Parasitology Practice Questions

Q: Which type of malaria is most commonly associated with renal failure?

Falciparum. ***Falciparum*** - **Plasmodium falciparum** is notorious for its ability to cause severe and complicated malaria, including **renal failure** due to its high parasitic biomass and tendency to block microvasculature [1]. - The parasite causes red blood cells to become **sticky**, leading to sequestration in capillaries of vital organs, including the kidneys, resulting in acute tubular necrosis [1]. *Vivax* - **Plasmodium vivax** typically causes milder forms of malaria, though it can occasionally lead to severe manifestations, **renal complications are rare** compared to P. falciparum [1]. - While it can cause some organ dysfunction, it generally does not cause the severe multi-organ involvement, particularly **acute renal failure**, that P. falciparum is known for [1]. *Malariae* - **Plasmodium malariae** is associated with a chronic form of malaria and is known to cause **nephrotic syndrome** (specifically malarial nephropathy) due to immune complex deposition, rather than acute renal failure [1]. - The renal pathology in P. malariae infection is typically a **glomerulonephritis** that develops after repeated infections, which is distinct from the acute renal failure seen with P. falciparum [1]. *Ovale* - **Plasmodium ovale** is the least common type of malaria and causes a benign form of the disease, similar to P. vivax [1]. - It rarely, if ever, causes severe complications like **renal failure** [1].

Q: Who discovered the malarial parasite?

Charles Louis Alphonse Laveran. ***Charles Louis Alphonse Laveran*** - **Charles Louis Alphonse Laveran** was a French physician who, in **1880**, observed parasites in the blood of a malaria patient. - He was awarded the **Nobel Prize in Physiology or Medicine in 1907** for his discovery of the role of protozoa in causing diseases, specifically recognizing the malarial parasite. *Ronald Ross* - **Ronald Ross** was a British physician who, in **1897**, demonstrated that **malaria is transmitted by mosquitoes**. - While he elucidated the **transmission cycle**, it was Laveran who first identified the parasite itself in human blood. - He received the **Nobel Prize in 1902** for this work. *Paul Muller* - **Paul Muller** was a Swiss chemist who was awarded the **Nobel Prize in Physiology or Medicine in 1948** for his discovery of the insecticidal properties of **DDT (dichlorodiphenyltrichloroethane)**. - His work was significant in combating insect-borne diseases like malaria, but he was not involved in the discovery of the malarial parasite. *Pampania* - This name does not correspond to any recognized figure in the discovery of the malarial parasite or its transmission. - This is a distractor option in the original examination question.

Q: The Hanging Drop method is primarily used for studying which of the following microorganisms?

Trichomonas vaginalis. ***Trichomonas vaginalis*** - The **hanging drop method** is excellent for observing the **motility** of this parasite, which is crucial for its identification due to its characteristic jerky, tumbling movement. - This method helps differentiate it from other non-motile organisms in vaginal fluid samples. *Plasmodium falciparum* - This parasite is primarily identified through examination of **blood smears** (thick and thin films) for its characteristic **intraerythrocytic stages** (rings, trophozoites, schizonts, gametocytes). - It is an **intracellular parasite** and does not exhibit free motility in a hanging drop preparation. *Toxoplasma gondii* - Diagnosis typically involves **serological tests** for antibodies or **PCR** for detecting parasitic DNA, as well as histological examination of tissue biopsies. - While it can move, it's an **obligate intracellular parasite** and is not primarily identified by its motility in a simple hanging drop preparation from clinical samples. *Cryptosporidium parvum* - This parasite is diagnosed by detecting its **oocysts in stool samples** using specialized staining techniques like **acid-fast stain** or immunofluorescence assays. - The oocysts are non-motile and are not identified using the hanging drop method.

Q: Rhabditiform larvae are seen in which of the following?

Strongyloides stercoralis. ***Strongyloides stercoralis*** - *Strongyloides stercoralis* is unique among intestinal nematodes in that it can produce **rhabditiform larvae** in the stool. These larvae can then mature into infective **filariform larvae** either in the soil or within the host. - The presence of **rhabditiform larvae in fresh stool samples** is a key diagnostic feature differentiating *Strongyloides* from other parasitic infections that typically shed eggs. *Taenia solium* - *Taenia solium* (pork tapeworm) is transmitted by **ingesting undercooked pork** containing cysticerci. - The parasite is diagnosed by finding **eggs or proglottids in stool**, not rhabditiform larvae. *Diphyllobothrium latum* - *Diphyllobothrium latum* (fish tapeworm) infects humans upon consumption of **undercooked or raw freshwater fish**. - Diagnosis is made by identifying characteristic **operculated eggs in stool samples**, which do not contain rhabditiform larvae. *Trichinella spiralis* - *Trichinella spiralis* causes trichinosis, usually acquired by eating **undercooked meat infected with encysted larvae**. - This parasite is typically diagnosed by **muscle biopsy** showing encysted larvae or serological tests, as it does not produce rhabditiform larvae in stool.

