Parasitology Practice Questions

Q: A boy presented with a fever and chills. Rapid test was positive for specific antigen HRP-2. Which of the following species of Plasmodium is the most likely causative agent?

Plasmodium falciparum. ***Plasmodium falciparum*** - The **histidine-rich protein 2 (HRP-2)** antigen is specifically produced by **P. falciparum** and is targeted by most rapid diagnostic tests for malaria. - A positive HRP-2 test in a patient with fever and chills indicates a high likelihood of **P. falciparum** infection, which is often the most severe form of malaria. *Plasmodium malariae* - **P. malariae** does not produce **HRP-2 antigen**, therefore, a rapid diagnostic test targeting HRP-2 would be negative for this species. - This species can cause a **quartan fever pattern** (fever every 72 hours) and usually presents with less severe symptoms compared to P. falciparum. *Plasmodium vivax* - **P. vivax** produces **_Plasmodium_ lactate dehydrogenase (pLDH)** and **aldolase antigens**, but not HRP-2. Some rapid tests combine detection of HRP-2 with pLDH to identify both *P. falciparum* and *P. vivax*. - While *P. vivax* causes fever and chills, its presence would not be indicated by a positive HRP-2 specific test alone. *Plasmodium ovale* - **P. ovale** also produces **pLDH and aldolase antigens**, similar to *P. vivax*, and does not produce **HRP-2**. - Infections with *P. ovale* are relatively rare and generally cause milder disease than *P. falciparum*, often with a **tertian fever pattern**.

Q: In a patient presented with a fever and a positive filarial antigen test, what is the next appropriate method of management?

Detection of microfilariae in the blood smear. ***Detection of microfilariae in the blood smear*** - A positive **filarial antigen test** indicates the presence of adult worms, and the next step is to confirm active infection by identifying **microfilariae**. [1] - **Nocturnal blood samples** are crucial because microfilariae of *Wuchereria bancrofti* and *Brugia malayi* exhibit **nocturnal periodicity**, meaning they are most abundant in peripheral blood between 10 PM and 2 AM. [1] *Bone marrow biopsy* - This procedure is typically used to diagnose **hematological disorders**, such as leukemia or lymphoma, or investigate causes of unexplained fever, but it is not indicated for filariasis. - While filariasis can rarely lead to **eosinophilia**, a bone marrow biopsy is not a diagnostic tool for filarial infection itself. *DEC provocation test* - The **diethylcarbamazine (DEC) provocation test** is used to bring out microfilariae into the peripheral blood during the daytime for species that exhibit nocturnal periodicity. [1] - However, it carries a risk of severe adverse reactions due to rapid killing of microfilariae, especially in cases of heavy infection, and is generally avoided when antigen tests are positive. [1] *Ultrasound of the scrotum* - Scrotal ultrasound can detect the characteristic "filarial dance sign" (motile adult worms) in the **lymphatic vessels of the scrotum and epididymis**, confirming lymphatic filariasis. [2] - While useful for assessing advanced disease manifestations like **hydrocele**, it does not quantify microfilaremia or replace the need for microscopic confirmation of circulating microfilariae to guide treatment.

Q: A lady from West Rajasthan presented with an ulcer surrounded by erythema on the right leg. Microscopy of the biopsy from the edge of the ulcer showed organisms with dark staining nuclei and kinetoplast. What is the most likely causative agent? (Refer to the provided image)

Leishmania tropica. ***Leishmania tropica*** - The presence of an ulcer with surrounding erythema in **West Rajasthan**, along with microscopy showing organisms with a **nucleus and kinetoplast**, is highly characteristic of **cutaneous leishmaniasis** caused by *Leishmania tropica*. - The organisms seen are **amastigotes** within macrophages in skin lesions, which are identified by their distinct **nucleus and kinetoplast** on microscopy. - West Rajasthan is an **endemic area** for cutaneous leishmaniasis. *Babesia microti* - *Babesia microti* causes **babesiosis**, a tick-borne illness affecting red blood cells, leading to **hemolytic anemia** and malaria-like symptoms. - It does not typically cause **skin ulcers** and its characteristic form in smears is a **ring form or tetrad ("Maltese cross")** within red blood cells, not organisms with kinetoplasts in macrophages. *Trypanosoma brucei* - *Trypanosoma brucei* causes **African trypanosomiasis (sleeping sickness)**, presenting with fever, headaches, joint pain, and neurological symptoms, possibly a **chancre** at the inoculation site. - While it has a **kinetoplast**, it exists as a flagellated **trypomastigote** in the blood and CSF, not as an **amastigote** in macrophages within a skin ulcer. - Additionally, this is **geographically incorrect** for West Rajasthan. *Histoplasma capsulatum* - *Histoplasma capsulatum* is a **fungus** that causes **histoplasmosis**, primarily affecting the respiratory system, especially in immunocompromised individuals. - It does **not possess a kinetoplast** and while it can cause disseminated disease with skin lesions, the microscopic appearance would be **yeast forms** within macrophages, not organisms with kinetoplasts.

