Parasitology Practice Questions

Q: Which stage of Leishmania is found in spleen aspirate of a patient?

Amastigote stage. ***Amastigote stage*** - The **amastigote stage** is the **intracellular, non-flagellated form** of Leishmania that replicates within **macrophages** of the vertebrate host, including humans. - In visceral leishmaniasis, these **amastigotes** are abundant in organs like the **spleen**, liver, and bone marrow, making them detectable in spleen aspirates. *Promastigote stage* - The **promastigote stage** is the **extracellular, flagellated form** of Leishmania found in the digestive tract of the **sand fly vector**. - It is typically **not found** in human tissues or spleen aspirates. *Epimastigote stage* - The **epimastigote stage** is a flagellated form of **trypanosomes** (e.g., *Trypanosoma cruzi*) but **not Leishmania**. - It is found in the **vector's gut** for trypanosomes and is not part of the Leishmania life cycle in humans. *Trypomastigote stage* - The **trypomastigote stage** is another flagellated form characteristic of **trypanosomes** (e.g., *Trypanosoma cruzi* and *Trypanosoma brucei*). - It circulates in the **blood of the vertebrate host** for trypanosomes and is not observed in Leishmania infections within human organs like the spleen.

Q: Which of the following is the causative organism of Acanthamoeba keratitis?

Acanthamoeba. ***Acanthamoeba*** - **Acanthamoeba keratitis** is a serious and painful infection of the eye's cornea caused by species of the **free-living amoeba Acanthamoeba**. - This infection is commonly associated with contact lens wear, particularly when proper hygiene and disinfection practices are not followed. *Plasmodium* - **Plasmodium** species are the causative agents of **malaria**, a mosquito-borne infectious disease affecting red blood cells and the liver. - It does not cause eye infections like keratitis and is transmitted through the bite of an infected Anopheles mosquito. *Toxoplasma* - **Toxoplasma gondii** is an intracellular parasitic protozoon that causes **toxoplasmosis**, which can manifest as chorioretinitis, encephalitis, or lymphadenopathy. - While it can affect the eye (**ocular toxoplasmosis**), it causes retinitis or chorioretinitis, not keratitis. *W. bancrofti* - **Wuchereria bancrofti** is a filarial nematode that causes **lymphatic filariasis**, an infection leading to elephantiasis and other lymphatic disorders. - It primarily affects the lymphatic system and subcutaneous tissues, not the cornea.

Q: Calabar swelling is produced by?

Loa loa. ***Loa loa*** - **Calabar swellings** are a pathognomonic feature of **loiasis**, caused by the **filarial nematode** *Loa loa*. - These are **transient, non-tender, subcutaneous edemas** that can reappear in different locations due to the migration of the adult worm. *Onchocerca volvulus* - This parasite causes **onchocerciasis** (river blindness), which is characterized by **subcutaneous nodules** (onchocercomas) and **dermatitis**, not migratory swellings. - Ocular involvement leading to blindness is a significant complication. *Brugia malayi* - This is one of the causes of **lymphatic filariasis**, primarily leading to **lymphedema** and **elephantiasis** in the lower limbs. - It does not typically cause Calabar swellings. *Wuchereria bancrofti* - This is the most common cause of **lymphatic filariasis**, also resulting in **lymphedema** and **elephantiasis**, particularly in the legs and genitalia. - It is not associated with migratory Calabar swellings.

Q: Tropical pulmonary eosinophilia is specifically associated with which of the following conditions?

Occult filariasis. ***Occult filariasis*** - **Tropical pulmonary eosinophilia (TPE)** is a hypersensitivity reaction specifically caused by infection with **filarial parasites**, primarily *Wuchereria bancrofti* or *Brugia malayi*, in individuals living in endemic areas [1]. - The disease involves migration of microfilariae to the lungs, stimulating a strong **IgE-mediated immune response** leading to high eosinophil counts in the blood and lung tissue [1]. *Cerebral malaria* - **Cerebral malaria** is caused by the parasite *Plasmodium falciparum* and is characterized by neurological complications, not pulmonary eosinophilia. - It involves sequestration of parasitized red blood cells in the brain's microvasculature, leading to coma and other neurological symptoms. *Pneumonic plague* - **Pneumonic plague** is a severe bacterial infection caused by *Yersinia pestis*, affecting the lungs and leading to pneumonia. - It is not associated with eosinophilia and requires antibiotic treatment. *Asthmatic bronchitis* - **Asthmatic bronchitis** is a general term referring to inflammation of the bronchi combined with features of asthma, often triggered by allergens, irritants, or infections. - While it can involve eosinophilic inflammation, it is a broader syndrome and not specifically linked to occult filariasis in the way TPE is.

Q: Mucocutaneous leishmaniasis is caused by which of the following?