Q: Flame cells are primarily associated with which of the following organisms?

Trematodes. ***Correct: Trematodes*** - **Flame cells** are specialized **excretory/osmoregulatory structures** found in **Platyhelminthes (flatworms)**, which include **Trematodes** (flukes) and Cestodes (tapeworms). - These cells have a **tuft of cilia** that beat in a flickering motion (resembling a flame), driving fluid through tubules for waste removal and osmoregulation. - **Trematodes** are the most appropriate answer among the given options as they are medically important flatworms with flame cells. *Incorrect: Protozoa* - Protozoa are **single-celled organisms** that use **contractile vacuoles** for osmoregulation, not flame cells. - Examples include Entamoeba, Giardia, and Plasmodium species. *Incorrect: Nematodes* - **Nematodes** (roundworms) belong to phylum Nematoda and possess a distinct excretory system with **renette cells** or **H-shaped/tubular excretory canals**, not flame cells. - Examples include Ascaris, Enterobius, and hookworms. *Incorrect: None of the options* - This is incorrect because **Trematodes** do possess flame cells and is the correct answer among the choices provided.

Q: A 5-year-old child presented with fever, fatigue, abdominal pain, and vomiting. On further history evaluation, he had a habit of eating dog feces. Investigations show visceral larva migrans. Which animal is the most likely source of this infection in this child?

Dogs. ***Dogs*** - The history of eating **dog feces** directly links to the transmission of **Toxocara canis** eggs, the primary cause of visceral larva migrans. - Humans, especially children, can get infected by ingesting infective eggs from contaminated soil or dog feces. *Pig* - While pigs can harbor parasites like **Taenia solium** (pork tapeworm) and **Trichinella spiralis**, these do not typically cause visceral larva migrans. - Transmission from pigs usually involves consumption of undercooked pork, not direct contact with feces in the context of visceral larva migrans. *Monkeys* - Monkeys are not a common source of parasites causing human visceral larva migrans. - Parasitic infections associated with monkeys in humans are generally rare and usually specific to certain geographical contexts or exotic pet exposure. *Cows* - Cows can be hosts for parasites such as **Taenia saginata** (beef tapeworm), but they are not associated with visceral larva migrans caused by *Toxocara* species. - Ingestion of raw or undercooked beef is the typical mode of transmission for cow-related parasitic infections.

Q: Congenital toxoplasmosis: False is

IgA is more sensitive than IgM for detection. ***IgA is more sensitive than IgM for detection*** - This statement is **FALSE** - IgM and IgA have **similar sensitivity** (both around 20-30%) for detecting congenital toxoplasmosis - While IgA may persist longer than IgM, it is not definitively "more sensitive" for initial detection - Both tests are often used together to improve diagnostic accuracy in neonates *Diagnosed by detection of IgM in cord blood* - This is **TRUE** - detection of specific IgM antibodies in cord blood or neonatal serum is a standard diagnostic method - However, sensitivity is limited (20-30%), so negative IgM does not rule out infection - IgM does not cross the placenta, so its presence indicates fetal infection *Dye test is gold standard for IgG* - This is **TRUE** - the **Sabin-Feldman dye test** is the gold standard serological test for detecting IgG antibodies against *Toxoplasma gondii* - In newborns, maternal IgG crosses the placenta, so IgG alone cannot confirm congenital infection - Serial testing showing persistent or rising IgG titers beyond 12 months suggests congenital infection *Avidity testing is used to date the time of maternal infection* - This is **TRUE** - **IgG avidity testing** measures the binding strength of IgG antibodies - Low avidity indicates recent infection (within 3-4 months), high avidity suggests infection occurred >4 months ago - This helps assess the risk of congenital transmission by determining if maternal infection occurred during pregnancy

Q: Which organism is characterized by the Maltese cross formation?

Babesia microti. ***Babesia microti*** - The **Maltese cross formation** is a characteristic intraerythrocytic tetrad of merozoites, pathognomonic for *Babesia microti* infection in stained blood smears. - This formation is crucial for the microscopic diagnosis of **babesiosis**, a tick-borne parasitic disease. *Penicillium marneffei* - This is a **thermally dimorphic fungus** endemic to Southeast Asia, causing disseminated infections. - It is known for its intracellular yeast-like cells that reproduce by **fission**, not by forming Maltese crosses. *Cryptococcus neoformans* - This organism is a **yeast** known for its **polysaccharide capsule**, which is visualized with India ink stain. - It typically causes **meningitis** and pulmonary infections, especially in immunocompromised individuals, and does not form Maltese crosses. *Blastomyces dermatitidis* - This is a **dimorphic fungus** that causes **blastomycosis**, primarily affecting the lungs and skin. - It is characterized by relatively large, **broad-based budding yeast cells** in tissue samples and does not form Maltese crosses.

