Parasitology — MCQs

Parasitology Indian Medical PG Practice Questions and MCQs

Question 891: In malaria, pre-erythrocytic schizogony occurs in -

A. Lung
B. Liver (Correct Answer)
C. Spleen
D. Kidney

Explanation: ***Liver*** - After being introduced by a mosquito bite, **Plasmodium sporozoites** rapidly travel to the liver - In the liver, they invade **hepatocytes** and undergo asexual reproduction, known as **pre-erythrocytic (or hepatic) schizogony**, forming merozoites - This is the exo-erythrocytic cycle that occurs before red blood cell invasion *Lung* - The lungs are not a primary site for **Plasmodium** development or asexual reproduction in the human host - While some parasite components or host immune responses might involve the lungs in severe malaria, it is not where pre-erythrocytic schizogony occurs *Spleen* - The **spleen** is primarily involved in clearing infected red blood cells and acts as a site for immune responses to malaria, but not for initial schizogony - It plays a significant role in the **erythrocytic stage** of malaria by filtering and destroying parasitized red blood cells *Kidney* - The **kidneys** are not involved in the life cycle of the **Plasmodium parasite** during pre-erythrocytic schizogony - While malaria can cause **renal complications** (such as acute kidney injury in severe cases), this is a pathological effect, not a site of parasite development

Question 892: Consumption of uncooked pork is likely to cause which of the following helminthic disease -

A. Taenia saginata
B. Taenia solium (Correct Answer)
C. Trichuris trichiura
D. None of the options

Explanation: ***Taenia solium*** - Infection with **_Taenia solium_** (pork tapeworm) occurs by consuming raw or undercooked **pork** containing **cysticerci** (larval cysts). - This can lead to **taeniasis** (intestinal tapeworm infection) and, if humans ingest the eggs, **cysticercosis**, a more severe disease involving larval cysts in tissues like the brain. *Taenia saginata* - **_Taenia saginata_** (beef tapeworm) is acquired by eating raw or undercooked **beef** containing larval cysts, not pork. - While it causes gastrointestinal symptoms, it does not typically lead to systemic cysticercosis in humans. *Trichuris trichiura* - **_Trichuris trichiura_** (whipworm) infection is caused by ingesting **embryonated eggs** from contaminated soil, typically associated with poor sanitation. - It is not transmitted through the consumption of undercooked meat. *None of the options* - This option is incorrect because **_Taenia solium_** is definitively associated with the consumption of uncooked pork.

Question 893: Which of the following is the only ovoviviparous parasite among the options provided?

A. Ascaris
B. Strongyloides (Correct Answer)
C. Enterobius
D. Ancylostoma

Explanation: ***Strongyloides*** - *Strongyloides stercoralis* stands out as the only **ovoviviparous** parasite among the options, meaning that its eggs hatch while still inside the uterus of the female worm. - The female worm lays **larvated eggs** that quickly hatch into **rhabditiform larvae** in the intestine or intestinal wall, which are then passed in the feces. *Ascaris* - *Ascaris lumbricoides* is **oviparous**, laying **unembryonated eggs** that are passed in the feces and require a period of maturation in the soil to become infective. - The eggs are robust and can survive for long periods in the environment before they are ingested. *Enterobius* - *Enterobius vermicularis* (pinworm) is also **oviparous**, with the female worm migrating to the perianal region to lay **embryonated eggs** on the skin. - These eggs are immediately infective to humans upon ingestion. *Ancylostome* - Ancylostomes (hookworms) are **oviparous** and lay **thin-shelled eggs** that are passed in the feces and hatch into rhabditiform larvae in the soil. - These larvae then develop into infective **filariform larvae** that penetrate the skin.

Question 894: Which Schistosoma species is primarily associated with eggs being discharged in urine?

