Parasitology Practice Questions

Q: A 36-year-old male patient complaining of cough, cold, fever, and rusty sputum, with a history of travel to China and consumption of crab. Name the infection.

Paragonimus westermani. ***Paragonimus westermani*** - This patient's symptoms of **cough**, **fever**, and **rusty sputum**, combined with a history of **travel to China** and consumption of **crab**, are highly suggestive of **paragonimiasis**. - *Paragonimus westermani* is a **lung fluke** endemic to East Asia, and its larvae are acquired by ingesting undercooked **crabs** or **crayfish**. *Fasciola hepatica* - *Fasciola hepatica* causes **fascioliasis**, primarily affecting the **liver** and **biliary ducts**, leading to symptoms like **fever**, **abdominal pain**, and **hepatomegaly**. - It is acquired by consuming **contaminated watercress** or other aquatic plants, not crabs. *Fasciolopsis buski* - *Fasciolopsis buski* causes **fasciolopsiasis**, an **intestinal fluke infection** presenting with **abdominal pain**, **diarrhea**, and **malabsorption**. - It is transmitted through ingestion of **contaminated aquatic plants**, and does not typically cause respiratory symptoms or "rusty sputum." *Entamoeba histolytica* - *Entamoeba histolytica* is a **protozoan** that causes **amoebiasis**, primarily presenting as **dysentery** or **amoebic liver abscess**. - While it can manifest as fever and liver involvement, it does not cause respiratory symptoms like "rusty sputum" and is not acquired from crabs.

Q: Identify the organism related to the blood smear image.

Plasmodium falciparum. ***Plasmodium falciparum*** - The image clearly displays multiple **ring-form trophozoites** within red blood cells, some of which are *appliqué* or *accolade* forms (rings on the periphery of the red blood cell) and **multiple rings per red blood cell**, which are characteristic of *P. falciparum*. - Presence of **multiple parasites per red blood cell** and various developmental stages including occasional **banana-shaped gametocytes**, though not prominent in this specific field, are key indicators of *P. falciparum* infection, differentiating it from other malarial species. - *P. falciparum* is the most dangerous malarial species and can cause **cerebral malaria** and other severe complications. *Salmonella Typhi* - This bacterium causes **typhoid fever** and is typically identified through **blood culture** or serological tests (Widal test), not by direct visualization within red blood cells on a peripheral blood smear. - *Salmonella Typhi* is an **intracellular bacterium** that primarily infects phagocytic cells (macrophages), not erythrocytes, and does not present as ring forms or other parasitic stages in blood smears. *Toxoplasma gondii* - This parasite causes **toxoplasmosis** and is typically found as **tachyzoites** or **bradyzoites** (within cysts) in tissue samples or less commonly in macrophages in disseminated disease, but not as ring forms within red blood cells on a peripheral blood smear. - Diagnosis usually involves **serological testing** for IgM/IgG antibodies or PCR, as opposed to direct visualization of unique forms in blood smears. *Treponema pallidum* - This is the spirochete responsible for **syphilis** and is too small and thin (0.1-0.2 μm diameter) to be seen with standard light microscopy on routine blood smears. - It is best identified using **dark-field microscopy** or serological tests (VDRL, RPR, TPPA, FTA-ABS) and does not infect red blood cells in the manner shown.

Q: A patient is having gastrointestinal problems including abdominal pain and distension, bloody or mucus-filled diarrhea, and tenesmus, with rectal prolapse. A stool, ova and parasites exam reveals the presence of typical barrel-shaped eggs. What is the possible causative agent?

