Classification of Parasites — MCQs
All of the following are helminthic waterborne disease except?
The following parasitic infections predispose to malignancies: A) Paragonimus westermani B) Guinea worm infection C) Clonorchiasis D) Schistosomiasis
Which of the following is the most common central nervous system parasitic infestation-
A patient from Bihar is admitted with splenomegaly and clinical features suggestive of leishmaniasis. What is the vector responsible for transmitting this disease?
Which of the following is the carrying agent for Lyme disease?
Man is a definitive host of which parasite?
Which of the following conditions is most commonly classified as a sexually transmitted disease?
Round worms cause all of the following conditions, except:
A parasitic smear shows 'double dot' chromatin pattern. Which morphological feature would confirm Babesia infection?
JSB stain is used for which parasite?
Classification of Parasites Indian Medical PG Practice Questions and MCQs
Question 1: All of the following are helminthic waterborne disease except?
- A. Hydatid cyst
- B. Roundworm
- C. Giardiasis (Correct Answer)
- D. Threadworm
Explanation: ***Giardiasis*** - **Giardiasis** is caused by the **protozoan parasite** *Giardia lamblia*, not a helminth. - It is a true waterborne disease, transmitted through contaminated water. - This is the correct answer as it is NOT a helminthic infection. *Hydatid cyst* - **Hydatid cyst disease** is caused by the larval stage of the **tapeworm** *Echinococcus granulosus*, a helminth. - Primarily transmitted through ingestion of eggs from dog feces (zoonotic), though contaminated water can occasionally serve as a vehicle. *Roundworm* - **Roundworm infection** (ascariasis) is caused by the nematode *Ascaris lumbricoides*, a helminth. - Classified as a soil-transmitted helminth (STH), acquired through ingestion of eggs from contaminated soil; water can occasionally act as a transmission vehicle. *Threadworm* - **Threadworm infection** (enterobiasis/pinworm) is caused by the nematode *Enterobius vermicularis*, a helminth. - Primarily transmitted person-to-person via the fecal-oral route through contaminated hands and fomites; water transmission is uncommon but possible in poor sanitation conditions.
Question 2: The following parasitic infections predispose to malignancies: A) Paragonimus westermani B) Guinea worm infection C) Clonorchiasis D) Schistosomiasis
- A. A and B
- B. C and D (Correct Answer)
- C. B and D
- D. A and C
Explanation: ***C and D*** - **Clonorchiasis**, caused by *Clonorchis sinensis*, is strongly linked to **cholangiocarcinoma**, cancer of the bile ducts. - **Schistosomiasis**, particularly infection with *Schistosoma haematobium*, is a significant risk factor for **bladder cancer** [1]. *A and B* - **Paragonimus westermani** (lung fluke) can cause chronic inflammation and fibrosis in the lungs but is not directly associated with malignancy. - **Guinea worm infection** (*Dracunculus medinensis*) causes painful ulcers but does not predispose to cancer. *B and D* - **Guinea worm infection** does not cause cancer. - While **Schistosomiasis** does predispose to malignancy [1], the pairing with Guinea worm makes this option incorrect overall. *A and C* - **Paragonimus westermani** is not known to cause malignancy. - **Clonorchiasis** is linked to malignancy, but its pairing with an incorrect option makes this choice wrong.
Question 3: Which of the following is the most common central nervous system parasitic infestation-
- A. Sparganosis
- B. Neurocysticercosis (Correct Answer)
- C. Paragonimiasis
- D. Echinococcosis
Explanation: ***Neurocysticercosis*** - **Neurocysticercosis** is caused by the larval stage of the **pork tapeworm**, *Taenia solium*, and is considered the most common parasitic infection of the central nervous system worldwide [1]. - It is a leading cause of **acquired epilepsy** in endemic areas due to the presence of cysts in the brain tissue. *Sparganosis* - **Sparganosis** is a rare parasitic infection caused by larvae of **Spirometra** tapeworms, typically acquired by ingesting contaminated water or undercooked amphibian/reptile meat. - While it can affect the CNS, it is significantly **less common** than neurocysticercosis. *Paragonimiasis* - **Paragonimiasis** is caused by the lung fluke, mainly *Paragonimus westermani*, and is primarily a **pulmonary infection**. - Although it can rarely lead to **cerebral paragonimiasis**, it is not the most common CNS parasitic infestation. *Echinococcosis* - **Echinococcosis**, or hydatid disease, is caused by tapeworms of the genus *Echinococcus*, leading to the formation of **hydatid cysts** [1]. - While it can affect the brain, causing neurohydatidosis, it is **less frequent** than neurocysticercosis and often presents as a space-occupying lesion.
