Parasitology Practice Questions

Q: All of the following are helminthic waterborne disease except?

Giardiasis. ***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.

Q: A man on return from East Asia complains of pain in abdomen, jaundice, with increased alkaline phosphatase and conjugated hyperbilirubinemia. Ultrasound shows blockage in the biliary tree. What could be the cause?

Clonorchis sinensis. ***Clonorchis sinensis*** - This parasitic fluke, common in East Asia, infects the **biliary ducts**, causing **cholangitis**, obstruction, and the symptoms described. - The combination of travel history, abdominal pain, jaundice, increased alkaline phosphatase, and conjugated hyperbilirubinemia, along with a blocked biliary tree on ultrasound, is highly suggestive of **clonorchiasis**. *Strongyloides* - This nematode primarily infects the **small intestine** and can cause abdominal pain, diarrhea, and malabsorption. - It does not typically cause biliary obstruction with jaundice and increased alkaline phosphatase. *Fasciola buski* - This fluke primarily infects the **small intestine** and causes symptoms like abdominal pain, diarrhea, and malabsorption, similar to Strongyloides. - While other Fasciola species (e.g., *F. hepatica*) can affect the biliary tree, *F. buski* is not known for causing biliary obstruction leading to jaundice. *Ancylostoma* - This hookworm primarily causes **iron-deficiency anemia** due to chronic blood loss in the intestines. - It does not typically cause symptoms related to biliary obstruction or jaundice.

Q: A 35-year-old heterosexual patient diagnosed with HIV presents with watery diarrhea. The colonoscopic biopsy is shown below. Which of the following is your most probable diagnosis?

Cryptosporidium. ***Cryptosporidium*** - The image shows numerous small, round **Cryptosporidium oocysts** lining the **brush border** of the intestinal epithelial cells, a classic histological finding in disseminated disease in immunocompromised patients. - In an HIV patient with watery diarrhea, **Cryptosporidiosis** is a common opportunistic infection, especially when CD4 counts are low. *Giardia* - **Giardia lamblia** typically appears as teardrop-shaped trophozoites or oval cysts. Trophozoites would be motile in stool samples or adhere to the brush border but are much larger and morphologically distinct from the structures seen here. - While it causes watery diarrhea, the histological appearance does not match the small, bead-like structures on the epithelial surface. *CMV* - **Cytomegalovirus (CMV)** infection in the gut would typically show **cytomegalic cells** with characteristic **intranuclear inclusions** (owl's eye inclusions) and sometimes intracytoplasmic inclusions within various cell types, including endothelial cells and fibroblasts. - The image does not display these large, virally infected cells or inclusion bodies; instead, it shows numerous small parasitic forms on the surface. *Microsporidia* - **Microsporidia** are intracellular parasites that infect enterocytes and cause watery diarrhea in HIV patients. They are extremely small and often require special stains (e.g., modified trichrome, Warthin-Starry silver stain) or electron microscopy for definitive identification. - While they are small, the parasites in the image appear more superficial and exhibit a distinct spherical shape consistent with *Cryptosporidium* oocysts rather than the typically intracellular, punctate forms of microsporidia, which are harder to see with routine H&E staining without significant intracellular disruption.

Q: Reduvid bug transmits-

Chagas disease. ***Correct Option: Chagas disease*** - Chagas disease, or **American trypanosomiasis**, is caused by the parasite **Trypanosoma cruzi**, which is transmitted to humans by the fecal contamination from the **triatomine bug** (reduviid bug or "kissing bug"). - The bug typically bites on the face during sleep, defecating nearby, and the parasite enters the body when the person rubs the feces into the bite wound, mucous membranes, or eyes. *Incorrect Option: Trench fever* - Trench fever is caused by the bacterium **Bartonella quintana** and is transmitted by the **human body louse (Pediculus humanus corporis)**, not the reduviid bug. - Symptoms include recurrent fever, headache, and shin pain, common during wartime conditions. *Incorrect Option: Relapsing fever* - Relapsing fever is caused by various species of **Borrelia bacteria** and is transmitted by **ticks (tick-borne relapsing fever)** or **lice (louse-borne relapsing fever)**. - It is characterized by recurrent episodes of fever, headache, muscle, and joint aches, with asymptomatic periods in between. *Incorrect Option: Kala-azar* - Kala-azar, or **visceral leishmaniasis**, is caused by **Leishmania donovani** and is transmitted by the bite of infected **sandflies (Phlebotomus argentipes in India)**. - It is a systemic disease affecting internal organs like the spleen, liver, and bone marrow, leading to fever, weight loss, and hepatosplenomegaly.

