Parasitology Practice Questions

Q: Which of the following parasite is shown below?

Cysticercus cellulosae. ***Cysticercus cellulosae*** - The image displays a **fluid-filled larval cyst** containing a **single invaginated scolex**, which is the characteristic morphology of *Cysticercus cellulosae*, the larval stage of *Taenia solium*. - The cyst has a thin outer wall enclosing a fluid-filled bladder, within which a single scolex is invaginated, distinguishing it from other parasitic cysts. - This morphology is pathognomonic for **cysticercosis**, caused by the larval stage of *Taenia solium*. *Echinococcus granulosus* - Hydatid cysts of *Echinococcus granulosus* are characterized by a thick, laminated outer wall (ectocyst) and an inner germinal layer (endocyst) from which **brood capsules** and **multiple protoscolices** bud off — features not seen in this image. *E. Histolytica* - *Entamoeba histolytica* is a **protozoan parasite** that causes amoebiasis, presenting as trophozoites or cysts; it does not form macroscopic cysts with complex internal structures like the one shown. - Amoebic abscesses are typically necrotic lesions, not true cysts with parasitic structures within. *Fasciola hepatica* - *Fasciola hepatica* is a **trematode (fluke)**, and its larval stages or adult worms do not form cysts with this characteristic morphology. - Liver flukes would appear as tissue sections of the flatworm itself in infected organs, not as a fluid-filled cyst with an invaginated scolex.

Q: Which of the following life cycle is shown below?

Clonorchiasis. ***Clonorchiasis*** - The diagram displays metacercariae (infective stage) in freshwater fish being ingested by a human host, a defining characteristic of the Clonorchis sinensis life cycle. - The life cycle involves freshwater snails (first intermediate host) and freshwater fish (second intermediate host), which aligns with the image showing cercariae encysting in fish. *Diphylobothrium latum* - The infective stage for *Diphylobothrium latum* (fish tapeworm) is the **plerocercoid larva** in raw or undercooked freshwater fish, not metacercariae. - While it also involves freshwater fish, its larval forms and overall life cycle stages are distinct from what is depicted. *Echinococcus granulosus* - This parasite causes **hydatid disease** and has a life cycle involving canids (definitive host) and herbivores (intermediate host), with humans being accidental intermediate hosts. - The life cycle does not involve freshwater fish or metacercariae for human infection. *Tenia solium* - The human is the definitive host for **Taenia solium** (pork tapeworm), acquiring infection by ingesting undercooked pork containing **cysticerci**. - The intermediate host is pigs, and the life cycle does not involve freshwater fish or metacercariae.

Q: Which of the following life cycle is shown below?

Diphyllobothrium latum. ***Diphyllobothrium latum*** - The diagram clearly illustrates a life cycle involving **freshwater fish** as a second intermediate host, where **plerocercoid larvae** are found, and humans ingesting these fish. The presence of **procercoid** and **plerocercoid larvae** in the depicted stages is characteristic of *Diphyllobothrium latum*. - The description mentions that humans are infected by ingesting fish containing **plerocercoid larvae**, which become adults in the intestine and discharge **operculated eggs that exit through a uterine pore and pass in feces**, which is consistent with the life cycle of the **fish tapeworm**. *Echinococcus granulosus* - This parasite's life cycle involves **dogs as definitive hosts** and **sheep or humans as intermediate hosts** developing **hydatid cysts**, which is distinctly different from the fish-involved cycle shown. - Infection occurs through ingestion of **eggs passed in dog feces**, and not through contaminated fish. *Taenia solium* - *Taenia solium* (pork tapeworm) involves **pigs as intermediate hosts** and humans as definitive hosts, or humans as intermediate hosts in the case of **cysticercosis**. - Its life cycle does not involve **fish** or the **plerocercoid/procercoid larval stages** as depicted. *Clonorchis sinensis* - While *Clonorchis sinensis* (Chinese liver fluke) also involves **freshwater fish** as an intermediate host, it is a **fluke, not a tapeworm**, and its larval stages are **cercariae** and **metacercariae**, not procercoid or plerocercoid larvae. - The adult worm primarily infects the **biliary ducts (liver)**, not maturing in the intestine with proglottids as shown for the tapeworm in the diagram.

Q: The following organism is called:

Cestode. ***Cestode*** - The image displays a long, **segmented, ribbon-like worm**, which is characteristic morphology of a **tapeworm (cestode)**. - Cestodes typically possess a head (scolex) for attachment and a body composed of repeating segments called **proglottids**. *Nematode* - **Nematodes** are generally **unsegmented**, cylindrical, and elongated worms, often described as roundworms. - They lack the distinct proglottids and flattened, ribbon-like appearance seen in the image. *Trematode* - **Trematodes**, also known as flukes, are typically **leaf-shaped** and **unsegmented**. - They are much broader and flatter than the organism shown, and do not have the visible segmentation. *Annelid* - **Annelids** are segmented worms like earthworms and leeches, but they have a **cylindrical body** with visible external ring-like segments. - Unlike cestodes, annelids have a complete digestive system and lack the flat, ribbon-like morphology and internal proglottid structure characteristic of tapeworms.

