Parasitology Practice Questions

Q: Which of the following is the only ovoviviparous parasite among the options provided?

Strongyloides. ***Strongyloides*** - *Strongyloides stercoralis* stands out as the only **ovoviviparous** parasite among the options, meaning that its eggs hatch while still inside the uterus of the female worm. - The female worm lays **larvated eggs** that quickly hatch into **rhabditiform larvae** in the intestine or intestinal wall, which are then passed in the feces. *Ascaris* - *Ascaris lumbricoides* is **oviparous**, laying **unembryonated eggs** that are passed in the feces and require a period of maturation in the soil to become infective. - The eggs are robust and can survive for long periods in the environment before they are ingested. *Enterobius* - *Enterobius vermicularis* (pinworm) is also **oviparous**, with the female worm migrating to the perianal region to lay **embryonated eggs** on the skin. - These eggs are immediately infective to humans upon ingestion. *Ancylostome* - Ancylostomes (hookworms) are **oviparous** and lay **thin-shelled eggs** that are passed in the feces and hatch into rhabditiform larvae in the soil. - These larvae then develop into infective **filariform larvae** that penetrate the skin.

Q: What is the infective form of Trypanosoma brucei?

Trypomastigote. ***Trypomastigote*** - The **trypomastigote** is the infective form of *Trypanosoma brucei* transmitted to humans by the **tsetse fly** bite. - In the human host, trypomastigotes multiply in the **blood and lymphatic system**, eventually invading the central nervous system. *Amastigote form* - The **amastigote** form is characteristic of *Trypanosoma cruzi* and *Leishmania* species, not *Trypanosoma brucei*. - **Amastigotes** are found intracellularly and lack a flagellum, responsible for replication within host cells for these other parasites. *Egg stage* - *Trypanosoma brucei* is a **protozoan parasite** and does not have an **egg stage** in its life cycle. - Egg stages are typical for helminths, such as **tapeworms** or **flukes**. *No infective form* - This statement is incorrect; **all parasitic organisms** must have an infective stage to be transmitted to their hosts. - The **trypomastigote** is specifically adapted for transmission and survival in the human host and vector.

Q: JSB stain is used for which parasite?

Filaria. ***Filaria*** - The **JSB stain (Jaswant Singh Battacharya stain)** is a rapid Romanowsky-type stain specifically developed for the diagnosis of **microfilariae** in blood films. - It allows for clear visualization of the sheaths and nuclei of microfilariae, which is crucial for species identification and diagnosis of **filariasis**. *Malaria* - **Giemsa stain** is the gold standard for identifying malaria parasites in thick and thin blood smears, not JSB stain. - Giemsa allows for detailed morphological differentiation of malaria species and stages within **red blood cells**. *Kala azar* - **Kala-azar (visceral leishmaniasis)** is diagnosed by detecting **Leishman bodies (amastigotes)** in bone marrow, splenic, or lymph node aspirates. - Stains like **Giemsa** or **Leishman stain** are traditionally used for visualizing these amastigotes. *Sleeping sickness* - **Sleeping sickness (African trypanosomiasis)** is diagnosed by identifying **trypomastigotes** in blood smears, lymph node aspirates, or cerebrospinal fluid. - **Giemsa stain** is commonly used for the microscopic examination of these specimens to detect the parasites.

Q: Maximum density of microfilariae in blood is reported to be between -

11 pm to 2 am. ***11 pm to 2 am*** - This period aligns with the **nocturnal periodicity** of *Wuchereria bancrofti* and *Brugia malayi* microfilariae, which are the most common causes of filariasis. - The microfilariae migrate to the **peripheral circulation** during these hours, making it the optimal time for blood smear collection for diagnosis. *9 pm to 11 pm* - While still within the active period for microfilarial migration, the **peak density** is generally observed slightly later. - Blood drawn during this time might show microfilariae, but in lower concentrations compared to the peak. *8 pm to 10 pm* - This timing is generally a little too early to consistently capture the **highest microfilarial load** in nocturnal periodic infections. - The microfilariae are still in the process of migrating from deeper tissues to the peripheral blood. *2 am to 5 am* - By this time, the microfilarial density in the peripheral blood of **nocturnal periodic species** usually starts to decline. - While some microfilariae may still be present, the count would likely be lower than during the earlier peak hours.

Q: A 4 year old child presents with acute watery diarrhea and abdominal cramps. Stool microscopy reveals trophozoites with falling leaf motility. What is the etiological agent?

Giardia lamblia. **Giardia lamblia** - The presence of **trophozoites** with characteristic **falling leaf motility** in stool microscopy is pathognomonic for **Giardia lamblia** infection. - **Giardiasis** commonly causes **acute watery diarrhea** and **abdominal cramps** in children, often acquired through contaminated water or food. *Entamoeba histolytica* - **Entamoeba histolytica** causes **amoebic dysentery**, characterized by bloody diarrhea, unlike the watery diarrhea described. - Its trophozoites exhibit **directional motility** with pseudopods and may contain ingested red blood cells, not falling leaf motility. *Trichomonas tenax* - **Trichomonas tenax** is found in the **oral cavity** and is not associated with intestinal infections or diarrhea. - Its typical habitat and clinical presentation are entirely different from the symptoms described. *Balantidium coli* - **Balantidium coli** is a large, ciliated protozoan whose trophozoites have a **distinctive kidney-shaped macronucleus** and rotary motility with cilia. - It causes **balantidiasis**, which can range from asymptomatic to dysentery, but its trophozoite morphology and motility are distinct from falling leaf.

