoplasma gondii*. It presents as tachyzoites (active infection) or bradyzoites (tissue cysts), not L.D. bodies. * **Malaria:** Caused by *Plasmodium* species. Diagnostic stages include ring forms, trophozoites, schizonts, and gametocytes within RBCs. * **Sleeping sickness (African Trypanosomiasis):** Caused by *Trypanosoma brucei*. It exists only in the **trypomastigote** stage (extracellular flagellates) in human blood and CSF; it does not have an amastigote stage. **High-Yield Clinical Pearls for NEET-PG:** * **Vector:** Sandfly (*Phlebotomus argentipes*). * **Infective stage:** Promastigote (found in the sandfly). * **Diagnostic stage:** Amastigote (L.D. body). * **Morphology of L.D. Body:** Contains a nucleus and a rod-shaped **kinetoplast**. * **Culture:** NNN (Novy-MacNeal-Nicolle) medium. * **Drug of Choice:** Liposomal Amphotericin B.

Q: A 32-year-old man presented with various signs and symptoms after consuming crab from a local restaurant. Which parasite can be transmitted through consuming crab?

Paragonimus westermanii. **Explanation:** The correct answer is **Paragonimus westermanii**, also known as the **Oriental Lung Fluke**. **1. Why Paragonimus westermanii is correct:** The life cycle of *Paragonimus westermanii* involves two intermediate hosts. The first is a snail, and the second is a **crustacean (crab or crayfish)**. Humans become infected by ingesting raw or undercooked crabs containing the infective stage, the **metacercariae**. Once ingested, the larvae excyst in the duodenum, penetrate the intestinal wall, migrate through the diaphragm, and eventually mature in the lungs, leading to symptoms like hemoptysis (mimicking tuberculosis). **2. Why other options are incorrect:** * **A. Diphyllobothrium latum:** This is the fish tapeworm. Infection occurs via the consumption of undercooked **freshwater fish** containing plerocercoid larvae. * **B. Clonorchis sinensis:** Known as the Chinese Liver Fluke. While it also uses a snail as the first intermediate host, the second intermediate host is **freshwater fish**, not crabs. * **C. Enterobius vermicularis:** This is the pinworm. Transmission is primarily via the **fecal-oral route** (ingestion of embryonated eggs) or autoinfection; it does not involve an aquatic intermediate host. **Clinical Pearls for NEET-PG:** * **Classic Presentation:** A patient with a history of crab consumption presenting with chronic cough and "rusty-brown" sputum (containing eggs). * **Radiology:** May show ring-shadows or "cotton-wool" opacities in the lungs, often confused with TB. * **Diagnosis:** Identification of operculated eggs in sputum or feces. * **Drug of Choice:** Praziquantel.

Q: An 8-year-old child presents with crampy abdominal pain, nausea, and mild diarrhea for two weeks. The day before the visit, a cylindrical white worm, approximately 30 cm in length, was vomited and preserved. What is the most likely mode of acquisition for this organism?

Ingestion of eggs from human feces. **Explanation:** The clinical presentation of a large (30 cm), cylindrical white worm being vomited is pathognomonic for **Ascaris lumbricoides** (Giant Roundworm). Ascariasis is the most common helminthic infection worldwide. **1. Why Option D is Correct:** *Ascaris lumbricoides* is a soil-transmitted helminth. The life cycle begins when an infected human defecates in the soil. The eggs must undergo a period of maturation (embryonation) in the soil for 2–3 weeks to become infective. Humans acquire the infection via the **fecal-oral route** by ingesting these embryonated eggs from contaminated soil, food, or water. Since humans are the only reservoir, the eggs originate from human feces. **2. Why Other Options are Incorrect:** * **Option A (Autoinfection):** This is characteristic of *Strongyloides stercoralis* or *Enterobius vermicularis*. *Ascaris* eggs require time in the soil to become infective and cannot cause immediate autoinfection. * **Option B (Ingestion of cysts):** This is the mode of transmission for protozoa like *Giardia lamblia* or *Entamoeba histolytica*, not large nematodes. * **Option C (Infected pet):** While *Toxocara canis* (dog roundworm) is acquired from pets, it causes Visceral Larva Migrans in humans; the adult worms do not develop in the human intestine and are not vomited. **Clinical Pearls for NEET-PG:** * **Löffler Syndrome:** Pulmonary phase of *Ascaris* migration characterized by eosinophilic pneumonia, cough, and wheezing. * **Complications:** Intestinal obstruction (at the ileocecal valve), biliary colic, or pancreatitis due to worm migration. * **Diagnosis:** Stool microscopy for bile-stained, mamillated eggs. * **Treatment:** Albendazole (400 mg single dose) is the drug of choice.

Q: Barrel-shaped eggs are seen in which of the following parasites?