Q: Which of the following is a trematode?

Schistosoma mansoni. ***Schistosoma mansoni*** - This is a genus of **trematodes**, commonly known as blood flukes, which cause **schistosomiasis**. - Trematodes are characterized by their **leaf-like body shape** and often complex life cycles involving intermediate hosts like snails. *Diphyllobothrium latum* - This is a **cestode**, or tapeworm, known as the broad fish tapeworm. - Cestodes are typically **segmented flatworms** with a scolex, distinct from the unsegmented body of a trematode. *Taenia saginata* - This is another example of a **cestode**, specifically the beef tapeworm. - Like other cestodes, it has a **scolex and proglottids**, which are absent in trematodes. *Echinococcus granulosus* - This is a **cestode** that causes **hydatid disease** in humans. - It is a small tapeworm, and its larval stage forms **hydatid cysts**, which is a characteristic feature of cestodes.

Q: Toxoplasmosis in the fetus can be best confirmed by:

IgM antibodies against toxoplasmosis in the fetus. ***IgM antibodies against toxoplasmosis in the fetus*** - The presence of **IgM antibodies** in the fetus indicates an **active fetal immune response** to *Toxoplasma gondii*, meaning the fetus is currently infected. - Maternal IgM does not cross the placenta, so fetal IgM is a reliable marker of **congenital infection**. *IgG antibodies against toxoplasmosis in the mother* - Maternal **IgG antibodies** indicate either current or past exposure to *Toxoplasma gondii* in the mother. - These antibodies **cross the placenta** and can be present in the fetal circulation without indicating an active fetal infection. *IgG antibodies against toxoplasmosis in the fetus* - Fetal **IgG antibodies** are usually of maternal origin, having crossed the placenta, and therefore do not confirm an active fetal infection. - A positive IgG in the fetus only confirms maternal exposure, not necessarily fetal infection, unless there is a **rising titer** or specific patterns suggesting production by the fetal immune system. *IgM antibodies against toxoplasmosis in the mother* - Maternal **IgM antibodies** suggest a recent primary *Toxoplasma* infection in the mother. - While this indicates a risk of congenital transmission, it does not directly confirm the presence of **fetal infection**.

Question 1

Which type of malaria is most commonly associated with renal failure?

Accepted Answer

Falciparum

Answer

Vivax

Answer

Malariae

Answer

Ovale

Question 2

Who discovered the malarial parasite?

Accepted Answer

Charles Louis Alphonse Laveran

Answer

Ronald Ross

Answer

Paul Muller

Answer

Pampania

Question 3

The Hanging Drop method is primarily used for studying which of the following microorganisms?

Accepted Answer

Trichomonas vaginalis

Answer

Plasmodium falciparum

Answer

Toxoplasma gondii

Answer

Cryptosporidium parvum

Question 4

Rhabditiform larvae are seen in which of the following?

Accepted Answer

Strongyloides stercoralis

Answer

Taenia solium

Answer

Diphyllobothrium latum

Answer

Trichinella spiralis

Question 5

Flame cells are primarily associated with which of the following organisms?

Accepted Answer

Trematodes

Answer

Protozoa

Answer

Nematodes

Answer

None of the options

Question 6

A 5-year-old child presented with fever, fatigue, abdominal pain, and vomiting. On further history evaluation, he had a habit of eating dog feces. Investigations show visceral larva migrans. Which animal is the most likely source of this infection in this child?

Accepted Answer

Dogs

Answer

Pig

Answer

Monkeys

Answer

Cows

Question 7

Congenital toxoplasmosis: False is

Accepted Answer

IgA is more sensitive than IgM for detection

Answer

Diagnosed by detection of IgM in cord blood

Answer

Dye test is gold standard for IgG

Answer

Avidity testing is used to date the time of maternal infection

Question 8

Which organism is characterized by the Maltese cross formation?

Accepted Answer

Babesia microti

Answer

Penicillium marneffei

Answer

Cryptococcus neoformans

Answer

Blastomyces dermatitidis

Question 9

Which of the following is a trematode?

Accepted Answer

Schistosoma mansoni

Answer

Diphyllobothrium latum

Answer

Taenia saginata

Answer

Echinococcus granulosus

Question 10

Toxoplasmosis in the fetus can be best confirmed by:

Accepted Answer

IgM antibodies against toxoplasmosis in the fetus

Answer

IgG antibodies against toxoplasmosis in the mother

Answer

IgG antibodies against toxoplasmosis in the fetus

Answer

IgM antibodies against toxoplasmosis in the mother

Parasitology — MCQs

Parasitology — MCQs

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