Parasitology Practice Questions

Q: A 24-year-old patient presents with a high-grade fever, headache, and weakness since 5 days. He gives a history of blood transfusion 4 months back. The microscopic examination of the thin blood smear is given below. What is the most probable causative agent?

Babesia microti. ***Babesia microti*** - The image displays **intraerythrocytic pleomorphic ring forms** and classic **tetrad formations (Maltese cross)**, which are pathognomonic for **Babesia microti** infection. - The patient's history of **blood transfusion** 4 months prior is highly suggestive, as babesiosis can be transmitted through contaminated blood products with an incubation period fitting this timeline. - Clinical features include high-grade fever, headache, and weakness, consistent with babesiosis. *Leishmania donovani* - This parasite exists as **amastigotes within macrophages** and does not infect red blood cells or form ring structures as seen in the image. - While it causes fever and weakness (**visceral leishmaniasis/kala-azar**), its microscopic appearance on blood smear shows amastigotes in macrophages, not intraerythrocytic forms. *Plasmodium vivax* - While *P. vivax* infects red blood cells and forms ring stages, it is typically characterized by **enlarged infected RBCs with Schüffner's dots**, which are not seen here. - The **tetrad formations (Maltese cross)** seen in the image are pathognomonic for Babesia, not Plasmodium species. *Plasmodium falciparum* - This parasite typically presents with **multiple small ring forms per RBC** and **applique or "accole" forms** at the periphery of red blood cells. - While *P. falciparum* can cause high fever and severe disease, the specific **tetrad configuration (Maltese cross)** is characteristic of Babesia, not Plasmodium.

Q: Sabin Feldman dye test is used for:

Toxoplasma. ***Toxoplasma*** - The **Sabin-Feldman dye test** is a **serological assay** used to detect specific antibodies against *Toxoplasma gondii*. - This test measures the ability of antibodies in the patient's serum to prevent the cytoplasmic staining of live *Toxoplasma gondii* parasites by a basic dye. *Herpes* - Herpes simplex virus (HSV) infections are typically diagnosed using **viral culture**, **PCR**, or **antigen detection**, not the Sabin-Feldman dye test. - Serological tests for herpes usually involve detecting **IgG or IgM antibodies** to specific HSV glycoproteins. *Syphilis* - Syphilis, caused by *Treponema pallidum*, is diagnosed using **non-treponemal tests** (e.g., RPR, VDRL) and confirmed by **treponemal tests** (e.g., TP-PA, FTA-ABS). - The Sabin-Feldman dye test has no role in the diagnosis of syphilis. *Plasmodium* - *Plasmodium* species are the causative agents of malaria, diagnosed primarily by **microscopic examination of Giemsa-stained blood smears** to identify parasites. - **Rapid Diagnostic Tests (RDTs)** detecting *Plasmodium* antigens are also commonly used.

Q: Infection caused by which of the following organism may mimic as malignancy?

Echinococcus multilocularis. ***Echinococcus multilocularis*** - This parasite causes **alveolar echinococcosis**, which manifests as a **destructive, infiltrative growth** in organs, primarily the liver. [1] - The lesions can be difficult to differentiate from **malignant tumors** due to their invasive nature and irregular margins, often leading to misdiagnosis. [1] *Echinococcus oliganthus* - This species is known to cause **polycystic echinococcosis**, primarily affecting wild felids and occasionally humans through accidental ingestion of eggs. - While it forms cysts, its growth pattern is generally **cystic** rather than infiltrative, making it less likely to mimic malignancy compared to *E. multilocularis*. *Echinococcus vogeli* - This parasite causes **polycystic hydatid disease** (or polycystic echinococcosis), similar to *E. oliganthus*, but is primarily associated with dholes and causes lesions in humans. - The disease typically presents as **large, multiloculated cysts** in organs, which are distinct from the infiltrative, tumor-like lesions of *E. multilocularis*. *Echinococcus granulosus* - This species is responsible for **cystic echinococcosis** (or hydatid disease), forming slow-growing, unilocular cysts, most commonly in the liver and lungs. [1] - While these cysts can grow large, their **well-defined, encapsulated nature** generally makes them distinguishable from malignant tumors, unlike the invasive lesions of alveolar echinococcosis. [1]

Q: An Egyptian fisherman develops lower abdominal pain and pain on urination, and reports seeing blood in his urine. Which of the following parasites is the most likely cause of urinary symptoms in this patient?