Trichuris trichiura. ***Trichuris trichiura*** - The presence of **barrel-shaped eggs with polar plugs** in a stool exam is pathognomonic for **Trichuris trichiura (whipworm)** infection. - **Heavy infections** can lead to symptoms like **abdominal pain, bloody/mucus-filled diarrhea, tenesmus**, and sometimes **rectal prolapse**, especially in children. *Campylobacter* - This bacterium causes **bacterial gastroenteritis** with symptoms like **bloody diarrhea**, fever, and abdominal pain. - However, the diagnostic method involves **stool culture** for the bacteria, not the identification of barrel-shaped eggs. *Clostridium difficile* - This bacterium causes **pseudomembranous colitis**, typically following antibiotic use, with symptoms ranging from mild diarrhea to severe colitis. - Diagnosis is usually made by detecting **toxins (A and B)** in the stool, not via ova and parasite examination. *Giardia lamblia* - This parasite causes **giardiasis**, characterized by **malabsorptive diarrhea**, abdominal cramps, nausea, and bloating, usually without blood or mucus. - Stool examination would reveal **cysts or trophozoites** with a characteristic "falling leaf" motility, not barrel-shaped eggs.

Q: Parasitosis of extraocular eye muscles is seen in?

Trichinella infection. ***Trichinella infection*** - **Trichinellosis** (caused by *Trichinella spiralis*) commonly involves the **extraocular muscles** during the muscle encystment phase [1]. - Ocular symptoms like **periorbital edema**, eosinophilic myositis of extraocular muscles, and subconjunctival hemorrhage are characteristic [1]. *Cysticercus infection* - **Cysticercosis**, caused by *Taenia solium* larvae, can affect the eye, predominantly forming **subretinal** or **vitreous cysts** [2]. - While it can involve orbital muscles, involvement of extraocular muscles is less typical and less specific than in trichinellosis [2]. *Amoebic infection* - **Amoebic infections** primarily cause **keratitis** (e.g., *Acanthamoeba*) [3] or can lead to granulomatous encephalitis in immunocompromised individuals. - They do not typically cause direct parasitosis of the extraocular muscles. *Ascariasis infection* - **Ascariasis**, caused by *Ascaris lumbricoides*, is an intestinal nematode and is not known to infect the extraocular muscles. - Ocular manifestations are rare and usually involve migration of adult worms to the orbit or eyelid, not muscle encystment. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Infectious Diseases, pp. 404-405. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Infectious Diseases, pp. 403-404. [3] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 735-736.

Q: Recrudescences are commonly seen in which type of malaria:

P. falciparum. ***P. falciparum*** - **Recrudescence** refers to the reappearance of malaria symptoms after a period of remission, due to the survival and subsequent increase of asexual parasites in the blood [1]. - This is common in *P. falciparum* due to the high parasite burden and its ability to sequester in deep capillaries, evading splenic clearance and developing drug resistance. *P. vivax* - *P. vivax* is known for **relapses**, which are caused by the activation of dormant liver stages called **hypnozoites**, rather than a recrudescence of blood-stage parasites [1]. - Relapses can occur months or years after the initial infection, even after the blood-stage parasites have been cleared. *P. malariae* - *P. malariae* is uniquely characterized by infections that can persist for many years, even decades, causing symptoms of **recrudescence**, although less frequently than *P. falciparum* [1]. - It has a prolonged erythrocytic cycle, which can lead to chronic low-level parasitemia and sporadic symptomatic episodes. *P. ovale* - Similar to *P. vivax*, *P. ovale* also causes **relapses** due to the presence of **hypnozoites** in the liver [1]. - While it can manifest with symptoms similar to *P. vivax*, it is generally less common and causes milder disease.

Q: A woman traveling from Bihar to Delhi is suspected to have Kala-azar. Suitable investigation is?

