Parasitology Practice Questions

Q: How do hookworms infect humans?

Contaminated soil. ***Contaminated soil*** - Hookworm larvae (filariform larvae) present in **contaminated soil** can penetrate unbroken human skin, typically through the feet. - This penetration is the primary mode of infection for humans in endemic areas. *Water* - While some parasitic protozoa are transmitted through contaminated water, hookworms primarily infect via **skin penetration** from soil. - Ingestion of contaminated water is not a common or direct route for hookworm infection. *Food* - Hookworm infection is generally not acquired through the ingestion of **contaminated food**. - Infections spread via food usually involve other parasitic organisms like *Taenia* species or *Ascaris lumbricoides* eggs. *Human feces* - Human feces contain hookworm eggs, which hatch into rhabditiform larvae and then mature into infectious filariform larvae in the soil. - However, direct contact with **feces** itself is not the immediate infective route; the larvae in the soil are the infective stage.

Q: An HIV patient is admitted with malabsorption, fever, chronic diarrhea, and acid-fast positive organism. What is the likely causative agent?

Isospora. ***Isospora (Cystoisospora belli)*** - **Cystoisospora belli** (formerly *Isospora belli*) is a coccidian parasite common in HIV patients, causing **chronic watery diarrhea**, fever, and malabsorption, especially when the CD4 count is low. - The diagnosis is confirmed by identifying **acid-fast oocysts** in stool samples, which is the key distinguishing feature in this case. - The **acid-fast positive** property makes this the definitive answer among the given options. *Giardia* - **Giardia lamblia** causes malabsorption and chronic diarrhea but is typically characterized by **fatty, foul-smelling stools** and abdominal cramping. - While it can be diagnosed with stool examination, its cysts and trophozoites are **not acid-fast**, which excludes it based on the clinical description. *Microsporidia* - Microsporidia species like **Enterocytozoon bieneusi** can cause chronic diarrhea and malabsorption in HIV patients. - However, they are **intracellular obligate parasites** detected using specialized stains (modified trichrome or calcofluor white) rather than acid-fast staining, making them inconsistent with the **acid-fast positive** finding. *E. histolytica* - **Entamoeba histolytica** causes amebiasis, which can manifest as **amebic dysentery** with bloody stools or chronic non-bloody diarrhea. - Its trophozoites and cysts are **not acid-fast**, and the malabsorption syndrome is less prominent than with Cystoisospora, excluding it from consideration.

Q: Eosinophilic pneumonia caused by Ascaris lumbricoides is known as?

Loeffler's syndrome. ***Loeffler's syndrome*** - **Loeffler's syndrome** specifically refers to a transient pulmonary infiltrative disease with **eosinophilia** in the blood and sputum, often caused by parasitic infections, particularly *Ascaris lumbricoides* [1]. - It is characterized by migratory pulmonary infiltrates and a self-limiting course, presenting during the **larval migration phase** of the *Ascaris* life cycle through the lungs [1]. *Mafucci syndrome* - **Mafucci syndrome** is a rare, non-hereditary disorder characterized by the presence of **multiple enchondromas** (benign cartilage tumors) and **hemangiomas** (benign vascular tumors). - It primarily affects the bones and soft tissues, with no direct association with eosinophilic pneumonia or parasitic infections. *Primary pulmonary eosinophilia* - **Primary pulmonary eosinophilia** is a broader term encompassing various conditions characterized by **eosinophilic infiltration** of the lungs without a clear identifiable cause at the outset. - While Loeffler's syndrome is a type of pulmonary eosinophilia, using the more specific term "Loeffler's syndrome" for *Ascaris*-induced eosinophilic pneumonia is more accurate due to the distinct clinical context. *Sweet syndrome* - **Sweet syndrome** (acute febrile neutrophilic dermatosis) is an inflammatory skin condition characterized by the sudden onset of **fever**, **leukocytosis**, and tender, red plaques or nodules, often associated with a preceding infection or malignancy. - It primarily affects the skin and is not directly linked to eosinophilic pneumonia or parasitic infections.

Q: Sandfly acts as a vector to all of the following diseases, except which of the following?

Onchocerciasis. ***Onchocerciasis*** - **Onchocerciasis**, or river blindness, is transmitted by the **blackfly (Simulium species)**, not the sandfly. - The disease is caused by the filarial nematode *Onchocerca volvulus*, which is introduced into humans through the bite of an infected blackfly. *Pappataci fever* - **Pappataci fever**, also known as sandfly fever, is a viral disease transmitted by the bite of infected **sandflies (Phlebotomus species)**. - This disease is characterized by a sudden onset of fever, headache, and muscle pain. *Kala-azar* - **Kala-azar**, or visceral leishmaniasis, is a severe form of **leishmaniasis** transmitted by the bite of an infected female **sandfly (Phlebotomus species)**. - It is caused by intracellular parasites of the genus *Leishmania* and affects internal organs. *Leishmaniasis* - **Leishmaniasis** in its various forms (cutaneous, mucocutaneous, visceral) is transmitted by the bite of an infected female **sandfly**. - The sandfly acts as the definitive host and vector for the *Leishmania* parasites.

