Parasitology Practice Questions

Q: Cercariae are the infective form of which of the following parasites?

Schistosoma hematobium. ***Schistosoma hematobium*** - **Cercariae** are the motile, free-swimming larval stage of **Schistosoma** species, including *S. hematobium* - They **actively penetrate human skin** to initiate infection, making cercariae the infective form for humans *Paragonimus westermani* - The infective form for humans is **metacercariae**, which are ingested by consuming insufficiently cooked **crabs or crayfish** - Cercariae develop into metacercariae in secondary intermediate hosts (crustaceans) *Fasciola hepatica* - Humans are infected by ingesting **metacercariae** present on aquatic vegetation, such as **watercress** - Cercariae encyst on plants to form metacercariae, not directly infective *Taenia solium* - The infective forms are **cysticerci** in undercooked pork (for adult tapeworm) or **embryonated eggs** (causing cysticercosis) - This cestode has a different life cycle and does **not** involve cercariae

Q: What is the most common protozoan associated with keratitis?

Acanthamoeba. ***Acanthamoeba*** - **Acanthamoeba keratitis** is a serious and painful infection of the eye's cornea, most commonly associated with **contact lens wearers** who do not properly disinfect their lenses. - The organism is a **free-living protozoan** found in soil and water. *Plasmodium* - **Plasmodium** species are the causative agents of **malaria**, a disease that primarily affects **red blood cells** and the liver. - While it can manifest with ocular symptoms like **retinopathy**, it does not typically cause **keratitis**. *Toxoplasma* - **Toxoplasma gondii** causes **toxoplasmosis**, an infection that can lead to **chorioretinitis** (inflammation of the retina and choroid), especially in immunocompromised individuals or congenitally infected infants. - It does not directly cause **keratitis** as its primary ocular manifestation. *Entamoeba histolytica* - **Entamoeba histolytica** is the protozoan responsible for **amebiasis**, particularly **amoebic dysentery** and **liver abscesses**. - Ocular involvement with *Entamoeba histolytica* is extremely rare and typically involves **metastatic lesions** to the orbit or eyelids, not directly primary keratitis.

Q: Which type of malaria is most commonly associated with renal failure?

Falciparum. ***Falciparum*** - **Plasmodium falciparum** is notorious for its ability to cause severe and complicated malaria, including **renal failure** due to its high parasitic biomass and tendency to block microvasculature [1]. - The parasite causes red blood cells to become **sticky**, leading to sequestration in capillaries of vital organs, including the kidneys, resulting in acute tubular necrosis [1]. *Vivax* - **Plasmodium vivax** typically causes milder forms of malaria, though it can occasionally lead to severe manifestations, **renal complications are rare** compared to P. falciparum [1]. - While it can cause some organ dysfunction, it generally does not cause the severe multi-organ involvement, particularly **acute renal failure**, that P. falciparum is known for [1]. *Malariae* - **Plasmodium malariae** is associated with a chronic form of malaria and is known to cause **nephrotic syndrome** (specifically malarial nephropathy) due to immune complex deposition, rather than acute renal failure [1]. - The renal pathology in P. malariae infection is typically a **glomerulonephritis** that develops after repeated infections, which is distinct from the acute renal failure seen with P. falciparum [1]. *Ovale* - **Plasmodium ovale** is the least common type of malaria and causes a benign form of the disease, similar to P. vivax [1]. - It rarely, if ever, causes severe complications like **renal failure** [1].

Q: Which of the following statements is true regarding Diphyllobothrium?

The operculated egg is a diagnostic feature. ***The operculated egg is a diagnostic feature*** - *Diphyllobothrium latum*, also known as the **fish tapeworm**, produces characteristic **operculated eggs** that are oval-shaped with an operculum (cap) at one end and a small knob at the other. - The presence of these **unembryonated eggs** in stool samples is the primary diagnostic method for diphyllobothriasis. *Humans are the only definitive host* - While humans are common definitive hosts, other **fish-eating mammals** such as bears, dogs, and cats can also serve as definitive hosts for *Diphyllobothrium latum*. - The definitive host is where the **adult worm resides** and reproduces sexually. *Vitamin B12 deficiency always occurs in infection* - **Vitamin B12 deficiency (megaloblastic anemia)** is a known complication of *Diphyllobothrium latum* infection, as the worm competes for B12 in the host's intestine. - However, it does **not occur in all infected individuals**; it is estimated to affect a significant minority, typically those with heavy worm burdens or prolonged infection, and can be influenced by dietary intake. *Fish are definitive hosts* - Fish (specifically freshwater fish like pike, perch, and salmon) act as **second intermediate hosts** for *Diphyllobothrium latum*, carrying the **plerocercoid larvae**. - **Humans and other fish-eating mammals** are the definitive hosts, where the plerocercoid larvae mature into adult tapeworms in the small intestine.