L. braziliensis. ***L. braziliensis*** - *Leishmania braziliensis* is the primary causative agent of **mucocutaneous leishmaniasis**, particularly in the New World (Central and South America). - This form of leishmaniasis is characterized by spread from the initial skin lesion to the **mucous membranes**, leading to progressive destructive lesions of the nose, mouth, and throat (espundia). - It causes significant morbidity due to tissue destruction and disfigurement. *L. tropica* - *Leishmania tropica* is typically associated with **cutaneous leishmaniasis** (Old World cutaneous leishmaniasis). - It causes localized skin lesions, often referred to as **"oriental sore,"** but generally does not progress to mucocutaneous forms. - Endemic in Mediterranean, Middle East, and parts of Asia. *L. donovani* - *Leishmania donovani* is the primary cause of **visceral leishmaniasis**, also known as **kala-azar**. - This severe systemic form affects internal organs like the spleen, liver, and bone marrow. - It is not associated with mucocutaneous lesions and presents with fever, hepatosplenomegaly, and pancytopenia. *L. mexicana* - *Leishmania mexicana* is a cause of **cutaneous leishmaniasis** in the New World, often presenting as chronic skin ulcers. - Although it can sometimes cause diffuse cutaneous leishmaniasis, it is **not** the primary species associated with mucocutaneous leishmaniasis leading to destructive mucosal lesions. - Endemic in Mexico, Central America, and northern South America.

Q: In which disease are tachyzoites commonly observed?

Toxoplasma. ***Toxoplasma*** - **Tachyzoites** are the rapidly multiplying form of **_Toxoplasma gondii_** that are responsible for acute infection and tissue damage. - They are commonly observed during the active phase of **toxoplasmosis**, especially in immunosuppressed individuals or during congenital infection. *Toxocara* - **Toxocara** species (e.g., **_Toxocara canis_**) cause toxocariasis, characterized by the migration of larval forms, not tachyzoites, through host tissues. - The diagnosis of **toxocariasis** is typically made by serology detecting antibodies to larval antigens. *Pulmonary eosinophilia* - **Pulmonary eosinophilia** is a syndrome characterized by an abnormal accumulation of **eosinophils** in the lungs, often due to parasitic infections (e.g., Strongyloides, ascaris) or allergic reactions. - It is a host response and does not involve the observation of specific parasitic forms like tachyzoites in the lung tissue itself. *Ascaris* - **Ascaris lumbricoides** is a large intestinal nematode that causes ascariasis; its life cycle involves eggs, larval stages (passed in feces), and adult worms. - The disease is diagnosed by finding **ova in stool samples** or observing adult worms, not tachyzoites.

Q: Which of the following protozoan parasites does not have a cystic form in humans?

Trichomonas. ***Trichomonas*** - *Trichomonas vaginalis* exists only as a **trophozoite** form, lacking a protective cystic stage, which limits its survival outside the host. - Its transmission typically occurs directly through **sexual contact**, as it cannot survive in the environment. *E.histolytica* - *Entamoeba histolytica* forms **cysts** that are resistant to environmental conditions and are the infective stage, transmitted via the fecal-oral route. - These cysts allow the parasite to survive stomach acid and excyst in the small intestine to release trophozoites. *Giardia* - *Giardia lamblia* has a **resistant cyst form** that is responsible for environmental survival and transmission through contaminated water or food. - The cysts are hardy and can survive for extended periods, facilitating the spread of giardiasis. *Toxoplasma* - *Toxoplasma gondii* exists in various forms, including environmentally resistant **oocysts** (shed in cat feces) and **tissue cysts** found in infected meat. - These cystic forms are crucial for its transmission to humans, either through ingestion of contaminated food/water or undercooked meat.

Q: A patient presents with headache, high fever, and meningismus. Within 3 days, he becomes unconscious. What is the most probable causative agent? Refer to the image for diagnosis.

Naegleria fowleri infection. ***Naegleria fowleri infection*** - The image shows **trophozoites of *Naegleria fowleri***, characterized by their amoeboid shape and often prominent nucleolus visible within the nucleus. - The clinical presentation of rapidly progressing **headache, high fever, meningismus**, and quick deterioration to unconsciousness (within 3 days) is classic for **Primary Amoebic Meningoencephalitis (PAM)** caused by *Naegleria fowleri*. *Acanthamoeba infection* - *Acanthamoeba* causes **Granulomatous Amoebic Encephalitis (GAE)**, which typically has a more **subacute to chronic course** (weeks to months) rather than the rapid progression described. - While *Acanthamoeba* can cause CNS infections and trophozoites can be seen, the rapid clinical decline points against GAE. *Trypanosoma infection* - **African trypanosomiasis (sleeping sickness)** is caused by *Trypanosoma brucei* and features symptoms like fever, headache, and neurological signs, but its progression is usually **slower and more chronic** (weeks to months or even years) compared to the acute presentation here. - **American trypanosomiasis (Chagas disease)** can cause neurological symptoms, but it's often linked to the chronic phase of the disease or congenital infection, and the rapid progression of fulminant meningoencephalitis is not typical. *Entamoeba infection* - While *Entamoeba histolytica* can cause **amoebic liver abscesses** and, rarely, direct brain abscesses, it typically does not present as an acute, fulminant meningoencephalitis like that caused by *Naegleria fowleri*. - The morphology of *Entamoeba* trophozoites, with a single, small, central karyosome in the nucleus, also differs from the features seen in the image.

