Parasitology Practice Questions

Q: Most sensitive test for detecting microfilariae?

Membrane filtration technique. ***Membrane filtration technique*** - The **membrane filtration technique** is considered the most sensitive test for detecting **microfilariae** because it concentrates microfilariae from a larger volume of blood (typically 1 mL or more) onto a filter membrane, increasing detection rates, especially in low-parasite density infections. - This method physically traps the microfilariae, allowing for microscopic examination of the concentrated sample after staining, which enhances visualization. *Diethylcarbamazine (DEC) challenge test* - The **DEC challenge test** uses **diethylcarbamazine** to provoke the release of microfilariae into the peripheral blood, especially in cases of occult filariasis or when microfilaria numbers are low. - While it can be useful in certain diagnostic situations, it is **less sensitive** than membrane filtration for directly detecting circulating microfilariae and carries the risk of inducing severe adverse reactions due to rapid parasite killing. *Fluorescence-based immunoassay* - **Fluorescence-based immunoassays** detect **antigens** or **antibodies** related to filarial infection, providing evidence of exposure or active infection. - While valuable for diagnosis, especially in antibody detection for chronic or occult infections, they do not directly detect live microfilariae and thus are not the most sensitive method for *detecting microfilariae themselves*. *Thick blood smear* - A **thick blood smear** is a common and quick method for detecting microfilariae by examining a drop of blood for their presence. - However, it is **less sensitive** than the membrane filtration technique, particularly in persons with low microfilaremia, as it examines a much smaller volume of blood.

Q: Smallest cestode among the following:

H. nana. ***H. nana*** - *Hymenolepis nana* (dwarf tapeworm) is the **smallest cestode** infecting humans, typically measuring only 15-40 mm in length. - Its small size and direct life cycle (often without an intermediate host) contribute to its ability to cause **autoinfection**. *Schistosoma* - *Schistosoma* species are **trematodes (flukes)**, not cestodes (tapeworms). - They are known for causing **schistosomiasis** and are distinct from tapeworms in morphology and life cycle. *T. saginata* - *Taenia saginata* (beef tapeworm) is one of the **largest human tapeworms**, often reaching lengths of 4-12 meters. - Its large size and characteristic **proglottids** (segments) are key identifying features. *T. Solium* - *Taenia solium* (pork tapeworm) is also a **large cestode**, measuring 2-7 meters in length. - It is clinically significant for causing **cysticercosis** if humans ingest its eggs.

Q: In Plasmodium vivax malaria, relapse is caused by:

Hypnozoite. ***Hypnozoite*** - **Hypnozoites** are dormant forms of *Plasmodium vivax* and *P. ovale* that persist in the liver for months to years after initial infection. - These dormant hepatic stages can later reactivate, develop into merozoites, and cause a **relapse** of malaria symptoms even after successful treatment of the blood-stage infection. - Relapses are a defining feature of *P. vivax* malaria and require treatment with **primaquine** or **tafenoquine** for radical cure to eliminate hypnozoites. *Incorrect: Schizont* - **Schizonts** are stages where asexual reproduction occurs, either in liver cells (hepatic schizonts) or red blood cells (erythrocytic schizonts). - Erythrocytic schizonts cause acute malaria symptoms but do not cause delayed relapses as they are cleared by standard antimalarial treatments. - Hepatic schizonts complete their cycle within 1-2 weeks and do not remain dormant. *Incorrect: Sporozoite* - **Sporozoites** are the infective stage injected by the mosquito that travel to the liver to initiate infection. - They differentiate into either developing schizonts or dormant hypnozoites but do not directly cause relapses. - Sporozoites represent the initial infection, not the mechanism of relapse. *Incorrect: Gametocyte* - **Gametocytes** are the sexual stage found in human blood that are ingested by mosquitoes to continue the parasite lifecycle. - They are responsible for transmission to mosquitoes but do not cause human symptoms or relapses in the host. - Gametocytes do not remain dormant in the liver.

Q: Tropical pulmonary eosinophilia is most characteristically seen due to which of the following infections?

