Parasitic Infections — MCQs
In a rural clinic, a 3-year-old girl child is brought by her mother and is emaciated. Her hemoglobin was 5 g/dL. The girl also has edema over her knees and ankles with discrete rash on her knees, ankles and elbows. The most likely worm infestation causing these manifestations is:
What is the most common route of transmission for Toxoplasma gondii in adults?
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 patient living with HIV presents with foulsmelling stools. Microscopic examination of the stool reveals no cysts or ova, but a 200-micrometer larva is observed. What is the most likely pathogen?
Cysticercus cellulosae are pathogenic forms of which parasite?
Which of the following symptoms is commonly associated with giardiasis?
Toxoplasma in children causes:
A patient presents with severe abdominal pain and jaundice. Imaging reveals calcified cysts in the liver, and serological testing is positive for Echinococcus. What is a potential complication of this infection?
A child presented with perianal itching. The swab specimen is shown in the image. What is the diagnosis?
A child presents with a fever and a rash. Urine examination showed cells with owl's eye appearance. What is the most likely diagnosis?
Parasitic Infections Indian Medical PG Practice Questions and MCQs
Question 1: In a rural clinic, a 3-year-old girl child is brought by her mother and is emaciated. Her hemoglobin was 5 g/dL. The girl also has edema over her knees and ankles with discrete rash on her knees, ankles and elbows. The most likely worm infestation causing these manifestations is:
- A. Roundworm
- B. Pinworm
- C. Whipworm
- D. Hookworm (Correct Answer)
Explanation: ***Hookworm*** - **Hookworm infection** (Ancylostoma duodenale/Necator americanus) leads to chronic blood loss from the intestines, causing **microcytic hypochromic anemia** and **severe emaciation** due to persistent nutrient loss and malabsorption. - The combination of severe **anemia (Hb 5 g/dL)**, **emaciation**, and **edema** (due to **hypoalbuminemia**, a consequence of protein-losing enteropathy and poor nutrition) is highly characteristic of hookworm infestation in children. - The **discrete rash** on pressure points (knees, ankles, elbows) may represent **ground itch** (pruritic papulovesicular rash at larval penetration sites) or dermatitis secondary to malnutrition and edema. *Roundworm* - **Ascaris lumbricoides** can cause malnutrition and growth delays, but typically does not lead to the severe anemia and edema seen here unless there is a massive infestation leading to intestinal obstruction or biliary obstruction. - Its primary impact is often related to **nutrient competition** and mechanical obstruction, not significant blood loss. *Pinworm* - **Enterobius vermicularis** (pinworm) infection primarily causes **perianal itching**, especially at night. - It does not typically cause systemic symptoms like **severe anemia**, **emaciation**, or **edema**, as it does not feed on blood or cause significant nutrient malabsorption. *Whipworm* - **Trichuris trichiura** (whipworm) can cause chronic dysentery, **rectal prolapse**, and **anemia** in heavy infections due to blood loss. - While it can contribute to **growth retardation** and anemia, it is less likely to cause the profound emaciation and edema described compared to hookworm, especially with a hemoglobin level of 5 g/dL, which points strongly to major chronic blood loss.
Question 2: What is the most common route of transmission for Toxoplasma gondii in adults?
- A. Transmission through blood transfusion
- B. Ingestion of undercooked meat containing tissue cysts (Correct Answer)
- C. Congenital transmission from mother to fetus
- D. Fecal-oral transmission via contaminated cat feces
Explanation: ***Ingestion of undercooked meat containing tissue cysts*** - Consuming **undercooked or raw meat** (especially pork and lamb) containing **tissue cysts (bradyzoites)** is the **most common route** of *Toxoplasma gondii* transmission in adults in most countries - These cysts are highly resistant and survive digestion, releasing bradyzoites that cause systemic infection - This accounts for **30-63%** of infections in various populations *Fecal-oral transmission via contaminated cat feces* - Contact with **oocysts** from cat feces (in litter boxes, contaminated soil/water) is an important route - However, it's less common than meat consumption in most developed countries - Oocysts require 1-5 days to sporulate and become infective *Transmission through blood transfusion* - **Rare route** - tachyzoites have short survival in stored blood - Modern screening practices have made this extremely uncommon - Not a significant transmission route in general populations *Congenital transmission from mother to fetus* - Occurs when **primary maternal infection** happens during pregnancy - Important clinically but represents a small proportion of total infections - Does not apply to adult acquisition of infection
Question 3: 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 4: A patient living with HIV presents with foulsmelling stools. Microscopic examination of the stool reveals no cysts or ova, but a 200-micrometer larva is observed. What is the most likely pathogen?