Rk-39 test. ***Rk-39 test*** - The **Rk-39 test** is a rapid diagnostic test highly sensitive and specific for detecting antibodies against the **kinesin-related protein K39** of *Leishmania donovani*, the causative agent of **Kala-azar (visceral leishmaniasis)**. - It is particularly useful in **endemic regions** like Bihar for quick and accurate diagnosis, especially in patients with suspected Kala-azar presenting with fever, splenomegaly, and pancytopenia. *P24 antigen* - **P24 antigen** testing is primarily used for the diagnosis of **HIV infection**. - It detects the **core protein p24** of the HIV virus, which is not relevant for the diagnosis of Kala-azar. *Combo RDT* - A **Combo RDT** (Rapid Diagnostic Test), without further specification, typically refers to tests for **malaria**, which detect antigens like **HRP-2** and **aldolase**. - While RDTs are used for parasitic diseases, this general term does not specifically refer to a test for **Kala-azar**. *HRP-2 antigen* - **HRP-2 (Histidine-rich protein 2) antigen** is a specific marker for **Plasmodium falciparum**, used in the diagnosis of **malaria**. - It is not associated with the diagnosis of **Kala-azar**, which is caused by *Leishmania donovani*.

Q: Duodenal aspirate is used in diagnosis of:

Giardia lamblia. ***Giardia lamblia*** - **Duodenal aspiration** is a highly sensitive method for detecting **Giardia lamblia trophozoites** or cysts, especially in cases where stool examination is inconclusive. - This parasite primarily inhabits the **duodenum** and **upper jejunum**, making aspirate from this region an ideal diagnostic sample. *E histolytica* - **Entamoeba histolytica** (causes amoebiasis) is typically diagnosed by identifying **trophozoites** or **cysts** in **stool samples**, or through serology for invasive disease. - While it can affect the gastrointestinal tract, its primary site of colonization and pathology is the **colon**, not the duodenum. *Taenia solium* - **Taenia solium** (pork tapeworm) is diagnosed by identifying **proglottids** or **eggs** in **stool samples**. - It resides in the **small intestine**, but **duodenal aspirate** is not a standard diagnostic method for its detection. *Leishmania* - **Leishmania species** cause **leishmaniasis**, a disease diagnosed by detecting **amastigotes** in tissue biopsies (e.g., bone marrow, spleen, skin lesions) or through serological tests. - These parasites are intracellular and do not inhabit the **duodenal lumen**, making duodenal aspirate irrelevant for diagnosis.

Q: Incubation period of *Plasmodium vivax* is:

10-14 days. ***10-14 days*** - The typical incubation period for **_Plasmodium vivax_** is **10 to 14 days**, though it can sometimes be shorter or longer. - This period includes the time from the mosquito bite to the appearance of clinical symptoms, involving **hepatic schizogony** and early erythrocytic stages. *5-7 days* - An incubation period of 5-7 days is **unusually short** for _Plasmodium vivax_ and is more characteristic of **_Plasmodium falciparum_** in some cases. - While possible in rare instances due to a high inoculum, it's not the average or most common presentation for _P. vivax_. *7-10 days* - This duration is **shorter than the average** for _Plasmodium vivax_ and might be seen in cases with high parasitic load or specific endemic regions. - However, the most commonly cited average incubation period extends beyond this range. *15-30 days* - While _Plasmodium vivax_ can have **prolonged incubation periods** due to the presence of **hypnozoites** that can delay primary attacks, 15-30 days is a longer range. - Such longer periods are often associated with **relapses** or **delayed primary attacks**, rather than the typical initial symptomatic presentation.

Q: Trypanosoma cruzi is transmitted by which of the following?

Reduviid bug. ***Reduviid bug*** - *Trypanosoma cruzi*, the causative agent of **Chagas disease**, is primarily transmitted to humans through the feces of infected **reduviid bugs**, also known as **kissing bugs**. - The bug typically bites a person, often around the face, and then defecates near the bite wound, allowing the parasite to enter when the person scratches or rubs the area. *Tse tse fly* - The **tsetse fly** is the vector for **African trypanosomiasis** (sleeping sickness), caused by *Trypanosoma brucei*. - This fly is geographically restricted to sub-Saharan Africa, whereas *Trypanosoma cruzi* is prevalent in the Americas. *Culex mosquito* - **Culex mosquitoes** are known vectors for various diseases, including **West Nile virus**, **Japanese encephalitis**, and **filariasis**. - They are not involved in the transmission of *Trypanosoma cruzi*. *Sand fly* - **Sand flies** transmit **Leishmaniasis**, a parasitic disease caused by various species of *Leishmania*. - They are also responsible for transmitting **Bartonellosis** and some types of **Arboviruses**, but not Chagas disease.