A. S. haematobium (Correct Answer)
B. S. japonicum
C. S. mansoni
D. S. mekongi

Explanation: ***S. haematobium*** - *S. haematobium* specifically targets the **urinary bladder plexus**, leading to the discharge of eggs in the **urine**. - Infection with *S. haematobium* is the primary cause of **urinary schistosomiasis** and is associated with complications like **hematuria** and bladder cancer. *S. japonicum (intestinal)* - *S. japonicum* primarily infects the **mesenteric veins of the small intestine** and discharges its eggs in **feces**, not urine. - This species is known for causing severe **intestinal and hepatic schistosomiasis** due to the large number of eggs produced. *S. mansoni (intestinal)* - *S. mansoni* also primarily infects the **mesenteric veins, mainly of the large intestine**, and its eggs are excreted in **feces**. - It is a common cause of **intestinal schistosomiasis**, leading to symptoms such as abdominal pain, diarrhea, and hepatosplenomegaly. *S. mekongi* - *S. mekongi* is another **intestinal schistosome**, closely related to *S. japonicum*, and its eggs are discharged in **feces**. - This species is found in specific regions of Southeast Asia and causes similar symptoms to other intestinal schistosomes.

Question 895: What is the infective form of Trypanosoma brucei?

A. Trypomastigote (Correct Answer)
B. Amastigote form
C. Egg stage
D. No infective form

Explanation: ***Trypomastigote*** - The **trypomastigote** is the infective form of *Trypanosoma brucei* transmitted to humans by the **tsetse fly** bite. - In the human host, trypomastigotes multiply in the **blood and lymphatic system**, eventually invading the central nervous system. *Amastigote form* - The **amastigote** form is characteristic of *Trypanosoma cruzi* and *Leishmania* species, not *Trypanosoma brucei*. - **Amastigotes** are found intracellularly and lack a flagellum, responsible for replication within host cells for these other parasites. *Egg stage* - *Trypanosoma brucei* is a **protozoan parasite** and does not have an **egg stage** in its life cycle. - Egg stages are typical for helminths, such as **tapeworms** or **flukes**. *No infective form* - This statement is incorrect; **all parasitic organisms** must have an infective stage to be transmitted to their hosts. - The **trypomastigote** is specifically adapted for transmission and survival in the human host and vector.

Question 896: JSB stain is used for which parasite?

A. Kala azar
B. Sleeping sickness
C. Malaria
D. Filaria (Correct Answer)

Explanation: ***Filaria*** - The **JSB stain (Jaswant Singh Battacharya stain)** is a rapid Romanowsky-type stain specifically developed for the diagnosis of **microfilariae** in blood films. - It allows for clear visualization of the sheaths and nuclei of microfilariae, which is crucial for species identification and diagnosis of **filariasis**. *Malaria* - **Giemsa stain** is the gold standard for identifying malaria parasites in thick and thin blood smears, not JSB stain. - Giemsa allows for detailed morphological differentiation of malaria species and stages within **red blood cells**. *Kala azar* - **Kala-azar (visceral leishmaniasis)** is diagnosed by detecting **Leishman bodies (amastigotes)** in bone marrow, splenic, or lymph node aspirates. - Stains like **Giemsa** or **Leishman stain** are traditionally used for visualizing these amastigotes. *Sleeping sickness* - **Sleeping sickness (African trypanosomiasis)** is diagnosed by identifying **trypomastigotes** in blood smears, lymph node aspirates, or cerebrospinal fluid. - **Giemsa stain** is commonly used for the microscopic examination of these specimens to detect the parasites.

Question 897: Maximum density of microfilariae in blood is reported to be between -

A. 9 pm to 11 pm
B. 11 pm to 2 am (Correct Answer)
C. 8 pm to 10 pm
D. 2 am to 5 am

Explanation: ***11 pm to 2 am*** - This period aligns with the **nocturnal periodicity** of *Wuchereria bancrofti* and *Brugia malayi* microfilariae, which are the most common causes of filariasis. - The microfilariae migrate to the **peripheral circulation** during these hours, making it the optimal time for blood smear collection for diagnosis. *9 pm to 11 pm* - While still within the active period for microfilarial migration, the **peak density** is generally observed slightly later. - Blood drawn during this time might show microfilariae, but in lower concentrations compared to the peak. *8 pm to 10 pm* - This timing is generally a little too early to consistently capture the **highest microfilarial load** in nocturnal periodic infections. - The microfilariae are still in the process of migrating from deeper tissues to the peripheral blood. *2 am to 5 am* - By this time, the microfilarial density in the peripheral blood of **nocturnal periodic species** usually starts to decline. - While some microfilariae may still be present, the count would likely be lower than during the earlier peak hours.