Q: Vector for transmission of sleeping sickness?

Tse-tse fly. ***Tse-tse fly*** - The **tsetse fly** (genus *Glossina*) is the exclusive biological vector for the transmission of **African trypanosomiasis**, also known as sleeping sickness. - The fly transmits the parasites (*Trypanosoma brucei*) to humans through its bite after becoming infected by feeding on an infected host. *Sandfly* - **Sandflies** (family Psychodidae) are vectors for diseases such as **leishmaniasis** and **Bartonellosis** (Carrion's disease), but not sleeping sickness. - They are typically smaller than tsetse flies and have distinct hairy bodies and wings. *Black fly* - **Black flies** (family Simuliidae) are vectors for **onchocerciasis** (river blindness), caused by the *Onchocerca volvulus* parasite. - They are characterized by their hump-backed appearance and prefer to breed in fast-flowing rivers. *Hard tick* - **Hard ticks** (family Ixodidae) are vectors for a variety of diseases, including **Lyme disease**, **Rocky Mountain spotted fever**, and **Crimean-Congo hemorrhagic fever**. - They are arachnids, not insects, and transmit pathogens through prolonged feeding.

Q: A patient presents with fever. Peripheral smear shows band across the erythrocytes. What is the diagnosis?

P. malariae. ***P. malariae*** - The presence of a **band across the erythrocytes** on a peripheral smear is a classic morphological feature of the **trophozoite stage of *Plasmodium malariae***. - This characteristic "band form" helps distinguish *P. malariae* from other *Plasmodium* species. *P. falciparum* - Characteristically presents with **ring forms** and **gametocytes (banana-shaped)** in red blood cells on peripheral smears. - It does not typically form **bands across erythrocytes**. *P. vivax* - Known for forming large, amoeboid trophozoites and schizonts in **enlarged red blood cells** with **Schüffner's dots**. - It does not exhibit the specific "band form" seen in *P. malariae*. *P. ovale* - Infestations often present with **oval-shaped erythrocytes** and contain **Schüffner's dots**. - While it has some similarities to *P. vivax*, it does not show the distinctive band form on the smear.

Question 1

Which stage of Leishmania is found in spleen aspirate of a patient?

Accepted Answer

Amastigote stage

Answer

Promastigote stage

Answer

Epimastigote stage

Answer

Trypomastigote stage

Question 2

Which of the following is the causative organism of Acanthamoeba keratitis?

Accepted Answer

Acanthamoeba

Answer

Plasmodium

Answer

Toxoplasma

Answer

W. bancrofti

Question 3

Calabar swelling is produced by?

Accepted Answer

Loa loa

Answer

Brugia malayi

Answer

Onchocerca volvulus

Answer

Wuchereria bancrofti

Question 4

Tropical pulmonary eosinophilia is specifically associated with which of the following conditions?

Accepted Answer

Occult filariasis

Answer

Asthmatic bronchitis

Answer

Pneumonic plague

Answer

Cerebral malaria

Question 5

Mucocutaneous leishmaniasis is caused by which of the following?

Accepted Answer

L. braziliensis

Answer

L. tropica

Answer

L. donovani

Answer

L. mexicana

Question 6

In which disease are tachyzoites commonly observed?

Accepted Answer

Toxoplasma

Answer

Toxocara

Answer

Pulmonary eosinophilia

Answer

Ascaris

Question 7

Which of the following protozoan parasites does not have a cystic form in humans?

Accepted Answer

Trichomonas

Answer

E.histolytica

Answer

Giardia

Answer

Toxoplasma

Question 8

A patient presents with headache, high fever, and meningismus. Within 3 days, he becomes unconscious. What is the most probable causative agent? Refer to the image for diagnosis.

Accepted Answer

Naegleria fowleri infection

Answer

Acanthamoeba infection

Answer

Trypanosoma infection

Answer

Entamoeba infection

Question 9

Vector for transmission of sleeping sickness?

Accepted Answer

Tse-tse fly

Answer

Sandfly

Answer

Black fly

Answer

Hard tick

Question 10

A patient presents with fever. Peripheral smear shows band across the erythrocytes. What is the diagnosis?

Accepted Answer

P. malariae

Answer

P. falciparum

Answer

P. vivax

Answer

P. ovale

Parasitology — MCQs

Parasitology — MCQs

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