Parasitology Practice Questions

Q: Which of the following statements about Helminths is false?

Body cavity is present in trematodes. ***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.

Q: 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?

Giardia lamblia. **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.

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

11 pm to 2 am. ***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.

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

S. haematobium. ***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.

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

Strongyloides. ***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.

Q: In malaria, pre-erythrocytic schizogony occurs in -

Liver. ***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

Q: Which of the following amoebae does not have a neuropathogenic effect?

Dientamoeba. ***Dientamoeba*** - *Dientamoeba fragilis* is an intestinal flagellate (often mistakenly classified as an amoeba) that causes **gastrointestinal symptoms** like diarrhea and abdominal pain. - It has **no known neuropathogenic effects** and does not invade the central nervous system. *Naegleria* - *Naegleria fowleri* is a highly virulent amoeba that causes **primary amoebic meningoencephalitis (PAM)**, a rapidly fatal infection of the central nervous system. - It typically invades the brain after **nasal insufflation** of contaminated water. *Acanthamoeba* - *Acanthamoeba* species can cause **granulomatous amoebic encephalitis (GAE)**, a subacute to chronic central nervous system infection, particularly in immunocompromised individuals. - They are also known to cause **amoebic keratitis**, a severe eye infection. *Balamuthia* - *Balamuthia mandrillaris* causes **granulomatous amoebic encephalitis (GAE)**, similar to *Acanthamoeba*, but often in both immunocompetent and immunocompromised individuals. - It can also lead to **skin lesions** and has a tropism for the brain, causing severe neurological damage.

Q: Child having perianal pruritus with the following eggs is due to -

E. vermicularis. ***E. vermicularis*** - **Enterobius vermicularis**, or **pinworm**, is a common cause of **perianal pruritus** in children, particularly at night, due to the female worms migrating to the perianal region to lay eggs. - The characteristic eggs are **oval, flattened on one side**, and are typically identified via the **scotch tape test** around the anus. *Ascaris* - **Ascaris lumbricoides** causes **ascariasis**, which usually presents with **gastrointestinal symptoms** or **pulmonary symptoms** during larval migration, not typically perianal pruritus. - Their eggs are characteristically **mammillated** (roughened outer layer) and typically found in **feces**, not perianal region. *Ancylostoma duodenale* - **Ancylostoma duodenale** causes **hookworm infection**, leading to **iron deficiency anemia** due to blood loss in the intestines. - Hookworm eggs are characteristically **oval, thin-shelled**, and contain a developing **larva**, found in feces. *S. stercoralis* - **Strongyloides stercoralis** causes **strongyloidiasis**, which can present with skin manifestations (larva currens), gastrointestinal issues, or pulmonary symptoms. - It is unique because it causes **auto-infection** and primarily diagnostic stages are **rhabditiform larvae** in stool, not eggs, although eggs are rarely seen in stool.

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

Taenia solium. ***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.

Q: Most common site for hydatid cyst

Liver. ***Liver*** - The **liver** is the most common site for hydatid cysts, accounting for approximately **60-70%** of cases [1]. - It often leads to **biliary obstruction** and liver dysfunction, highlighting its impact on the organ. *Kidney* - Hydatid cysts in the **kidney** are rare and account for a small percentage of cases (around **2-5%**). - Symptoms are often nonspecific, including **flank pain** or hematuria, which are not primary concerns. *Brain* - While the **brain** can be affected, it is not a common site; CNS involvement occurs in only **1-2%** of hydatid disease cases. - Symptoms are related to increased intracranial pressure or focal neurological deficits, not typical for hydatid cysts. *Lung* - The **lung** is another site for hydatid cysts but accounts for about **10-20%** of cases. - Presentation may include **cough** and chest pain, making it less common compared to liver involvement.

Question 1

Which of the following statements about Helminths is false?

Accepted Answer

Body cavity is present in trematodes

Answer

Alimentary canal is complete in Nematodes

Answer

Nematodes have separate sexes

Answer

Alimentary canal is present but incomplete in trematodes

Question 2

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?

Accepted Answer

Giardia lamblia

Answer

Trichomonas tenax

Answer

Balantidium coli

Answer

Entamoeba histolytica

Question 3

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

Accepted Answer

11 pm to 2 am

Answer

9 pm to 11 pm

Answer

8 pm to 10 pm

Answer

2 am to 5 am

Question 4

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

Accepted Answer

S. haematobium

Answer

S. japonicum

Answer

S. mansoni

Answer

S. mekongi

Question 5

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

Accepted Answer

Strongyloides

Answer

Ascaris

Answer

Enterobius

Answer

Ancylostoma

Question 6

In malaria, pre-erythrocytic schizogony occurs in -

Accepted Answer

Liver

Answer

Lung

Answer

Spleen

Answer

Kidney

Question 7

Which of the following amoebae does not have a neuropathogenic effect?

Accepted Answer

Dientamoeba

Answer

Naegleria

Answer

Acanthamoeba

Answer

Balamuthia

Question 8

Child having perianal pruritus with the following eggs is due to -

Accepted Answer

E. vermicularis

Answer

Ascaris

Answer

Ancylostoma duodenale

Answer

S. stercoralis

Question 9

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

Accepted Answer

Taenia solium

Answer

Taenia saginata

Answer

Trichuris trichiura

Answer

None of the options

Question 10

Most common site for hydatid cyst

Accepted Answer

Liver

Answer

Lung

Answer

Brain

Answer

Kidney

Parasitology — MCQs

Parasitology — MCQs

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