Q: Chagas disease is transmitted by the following:

Kissing bugs. ***Kissing bugs*** - Chagas disease is primarily transmitted by the feces of infected **triatomine bugs**, commonly known as **kissing bugs**, which typically feed at night. - These bugs transmit the parasite *Trypanosoma cruzi* when they defecate near the bite wound or mucous membranes. *Birds* - Birds are not known vectors for the transmission of **Chagas disease**. - While some birds can carry other diseases, they do not carry the **triatomine bug** or the *Trypanosoma cruzi* parasite. *Tsetse flies* - **Tsetse flies** are the primary vectors for **African trypanosomiasis** (sleeping sickness), caused by *Trypanosoma brucei*. - They are not involved in the transmission of **Chagas disease** (*Trypanosoma cruzi*). *Dogs* - While dogs can be reservoirs for the *Trypanosoma cruzi* parasite and can become infected with **Chagas disease**, they are not directly responsible for transmitting the disease to humans. - Transmission to dogs and humans occurs through the bite of an infected **kissing bug**.

Q: Reduviid bug is a vector for the transmission of:

Chagas disease. ***Chagas disease*** - Reduviid bugs, specifically the **Triatominae subfamily (kissing bugs)**, are the vectors for the transmission of **Trypanosoma cruzi**, the parasite that causes Chagas disease. - The parasite is transmitted through the bug's feces, which are often deposited on the skin near the bite site, and then rubbed into the wound or mucous membranes. *Relapsing fever* - Relapsing fever is primarily transmitted by **soft ticks (Ornithodoros species)**, for the endemic form, or by **lice (Pediculus humanus humanus)** for the epidemic form. - The causative agents are spirochetes from the genus **Borrelia**. *Scrub typhus* - Scrub typhus is transmitted by the larvae of **chigger mites (trombiculid mites)**, specifically those belonging to the genus Leptotrombidium. - The causative agent is **Orientia tsutsugamushi**. *Lyme disease* - Lyme disease is transmitted by **hard ticks** from the genus **Ixodes**, commonly known as deer ticks or black-legged ticks. - The causative agent is the spirochete **Borrelia burgdorferi**.

Q: Chiggerosis is due to

Chigger. ***Chigger (Trombiculid mite larva)*** - **Chiggerosis**, also known as **trombiculosis**, is an intensely itchy dermatitis caused by the bite of the larval stage of **trombiculid mites**. - These larvae attach to the skin, inject digestive enzymes, and feed on liquefied tissue, causing characteristic **pruritic red papules**. *Louse* - **Lice** (e.g., *Pediculus humanus* or *Pthirus pubis*) cause **pediculosis**, characterized by pruritus, excoriations, and nits attached to hair shafts. - Their bites are typically small, red papules, but do not produce the intense, persistent inflammatory reaction associated with chigger bites. *Tick* - **Ticks** are larger arachnids that burrow their mouthparts into the skin to feed on blood, which can transmit various **pathogens** (e.g., Lyme disease, Rocky Mountain spotted fever). - While tick bites can cause localized irritation, they do not typically result in the widespread, intensely itchy rash seen in chiggerosis. *Bed bug* - **Bed bugs** (*Cimex lectularius*) are nocturnal insects that feed on human blood, typically producing small, **itchy red welts** often arranged in a linear pattern ("breakfast, lunch, and dinner"). - The rash is distinct from chiggerosis, which presents as highly inflammatory, localized papules often found in skin folds or tight clothing areas.

Q: What type of life cycle does the malaria parasite exhibit?

Cyclopropagative. ***Cyclopropagative*** - The malaria parasite (Plasmodium) exhibits a **cyclopropagative life cycle** where it undergoes both **developmental changes** and **multiplication** within the mosquito vector. - In the mosquito, the parasite undergoes **sporogony**: gametocytes → gametes → zygote → ookinete → oocyst → **thousands of sporozoites**, demonstrating both morphological development and significant numerical increase. - This is the **standard classification** found in parasitology textbooks for arthropod-borne parasites that both develop and multiply in their vectors. *Cyclodevelopmental* - A **cyclodevelopmental life cycle** involves development and morphological changes within the vector but **without significant multiplication**. - Example: **Filarial worms** (Wuchereria bancrofti) develop through larval stages (L1→L2→L3) in mosquitoes but do not multiply significantly. - While malaria parasites do undergo developmental changes, they also undergo **massive multiplication** (one oocyst produces thousands of sporozoites), making cyclopropagative the correct term. *Propagative* - A **propagative life cycle** involves only **multiplication** within the vector without significant developmental or morphological changes. - Example: **Trypanosomes** multiply by binary fission in the tsetse fly without major morphological transformation. - This does not apply to malaria parasites, which undergo distinct **developmental stages** (sexual reproduction, ookinete formation, sporogony) in addition to multiplication. *None of the options* - This option is incorrect because the malaria parasite life cycle is accurately described as **cyclopropagative**. - The combination of both developmental stages and multiplication in the mosquito vector is a defining characteristic of the Plasmodium life cycle.

Q: A patient presents with a headache, high fever and meningismus. Within 3 days he becomes unconscious. Most probable causative agent?

