Cestodes — MCQs
A 35 year old man presented with dry cough and rusty colored sputum. He has a history of eating in a Chinese restaurant very often with consumption of crabs. What is the probable causative agent in this condition?
An Egyptian fisherman develops lower abdominal pain and pain on urination, and reports seeing blood in his urine. Which of the following parasites is the most likely cause of urinary symptoms in this patient?
What is the most common route of transmission for Toxoplasma gondii in adults?
Infection caused by which of the following organism may mimic as malignancy?
Cysticercus cellulosae are pathogenic forms of which parasite?
A 65-year old man presented with skin lesions on his chest and left arm and shoulder six weeks after returning from a vacation in Belize at the beach in the rain forest. The lesions occasionally stung, drained a dark exudates, and enlarged despite two weeks of treatment with cephalexin. The patient had no constitutional symptoms. Physical examination revealed five nodules of varying sizes with surrounding erythema and a central pore through which a single, moving larva was observed. The larvae coming out of the pores are-
The following organism is called:
Which of the following life cycles is shown below?
Which of the following parasite is shown below?
What is the primary cause of malignant hydatid disease?
Cestodes Indian Medical PG Practice Questions and MCQs
Question 1: A 35 year old man presented with dry cough and rusty colored sputum. He has a history of eating in a Chinese restaurant very often with consumption of crabs. What is the probable causative agent in this condition?
- A. Pneumocystis jirovecii
- B. Paragonimus westermani (Correct Answer)
- C. Strongyloides stercoralis
- D. Diphyllobothrium latum
Explanation: ***Paragonimus westermani*** - The key clinical features are **dry cough**, **rusty-colored sputum**, and a history of consuming **crabs**. These are classic indicators of **paragonimiasis**. - *Paragonimus westermani* is a **lung fluke** acquired by eating undercooked freshwater crabs or crayfish. *Pneumocystis jirovecii* - This fungus typically causes pneumonia in **immunocompromised individuals**, like those with HIV/AIDS. - While it can cause a dry cough, **rusty-colored sputum** is not a characteristic sign, and there's no mention of immunocompromise. *Strongyloides stercoralis* - This parasite primarily causes **gastrointestinal symptoms** (e.g., abdominal pain, diarrhea) and can lead to cutaneous manifestations (larva currens). - While lung involvement can occur in severe cases (hyperinfection), it does not typically present with **rusty sputum** or a direct association with crab consumption. *Diphyllobothrium latum* - This is the **fish tapeworm**, acquired by eating undercooked freshwater fish. - It primarily causes **gastrointestinal symptoms** such as abdominal pain and diarrhea, and is known for causing **vitamin B12 deficiency** leading to megaloblastic anemia, not pulmonary symptoms.
Question 2: An Egyptian fisherman develops lower abdominal pain and pain on urination, and reports seeing blood in his urine. Which of the following parasites is the most likely cause of urinary symptoms in this patient?
- A. Clonorchis sinensis
- B. Schistosoma haematobium (Correct Answer)
- C. Fasciola hepatica
- D. Diphyllobothrium latum
Explanation: ***Schistosoma haematobium*** - The patient's presentation with **lower abdominal pain**, **dysuria**, and **hematuria** is highly characteristic of urinary schistosomiasis, caused by *Schistosoma haematobium*. - The patient's origin as an **Egyptian fisherman** places him in an **endemic area** where contact with contaminated fresh water containing the parasite's larval forms (cercariae) is common. *Clonorchis sinensis* - This parasite causes **clonorchiasis**, an infection primarily affecting the **biliary tract** and liver, leading to symptoms like cholangitis, cholecystitis, and hepatomegaly. - It is typically acquired by consuming **raw or undercooked freshwater fish**, but does not cause urinary symptoms. *Fasciola hepatica* - *Fasciola hepatica* causes **fascioliasis**, a **liver fluke infection** that primarily affects the **biliary ducts** leading to symptoms like right upper quadrant pain, fever, and jaundice. - It is acquired by ingesting **metacercariae on aquatic plants**, particularly watercress, and does not cause urinary manifestations. *Diphyllobothrium latum* - This is the **fish tapeworm**, which causes **diphyllobothriasis**, an intestinal infection. - Symptoms are usually mild or asymptomatic, but can include abdominal discomfort, nausea, and notably **vitamin B12 deficiency** leading to megaloblastic anemia, not urinary symptoms.
Question 3: 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 4: Infection caused by which of the following organism may mimic as malignancy?