Q: Largest intestinal protozoan is?

Balantidium coli. ***Balantidium coli*** - *Balantidium coli* is the **largest protozoan parasite** known to infect humans, specifically found in the intestines. - It causes **balantidiasis**, an intestinal infection, and is notable for its ciliated trophozoite stage. *E. coli* - *E. coli* is a **bacterium**, not a protozoan. - While it is a common inhabitant of the intestines, it is significantly smaller than parasitic protozoa. *Giardia* - *Giardia lamblia* (or *intestinalis*) is a **flagellate protozoan** that causes giardiasis. - Though an intestinal parasite, it is considerably smaller than *Balantidium coli*. *T. gondii* - *Toxoplasma gondii* is an **intracellular protozoan parasite** known for causing toxoplasmosis. - It is much smaller than *Balantidium coli* and primarily infects cells, not existing as a large free-living form in the intestine.

Q: Katayama fever is caused by which of the following?

S. japonicum. ***Correct: S. japonicum*** - Katayama fever, also known as **acute schistosomiasis**, is a systemic hypersensitivity reaction to the migrating schistosomula and oviposition of eggs that primarily occurs in infections with **_Schistosoma japonicum_** or _S. mansoni_. - It presents with fever, chills, cough, diarrhea, abdominal pain, hepatosplenomegaly, and eosinophilia, typically 2-8 weeks after exposure to contaminated water. - S. japonicum tends to cause the most severe form of Katayama fever. *Incorrect: F. hepatica* - **_Fasciola hepatica_** causes fascioliasis, an infection of the bile ducts and liver, which can present with fever and eosinophilia, but it does not typically cause the acute systemic reaction known as Katayama fever. - The disease is usually acquired by ingesting **metacercariae** on aquatic vegetation or in contaminated water. *Incorrect: C. sinensis* - **_Clonorchis sinensis_** is the Chinese liver fluke, causing clonorchiasis, an infection primarily of the bile ducts. - Symptoms are often mild or asymptomatic but can include abdominal pain, indigestion, diarrhea, and jaundice in heavy infections, without the distinct acute systemic syndrome of Katayama fever. *Incorrect: A. lumbricoides* - **_Ascaris lumbricoides_** is a roundworm that causes ascariasis, primarily affecting the gastrointestinal tract. - While it can cause pulmonary symptoms during larval migration (Löffler's syndrome), it does not cause Katayama fever, which is specific to schistosomiasis.

Q: Which of the following statements about trematodes is true?

Two hosts required. ***Two hosts required (Correct)*** - Trematodes typically require at least **two hosts** to complete their life cycle: an intermediate host (usually a **snail**) and a definitive host (a vertebrate). - This complex lifecycle involving multiple hosts is a characteristic feature of **flukes**. - This is a fundamental distinguishing feature that separates trematodes from some other helminths. *Segmented (Incorrect)* - Trematodes (flukes) have **unsegmented, leaf-shaped or cylindrical bodies**, unlike cestodes (tapeworms) which are segmented. - The absence of body segmentation is a key morphological distinction from other helminths. *Anus present (Incorrect)* - Trematodes have an **incomplete digestive system** with a mouth and an esophagus, but **no anus**. - Waste products are expelled back through the **mouth**. - This blind-ending gut is characteristic of the class Trematoda. *Body cavity present (Incorrect)* - Trematodes are **acoelomates**, meaning they lack a true fluid-filled body cavity (coelom). - Their internal organs are embedded in **parenchymatous tissue** filling the space between body wall and organs.

Q: Rhabditiform larvae are seen in which of the following?

Strongyloides stercoralis. ***Strongyloides stercoralis*** - *Strongyloides stercoralis* is unique among intestinal nematodes in that it can produce **rhabditiform larvae** in the stool. These larvae can then mature into infective **filariform larvae** either in the soil or within the host. - The presence of **rhabditiform larvae in fresh stool samples** is a key diagnostic feature differentiating *Strongyloides* from other parasitic infections that typically shed eggs. *Taenia solium* - *Taenia solium* (pork tapeworm) is transmitted by **ingesting undercooked pork** containing cysticerci. - The parasite is diagnosed by finding **eggs or proglottids in stool**, not rhabditiform larvae. *Diphyllobothrium latum* - *Diphyllobothrium latum* (fish tapeworm) infects humans upon consumption of **undercooked or raw freshwater fish**. - Diagnosis is made by identifying characteristic **operculated eggs in stool samples**, which do not contain rhabditiform larvae. *Trichinella spiralis* - *Trichinella spiralis* causes trichinosis, usually acquired by eating **undercooked meat infected with encysted larvae**. - This parasite is typically diagnosed by **muscle biopsy** showing encysted larvae or serological tests, as it does not produce rhabditiform larvae in stool.