Naegleria fowleri. ***Naegleria fowleri*** - This protozoan causes **Primary Amebic Meningoencephalitis (PAM)**, characterized by rapid onset of headache, high fever, meningismus, and rapid progression to coma and death within days. - The disease is often acquired through **nasal insufflation of contaminated water**, allowing the amoeba to migrate to the brain. *Acanthamoeba castellanii* - This amoeba causes **Granulomatous Amebic Encephalitis (GAE)**, which is typically a chronic or subacute infection, progressing over weeks to months, unlike the rapid onset described. - GAE often occurs in **immunocompromised individuals** and can also cause keratitis or disseminated disease. *Trypanosoma cruzi* - This parasite causes **Chagas disease**, which can involve the central nervous system in acute or chronic stages, but does not typically present as acute fulminant meningoencephalitis with rapid progression to unconsciousness in days. - Neurological manifestations in Chagas disease are more varied and often associated with **cardiomyopathy** or gastrointestinal involvement. *Entamoeba histolytica* - This parasite is primarily known for causing **amebic dysentery** and **liver abscesses**. - While it can rarely cause brain abscesses, this is not the typical presentation of an acute, rapidly progressive meningoencephalitis with meningismus and high fever as described.

Q: Common cause of diarrhoea in AIDS cases is due to

Cryptosporidium. ***Cryptosporidium*** - **Cryptosporidium parvum** is a common opportunistic pathogen causing severe and prolonged diarrhea in immunocompromised individuals, particularly those with AIDS [1]. - This parasite causes **self-limiting diarrhea** in immunocompetent individuals but can lead to **chronic, watery diarrhea** and malabsorption in AIDS patients due to their impaired cell-mediated immunity [1]. *Taenia solium* - **Taenia solium** (pork tapeworm) can cause mild gastrointestinal symptoms, but it is primarily known for causing **cysticercosis** in humans, an infection with larval cysts. - While it can cause abdominal discomfort and diarrhea in some cases, it is not a common or severe cause of diarrhea in AIDS patients compared to opportunistic parasites. *Plasmodium falciparum* - **Plasmodium falciparum** is the most virulent species of malaria parasites, causing **fever, chills, headache**, and other systemic symptoms. - While malaria can cause some gastrointestinal symptoms, including diarrhea, it is not considered a common or direct cause of chronic diarrhea associated with AIDS. *Ascaris lumbricoides* - **Ascaris lumbricoides** (roundworm) is a common intestinal nematode that can cause abdominal discomfort, malnutrition, and, in severe cases, intestinal obstruction or biliary complications. - While ascariasis can be present in immunocompromised individuals, it is not typically recognized as a primary or common cause of severe, chronic diarrhea in AIDS patients.

Question 1

All of the following are helminthic waterborne disease except?

Accepted Answer

Giardiasis

Answer

Hydatid cyst

Answer

Roundworm

Answer

Threadworm

Question 2

A man on return from East Asia complains of pain in abdomen, jaundice, with increased alkaline phosphatase and conjugated hyperbilirubinemia. Ultrasound shows blockage in the biliary tree. What could be the cause?

Accepted Answer

Clonorchis sinensis

Answer

Strongyloides

Answer

Fasciola buski

Answer

Ancylostoma

Question 3

A 35-year-old heterosexual patient diagnosed with HIV presents with watery diarrhea. The colonoscopic biopsy is shown below. Which of the following is your most probable diagnosis?

Accepted Answer

Cryptosporidium

Answer

Giardia

Answer

CMV

Answer

Microsporidia

Question 4

Reduvid bug transmits-

Accepted Answer

Chagas disease

Answer

Trench fever

Answer

Relapsing fever

Answer

Kala-azar

Question 5

Chagas disease is transmitted by the following:

Accepted Answer

Kissing bugs

Answer

Birds

Answer

Tsetse flies

Answer

Dogs

Question 6

Reduviid bug is a vector for the transmission of:

Accepted Answer

Chagas disease

Answer

Relapsing fever

Answer

Scrub typhus

Answer

Lyme disease

Question 7

Chiggerosis is due to

Accepted Answer

Chigger

Answer

Louse

Answer

Tick

Answer

Bed bug

Question 8

What type of life cycle does the malaria parasite exhibit?

Accepted Answer

Cyclopropagative

Answer

None of the options

Answer

Cyclodevelopmental

Answer

Propagative

Question 9

A patient presents with a headache, high fever and meningismus. Within 3 days he becomes unconscious. Most probable causative agent?

Accepted Answer

Naegleria fowleri

Answer

Acanthamoeba castellanii

Answer

Trypanosoma cruzi

Answer

Entamoeba histolytica

Question 10

Common cause of diarrhoea in AIDS cases is due to

Accepted Answer

Cryptosporidium

Answer

Taenia solium

Answer

Plasmodium falciparum

Answer

Ascaris lumbricoides

Parasitology — MCQs

Parasitology — MCQs

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