Filaria. *Filaria* - **Tropical pulmonary eosinophilia (TPE)** is a hypersensitivity reaction to microfilariae from filarial nematodes like *Wuchereria bancrofti* and *Brugia malayi* [1]. - It is characterized by cough, dyspnea, wheezing, and marked **peripheral eosinophilia**, with interstitial infiltrates on chest X-ray [1]. *Roundworm* - **Ascaris lumbricoides** can cause **Loeffler's syndrome**, a transient pulmonary infiltration with eosinophilia during larval migration, but not chronic TPE [2]. - Symptoms are usually less severe and self-limiting compared to TPE [2]. *Trichinella* - **Trichinella spiralis** causes **trichinellosis**, presenting with muscle pain, fever, and periorbital edema, possibly with eosinophilia, but typically does not manifest as TPE. - Pulmonary involvement is rare and not the characteristic feature. *Ancylostoma* - **Hookworm (Ancylostoma duodenale, Necator americanus)** larvae can cause mild pulmonary symptoms and eosinophilia during migration through the lungs [3]. - However, they also do not typically lead to the severe and chronic pulmonary symptoms seen in TPE [3].

Q: Babesiosis is most commonly transmitted by:

Ticks. **_Ticks_** - Babesiosis is a **tick-borne illness** caused by *Babesia* parasites, primarily *Babesia microti* in North America. - The main vector is the **deer tick** (*Ixodes scapularis*), which also transmits **Lyme disease**. *Rats* - Rats are known reservoirs for various diseases (e.g., **hantavirus**, **leptospirosis**), but they are not the primary vectors for babesiosis. - While *Babesia microti* can infect rodents, **direct transmission** to humans from rats is not the most common route. *Sand fly* - Sand flies are vectors for diseases like **leishmaniasis** and **Bartonellosis**. - They are not associated with the transmission of *Babesia* parasites. *Pigs* - Pigs can be reservoirs for certain zoonotic diseases (e.g., **cysticercosis**, **trichinellosis**). - They do not typically serve as vectors for babesiosis transmission to humans.

Q: Montenegro test is used for diagnosis of:

Kala azar. ***Kala azar*** - The Montenegro test, also known as the **leishmanin skin test (LST)**, detects delayed-type hypersensitivity to **Leishmania antigens**, indicating past or present infection with *Leishmania donovani*, the causative agent of **kala azar (visceral leishmaniasis)** [1]. - A **positive reaction** (induration of 5 mm or more) signifies cell-mediated immunity against the parasite [1]. *Leptospirosis* - Diagnosed primarily through **serological tests** like the **Microscopic Agglutination Test (MAT)** or by detecting the organism through **culture** or **PCR**. - The Montenegro test is not used for the diagnosis of **leptospirosis**. *Malaria* - Diagnosed by identifying **parasites in blood smears** (thick and thin films) or by **antigen detection rapid diagnostic tests (RDTs)**. - The Montenegro test plays no role in the diagnosis of **malaria**. *Leprosy* - Diagnosed through **clinical signs and symptoms**, microscopic examination of **skin or nerve biopsies for acid-fast bacilli**, or sometimes the **lepromin skin test**. - While the lepromin test is a skin test, it targets *Mycobacterium leprae* antigens and is distinct from the Montenegro test for leishmaniasis.

Q: The following parasitic infections predispose to malignancies: A) Paragonimus westermani B) Guinea worm infection C) Clonorchiasis D) Schistosomiasis

C and D. ***C and D*** - **Clonorchiasis**, caused by *Clonorchis sinensis*, is strongly linked to **cholangiocarcinoma**, cancer of the bile ducts. - **Schistosomiasis**, particularly infection with *Schistosoma haematobium*, is a significant risk factor for **bladder cancer** [1]. *A and B* - **Paragonimus westermani** (lung fluke) can cause chronic inflammation and fibrosis in the lungs but is not directly associated with malignancy. - **Guinea worm infection** (*Dracunculus medinensis*) causes painful ulcers but does not predispose to cancer. *B and D* - **Guinea worm infection** does not cause cancer. - While **Schistosomiasis** does predispose to malignancy [1], the pairing with Guinea worm makes this option incorrect overall. *A and C* - **Paragonimus westermani** is not known to cause malignancy. - **Clonorchiasis** is linked to malignancy, but its pairing with an incorrect option makes this choice wrong.

Q: Which disease is transmitted by all components of blood?