Schistosoma haematobium. ***Schistosoma haematobium*** - The patient's presentation with **lower abdominal pain**, **dysuria**, and **hematuria** is highly characteristic of urinary schistosomiasis, caused by *Schistosoma haematobium*. - The patient's origin as an **Egyptian fisherman** places him in an **endemic area** where contact with contaminated fresh water containing the parasite's larval forms (cercariae) is common. *Clonorchis sinensis* - This parasite causes **clonorchiasis**, an infection primarily affecting the **biliary tract** and liver, leading to symptoms like cholangitis, cholecystitis, and hepatomegaly. - It is typically acquired by consuming **raw or undercooked freshwater fish**, but does not cause urinary symptoms. *Fasciola hepatica* - *Fasciola hepatica* causes **fascioliasis**, a **liver fluke infection** that primarily affects the **biliary ducts** leading to symptoms like right upper quadrant pain, fever, and jaundice. - It is acquired by ingesting **metacercariae on aquatic plants**, particularly watercress, and does not cause urinary manifestations. *Diphyllobothrium latum* - This is the **fish tapeworm**, which causes **diphyllobothriasis**, an intestinal infection. - Symptoms are usually mild or asymptomatic, but can include abdominal discomfort, nausea, and notably **vitamin B12 deficiency** leading to megaloblastic anemia, not urinary symptoms.

Q: Which of the following is the most common central nervous system parasitic infestation-

Neurocysticercosis. ***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.

Q: Painless terminal hematuria is seen as one of the manifestations in the infection caused by ?

Schistosoma haematobium. ***Schistosoma haematobium*** - *Schistosoma haematobium* characteristically infects the **urinary bladder**, leading to inflammation and ulceration of the bladder wall [1]. - This irritation often manifests as **painless terminal hematuria**, which is the passage of blood at the end of micturition without associated pain [1]. *Plasmodium falciparum* - *Plasmodium falciparum* is the causative agent of **malaria**, a parasitic infection that primarily affects red blood cells and the liver. - While it can cause severe systemic symptoms, **hematuria** is not a typical or distinguishing feature of *P. falciparum* infection; rather, it often presents with fever, chills, and organ damage. *Schistosoma japonicum* - *Schistosoma japonicum* primarily infects the **mesenteric veins** of the small intestine, leading to intestinal and hepatic schistosomiasis [1]. - Symptoms are usually gastrointestinal (e.g., abdominal pain, diarrhea) or hepatic (e.g., hepatosplenomegaly), with **urinary tract involvement** and hematuria being highly uncommon [1]. *Schistosoma mansoni* - *Schistosoma mansoni* mainly infects the **mesenteric veins** of the large intestine, causing intestinal schistosomiasis. - Its clinical manifestations typically include **abdominal pain**, bloody diarrhea, and liver fibrosis, but not urinary symptoms like **hematuria**.

Q: Peripheral blood smear in Plasmodium falciparum infection may show all of the following except -

Schizont. ***Schizont*** - While schizonts are a stage in the *Plasmodium falciparum* life cycle, **mature schizonts** (containing merozoites) are typically not seen in peripheral blood smears of infected patients. - They tend to **sequester in deep capillaries** of organs, making their detection in circulating blood extremely rare. *Female gametocyte* - **Crescent-shaped gametocytes** (both male and female) are a characteristic feature of *Plasmodium falciparum* infection that are readily identified in peripheral blood smears. - These forms are responsible for transmission to the mosquito vector. *Trophozoite* - **Ring-form trophozoites** are the most commonly seen stage of *P. falciparum* in peripheral blood smears. - They are typically thin, delicate rings, often with **double chromatin dots** or appliqué forms. *Male gametocyte* - Similar to female gametocytes, **crescent-shaped male gametocytes** are routinely observed in peripheral blood smears of *Plasmodium falciparum* infected individuals. - They are essential for sexual reproduction within the mosquito.

Q: Man is the only host for

Wuchereria bancrofti. ***Wuchereria bancrofti*** - This parasite is largely **restricted to humans** as its definitive host, causing **lymphatic filariasis**. - Its life cycle involves transmission via mosquitoes, but it relies solely on humans for the maturation of adult worms and the production of microfilariae. *Onchocerca volvulus* - While humans are the primary definitive hosts for **Onchocerca volvulus**, leading to **onchocerciasis** or **river blindness**, certain **simian primates** have also been found to harbor the parasite, making humans not the *exclusive* host. - The parasite is transmitted by **blackflies**. *Trichuris trichiura* - This parasite, commonly known as the **human whipworm**, primarily infects humans. - However, **other primates** like monkeys and apes can also be infected, thus humans are not the sole host. *Dracunculus medinensis* - While humans are the main and most well-known definitive host for **Dracunculus medinensis** (guinea worm), **dogs** and **other carnivores** have also been identified as hosts. - The infection is acquired by ingesting **copepods** containing larvae in contaminated water.