Q: A 15-year-old boy presented with fever and chills for 3 days. On examination, he was found to have delayed skin pinch time and dry oral mucosa. A peripheral blood smear revealed multiple delicate ring forms within red blood cells, with some red blood cells containing more than one ring form. No other developmental stages were observed. Identify the pathogen involved.

Plasmodium falciparum. ***Plasmodium falciparum*** - The presence of **multiple delicate ring forms** with **multiply infected red blood cells** (more than one ring per RBC) on peripheral blood smear is characteristic of *Plasmodium falciparum* infection. - A key distinguishing feature of *P. falciparum* is that **only ring forms** are typically seen in peripheral blood due to **sequestration of mature stages** (trophozoites and schizonts) in deep capillaries of internal organs. - The clinical presentation with fever, chills, and signs of dehydration is consistent with falciparum malaria, which can progress to severe complications. *Plasmodium vivax* - *Plasmodium vivax* also causes malaria and shows ring forms, but typically presents with **enlarged red blood cells** (due to preferential infection of reticulocytes) and **all developmental stages visible** in peripheral blood, including trophozoites, schizonts, and gametocytes. - The absence of enlarged RBCs and other developmental stages, combined with multiply infected cells, makes *P. vivax* less likely. *Babesia* - While **Babesia** also infects red blood cells and can show ring forms, its characteristic finding is **pear-shaped trophozoites** arranged in **tetrads (Maltese cross appearance)**. - **Babesiosis** is typically transmitted by ticks and is more common in immunocompromised individuals or in specific geographic regions (e.g., northeastern United States). *Salmonella typhi* - **Salmonella typhi** causes **typhoid fever**, which presents with prolonged fever, headache, and gastrointestinal symptoms, but it is a **bacterial infection** and does not involve infection of red blood cells. - Diagnosis is made by **blood culture** or **bone marrow culture**, not by microscopic examination of red blood cells for parasites.

Q: Identify the parasite shown in the image.

Trichuris trichiura. ***Trichuris trichiura*** - The image displays characteristic **lemon-shaped** or **barrel-shaped eggs** with distinctive **polar plugs** at each end, which are pathognomonic for *Trichuris trichiura* (whipworm) eggs. - These eggs are thick-shelled and typically measure 50-55 µm by 20-25 µm, containing an undeveloped larva when passed in feces. *Ancylostoma duodenale* - Eggs of *Ancylostoma duodenale* (Old World hookworm) are **oval-shaped** with blunt ends, and a **thin shell**. - They typically contain a **segmented ovum** or an early-stage larva, lacking the polar plugs seen in the image. *Paragonimus westermani* - *Paragonimus westermani* (lung fluke) eggs are generally **oval-shaped** with a **flattened operculum** at one end, which is not visible in the image. - They are larger than *Trichuris* eggs, often measuring around 80-120 µm by 45-70 µm, and are often coughed up in sputum or passed in feces. *Strongyloides stercoralis* - *Strongyloides stercoralis* primarily produces **larvae** (rhabditiform or filariform) in stool samples rather than eggs. - If eggs are seen (rarely, in cases of severe diarrhea), they are small, thin-shelled, and typically contain a developed larva, unlike the eggs shown.

Q: Green frothy vaginal discharge is produced by –

Trichomonas vaginalis. ***Trichomonas vaginalis*** - **Trichomoniasis**, caused by *Trichomonas vaginalis*, classically presents with a **yellowish-green, frothy, malodorous vaginal discharge**. - It is a **sexually transmitted infection** that can also cause vaginal itching, burning, and dyspareunia. *Herpes simplex* - Herpes simplex virus typically causes **painful genital ulcers** or sores, not a frothy discharge. - The discharge, if present, is usually clear or serous and associated with the open lesions. *Candida albicans* - *Candida albicans* (yeast infection) commonly produces a **thick, white, "cottage cheese-like" discharge** that is often associated with intense itching. - It does not typically cause a frothy, green discharge. *Normal vaginal flora* - Normal vaginal flora maintains a healthy vaginal environment and produces a **clear to whitish, non-irritating discharge** with no strong odor. - It does not cause a green, frothy discharge, which indicates an infection.