Question 4: A patient from Bihar is admitted with splenomegaly and clinical features suggestive of leishmaniasis. What is the vector responsible for transmitting this disease?
- A. Phlebotomus (Correct Answer)
- B. Rat flea
- C. Black fly
- D. Chrysops fly
Explanation: ***Phlebotomus*** - **Phlebotomus** (sandfly), specifically ***Phlebotomus argentipes*** in India, is the principal vector for transmitting **Leishmania donovani** parasites causing **visceral leishmaniasis (kala-azar)**. - Bihar is a highly endemic region for kala-azar in India. - The sandfly transmits the parasite when it takes a blood meal from an infected host and then bites an uninfected individual. *Rat flea* - The **rat flea** (**Xenopsylla cheopis**) is the primary vector for diseases like **bubonic plague** and **murine typhus**, not leishmaniasis. - It transmits bacteria such as *Yersinia pestis* and *Rickettsia typhi*. *Black fly* - **Black flies** (**Simulium species**) are vectors for **onchocerciasis** (river blindness), caused by the parasitic worm *Onchocerca volvulus*. - They transmit the microfilariae when biting humans. *Chrysops fly* - The **Chrysops fly** (deer fly or mango fly) is the vector for **Loa loa filariasis** (African eye worm). - It transmits *Loa loa* eyeworm larvae when it bites humans.
Question 5: Which of the following is the carrying agent for Lyme disease?
- A. Anopheles
- B. Ixodes scapularis ticks (Correct Answer)
- C. Louse
- D. Rat flea
Explanation: ***Ixodes scapularis ticks*** - *Ixodes scapularis* ticks (deer ticks) are the primary **vectors for Lyme disease** (caused by *Borrelia burgdorferi*) in North America [1]. - In Europe, *Ixodes ricinus* is the main vector for Lyme disease. - Lyme disease presents with characteristic **erythema migrans** rash, followed by potential neurological, cardiac, and arthritic complications [1]. - Lyme arthritis commonly affects large joints, particularly the **knee**, causing inflammatory arthritis [1]. *Anopheles* - **Anopheles mosquitoes** are the primary vectors for **malaria**, not Lyme disease [2]. - Malaria is caused by *Plasmodium* parasites and presents with fever, chills, and hemolytic anemia [2]. *Louse* - **Lice** are vectors for diseases such as **epidemic typhus** (caused by *Rickettsia prowazekii*) and **relapsing fever** (caused by *Borrelia recurrentis*) [3]. - They are not associated with the transmission of Lyme disease. *Rat flea* - **Rat fleas** (e.g., *Xenopsylla cheopis*) are the primary vectors for **bubonic plague** (caused by *Yersinia pestis*) and **murine typhus**. - These insects do not transmit Lyme disease. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Infectious Diseases, pp. 389-390. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Infectious Diseases, p. 400. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Infectious Diseases, pp. 392-393.
Question 6: Man is a definitive host of which parasite?
- A. Taenia solium
- B. Plasmodium
- C. Wuchereria bancrofti (Correct Answer)
- D. Taenia saginata
Explanation: ***Wuchereria bancrofti*** - Humans are the **only definitive host** for *Wuchereria bancrofti*, where adult worms reside in the **lymphatic system** and undergo **sexual reproduction**. - The parasite causes **lymphatic filariasis**, leading to conditions like **elephantiasis** and **hydrocele**. - The **microfilariae** (larval stage) circulate in blood and are transmitted by mosquito vectors (intermediate hosts). *Plasmodium* - Humans are the **intermediate host** for *Plasmodium* species that cause malaria. - The **sexual reproductive cycle** (definitive host stage) occurs in the **Anopheles mosquito**, not in humans. - Humans harbor the **asexual stages** (liver schizonts and blood-stage merozoites). *Taenia solium* - Humans can be **either** the definitive host (harboring adult tapeworms in the intestine) **or** an intermediate host (developing **cysticercosis** from ingesting eggs). - This dual role makes it less representative of a parasite where humans are exclusively the definitive host. *Taenia saginata* - Humans are the **definitive host** for *Taenia saginata* (beef tapeworm) in the small intestine. - However, unlike *Wuchereria bancrofti*, cattle serve as the intermediate host in the life cycle. - *Wuchereria bancrofti* is the more commonly cited example in parasitology for human definitive host status.