Q: Which of the following statements is true regarding Wuchereria bancrofti?

Tail tip free from nuclei. ***Tail tip free from nuclei*** - The **microfilariae** of *Wuchereria bancrofti* are characterized by a **clean tail tip**, meaning there are no nuclei extending into the very end of the tail. - This feature is crucial for differentiating it from other microfilariae like *Brugia malayi*, which has two distinct nuclei in its tail tip. *Unsheathed* - *Wuchereria bancrofti* microfilariae are **sheathed**, meaning they retain an egg envelope as a loose covering. - An unsheathed microfilaria, like that of *Onchocerca volvulus*, lacks this outer covering. *Non-periodic* - *Wuchereria bancrofti* exhibits **nocturnal periodicity**, meaning its microfilariae are most abundant in the peripheral blood during the night. - Non-periodic microfilariae are found in the blood at any time of day, as seen with *Loa loa*. *None of the options* - This statement is incorrect because "Tail tip free from nuclei" is a true characteristic of *Wuchereria bancrofti* microfilariae.

Q: Which of the following does not penetrate the skin?

Taenia saginata. ***Taenia saginata*** - *Taenia saginata*, the **beef tapeworm**, is acquired by consuming **undercooked beef** containing infective cysts (cysticerci). - Its life cycle does not involve larval penetration of the skin; instead, infection occurs via the **oral route**. *Necator americanus* - *Necator americanus*, also known as the **New World hookworm**, typically infects humans through **skin penetration** by filariform larvae. - The larvae are often found in **contaminated soil** and penetrate the skin, usually of the feet. *Strongyloides stercoralis* - *Strongyloides stercoralis* larvae can penetrate unbroken skin, establishing infection through this route. - It is unique among intestinal nematodes for its ability to cause **autoinfection**, where larvae mature within the host and reinfect without leaving the host. *Ancylostoma duodenale* - *Ancylostoma duodenale*, the **Old World hookworm**, also infects humans when its **filariform larvae** penetrate intact skin, primarily from contact with contaminated soil. - These larvae then migrate through the bloodstream to the lungs and are eventually swallowed to mature in the intestines.

Q: Which of the following is seen encysted in skeletal muscle of humans?

Trichinella spiralis. ***Trichinella spiralis*** - This nematode causes **trichinellosis**, with its larvae forming the **classic encysted form** in **skeletal muscle** of humans. - The larvae form a distinctive **nurse cell-larva complex** in striated muscle, which is the **pathognomonic feature** of trichinellosis. - Ingestion of undercooked meat (especially pork) containing these **encysted larvae** is the primary mode of transmission. - This is the **textbook example** of skeletal muscle encystation in parasitology. *Entamoeba histolytica* - This is an **intestinal amoeba** that causes **amoebiasis**, affecting the colon and potentially leading to liver abscesses. - It does not encyst in skeletal muscle but forms **cysts** in the intestinal lumen for fecal-oral transmission. *Leishmania spp.* - These are **intracellular parasites** transmitted by **sandflies**, causing various forms of **leishmaniasis**. - They primarily infect **macrophages** in skin, mucous membranes, or visceral organs (liver, spleen), not skeletal muscle. *Toxoplasma gondii* - While this parasite can form **tissue cysts** containing bradyzoites in skeletal muscle, brain, and heart, skeletal muscle is **not its characteristic location**. - The **classic site** for *Toxoplasma* cysts is the **brain** (causing encephalitis in immunocompromised patients). - Unlike *Trichinella*, *Toxoplasma* muscle cysts are not the primary diagnostic or clinical feature of the infection.

Q: Which worm can reach the longest length?

T. Saginata. ***T. Saginata*** - The **beef tapeworm**, *Taenia saginata*, can reach impressive lengths of up to **25 meters** in the human intestine. - Its long, ribbon-like body consists of thousands of proglottids, each containing reproductive organs, allowing for extensive growth. *Hookworm* - Hookworms, such as *Ancylostoma duodenale* and *Necator americanus*, are relatively small, typically measuring only **0.8 to 1.3 cm**. - They are known for causing **iron deficiency anemia** due to chronic blood loss. *A. Lumbricoides* - *Ascaris lumbricoides*, the **giant intestinal roundworm**, is the largest intestinal nematode, but its maximum length is around **35-40 cm**. - While significant, this is considerably shorter than the tapeworm *T. saginata*. *T. solium* - *Taenia solium*, the **pork tapeworm**, typically reaches lengths of **2 to 8 meters**. - While long, it is generally **shorter than *T. saginata*** and is medically significant due to the risk of **neurocysticercosis**.