Malaria. ***Malaria*** - **Malaria** is caused by *Plasmodium* parasites and is uniquely transmissible through **all blood components** including whole blood, packed RBCs, platelets, fresh frozen plasma, and cryoprecipitate - The parasites exist within **red blood cells** during the blood stage and can also be present as **free merozoites** in plasma during rupture of RBCs - **Critical for blood bank safety**: Even small volumes of any blood component from an infected donor can transmit malaria - Blood donations require extensive screening for malaria in endemic areas and from donors with travel history *Hepatitis B* - **Hepatitis B virus (HBV)** is highly transmissible through blood and present in plasma, but modern blood banking practice includes **universal HBsAg screening** which has virtually eliminated transmission - While technically present in multiple components, the question emphasizes diseases where **all components** pose equal transmission risk without modern screening *Syphilis* - **Syphilis** caused by *Treponema pallidum* can be transmitted via blood transfusion, but the organism is **fragile** and does not survive beyond 72-96 hours in refrigerated blood - Transmission risk is significantly reduced by standard blood storage conditions and routine serological screening - Not efficiently transmitted through all stored blood components *Toxoplasma* - **Toxoplasma gondii** transmission occurs primarily through **leukocyte-containing products** (whole blood, platelet concentrates) - Transmission via **cell-free plasma** or washed RBCs is uncommon - Does not have the same broad transmission profile across all blood components as malaria

Q: All of the following diseases may be acquired by ingestion except -

Leishmaniasis. ***Leishmaniasis*** - Leishmaniasis is typically acquired through the bite of an infected **sandfly vector**, not by ingestion. - The parasite lives and multiplies in the sandfly's midgut and is transmitted to humans during a blood meal. *Taeniasis* - **Taeniasis** is acquired by ingesting undercooked meat containing **Taenia larvae** (cysticerci). - Humans can get infected by eating raw or undercooked beef (for *Taenia saginata*) or pork (for *Taenia solium*). *Guinea worm* - **Guinea worm disease** (*Dracunculus medinensis*) is acquired by ingesting water contaminated with water fleas (copepods) that harbor the infective larvae. - The larvae mature in the human host after ingestion of the infected water. *Toxoplasmosis* - **Toxoplasmosis** can be acquired by ingesting undercooked meat containing **Toxoplasma cysts** or by consuming food/water contaminated with cat feces (containing oocysts). - It can also be transmitted congenitally from mother to fetus.

Question 1

Most sensitive test for detecting microfilariae?

Accepted Answer

Membrane filtration technique

Answer

Diethylcarbamazine (DEC) challenge test

Answer

Fluorescence-based immunoassay

Answer

Thick blood smear

Question 2

Smallest cestode among the following:

Accepted Answer

H. nana

Answer

Schistosoma

Answer

T. saginata

Answer

T. solium

Question 3

In Plasmodium vivax malaria, relapse is caused by:

Accepted Answer

Hypnozoite

Answer

Schizont

Answer

Sporozoite

Answer

Gametocyte

Question 4

Tropical pulmonary eosinophilia is most characteristically seen due to which of the following infections?

Accepted Answer

Filaria

Answer

Roundworm

Answer

Trichinella

Answer

Ancylostoma

Question 5

Babesiosis is most commonly transmitted by:

Accepted Answer

Ticks

Answer

Rats

Answer

Sand fly

Answer

Pigs

Question 6

Montenegro test is used for diagnosis of:

Accepted Answer

Kala azar

Answer

Leptospirosis

Answer

Malaria

Answer

Leprosy

Question 7

Which of the following statements regarding diagnosis of malaria are true?

Accepted Answer

Jaswant Singh Bhattacharya (JSB) Stain is used.

Answer

Thin blood film is used to determine parasite concentration.

Answer

As the sensitivity of microscopy is low, it is useful to detect parasite load at high concentrations only.

Answer

Thick blood film is used to detect plasmodium species causing infection.

Question 8

The following parasitic infections predispose to malignancies: A) Paragonimus westermani B) Guinea worm infection C) Clonorchiasis D) Schistosomiasis

Accepted Answer

C and D

Answer

A and B

Answer

B and D

Answer

A and C

Question 9

Which disease is transmitted by all components of blood?

Accepted Answer

Malaria

Answer

Syphilis

Answer

Toxoplasma

Answer

Hepatitis B

Question 10

All of the following diseases may be acquired by ingestion except -

Accepted Answer

Leishmaniasis

Answer

Taeniasis

Answer

Guinea worm

Answer

Toxoplasmosis

Parasitology — MCQs

Parasitology — MCQs

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