- A. Echinococcus oliganthus
- B. Echinococcus multilocularis (Correct Answer)
- C. Echinococcus vogeli
- D. Echinococcus granulosus
Explanation: ***Echinococcus multilocularis*** - This parasite causes **alveolar echinococcosis**, which manifests as a **destructive, infiltrative growth** in organs, primarily the liver. [1] - The lesions can be difficult to differentiate from **malignant tumors** due to their invasive nature and irregular margins, often leading to misdiagnosis. [1] *Echinococcus oliganthus* - This species is known to cause **polycystic echinococcosis**, primarily affecting wild felids and occasionally humans through accidental ingestion of eggs. - While it forms cysts, its growth pattern is generally **cystic** rather than infiltrative, making it less likely to mimic malignancy compared to *E. multilocularis*. *Echinococcus vogeli* - This parasite causes **polycystic hydatid disease** (or polycystic echinococcosis), similar to *E. oliganthus*, but is primarily associated with dholes and causes lesions in humans. - The disease typically presents as **large, multiloculated cysts** in organs, which are distinct from the infiltrative, tumor-like lesions of *E. multilocularis*. *Echinococcus granulosus* - This species is responsible for **cystic echinococcosis** (or hydatid disease), forming slow-growing, unilocular cysts, most commonly in the liver and lungs. [1] - While these cysts can grow large, their **well-defined, encapsulated nature** generally makes them distinguishable from malignant tumors, unlike the invasive lesions of alveolar echinococcosis. [1]
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: A 65-year old man presented with skin lesions on his chest and left arm and shoulder six weeks after returning from a vacation in Belize at the beach in the rain forest. The lesions occasionally stung, drained a dark exudates, and enlarged despite two weeks of treatment with cephalexin. The patient had no constitutional symptoms. Physical examination revealed five nodules of varying sizes with surrounding erythema and a central pore through which a single, moving larva was observed. The larvae coming out of the pores are-
- A. Loa loa
- B. Diphyllobothrium latum
- C. Dermatobia hominis (Correct Answer)
- D. Dracunculus medinensis
Explanation: ***Dermatobia hominis*** - The description of **cutaneous nodules** with a central pore from which a **moving larva** is observed, particularly after travel to a tropical region like Belize, is classic for **furuncular myiasis** caused by **Dermatobia hominis** larvae (human botfly). - The **"occasional stinging"** and **"dark exudate"** are characteristic symptoms of the larva burrowing in the skin and secreting waste products. *Loa loa* - **Loa loa** (African eye worm) is a filarial nematode that migrates through **subcutaneous tissues** and occasionally across the eye, causing **Calabar swellings**. - It does not present as a **furuncular lesion** with a visible central moving larva emerging from a pore. *Diphyllobothrium latum* - **Diphyllobothrium latum** is a **tapeworm** that infects the intestines and is acquired by consuming undercooked infected fish. - It causes gastrointestinal symptoms and can lead to **vitamin B12 deficiency**, but it does not produce **skin lesions with moving larvae**. *Dracunculus medinensis* - **Dracunculus medinensis** (guinea worm) infection typically results in a **painful blister** on the lower limbs, from which the female worm emerges to release larvae when exposed to water. - While it involves a skin lesion, the presentation of **multiple nodules with a central pore revealing a moving larva** is not consistent with **dracunculiasis**.
Question 7: The following organism is called:
- A. Cestode (Correct Answer)
- B. Nematode
- C. Trematode
- D. Annelid
Explanation: ***Cestode*** - The image displays a long, **segmented, ribbon-like worm**, which is characteristic morphology of a **tapeworm (cestode)**. - Cestodes typically possess a head (scolex) for attachment and a body composed of repeating segments called **proglottids**. *Nematode* - **Nematodes** are generally **unsegmented**, cylindrical, and elongated worms, often described as roundworms. - They lack the distinct proglottids and flattened, ribbon-like appearance seen in the image. *Trematode* - **Trematodes**, also known as flukes, are typically **leaf-shaped** and **unsegmented**. - They are much broader and flatter than the organism shown, and do not have the visible segmentation. *Annelid* - **Annelids** are segmented worms like earthworms and leeches, but they have a **cylindrical body** with visible external ring-like segments. - Unlike cestodes, annelids have a complete digestive system and lack the flat, ribbon-like morphology and internal proglottid structure characteristic of tapeworms.
Question 8: Which of the following life cycles is shown below?