Q: A stained smear of vaginal discharge shows the following. Identify the organism responsible.

Trichomonas vaginalis. ***Trichomonas vaginalis*** - The image shows numerous flagellated protozoa, characterized by their **pear-shaped appearance** on examination. - **Trichomonas vaginalis** is a flagellated protozoan parasite causing vaginitis, typically presenting with frothy, yellow-green vaginal discharge and strawberry cervix. - Stained smear microscopy demonstrating the characteristic pear-shaped trophozoites is a diagnostic method for trichomoniasis. *Neisseria gonorrhoeae* - This bacterium is a **gram-negative diplococcus**, typically seen intracellularly within neutrophils on Gram stain. - It does not present as flagellated protozoa on microscopy. *Chlamydia* - **Chlamydia trachomatis** is an obligate intracellular bacterium, not visible on routine wet mount microscopy. - Diagnosis requires specialized staining (Giemsa), immunofluorescence, or molecular tests (NAAT). *Treponema pallidum* - This is a **spirochete** responsible for syphilis, typically identified using dark-field microscopy from ulcer exudate or serological tests. - It does not present as the large, flagellated protozoa characteristic of Trichomonas.

Q: A 25 -year-old complains of a gradually enlarging painless mass in the right upper quadrant. Which among the following statement regarding this patient is false? (Recent NEET Pattern 2016-17)

Human is the definitive host of the causative organism. ***Human is the definitive host of the causative organism*** - This statement is **false** because humans are **intermediate hosts** for *Echinococcus granulosus*, not definitive hosts. The **definitive hosts** are canids (e.g., dogs), where the adult tapeworm resides. - The image shows multiple cystic lesions in the liver, consistent with **hydatid cysts**, which are the larval stage of *Echinococcus granulosus* in intermediate hosts. *Can rupture into biliary tree* - **Hydatid cysts**, especially those in the liver, can **rupture spontaneously** or due to trauma, commonly into the biliary tree. - Rupture into the biliary tree can lead to complications such as **biliary colic**, **cholangitis**, or **obstructive jaundice**. *Causative agent is Echinococcus granulosus* - The clinical presentation of a gradually enlarging painless mass in the liver, along with the imaging showing multiple cysts, is highly characteristic of **cystic echinococcosis** (hydatid disease). - This condition is caused by the larval stage of the tapeworm **_Echinococcus granulosus_**. *Precipitation line in immunoelectrophoresis is most specific test* - While various serological tests are available, the detection of **specific antibodies** by immunoelectrophoresis showing a **precipitation line (arc 5)** is considered highly specific for diagnosing cystic echinococcosis. - Other serological tests like **ELISA** are more sensitive but less specific than immunoelectrophoresis with arc 5 detection.

Q: Identify the parasite shown in the image.

Sarcoptes scabiei. ***Sarcoptes scabiei*** - The image displayed is a characteristic microscopic view of **_Sarcoptes scabiei_**, the mite responsible for scabies. Key features include its **round to oval body** shape and the presence of **spines and setae** on its dorsal surface, which are visible. - The short, stubby legs with prominent suckers are consistent with the morphology used for burrowing into the skin. *Pediculus humanus capitis* - This parasite, the **head louse**, has a more **elongated body** shape and distinct legs with claws adapted for gripping hair shafts, which is not what is seen in the image. - Head lice are typically found on the scalp and attach nits (eggs) to hair, unlike the burrowing nature of the organism shown. *Pthirus Pubis* - **_Pthirus pubis_**, or the **pubic louse** (crab louse), has a distinctly **crab-like appearance** with broad bodies and large, clawed legs, especially the second and third pairs, which is not consistent with the image. - These lice typically infest coarse body hair, such as pubic hair, eyelashes, and eyebrows. *Dermatobia hominis* - **_Dermatobia hominis_** is the **human botfly**, and its larval stage (maggot) causes **cutaneous myiasis**. The image does not show a maggot-like larva but rather a microscopic mite. - The morphology of a botfly larva is worm-like and segmented, featuring prominent spines for anchoring within the host's skin.