Question 7: Which of the following conditions is most commonly classified as a sexually transmitted disease?
- A. Trichomoniasis
- B. Giardiasis
- C. Amoebiasis
- D. Chlamydia (Correct Answer)
Explanation: ***Chlamydia*** - **Chlamydia trachomatis** is a bacterial infection that is exclusively transmitted through **sexual contact**, making it a classic sexually transmitted disease. - It often presents with **asymptomatic infections** but can lead to serious complications if untreated, such as pelvic inflammatory disease (PID) and infertility. *Trichomoniasis* - Caused by the **protozoan Trichomonas vaginalis**, it is also a sexually transmitted infection. - While sexually transmitted, **Chlamydia** is generally more prevalent and often considered the *most commonly* classified or reported bacterial STD. *Giardiasis* - Caused by the parasite **Giardia lamblia**, it is typically acquired through the ingestion of contaminated water or food. - It is primarily an **enteric infection** and not classified as a sexually transmitted disease, although anal-oral contact can be a route of transmission in some cases. *Amoebiasis* - Caused by the parasite **Entamoeba histolytica**, it is spread through the fecal-oral route, usually via contaminated food or water. - **Amoebiasis** is an infection of the intestines and liver, and it is not considered a sexually transmitted disease.
Question 8: Round worms cause all of the following conditions, except:
- A. Intestinal obstruction
- B. Intestinal perforation (Correct Answer)
- C. Obstructive jaundice
- D. Pancreatitis
Explanation: ***Intestinal perforation*** - While **Ascaris lumbricoides** can cause obstructions, migration, and inflammation, **bowel perforation** is an extremely rare complication, usually associated with massive worm burdens or pre-existing bowel damage. - The thick cuticle of the adult worm is not typically capable of directly perforating healthy intestinal wall tissue. *Obstructive jaundice* - **Ascaris worms** can migrate into the **biliary tree**, especially the common bile duct, leading to its obstruction. - This obstruction can cause symptoms and signs of **obstructive jaundice**, such as yellowing of skin and eyes, dark urine, and pale stools. *Pancreatitis* - Migrating adult **Ascaris worms** can enter the **pancreatic duct** via the ampulla of Vater. - This can obstruct the duct and lead to **acute pancreatitis**, characterized by severe abdominal pain and elevated pancreatic enzymes. *Intestinal obstruction* - A large number of **adult Ascaris worms** can form a tightly packed bolus within the lumen of the small intestine. - This **worm bolus** can cause a mechanical blockage, leading to **intestinal obstruction**, which is a common and serious complication.
Question 9: A parasitic smear shows 'double dot' chromatin pattern. Which morphological feature would confirm Babesia infection?
- A. Schüffner's dots
- B. James' dots
- C. Tetrad formation (Correct Answer)
- D. Maurer's clefts
Explanation: ***Tetrad formation*** - The formation of a **tetrad** (also called the **Maltese cross** appearance) is the **pathognomonic morphological feature** of *Babesia* species within red blood cells. - This characteristic arrangement of **four merozoites** in a cross-like pattern is the key distinguishing feature that confirms *Babesia* infection. - While *Babesia* may initially show ring forms similar to *Plasmodium*, the tetrad/Maltese cross formation is diagnostic. *Schüffner's dots* - Schüffner's dots are characteristic of red blood cells infected with ***Plasmodium vivax*** or ***Plasmodium ovale***, appearing as fine, reddish stippling throughout the RBC cytoplasm. - These dots represent caveolae-vesicle complexes and are **not associated** with *Babesia* infection. *James' dots* - James' dots are stippling found in red blood cells infected with ***Plasmodium ovale***, similar to Schüffner's dots but typically larger and less numerous. - They help differentiate *P. ovale* from other *Plasmodium* species and are **not seen** in *Babesia*. *Maurer's clefts* - Maurer's clefts are irregular, comma-shaped or cleft-like structures seen in red blood cells infected with ***Plasmodium falciparum***. - They represent parasite-modified structures involved in protein transport and are **specific to falciparum malaria**, not *Babesia*.
Question 10: 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.
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