Whipworm. **Explanation:** The correct answer is **Whipworm (*Trichuris trichiura*)**. **1. Why Whipworm is correct:** The eggs of *Trichuris trichiura* possess a highly characteristic morphology often described as **barrel-shaped**, lemon-shaped, or tea-tray shaped. Key diagnostic features include a thick, smooth brown shell (bile-stained) and the presence of **prominent clear mucoid bipolar plugs** at both ends. These eggs are unembryonated when passed in feces. **2. Why other options are incorrect:** * **Hookworm (*Ancylostoma duodenale/Necator americanus*):** Eggs are oval or elliptical, colorless (non-bile stained), and surrounded by a thin, transparent hyaline shell. They typically contain a segmented ovum (usually 4–8 blastomeres) with a clear space between the shell and the embryo. * **Pinworm (*Enterobius vermicularis*):** Eggs are characterized by a unique **planoconvex** shape (one side flattened, the other convex), resembling the letter ‘D’. They are non-bile stained and contain a fully formed tadpole-like larva. * **Roundworm (*Ascaris lumbricoides*):** Fertilized eggs are typically round or oval with a thick, lumpy, outer **mammillated (albuminous) coat** stained golden-brown by bile. **3. NEET-PG Clinical Pearls:** * **Habitat:** *Trichuris trichiura* lives in the **caecum** and large intestine. * **Clinical Presentation:** Heavy infestation in children can lead to **rectal prolapse** due to mucosal irritation and increased peristalsis. * **Morphology:** The adult worm has a thin, thread-like anterior end and a thick posterior end, resembling a whip. * **Treatment:** Albendazole or Mebendazole are the drugs of choice.

Q: Which of the following diseases is NOT transmitted by hard ticks?

Relapsing fever. **Explanation:** The correct answer is **Relapsing fever**. In medical parasitology, it is crucial to distinguish between diseases transmitted by **Hard ticks (Ixodidae)** and **Soft ticks (Argasidae)**. 1. **Why Relapsing Fever is the correct answer:** Relapsing fever exists in two forms: **Epidemic** (transmitted by body lice) and **Endemic** (transmitted by **Soft ticks** of the genus *Ornithodoros*). Both are caused by *Borrelia* species. Since it is transmitted by soft ticks, it is not associated with hard ticks. 2. **Analysis of Incorrect Options:** * **Hemorrhagic fever:** Specifically, **Crimean-Congo Hemorrhagic Fever (CCHF)** is a viral disease transmitted primarily by *Hyalomma* ticks (a genus of hard ticks). Kyasanur Forest Disease (KFD) is also transmitted by hard ticks (*Haemaphysalis*). * **Tick typhus:** Also known as Indian Tick Typhus (caused by *Rickettsia conorii*), it is transmitted by hard ticks like *Rhipicephalus sanguineus*. * **Tularemia:** Caused by *Francisella tularensis*, this zoonosis can be transmitted by various routes, but hard ticks (*Dermacentor* and *Amblyomma*) are major biological vectors. **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic for Hard Tick diseases:** "**I**ndian **T**ick **T**yphus, **K**FD, **B**abesiosis, **T**ularemia, **B**ull’s eye rash (Lyme), **C**CHF" (**I T**ake **K**ids **B**ack **T**o **B**ig **C**ities). * **Soft Tick (Argasidae):** Primarily transmits **Endemic Relapsing Fever** (*Borrelia duttoni*). * **Hard Tick (Ixodidae):** Characterized by a dorsal **scutum**, anterior capitulum, and slow feeding (days). * **Lyme Disease:** Transmitted by *Ixodes* (Hard tick); look for Erythema Chronicum Migrans in clinical vignettes.

Question 1

Which of the following is caused by Leishmania?

Accepted Answer

Leishmania

Answer

Trypanosoma

Answer

Treponema

Answer

Toxoplasma

Question 2

A Pap smear from a 30-year-old woman demonstrates protozoal parasites. What are these organisms most likely to be?

Accepted Answer

Trichomonas vaginalis

Answer

Cryptosporidium parvum

Answer

Entamoeba histolytica

Answer

Giardia lamblia

Question 3

Which of the following organisms does not cause neurodegeneration?

Accepted Answer

Iodamoeba

Answer

Balamuthia

Answer

Naegleria

Answer

Entamoeba

Question 4

Cerebral malaria is caused by which Plasmodium species?

Accepted Answer

Falciparum

Answer

Ovale

Answer

Vivax

Answer

Malariae

Question 5

Which of the following is false regarding Trichomonas vaginalis?

Accepted Answer

Mature cysts are passed in feces.

Answer

Trophozoites have 5 anterior flagella.

Answer

Exhibits twitching motility.

Answer

Drug of choice is metronidazole.

Question 6

L.D. bodies are seen in which of the following conditions?

Accepted Answer

Kala-azar

Answer

Toxoplasmosis

Answer

Malaria

Answer

Sleeping sickness

Question 7

A 32-year-old man presented with various signs and symptoms after consuming crab from a local restaurant. Which parasite can be transmitted through consuming crab?

Accepted Answer

Paragonimus westermanii

Answer

Diphyllobothrium

Answer

Clonorchis sinensis

Answer

Enterobius

Question 8

An 8-year-old child presents with crampy abdominal pain, nausea, and mild diarrhea for two weeks. The day before the visit, a cylindrical white worm, approximately 30 cm in length, was vomited and preserved. What is the most likely mode of acquisition for this organism?

Accepted Answer

Ingestion of eggs from human feces

Answer

Autoinfection

Answer

Ingestion of cysts in contaminated water

Answer

Ingestion of eggs from an infected pet

Question 9

Barrel-shaped eggs are seen in which of the following parasites?

Accepted Answer

Whipworm

Answer

Hookworm

Answer

Pinworm

Answer

Roundworm

Question 10

Which of the following diseases is NOT transmitted by hard ticks?

Accepted Answer

Relapsing fever

Answer

Hemorrhagic fever

Answer

Tick typhus

Answer

Tularemia

Parasitology — MCQs

Parasitology — MCQs

On this page

Practice by Chapter

Want unlimited practice?