Q: Which of the following is not a recognized transmission route for amoebiasis?

Vector transmission. ***Vector transmission*** - Amoebiasis, caused by *Entamoeba histolytica*, is primarily an **intestinal infection** transmitted through the **fecal-oral route**. - Its life cycle **does not involve any arthropod vector** (e.g., mosquito, tick, fly) for transmission. - This is the **only route among the options that is definitively NOT recognized** for amoebiasis transmission. *Sexual transmission* - Amoebiasis **can be transmitted** through **oral-anal sexual contact**, particularly documented in men who have sex with men (MSM). - This represents an **indirect fecal-oral transmission** route and is a recognized mode of spread. *Blood and blood products* - While *E. histolytica* can disseminate to cause **amoebic liver abscesses** and rarely systemic disease, transmission via blood transfusion is **extremely rare and not well-documented**. - However, theoretically possible in cases of parasitemia during invasive disease. - Unlike vector transmission, this cannot be definitively ruled out as "not recognized." *Fecal-oral route* - This is the **primary and most important transmission route** for amoebiasis. - Infection occurs through ingestion of **cysts** from contaminated food, water, or through direct person-to-person contact with poor hand hygiene.

Question 1

A 36-year-old male patient complaining of cough, cold, fever, and rusty sputum, with a history of travel to China and consumption of crab. Name the infection.

Accepted Answer

Paragonimus westermani

Answer

Fasciola hepatica

Answer

Fasciolopsis buski

Answer

Entamoeba histolytica

Question 2

Identify the organism related to the blood smear image.

Accepted Answer

Plasmodium falciparum

Answer

Salmonella Typhi

Answer

Toxoplasma gondii

Answer

Treponema pallidum

Question 3

A patient is having gastrointestinal problems including abdominal pain and distension, bloody or mucus-filled diarrhea, and tenesmus, with rectal prolapse. A stool, ova and parasites exam reveals the presence of typical barrel-shaped eggs. What is the possible causative agent?

Accepted Answer

Trichuris trichiura

Answer

Campylobacter

Answer

Clostridium difficile

Answer

Giardia lamblia

Question 4

Parasitosis of extraocular eye muscles is seen in?

Accepted Answer

Trichinella infection

Answer

Cysticercus infection

Answer

Amoebic infection

Answer

Ascariasis infection

Question 5

Recrudescences are commonly seen in which type of malaria:

Accepted Answer

P. falciparum

Answer

P. vivax

Answer

P. malariae

Answer

P. ovale

Question 6

A woman traveling from Bihar to Delhi is suspected to have Kala-azar. Suitable investigation is?

Accepted Answer

Rk-39 test

Answer

P24 antigen

Answer

Combo RDT

Answer

HRP-2 antigen

Question 7

Duodenal aspirate is used in diagnosis of:

Accepted Answer

Giardia lamblia

Answer

E histolytica

Answer

Taenia solium

Answer

Leishmania

Question 8

Incubation period of *Plasmodium vivax* is:

Accepted Answer

10-14 days

Answer

5-7 days

Answer

7-10 days

Answer

15-30 days

Question 9

Trypanosoma cruzi is transmitted by which of the following?

Accepted Answer

Reduviid bug

Answer

Tse tse fly

Answer

Culex mosquito

Answer

Sand fly

Question 10

Which of the following is not a recognized transmission route for amoebiasis?

Accepted Answer

Vector transmission

Answer

Sexual transmission

Answer

Blood and blood products

Answer

Fecal-oral route

Parasitology — MCQs

Parasitology — MCQs

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