Q: Cerebral malaria is primarily caused by which of the following?

P. falciparum. ***P. falciparum*** - **P. falciparum** is the most virulent species of malaria parasites and is responsible for almost all cases of **severe malaria**, including cerebral malaria. - Its ability to cause **sequestration** of infected red blood cells in the microvasculature of the brain leads to impaired blood flow and neurological complications. - Accounts for **>90% of cerebral malaria cases** worldwide. *P. vivax* - While *P. vivax* can cause severe disease, it is generally **less virulent** than *P. falciparum* and rarely causes cerebral malaria. - *P. vivax* primarily causes benign tertian malaria and is known for its ability to form **hypnozoites** in the liver, leading to relapses. *P. ovale* - *P. ovale* is the **least common** form of human malaria and causes a mild form of the disease with symptoms similar to *P. vivax*. - It is **not associated** with severe complications like cerebral malaria. - Also forms **hypnozoites** and can cause relapses. *P. malariae* - *P. malariae* causes **quartan malaria** (72-hour fever cycle) and is the mildest form of human malaria. - It is **not associated** with cerebral malaria but can cause chronic infection and **nephrotic syndrome** in long-standing cases.

Q: Which parasite is most characteristically known for its larval forms residing primarily in muscle tissue?

Trichinella spiralis. ***Trichinella spiralis*** - This parasite is renowned for its **larval forms** that encyst primarily in **striated muscle tissue** of its hosts, causing trichinosis. - Humans typically acquire the infection by consuming **undercooked meat**, especially pork and wild game, containing these encysted larvae. *Taenia solium* - While *Taenia solium* can cause **cysticercosis** in humans, where larvae (cysticerci) encyst in tissues, their primary target is often the **central nervous system**, eyes, and subcutaneous tissue, rather than muscle as the predominant site. - Infection occurs by ingesting *T. solium* **eggs**, not larvae in meat, and pigs serve as the intermediate host for muscle cyst formation. *Echinococcus granulosus* - This parasite causes **hydatid disease** where large cysts (hydatid cysts) develop, most commonly in the **liver** and **lungs**, although they can occur in other organs. - The disease is acquired by ingesting **eggs** from dog feces, and the larval stage does not primarily reside in muscle tissue. *All of the options* - This option is incorrect because while *Taenia solium* and *Echinococcus granulosus* have larval stages that can reside in various tissues, only **Trichinella spiralis** is primarily characterized by its larvae encysting in muscle tissue.

Question 1

How do hookworms infect humans?

Accepted Answer

Contaminated soil

Answer

Water

Answer

Food

Answer

Human feces

Question 2

An HIV patient is admitted with malabsorption, fever, chronic diarrhea, and acid-fast positive organism. What is the likely causative agent?

Accepted Answer

Isospora

Answer

Giardia

Answer

Microsporidia

Answer

E. histolytica

Question 3

Eosinophilic pneumonia caused by Ascaris lumbricoides is known as?

Accepted Answer

Loeffler's syndrome

Answer

Mafucci syndrome

Answer

Primary pulmonary eosinophilia

Answer

Sweet syndrome

Question 4

Sandfly acts as a vector to all of the following diseases, except which of the following?

Accepted Answer

Onchocerciasis

Answer

Kala-azar

Answer

Pappataci fever

Answer

Leishmaniasis

Question 5

Which of the following statements is true regarding Wuchereria bancrofti?

Accepted Answer

Tail tip free from nuclei

Answer

Unsheathed

Answer

Non-periodic

Answer

None of the options

Question 6

Which of the following does not penetrate the skin?

Accepted Answer

Taenia saginata

Answer

Necator americanus

Answer

Strongyloides stercoralis

Answer

Ancylostoma duodenale

Question 7

Which of the following is seen encysted in skeletal muscle of humans?

Accepted Answer

Trichinella spiralis

Answer

Entamoeba histolytica

Answer

Leishmania spp.

Answer

Toxoplasma gondii

Question 8

Which worm can reach the longest length?

Accepted Answer

T. Saginata

Answer

Hookworm

Answer

A. Lumbricoides

Answer

T. solium

Question 9

Cerebral malaria is primarily caused by which of the following?

Accepted Answer

P. falciparum

Answer

P. vivax

Answer

P. ovale

Answer

P. malariae

Question 10

Which parasite is most characteristically known for its larval forms residing primarily in muscle tissue?

Accepted Answer

Trichinella spiralis

Answer

Taenia solium

Answer

Echinococcus granulosus

Answer

All of the options

Parasitology — MCQs

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