Q: Which of the following statements about Helminths is false?

Body cavity is present in trematodes. ***Body cavity is present in trematodes*** - Trematodes are **flatworms** (Platyhelminthes), which are **acoelomate**, meaning they lack a true body cavity or coelom. - Their internal organs are embedded in a **parenchymal tissue** rather than being suspended within a fluid-filled cavity. *Alimentary canal is complete in Nematodes* - **Nematodes** (roundworms) possess a **complete alimentary canal**, with a distinct mouth, intestine, and anus. - This allows for **unidirectional flow of food** and waste through their digestive system. *Nematodes have separate sexes* - **Nematodes** are generally **dioecious**, meaning they have separate male and female individuals. - This sexual dimorphism is a characteristic feature for most species within this phylum. *Alimentary canal is Present but incomplete* - The statement refers to the digestive system of **Platyhelminthes** (flatworms) like trematodes and cestodes, where the alimentary canal is present but **incomplete** (lacking an anus). - This means they have a **single opening** that serves as both mouth and anus for digestion.

Q: Which of the following substances is toxic to parasites?

Peroxidase. ***Peroxidase*** - **Peroxidase** enzymes, especially those produced by **eosinophils**, generate toxic oxygen metabolites and hypohalous acids that are highly effective at damaging and killing parasites. - This enzyme plays a crucial role in the host's defense against larger parasites, such as **helminths (worms)**. *Interferon-alpha* - **Interferon-alpha** is an important cytokine primarily known for its **antiviral effects** and its role in activating natural killer (NK) cells. - While it modulates immune responses, it does not directly act as a toxic substance to parasites. *IL-2 (Interleukin-2)* - **IL-2** is a growth factor that primarily promotes the **proliferation and differentiation of T cells**, enhancing adaptive immune responses. - It does not directly kill parasites but rather supports the immune cells involved in parasite clearance. *IL-6 (Interleukin-6)* - **IL-6** is a pleiotropic cytokine involved in **inflammation, acute phase responses**, and the differentiation of B cells and T cells. - While it contributes to overall immune regulation, it lacks direct parasiticidal activity.

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: What is the correct sequence of the sexual cycle in malaria?

Gametocytes to sporozoites. ***Gametocytes to sporozoites*** - The sexual cycle begins when a mosquito ingests **gametocytes** during a blood meal. - These gametocytes develop into **gametes**, which fuse to form a **zygote**. The zygote matures into an **oocyst** and then releases **sporozoites**, which migrate to the mosquito's salivary glands, ready to infect a new human host. *Gametocytes to gametes* - This is an initial step within the sexual cycle where gametocytes differentiate into **male and female gametes**, respectively. - However, it's not the complete *sequence* of the sexual cycle, as it omits subsequent crucial stages like fertilization and sporozoite formation. *Sporozoites to gametocytes* - **Sporozoites** are injected into a human host and initiate the asexual cycle by infecting liver cells, then red blood cells. - **Gametocytes** are formed later during the asexual cycle in the human host, ready to be picked up by another mosquito; this sequence describes part of the human infection, not the sexual cycle in the mosquito. *Gametes to zygote* - This step represents **fertilization**, where male and female gametes fuse, forming a **zygote** in the mosquito gut. - While essential, it is only one part of the overall sexual cycle and doesn't encompass the full transformation from gametocytes to infective sporozoites.

Question 1

Which of the following is the only ovoviviparous parasite among the options provided?

Accepted Answer

Strongyloides

Answer

Ascaris

Answer

Enterobius

Answer

Ancylostoma

Question 2

What is the infective form of Trypanosoma brucei?

Accepted Answer

Trypomastigote

Answer

Amastigote form

Answer

Egg stage

Answer

No infective form

Question 3

JSB stain is used for which parasite?

Accepted Answer

Filaria

Answer

Kala azar

Answer

Sleeping sickness

Answer

Malaria

Question 4

Maximum density of microfilariae in blood is reported to be between -

Accepted Answer

11 pm to 2 am

Answer

9 pm to 11 pm

Answer

8 pm to 10 pm

Answer

2 am to 5 am

Question 5

A 4 year old child presents with acute watery diarrhea and abdominal cramps. Stool microscopy reveals trophozoites with falling leaf motility. What is the etiological agent?

Accepted Answer

Giardia lamblia

Answer

Trichomonas tenax

Answer

Balantidium coli

Answer

Entamoeba histolytica

Question 6

Which of the following statements about Helminths is false?

Accepted Answer

Body cavity is present in trematodes

Answer

Alimentary canal is complete in Nematodes

Answer

Nematodes have separate sexes

Answer

Alimentary canal is present but incomplete in trematodes

Question 7

Persons with heterozygous sickle cell trait are protected from infection by:

Accepted Answer

P. falciparum

Answer

Pneumococcus

Answer

P. vivax

Answer

Salmonella

Question 8

Which of the following substances is toxic to parasites?

Accepted Answer

Peroxidase

Answer

Interferon-alpha

Answer

IL-2 (Interleukin-2)

Answer

IL-6 (Interleukin-6)

Question 9

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 10

What is the correct sequence of the sexual cycle in malaria?

Accepted Answer

Gametocytes to sporozoites

Answer

Sporozoites to gametocytes

Answer

Gametocytes to gametes

Answer

Gametes to zygote

Parasitology — MCQs

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