- A. Strongyloides stercoralis (Correct Answer)
- B. Ascaris lumbricoides
- C. Ancylostoma duodenale
- D. Schistosoma mansoni
Explanation: ***Strongyloides stercoralis*** - The presence of **larvae** in the stool [2], particularly **rhabditiform larvae**, is characteristic of *Strongyloides stercoralis* infection, as this parasite has an **autoinfective cycle** involving larval stages in the human host [2]. - In HIV-positive patients, *Strongyloides* can cause **hyperinfection syndrome**, leading to severe gastrointestinal symptoms like foul-smelling stools, and increased larval shedding [2]. *Ascaris lumbricoides* - *Ascaris lumbricoides* is a large intestinal nematode, but it typically presents with **ova** (eggs) in the stool, not larvae, as the eggs hatch in the small intestine. - While it can cause gastrointestinal symptoms, the hallmark microscopic finding in stool samples is the presence of **mammillated or decorticated eggs**. *Ancylostoma duodenale* - *Ancylostoma duodenale* (hookworm) infections are identified by the presence of **eggs** in the stool [1], which are typically oval with a thin shell and contain a developing larva. - Hookworm larvae usually develop in **soil** and infect humans through skin penetration, rather than being commonly found in stool samples from intestinal infection [1]. *Schistosoma mansoni* - *Schistosoma mansoni* is a **blood fluke** that causes intestinal schistosomiasis, characterized by the presence of **spined eggs** in the stool. - The parasite's life cycle involves **freshwater snails** as intermediate hosts, and a **larval stage (cercariae)** that penetrates human skin, but larvae are not typically found in human stool.
Question 5: Cysticercus cellulosae are pathogenic forms of which parasite?
- A. Taenia solium (Correct Answer)
- B. Paragonimus westermani
- C. Enterobius vermicularis
- D. Taenia saginata
Explanation: ***Taenia solium*** - **Cysticercus cellulosae** is the larval stage (metacestode form) of the **pork tapeworm**, *Taenia solium*. - Humans can acquire **cysticercosis** by ingesting *T. solium* eggs, leading to the development of these cysticerci in various tissues, including the muscles, subcutaneous tissue, and central nervous system. *Paragonimus westermani* - This is a **lung fluke**; its larval stage is a metacercaria, not a cysticercus. - It causes **paragonimiasis**, characterized by lung symptoms. *Enterobius vermicularis* - This is the **pinworm**, a nematode, which does not have a cysticercus stage. - It primarily causes **perianal itching** and does not form cysts in tissues. *Taenia saginata* - This is the **beef tapeworm**, and its larval stage is known as a **Cysticercus bovis**, not Cysticercus cellulosae. - Humans acquire *T. saginata* infection by consuming undercooked beef containing C. bovis.
Question 6: Which of the following symptoms is commonly associated with giardiasis?
- A. Steatorrhea and flatulence (Correct Answer)
- B. All of the options
- C. Nausea and vomiting
- D. Abdominal pain
Explanation: ***Steatorrhea and flatulence*** - **Giardiasis** is an intestinal infection caused by the parasite *Giardia lamblia*, leading to malabsorption and characteristic symptoms [1]. - The parasite attaches to the intestinal lining, interfering with fat absorption, which results in **steatorrhea** (fatty, foul-smelling stools) and increased gas production causing **flatulence** [1]. *Nausea and vomiting* - While **nausea** can occur in giardiasis, **vomiting** is less common as a primary or dominant symptom. - These symptoms are more characteristic of other gastrointestinal infections like **viral gastroenteritis**. *Abdominal pain* - **Abdominal pain** is a general symptom that can occur with many gastrointestinal issues, including giardiasis [1]. - However, it's not as specific or as clinically defining for giardiasis as **steatorrhea** and **flatulence**, which are direct consequences of the parasite's impact on fat absorption. *All of the options* - Although some patients with giardiasis may experience nausea and abdominal pain, **steatorrhea** and **flatulence** are the most direct and specific indicators of the malabsorption caused by *Giardia lamblia* [1]. - Choosing "all of the above" would imply that all listed symptoms are equally common and specific, which is not the case for giardiasis.
Question 7: Toxoplasma in children causes:
- A. Chorioretinitis (Correct Answer)
- B. Keratitis
- C. Papillitis
- D. Conjunctivitis
Explanation: ***Chorioretinitis*** - **Toxoplasmosis** is a significant cause of **chorioretinitis** in children, particularly congenital infections. - Ocular toxoplasmosis often presents with **retinal lesions** that can lead to vision loss. *Conjunctivitis* - **Conjunctivitis** is an inflammation of the conjunctiva, typically caused by bacterial or viral infections. - While it can occur in children, it is not a primary or characteristic manifestation of **Toxoplasma infection**. *Keratitis* - **Keratitis** is an inflammation of the cornea, often caused by bacterial, viral, or fungal infections, or sometimes trauma. - Although eyes are affected by **Toxoplasma**, **keratitis** is not the typical ophthalmic presentation; **chorioretinitis** is. *Papillitis* - **Papillitis** refers to inflammation of the optic disc (optic nerve head). - While **Toxoplasma** can rarely affect the optic nerve, **papillitis** is not the most common or specific ocular manifestation compared to **chorioretinitis**.