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: Sabin-Feldman dye test is used for diagnosis of which of the following conditions:

Toxoplasmosis. ***Toxoplasmosis*** - The **Sabin-Feldman dye test** is a sensitive and specific serological test used to detect antibodies (primarily IgG) against *Toxoplasma gondii*, the parasitic causative agent of toxoplasmosis. - It measures the ability of specific antibodies in a patient's serum to prevent the **staining of live Toxoplasma tachyzoites** by methylene blue dye. *Granulomatosis with polyangiitis* - This is an autoimmune vasculitis primarily diagnosed using **biopsy** (showing granulomatous inflammation and necrotizing vasculitis) and serological testing for **antineutrophil cytoplasmic antibodies (ANCAs)**, specifically c-ANCA/PR3-ANCA. - The Sabin-Feldman dye test has no role in the diagnosis of this condition. *Hepatitis A virus infection* - Hepatitis A is a viral infection of the liver, diagnosed by detecting **IgM antibodies** to hepatitis A virus (anti-HAV IgM) in the acute phase of infection. - The Sabin-Feldman dye test is not and cannot be used for the diagnosis of viral hepatitis. *Clostridium botulinum infection* - Botulism, caused by toxins from *Clostridium botulinum*, is diagnosed by detecting the **botulinum toxin** in serum, stool, or wound samples, often through bioassays (e.g., mouse bioassay). - The Sabin-Feldman dye test is a parasitic serology test and is irrelevant to the diagnosis of bacterial toxin-mediated diseases.

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 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.

Question 1

A boy presented with a fever and chills. Rapid test was positive for specific antigen HRP-2.    Which of the following species of Plasmodium is the most likely causative agent?

Accepted Answer

Plasmodium falciparum

Answer

Plasmodium malariae

Answer

Plasmodium vivax

Answer

Plasmodium ovale

Question 2

In a patient presented with a fever and a positive filarial antigen test, what is the next appropriate method of management?

Accepted Answer

Detection of microfilariae in the blood smear

Answer

Bone marrow biopsy

Answer

DEC provocation test

Answer

Ultrasound of the scrotum

Question 3

A lady from West Rajasthan presented with an ulcer surrounded by erythema on the right leg. Microscopy of the biopsy from the edge of the ulcer showed organisms with dark staining nuclei and kinetoplast. What is the most likely causative agent? (Refer to the provided image)

Accepted Answer

Leishmania tropica

Answer

Babesia microti

Answer

Trypanosoma brucei

Answer

Histoplasma capsulatum

Question 4

A 15-year-old boy presented with fever and chills for 3 days. On examination, he was found to have delayed skin pinch time and dry oral mucosa. A peripheral blood smear revealed multiple delicate ring forms within red blood cells, with some red blood cells containing more than one ring form. No other developmental stages were observed. Identify the pathogen involved.

Accepted Answer

Plasmodium falciparum

Answer

Babesia

Answer

Salmonella typhi

Answer

Plasmodium vivax

Question 5

Identify the parasite shown in the image.

Accepted Answer

Trichuris trichiura

Answer

Ancylostoma duodenale

Answer

Strongyloides stercoralis

Answer

Paragonimus westermani

Question 6

Green frothy vaginal discharge is produced by –

Accepted Answer

Trichomonas vaginalis

Answer

Herpes simplex

Answer

Candida albicans

Answer

Normal vaginal flora

Question 7

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 8

Sabin-Feldman dye test is used for diagnosis of which of the following conditions:

Accepted Answer

Toxoplasmosis

Answer

Granulomatosis with polyangiitis

Answer

Hepatitis A virus infection

Answer

Clostridium botulinum infection

Question 9

Identify the organism related to the blood smear image.

Accepted Answer

Plasmodium falciparum

Answer

Salmonella Typhi

Answer

Toxoplasma gondii

Answer

Treponema pallidum

Question 10

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

Parasitology — MCQs

Parasitology — MCQs

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