Parasitology Practice Questions

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: Cutaneous larva migrans is due to ?

Ancylostoma braziliense. ***Ancylostoma braziliense*** - **Cutaneous larva migrans** is primarily caused by the larvae of **dog and cat hookworms**, especially *Ancylostoma braziliense*. - Humans become **accidental hosts** when these larvae penetrate the skin but cannot complete their life cycle, leading to **serpiginous tracks**. *W. bancrofti* - This parasite, **Wuchereria bancrofti**, is a filarial nematode that causes **lymphatic filariasis** (elephantiasis). - Its effects are characterized by **lymphedema** and **hydrocele**, not migrating skin lesions. *B. Malayi* - **Brugia malayi** is another filarial nematode responsible for **lymphatic filariasis** in humans, similar to *W. bancrofti*. - It primarily causes **swelling of the limbs** and scrotum, not cutaneous larva migrans. *D. medinensis* - **Dracunculus medinensis** is the parasite that causes **dracunculiasis**, also known as **Guinea worm disease**. - This infection is characterized by a **painful blister** and subsequent emergence of the adult worm, which is distinct from creeping eruptions.

Q: Trophozoites in stool are characteristically seen in which of the following conditions?

**Note:** This question has significant issues. Trophozoites in stool are characteristically seen in **protozoal infections** such as *Entamoeba histolytica* (amoebiasis), *Giardia lamblia*, or *Balantidium coli* [1][2] - none of which are listed as options. ***None of the given options is medically accurate*** for characteristic trophozoites in stool. However, if forced to choose from these options: *Ascariasis* - **Ascariasis** is caused by the nematode *Ascaris lumbricoides* - Diagnosis is by identifying **ova (eggs)** in stool, not trophozoites - Trophozoites are protozoal forms, not associated with helminthic infections [2] *Strongyloidiasis* - Caused by *Strongyloides stercoralis* (nematode) - Typically diagnosed by finding **rhabditiform or filariform larvae** in stool - Not characterized by trophozoites in routine stool examination *Eosinophilic gastroenteritis* - Inflammatory condition with **eosinophilic infiltration** of GI tract - Not a parasitic infection - No trophozoites present - diagnosis is by endoscopic biopsy showing eosinophils *Allergic colitis* - Inflammatory condition related to **food allergies** (common in infants) - Presents with blood and mucus in stool with eosinophilia - Not an infectious process - no trophozoites present **Clinical Pearl:** Trophozoites (motile feeding stage of protozoa) in stool are diagnostic of **acute intestinal protozoal infections** like amoebiasis or giardiasis, where they must be identified in fresh, warm stool samples as they rapidly deteriorate [1][2]. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Alimentary System Disease, pp. 364-365. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Gastrointestinal Tract, pp. 801-802.

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: Child having perianal pruritus with the following eggs is due to -

E. vermicularis. ***E. vermicularis*** - **Enterobius vermicularis**, or **pinworm**, is a common cause of **perianal pruritus** in children, particularly at night, due to the female worms migrating to the perianal region to lay eggs. - The characteristic eggs are **oval, flattened on one side**, and are typically identified via the **scotch tape test** around the anus. *Ascaris* - **Ascaris lumbricoides** causes **ascariasis**, which usually presents with **gastrointestinal symptoms** or **pulmonary symptoms** during larval migration, not typically perianal pruritus. - Their eggs are characteristically **mammillated** (roughened outer layer) and typically found in **feces**, not perianal region. *Ancylostoma duodenale* - **Ancylostoma duodenale** causes **hookworm infection**, leading to **iron deficiency anemia** due to blood loss in the intestines. - Hookworm eggs are characteristically **oval, thin-shelled**, and contain a developing **larva**, found in feces. *S. stercoralis* - **Strongyloides stercoralis** causes **strongyloidiasis**, which can present with skin manifestations (larva currens), gastrointestinal issues, or pulmonary symptoms. - It is unique because it causes **auto-infection** and primarily diagnostic stages are **rhabditiform larvae** in stool, not eggs, although eggs are rarely seen in stool.

Q: Infective form of Hookworms?

Filariform larva. ***Filariform larva*** - The **filariform larva (L3)** is the infective stage of hookworms, capable of penetrating intact skin. - Upon penetration, these larvae migrate through the bloodstream to the lungs, then up the bronchial tree to be swallowed, eventually maturing in the intestines. *Egg* - Hookworm **eggs** are passed in the feces of infected individuals and are not infective to humans directly. - They require favorable conditions (warm, moist soil) to embryonate and hatch into rhabditiform larvae. *Rhabditiform larva* - The **rhabditiform larva (L1)** is the first larval stage that hatches from the egg in the soil. - It is a non-infective, free-living stage that feeds on bacteria and molts twice to become the infective filariform larva. *Adult worm* - **Adult worms** reside in the small intestine of the host and are not the infective form. - They attach to the intestinal mucosa and feed on blood, causing the characteristic anemia associated with hookworm infection.