Q: A 34-year-old lady presents with high-grade fever with chills and rigors. On examination, a firm spleen is felt 3 cm below costal margin. Peripheral smear was prepared. Diagnosis is:

Plasmodium falciparum. ***Plasmodium falciparum*** - The image distinctly shows **delicate ring forms**, possible **multiple infection of erythrocytes**, and a **crescent-shaped gametocyte** (indicated by the arrow), which are characteristic of *P. falciparum* infection. - Clinical features like **high-grade fever with chills and rigors** and a **firmly palpable spleen** are consistent with malaria, and the microscopic findings on the peripheral smear confirm *P. falciparum*. *Plasmodium vivax* - While *P. vivax* causes malaria with similar systemic symptoms, it typically shows **enlarged red blood cells** with **Schüffner's dots** and **amoeboid trophozoites** on peripheral smear. - Its trophozoites are often amoeboid in appearance, and the morphology in the image is more consistent with *P. falciparum*. *Amebic liver abscess* - This condition is caused by *Entamoeba histolytica* and primarily presents with **fever** and **right upper quadrant pain**, sometimes referred to the shoulder. - Diagnosis is usually made by imaging (e.g., ultrasound, CT scan) and serology; it does not involve parasites in red blood cells on a peripheral smear. *Infectious mononucleosis* - Caused by the **Epstein-Barr virus**, it presents with fever, fatigue, **lymphadenopathy**, and **splenomegaly**, but not with parasitic forms in red blood cells. - The characteristic finding on a peripheral smear would be **atypical lymphocytes** (Downey cells), not malarial parasites.

Q: Which one among the following vectors transmits the filaria *Loa loa*?

Chrysops. ***Chrysops*** - **Deer flies** of the genus *Chrysops* are the **intermediate hosts** for *Loa loa*, transmitting the microfilariae when they bite. - These flies are typically found in the **humid rainforests of West and Central Africa**, where loiasis is endemic. *Cyclops* - *Cyclops* (copepods) are the **intermediate hosts** for **Dracunculus medinensis** (guinea worm) and **Diphyllobothrium latum** (fish tapeworm). - They are **freshwater crustaceans** and not involved in the transmission of filarial worms like *Loa loa*. *Simulium* - *Simulium* (blackflies) are the **vectors** for **Onchocerca volvulus**, which causes **onchocerciasis** (river blindness). - These flies breed in **fast-flowing rivers** and are known for their painful bites. *Culicoides* - *Culicoides* (biting midges) are the **vectors** for **Mansonella perstans** and **Mansonella streptocerca** filarial worms, as well as some viral diseases. - They are distinct from the *Chrysops* flies that transmit *Loa loa*.

Question 1

Which of the following parasite is shown below?

Accepted Answer

Cysticercus cellulosae

Answer

Echinococcus granulosus

Answer

E. Histolytica

Answer

Fasciola hepatica

Question 2

Which of the following life cycle is shown below?

Accepted Answer

Clonorchiasis

Answer

Diphylobothrium latum

Answer

Echinococcus granulosus

Answer

Tenia solium

Question 3

Which of the following life cycle is shown below?

Accepted Answer

Diphyllobothrium latum

Answer

Echinococcus granulosus

Answer

Taenia solium

Answer

Clonorchis sinensis

Question 4

The following organism is called:

Accepted Answer

Cestode

Answer

Nematode

Answer

Trematode

Answer

Annelid

Question 5

Post kidney transplantation, a patient presents with diarrhoea. The morphology of the worms is shown in the figure. Correct statement about the organism is: (AIIMS Nov 2018)

Accepted Answer

Loeffler pneumonia is caused by the same organism

Answer

Infection occurs by ingestion of embryonated eggs

Answer

Monoecious organism related with parthenogenesis

Answer

Transmitted by intake of contaminated food and water

Question 6

A stained smear of vaginal discharge shows the following. Identify the organism responsible.

Accepted Answer

Trichomonas vaginalis

Answer

Neisseria gonorrhoeae

Answer

Chlamydia

Answer

Treponema pallidum

Question 7

A 25 -year-old complains of a gradually enlarging painless mass in the right upper quadrant. Which among the following statement regarding this patient is false? (Recent NEET Pattern 2016-17)

Accepted Answer

Human is the definitive host of the causative organism

Answer

Can rupture into biliary tree

Answer

Causative agent is Echinococcus granulosus

Answer

Precipitation line in immunoelectrophoresis is most specific test

Question 8

Identify the parasite shown in the image.

Accepted Answer

Sarcoptes scabiei

Answer

Pediculus humanus capitis

Answer

Pthirus pubis

Answer

Dermatobia hominis

Question 9

A 34-year-old lady presents with high-grade fever with chills and rigors. On examination, a firm spleen is felt 3 cm below costal margin. Peripheral smear was prepared. Diagnosis is:

Accepted Answer

Plasmodium falciparum

Answer

Plasmodium vivax

Answer

Amebic liver abscess

Answer

Infectious mononucleosis

Question 10

Which one among the following vectors transmits the filaria *Loa loa*?

Accepted Answer

Chrysops

Answer

Cyclops

Answer

Simulium

Answer

Culicoides

Parasitology — MCQs

Parasitology — MCQs

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