- A. Hymenolepis nana (Correct Answer)
- B. Echinococcus granulosus
- C. Ascaris lumbricoides
- D. Toxocara canis
Explanation: ***Hymenolepis nana*** - The image clearly depicts the life cycle of *Hymenolepis nana*, showing direct human infection from ingesting **fertile eggs**, leading to the development of an **oncosphere** and then a **cercocyst** within the human host before maturing into an adult tapeworm in the intestine. - The presence of an "alternative rodent host (rat, mouse) of minor importance" is a characteristic feature of *Hymenolepis nana*, which can infect both humans and rodents. *Echinococcus granulosus* - This parasite's life cycle involves **dogs (definitive host)** and **sheep/humans (intermediate hosts)**, where humans develop **hydatid cysts**, which is not shown here. - The depiction of an adult tapeworm developing directly in humans after ingestion of eggs, with a rodent as an alternative host, is inconsistent with *Echinococcus granulosus*. *Ascaris lumbricoides* - This is a **roundworm (nematode)**, not a tapeworm, and its life cycle involves **lung migration** of larvae before returning to the intestines to mature, which is not illustrated. - The image shows development from an oncosphere to a cercocyst and then to an adult tapeworm, which is specific to certain **cestodes**. *Toxocara canis* - This is another **roundworm** primarily affecting **dogs**, and humans become **incidental hosts** by ingesting embryonated eggs, leading to visceral larva migrans, where larvae migrate through tissues but do not develop into adult worms in the human intestine. - The illustrated life cycle details, particularly the formation of an oncosphere and cercocyst within the human leading to an adult tapeworm, are not indicative of *Toxocara canis*.
Question 9: Which of the following parasite is shown below?
- A. Cysticercosis cellulosae
- B. Echinococcus granulosus (Correct Answer)
- C. E. Histolytica
- D. Fasciola hepatica
Explanation: ***Echinococcus granulosus*** - The image displays a **hydatid cyst**, characterized by its thick, laminated outer wall (ectocyst) and an inner germinal layer (endocyst) from which **brood capsules** and **protoscolices** (seen as invaginations) bud off. - This morphology is pathognomonic for **Echinococcus granulosus**, the causative agent of **cystic echinococcosis** (hydatid disease). *Cysticercosis cellulosae* - Cysts of *Cysticercus cellulosae* (larval stage of *Taenia solium*) typically appear as a fluid-filled bladder with a single **invaginated scolex** lacking the complex brood capsule arrangement seen in the image. - They also generally have a thinner cyst wall compared to *Echinococcus* cysts. *E. Histolytica* - *Entamoeba histolytica* is a **protozoan parasite** that causes amoebiasis, presenting as trophozoites or cysts; it does not form macroscopic cysts with complex internal structures like the one shown. - Amoebic abscesses are typically necrotic lesions, not true cysts with parasitic structures within. *Fasciola hepatica* - *Fasciola hepatica* is a **trematode (fluke)**, and its larval stages or adult worms do not form cysts with this characteristic morphology. - Liver flukes would appear as tissue sections of the flatworm itself in infected organs, not as a large, spherical cyst with internal budding structures.
Question 10: What is the primary cause of malignant hydatid disease?
- A. Malignant transformation of hydatid cysts
- B. Infection with Echinococcus multilocularis (Correct Answer)
- C. Hydatid disease in immunocompromised patients
- D. Caused by Echinococcus granulosus
Explanation: ***Infection with Echinococcus multilocularis*** - **Malignant hydatid disease** is specifically associated with *Echinococcus multilocularis*, which causes alveolar echinococcosis. - This parasite's larval stage grows in a highly **infiltrative** and **destructive** manner, resembling a malignant tumor, hence the term "malignant hydatid disease." *Malignant transformation of hydatid cysts* - Hydatid cysts themselves are parasitic structures and do not undergo **malignant transformation** in the conventional sense of human tissue developing cancer. - The term "malignant" in this context refers to the **aggressive growth pattern** of *E. multilocularis* rather than cellular anaplasia. *Hydatid disease in immunocompromised patients* - While immunocompromised individuals may experience more severe or disseminated hydatid disease, this does not directly cause the **"malignant" characteristic** of alveolar echinococcosis. - The inherent **aggressive growth** of *Echinococcus multilocularis* is the primary factor, regardless of host immune status. *Caused by Echinococcus granulosus* - *Echinococcus granulosus* causes **cystic echinococcosis** (CE), which typically forms unilocular cysts, often considered benign. - CE is generally less aggressive and does not exhibit the **infiltrative growth pattern** characteristic of "malignant hydatid disease" caused by *E. multilocularis*.
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