Question 8: A patient presents with severe abdominal pain and jaundice. Imaging reveals calcified cysts in the liver, and serological testing is positive for Echinococcus. What is a potential complication of this infection?
- A. Portal hypertension due to cyst compression
- B. Rupture of cysts leading to anaphylactic shock
- C. No significant complications
- D. Secondary bacterial infection of cysts (Correct Answer)
Explanation: ***Secondary bacterial infection of cysts*** - **Hydatid cysts** can become secondarily infected, typically after rupture or surgical manipulation, leading to an **abscess formation** within the liver. - This complication can present with features like fever, worsening abdominal pain, and an elevated **white blood cell count**, distinct from the initial presentation. *Rupture of cysts leading to anaphylactic shock* - While rupture of **hydatid cysts** can lead to **anaphylactic shock** due to the release of hydatid fluid, it is not the *most common immediate complication* or the scenario implied by abdominal pain and jaundice. - **Anaphylaxis** implies a rapid, severe systemic allergic reaction, which is a life-threatening acute event. *Portal hypertension due to cyst compression* - While large cysts can compress structures, significant **portal hypertension** due to direct compression of the portal vein by **hydatid cysts** is rare. - More commonly, portal hypertension is a complication of advanced **cirrhosis**, not typically direct cyst compression in the early stages described. *No significant complications* - **Echinococcosis** (hydatid disease) is a serious parasitic infection that almost always leads to significant morbidity if left untreated. - Cysts grow over time and inevitably cause **organ dysfunction**, pain, obstruction, or other complications.
Question 9: A child presented with perianal itching. The swab specimen is shown in the image. What is the diagnosis?
- A. Enterobius (Correct Answer)
- B. Ascaris
- C. Trichiura
- D. Ancylostoma
Explanation: ***Enterobius*** - The image shows **D-shaped** (plano-convex) and **transparent eggs**, which are characteristic of *Enterobius vermicularis* (**pinworm** or **threadworm**). - **Perianal itching**, especially at night, is the hallmark symptom due to the female worm migrating to the perianal region to lay eggs. *Ascaris* - *Ascaris lumbricoides* eggs are typically **round to oval**, with a thick, mamillated (bumpy) outer shell, or smooth in the case of decorticated eggs, which is different from the eggs pictured. - Infection with *Ascaris* can cause pulmonary symptoms (Loeffler's syndrome) and intestinal obstruction, but not typically perianal itching. *Trichiura* - *Trichuris trichiura* (**whipworm**) eggs are distinctly **barrel-shaped** with prominent **polar plugs** at each end, which is not seen in the image. - Whipworm infection is often associated with bloody diarrhea, rectal prolapse, and growth retardation, not primarily perianal itching. *Ancylostoma* - *Ancylostoma duodenale* and *Necator americanus* (hookworms) eggs are typically **oval** with a **thin shell** and segmented embryo (morula stage) within, which lacks the distinct D-shape and transparency of the pictured eggs. - Hookworm infection primarily causes iron-deficiency anemia and can lead to cutaneous larva migrans, not perianal itching as a primary symptom.
Question 10: A child presents with a fever and a rash. Urine examination showed cells with owl's eye appearance. What is the most likely diagnosis?
- A. Herpes simplex virus infection
- B. Toxoplasmosis caused by Toxoplasma gondii
- C. Cytomegalovirus (CMV) infection (Correct Answer)
- D. Infectious mononucleosis caused by Epstein-Barr virus
Explanation: ***Cytomegalovirus (CMV) infection*** - The presence of cells with an **owl's eye appearance** in urine sediment is a classic histological hallmark of **CMV infection**. - CMV can cause a variety of symptoms in children, including **fever and rash**, making this the most likely diagnosis. *Herpes simplex virus infection* - HSV causes characteristic **vesicular lesions** on mucocutaneous surfaces, often associated with fever. - While HSV can cause systemic illness, it does not typically present with **owl's eye inclusions** in urine cells. *Toxoplasmosis caused by Toxoplasma gondii* - **Toxoplasmosis** can cause fever and rash, especially in congenital infections or immunocompromised individuals. - However, it does not lead to **owl's eye inclusions** in urinary cells, which are pathognomonic for CMV. *Infectious mononucleosis caused by Epstein-Barr virus* - **Infectious mononucleosis** commonly presents with fever, fatigue, and lymphadenopathy, sometimes with a rash. - **Epstein-Barr virus (EBV)** infection does not produce cells with an **owl's eye appearance** in the urine; that is specific to CMV.
Want unlimited practice?
Get full access to all questions, explanations, and performance tracking.
Start For Free