Question 898: A 4 year old child presents with acute watery diarrhea and abdominal cramps. Stool microscopy reveals trophozoites with falling leaf motility. What is the etiological agent?

A. Giardia lamblia (Correct Answer)
B. Trichomonas tenax
C. Balantidium coli
D. Entamoeba histolytica

Explanation: **Giardia lamblia** - The presence of **trophozoites** with characteristic **falling leaf motility** in stool microscopy is pathognomonic for **Giardia lamblia** infection. - **Giardiasis** commonly causes **acute watery diarrhea** and **abdominal cramps** in children, often acquired through contaminated water or food. *Entamoeba histolytica* - **Entamoeba histolytica** causes **amoebic dysentery**, characterized by bloody diarrhea, unlike the watery diarrhea described. - Its trophozoites exhibit **directional motility** with pseudopods and may contain ingested red blood cells, not falling leaf motility. *Trichomonas tenax* - **Trichomonas tenax** is found in the **oral cavity** and is not associated with intestinal infections or diarrhea. - Its typical habitat and clinical presentation are entirely different from the symptoms described. *Balantidium coli* - **Balantidium coli** is a large, ciliated protozoan whose trophozoites have a **distinctive kidney-shaped macronucleus** and rotary motility with cilia. - It causes **balantidiasis**, which can range from asymptomatic to dysentery, but its trophozoite morphology and motility are distinct from falling leaf.

Question 899: Which of the following statements about Helminths is false?

A. Alimentary canal is complete in Nematodes
B. Nematodes have separate sexes
C. Body cavity is present in trematodes (Correct Answer)
D. Alimentary canal is present but incomplete in trematodes

Explanation: ***Body cavity is present in trematodes*** - Trematodes are **flatworms** (Platyhelminthes), which are **acoelomate**, meaning they lack a true body cavity or coelom. - Their internal organs are embedded in a **parenchymal tissue** rather than being suspended within a fluid-filled cavity. *Alimentary canal is complete in Nematodes* - **Nematodes** (roundworms) possess a **complete alimentary canal**, with a distinct mouth, intestine, and anus. - This allows for **unidirectional flow of food** and waste through their digestive system. *Nematodes have separate sexes* - **Nematodes** are generally **dioecious**, meaning they have separate male and female individuals. - This sexual dimorphism is a characteristic feature for most species within this phylum. *Alimentary canal is Present but incomplete* - The statement refers to the digestive system of **Platyhelminthes** (flatworms) like trematodes and cestodes, where the alimentary canal is present but **incomplete** (lacking an anus). - This means they have a **single opening** that serves as both mouth and anus for digestion.

Question 900: Infective form of Hookworms?

A. Egg
B. Rhabditiform larva
C. Filariform larva (Correct Answer)
D. Adult worm

Explanation: ***Filariform larva*** - The **filariform larva (L3)** is the infective stage of hookworms, capable of penetrating intact skin. - Upon penetration, these larvae migrate through the bloodstream to the lungs, then up the bronchial tree to be swallowed, eventually maturing in the intestines. *Egg* - Hookworm **eggs** are passed in the feces of infected individuals and are not infective to humans directly. - They require favorable conditions (warm, moist soil) to embryonate and hatch into rhabditiform larvae. *Rhabditiform larva* - The **rhabditiform larva (L1)** is the first larval stage that hatches from the egg in the soil. - It is a non-infective, free-living stage that feeds on bacteria and molts twice to become the infective filariform larva. *Adult worm* - **Adult worms** reside in the small intestine of the host and are not the infective form. - They attach to the intestinal mucosa and feed on blood, causing the characteristic anemia associated with hookworm infection.

Practice by Chapter

Classification of Parasites

Practice Questions

Intestinal Protozoa

Practice Questions

Blood and Tissue Protozoa

Practice Questions

Malaria Parasites

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Leishmaniasis

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Intestinal Helminths: Nematodes

Practice Questions

Tissue Nematodes

Practice Questions

Trematodes

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Cestodes

Practice Questions

Ectoparasites

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Antiparasitic Drugs

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Laboratory Diagnosis of Parasitic Infections

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