Parasitology Practice Questions

Q: Sheathed microfilariae with two nuclei at the tail tip is suggestive of?

Brugia malayi. ***Brugia malayi*** - Microfilariae of *Brugia malayi* are characterized by a **sheathed tail** with **two distinct nuclei** at the very tip of the tail. - This morphological feature, along with the presence of multiple discrete nuclei throughout the body, is key for its identification. *Wuchereria bancrofti* - While *Wuchereria bancrofti* also has a **sheathed tail**, its tail is typically **free of nuclei** or has terminal nuclei that are not distinct or paired. - The nuclei of *W. bancrofti* are more scattered and less clearly defined throughout the body compared to *Brugia*. *Onchocerca volvulus* - *Onchocerca volvulus* microfilariae are **unsheathed** and have a **tapered tail without nuclei**. - They are typically found in the skin, not the blood, and lack the characteristic two nuclei at the tail tip. *Loa loa* - *Loa loa* microfilariae are also **sheathed** but have a **tapered tail with nuclei extending to the tip**, not specifically two distinct nuclei at the tail. - Their nuclei are irregularly arranged within the tail, differentiating them from *Brugia malayi*.

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: 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: Cutaneous larva migrans is caused by which organism?

Ancylostoma braziliense. ***Ancylostoma braziliense*** - This **hookworm** species commonly found in dogs and cats is the most frequent cause of **cutaneous larva migrans** in humans. - The larvae penetrate the skin but cannot complete their life cycle in humans, instead migrating aimlessly creating **serpiginous tracks**. *Strongyloides* - **_Strongyloides stercoralis_** causes **strongyloidiasis**, which presents with a rapidly advancing (up to 10 cm/hr) migratory rash known as **larva currens**, and not the slower cutaneous larva migrans. - It differs from cutaneous larva migrans in its ability to complete its life cycle in humans, leading to **autoinfection**. *Toxocara canis* - **_Toxocara canis_** is the causative agent of **visceral larva migrans** and **ocular larva migrans**, not cutaneous larva migrans. - In visceral larva migrans, larvae migrate through internal organs, causing symptoms like **hepatomegaly** and **eosinophilia**. *Necator americanus* - This is a human hookworm that can cause **iron deficiency anemia** due to chronic blood loss in the intestines. - While its larvae can penetrate the skin, causing a transient itchy rash known as **ground itch**, they do not cause the prolonged, migratory cutaneous larva migrans.

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: 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: 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: 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: River blindness is caused by?

Onchocerca volvulus. ***Onchocerca volvulus*** - **River blindness**, or **onchocerciasis**, is caused by the parasitic nematode *Onchocerca volvulus*. - This parasite is transmitted by the bite of infected **blackflies** (genus *Simulium*), which breed in fast-flowing rivers. *Loa loa* - *Loa loa* causes **Loiasis**, also known as African eye worm disease. - While it can manifest as an eye worm and cause itching and swelling, it does not typically lead to permanent blindness or the widespread skin lesions associated with river blindness. *Ascaris* - *Ascaris lumbricoides* causes **ascariasis**, an intestinal infection. - Symptoms are primarily gastrointestinal, such as abdominal pain, malnutrition, and, in severe cases, intestinal obstruction; it does not affect the eyes or cause blindness. *B. malayi* - *Brugia malayi* is one of the causes of **lymphatic filariasis**, also known as **elephantiasis**. - This disease primarily affects the lymphatic system, causing severe swelling in the limbs and genitals, but it does not cause blindness.

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*.

Question 1

Sheathed microfilariae with two nuclei at the tail tip is suggestive of?

Accepted Answer

Brugia malayi

Answer

Onchocerca volvulus

Answer

Wuchereria bancrofti

Answer

Loa loa

Question 2

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 3

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 4

Cutaneous larva migrans is caused by which organism?

Accepted Answer

Ancylostoma braziliense

Answer

Strongyloides

Answer

Toxocara canis

Answer

Necator americanus

Question 5

Identify the organism related to the blood smear image.

Accepted Answer

Plasmodium falciparum

Answer

Salmonella Typhi

Answer

Toxoplasma gondii

Answer

Treponema pallidum

Question 6

Incubation period of *Plasmodium vivax* is:

Accepted Answer

10-14 days

Answer

5-7 days

Answer

7-10 days

Answer

15-30 days

Question 7

Duodenal aspirate is used in diagnosis of:

Accepted Answer

Giardia lamblia

Answer

E histolytica

Answer

Taenia solium

Answer

Leishmania

Question 8

Trypanosoma cruzi is transmitted by which of the following?

Accepted Answer

Reduviid bug

Answer

Tse tse fly

Answer

Culex mosquito

Answer

Sand fly

Question 9

River blindness is caused by?

Accepted Answer

Onchocerca volvulus

Answer

Loa loa

Answer

Ascaris

Answer

B. malayi

Question 10

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

Parasitology — MCQs

Parasitology — MCQs

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