Q: The life cycle of filaria in the mosquito is described as:

Cyclodevelopmental. ***Cyclodevelopmental*** - In a **cyclodevelopmental** life cycle, the parasite undergoes essential **developmental changes** within the vector without increasing significantly in number. - This precisely describes the filaria's existence in the mosquito, where microfilariae develop into infective larvae. *Propagative* - A **propagative** life cycle involves the parasite multiplying within the intermediate host or vector. - This is not characteristic of filaria in mosquitoes, as their primary goal is development, not proliferation, within the vector. *Cyclopropagative* - A **cyclopropagative** life cycle involves both **developmental changes** and **multiplication** of the parasite within the vector. - While there is development, significant multiplication does not occur in the mosquito vector for filarial worms, distinguishing it from this type. *None of the options* - This option is incorrect because the life cycle of filaria in the mosquito specifically fits the definition of **cyclodevelopmental**. - The other terms describe different patterns of parasite-vector interaction that do not apply here.

Q: Cyclodevelopmental life cycle is seen in:

Filaria. ***Filaria*** - The **cyclodevelopmental life cycle** refers to parasites that undergo **developmental changes** through distinct larval stages within the vector. - Filarial nematodes, such as *Wuchereria bancrofti* and *Brugia malayi*, undergo **developmental transformation** in the mosquito vector: microfilariae (L1) → L2 stage → infective L3 stage. - The L3 larvae then migrate to the mosquito's proboscis and are transmitted to the human host during a blood meal. - This developmental progression through larval stages in the vector characterizes the cyclodevelopmental pattern. *Malaria* - Malaria parasites (*Plasmodium* species) exhibit a **cyclopropagative life cycle** in the mosquito vector. - They undergo both **development** (gametocytes → ookinete → oocyst → sporozoites) and **multiplication** (sporogony produces thousands of sporozoites from one oocyst). - This combination of development with extensive multiplication distinguishes it from purely cyclodevelopmental transmission. *Plague* - Plague is caused by *Yersinia pestis*, transmitted by fleas. - This represents **propagative transmission** where bacteria multiply in the flea's gut but do not undergo developmental stage changes. - The bacteria block the flea's proventriculus, causing mechanical transmission during feeding attempts. *Yellow fever* - Yellow fever virus is transmitted by *Aedes* mosquitoes. - This is a **propagative life cycle** where the virus replicates within the mosquito vector. - Viruses do not undergo morphological developmental stages like parasites, only multiplication through replication.

Question 1

A 24-year-old patient presents with a high-grade fever, headache, and weakness since 5 days. He gives a history of blood transfusion 4 months back. The microscopic examination of the thin blood smear is given below. What is the most probable causative agent?

Accepted Answer

Babesia microti

Answer

Leishmania donovani

Answer

Plasmodium vivax

Answer

Plasmodium falciparum

Question 2

Sabin Feldman dye test is used for:

Accepted Answer

Toxoplasma

Answer

Herpes

Answer

Syphilis

Answer

Plasmodium

Question 3

Infection caused by which of the following organism may mimic as malignancy?

Accepted Answer

Echinococcus multilocularis

Answer

Echinococcus oliganthus

Answer

Echinococcus vogeli

Answer

Echinococcus granulosus

Question 4

An Egyptian fisherman develops lower abdominal pain and pain on urination, and reports seeing blood in his urine. Which of the following parasites is the most likely cause of urinary symptoms in this patient?

Accepted Answer

Schistosoma haematobium

Answer

Clonorchis sinensis

Answer

Fasciola hepatica

Answer

Diphyllobothrium latum

Question 5

Which of the following is the most common central nervous system parasitic infestation-

Accepted Answer

Neurocysticercosis

Answer

Sparganosis

Answer

Paragonimiasis

Answer

Echinococcosis

Question 6

Painless terminal hematuria is seen as one of the manifestations in the infection caused by ?

Accepted Answer

Schistosoma haematobium

Answer

Plasmodium falciparum

Answer

Schistosoma japonicum

Answer

Schistosoma mansoni

Question 7

Peripheral blood smear in Plasmodium falciparum infection may show all of the following except -

Accepted Answer

Schizont

Answer

Female gametocyte

Answer

Trophozoite

Answer

Male gametocyte

Question 8

Man is the only host for

Accepted Answer

Wuchereria bancrofti

Answer

Onchocerca volvulus

Answer

Trichuris trichiura

Answer

Dracunculus medinensis

Question 9

The life cycle of filaria in the mosquito is described as:

Accepted Answer

Cyclodevelopmental

Answer

Propagative

Answer

Cyclopropagative

Answer

None of the options

Question 10

Cyclodevelopmental life cycle is seen in:

Accepted Answer

Filaria

Answer

Malaria

Answer

Plague

Answer

Yellow fever

Parasitology — MCQs

Parasitology — MCQs

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