Parasitology Practice Questions

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

Loeffler pneumonia is caused by the same organism. ***Loeffler pneumonia is caused by the same organism*** - The image shows **Strongyloides stercoralis larvae** with characteristic motility. In a post-kidney transplant patient with diarrhea, this points to **Strongyloides hyperinfection** due to immunosuppression. - **Loeffler's syndrome (Loeffler pneumonia)** is a transient pulmonary infiltrative disease with eosinophilia, caused by larval migration through lungs. It is classically associated with *Strongyloides stercoralis*, *Ascaris lumbricoides*, and hookworms during their migratory phase. - This option represents an important **clinical association** that connects the organism to a significant pulmonary manifestation. *Monoecious organism related with parthenogenesis* - *Strongyloides stercoralis* is **dioecious (unisexual)**, not monoecious, meaning it has separate male and female forms. - While the parasitic females do exhibit **parthenogenesis** (reproducing without fertilization), the organism is not monoecious. *Transmitted by intake of contaminated food and water* - This is **incorrect**. *Strongyloides stercoralis* is transmitted through **percutaneous penetration** by filariform larvae from contaminated soil. - Fecal-oral transmission via contaminated food/water applies to parasites like *Entamoeba histolytica*, *Giardia*, *Ascaris*, and *Enterobius*, but not *Strongyloides*. *Infection occurs by filariform larvae* - This statement is **factually correct** - infection with *Strongyloides* does occur through **filariform (L3) larvae** penetrating intact skin. - However, in the context of this PYQ, Option C is preferred as it highlights the **clinically significant pulmonary manifestation** (Loeffler's syndrome) that is particularly relevant in immunocompromised patients, while this option merely describes the mode of transmission without clinical correlation.

Q: A wet mount preparation 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** with **jerky motility** on wet mount examination. - **Trichomonas vaginalis** is a flagellated protozoan parasite causing vaginitis, typically presenting with frothy, yellow-green vaginal discharge and strawberry cervix. - Wet mount microscopy showing motile trophozoites is the classic 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 vivax. ***Plasmodium vivax*** - The image distinctly shows **amoeboid trophozoites**, **enlarged red blood cells** with **Schüffner's dots**, and various stages of parasites within the red blood cells, which are characteristic of *P. vivax* infection. Additionally, a **banana-shaped gametocyte** is visible (indicated by the arrow), which can be seen in *P. vivax* but is more typically associated with *P. falciparum* (though it's not the primary distinguishing feature here). - 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. vivax*. *Plasmodium falciparum* - While *P. falciparum* causes severe malaria with similar systemic symptoms and can feature **banana-shaped gametocytes**, it typically does not cause **enlargement of red blood cells** or prominent **Schüffner's dots**. - Its trophozoites are often **ring forms**, and multiple parasites can infect a single red blood cell; the morphology in the image is more consistent with *P. vivax*. *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*.

Q: Match List-I with List-II and select the correct answer using the code given below the Lists:

A→3 B→4 C→1 D→2. ***A→3 B→4 C→1 D→2*** - This option correctly matches each condition with its primary causative agent: **Viral hepatitis** with **Hepatitis A, B, C**; **Amoebic liver abscess** with **Entamoeba histolytica**; **Ascending cholangitis** with **Enteric bacteria**; and **Hydatid liver disease** with **Echinococcus granulosus**. - This mapping accurately reflects established medical knowledge regarding the etiology of these liver and biliary tract conditions. *A→1 B→2 C→3 D→4* - This option incorrectly associates viral hepatitis with enteric bacteria and amoebic liver abscess with Echinococcus granulosus, which are not the primary causes. - The link between ascending cholangitis and hepatitis viruses is also incorrect, as ascending cholangitis is typically bacterial. *A→3 B→1 C→4 D→2* - This option correctly matches viral hepatitis, but incorrectly attributes amoebic liver abscess to enteric bacteria and ascending cholangitis to Entamoeba histolytica. - The causative agent for amoebic liver abscess is *Entamoeba histolytica*, not enteric bacteria, and ascending cholangitis is caused by bacteria, not *Entamoeba histolytica*. *A→2 B→4 C→1 D→3* - This option incorrectly links viral hepatitis to Echinococcus granulosus and hydatid liver disease to hepatitis viruses. - Hydatid liver disease is caused by *Echinococcus granulosus*, and viral hepatitis is caused by hepatitis viruses, so these are mismatched.

Question 1

Which of the following life cycle is shown below?

Accepted Answer

Diphyllobothrium latum

Answer

Echinococcus granulosus

Answer

Taenia solium

Answer

Clonorchis sinensis

Question 2

The following organism is called:

Accepted Answer

Cestode

Answer

Nematode

Answer

Trematode

Answer

Annelid

Question 3

Post kidney transplantation, a patient presents with diarrhoea. The motility 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

Monoecious organism related with parthenogenesis

Answer

Transmitted by intake of contaminated food and water

Answer

Infection occurs by filariform larvae

Question 4

A wet mount preparation of vaginal discharge shows the following. Identify the organism responsible.

Accepted Answer

Trichomonas vaginalis

Answer

Neisseria gonorrhoeae

Answer

Chlamydia

Answer

Treponema pallidum

Question 5

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 6

Identify the parasite shown in the image.

Accepted Answer

Sarcoptes scabiei

Answer

Pediculus humanus capitis

Answer

Pthirus pubis

Answer

Dermatobia hominis

Question 7

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 vivax

Answer

Plasmodium falciparum

Answer

Amebic liver abscess

Answer

Infectious mononucleosis

Question 8

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

Accepted Answer

Chrysops

Answer

Cyclops

Answer

Simulium

Answer

Culicoides

Question 9

Which one of the following statements is correct in the diagnosis of Giardiasis?

Accepted Answer

Stool sample at 2-3 days interval should be examined for cysts

Answer

String test is done to find out cysts of Giardia lamblia

Answer

Jejunal biopsy samples can show presence of larvae of Giardia lamblia

Answer

Cystic form of Giardia lamblia remains viable in water upto 1 week only

Question 10

Match List-I with List-II and select the correct answer using the code given below the Lists:

Accepted Answer

A→3  B→4  C→1  D→2

Answer

A→1  B→2  C→3  D→4

Answer

A→3  B→1  C→4  D→2

Answer

A→2  B→4  C→1  D→3

Parasitology — MCQs

Parasitology — MCQs

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