Q: Cylindrical helminths are -

Roundworms. ***Roundworms*** - **Roundworms**, also known as **nematodes**, are characterized by their **cylindrical body shape**. - Their unsegmented, tapered bodies distinguish them from flatworms like tapeworms and flukes. *Tapeworms* - **Tapeworms**, or **cestodes**, have **flat, ribbon-like bodies** segmented into proglottids. - They are not cylindrical but rather dorsoventrally flattened. *Flukes* - **Flukes**, or **trematodes**, have **flat, leaf-shaped bodies**, which are not cylindrical. - Their morphology includes suckers for attachment and they are not segmented. *Hookworms* - **Hookworms** are a type of **roundworm** (nematode), which means they are cylindrical. However, "Roundworms" is a broader and more accurate classification for the general term "cylindrical helminths." - While hookworms are indeed cylindrical, the option "Roundworms" encompasses all such cylindrical helminths, making it a more general and appropriate answer.

Q: Consumption of uncooked pork is likely to cause which of the following helminthic disease -

Taenia solium. ***Taenia solium*** - Infection with **_Taenia solium_** (pork tapeworm) occurs by consuming raw or undercooked **pork** containing **cysticerci** (larval cysts). - This can lead to **taeniasis** (intestinal tapeworm infection) and, if humans ingest the eggs, **cysticercosis**, a more severe disease involving larval cysts in tissues like the brain. *Taenia saginata* - **_Taenia saginata_** (beef tapeworm) is acquired by eating raw or undercooked **beef** containing larval cysts, not pork. - While it causes gastrointestinal symptoms, it does not typically lead to systemic cysticercosis in humans. *Trichuris trichiura* - **_Trichuris trichiura_** (whipworm) infection is caused by ingesting **embryonated eggs** from contaminated soil, typically associated with poor sanitation. - It is not transmitted through the consumption of undercooked meat. *None of the options* - This option is incorrect because **_Taenia solium_** is definitively associated with the consumption of uncooked pork.

Q: What does the hookworm primarily feed on?

Blood from intestinal mucosa. ***Blood from intestinal mucosa*** - Hookworms attach to the **intestinal wall** and ingest host blood, leading to blood loss and potential **anemia**. - They produce **anticoagulants** to facilitate continuous feeding from the mucosal capillaries. *Plasma proteins* - While plasma contains proteins, hookworms primarily feed directly on **whole blood**, not just isolated plasma proteins. - Feeding mainly on plasma proteins would not explain the significant **iron-deficiency anemia** associated with hookworm infection. *Lymphatic fluid* - Hookworms reside in the **small intestine** and do not typically feed on lymphatic fluid. - Other parasites, like **filarial worms**, are known to inhabit and obstruct the lymphatic system. *Interstitial fluid* - Interstitial fluid is found in the spaces between cells; hookworms feed from the **vascular supply** within the intestinal mucosa. - Feeding on interstitial fluid would not cause the characteristic **blood loss** seen in hookworm infections.

Question 1

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 2

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 3

Cutaneous larva migrans is due to ?

Accepted Answer

Ancylostoma braziliense

Answer

W.bancrofti

Answer

B. Malayi

Answer

D. medinensis

Question 4

Trophozoites in stool are characteristically seen in which of the following conditions?

Answer

Ascariasis

Answer

Strongyloidiasis

Answer

Allergic colitis

Answer

Eosinophilic gastroenteritis

Question 5

What is the infective form of Trypanosoma brucei?

Accepted Answer

Trypomastigote

Answer

Amastigote form

Answer

Egg stage

Answer

No infective form

Question 6

Child having perianal pruritus with the following eggs is due to -

Accepted Answer

E. vermicularis

Answer

Ascaris

Answer

Ancylostoma duodenale

Answer

S. stercoralis

Question 7

Infective form of Hookworms?

Accepted Answer

Filariform larva

Answer

Egg

Answer

Rhabditiform larva

Answer

Adult worm

Question 8

Cylindrical helminths are -

Accepted Answer

Roundworms

Answer

Tapeworms

Answer

Flukes

Answer

Hookworms

Question 9

Consumption of uncooked pork is likely to cause which of the following helminthic disease -

Accepted Answer

Taenia solium

Answer

Taenia saginata

Answer

Trichuris trichiura

Answer

None of the options

Question 10

What does the hookworm primarily feed on?

Accepted Answer

Blood from intestinal mucosa

Answer

Plasma proteins

Answer

Lymphatic fluid

Answer

Interstitial fluid

Parasitology — MCQs

Parasitology — MCQs

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