Q: Flame cells are primarily associated with which of the following organisms?

Trematodes. ***Correct: Trematodes*** - **Flame cells** are specialized **excretory/osmoregulatory structures** found in **Platyhelminthes (flatworms)**, which include **Trematodes** (flukes) and Cestodes (tapeworms). - These cells have a **tuft of cilia** that beat in a flickering motion (resembling a flame), driving fluid through tubules for waste removal and osmoregulation. - **Trematodes** are the most appropriate answer among the given options as they are medically important flatworms with flame cells. *Incorrect: Protozoa* - Protozoa are **single-celled organisms** that use **contractile vacuoles** for osmoregulation, not flame cells. - Examples include Entamoeba, Giardia, and Plasmodium species. *Incorrect: Nematodes* - **Nematodes** (roundworms) belong to phylum Nematoda and possess a distinct excretory system with **renette cells** or **H-shaped/tubular excretory canals**, not flame cells. - Examples include Ascaris, Enterobius, and hookworms. *Incorrect: None of the options* - This is incorrect because **Trematodes** do possess flame cells and is the correct answer among the choices provided.

Q: Who discovered the malarial parasite?

Charles Louis Alphonse Laveran. ***Charles Louis Alphonse Laveran*** - **Charles Louis Alphonse Laveran** was a French physician who, in **1880**, observed parasites in the blood of a malaria patient. - He was awarded the **Nobel Prize in Physiology or Medicine in 1907** for his discovery of the role of protozoa in causing diseases, specifically recognizing the malarial parasite. *Ronald Ross* - **Ronald Ross** was a British physician who, in **1897**, demonstrated that **malaria is transmitted by mosquitoes**. - While he elucidated the **transmission cycle**, it was Laveran who first identified the parasite itself in human blood. - He received the **Nobel Prize in 1902** for this work. *Paul Muller* - **Paul Muller** was a Swiss chemist who was awarded the **Nobel Prize in Physiology or Medicine in 1948** for his discovery of the insecticidal properties of **DDT (dichlorodiphenyltrichloroethane)**. - His work was significant in combating insect-borne diseases like malaria, but he was not involved in the discovery of the malarial parasite. *Pampania* - This name does not correspond to any recognized figure in the discovery of the malarial parasite or its transmission. - This is a distractor option in the original examination question.

Question 1

Cercariae are the infective form of which of the following parasites?

Accepted Answer

Schistosoma hematobium

Answer

Paragonimus westermani

Answer

Fasciola hepatica

Answer

Taenia solium

Question 2

What is the most common protozoan associated with keratitis?

Accepted Answer

Acanthamoeba

Answer

Plasmodium

Answer

Toxoplasma

Answer

Entamoeba histolytica

Question 3

Which type of malaria is most commonly associated with renal failure?

Accepted Answer

Falciparum

Answer

Vivax

Answer

Malariae

Answer

Ovale

Question 4

Which of the following statements is true regarding Diphyllobothrium?

Accepted Answer

The operculated egg is a diagnostic feature

Answer

Humans are the only definitive host

Answer

Vitamin B12 deficiency always occurs in infection

Answer

Fish are definitive hosts

Question 5

Largest intestinal protozoan is?

Accepted Answer

Balantidium coli

Answer

E. coli

Answer

Giardia

Answer

T. gondii

Question 6

Katayama fever is caused by which of the following?

Accepted Answer

S. japonicum

Answer

F. hepatica

Answer

C. sinensis

Answer

A. lumbricoides

Question 7

Which of the following statements about trematodes is true?

Accepted Answer

Two hosts required

Answer

Segmented

Answer

Anus present

Answer

Body cavity present

Question 8

Rhabditiform larvae are seen in which of the following?

Accepted Answer

Strongyloides stercoralis

Answer

Taenia solium

Answer

Diphyllobothrium latum

Answer

Trichinella spiralis

Question 9

Flame cells are primarily associated with which of the following organisms?

Accepted Answer

Trematodes

Answer

Protozoa

Answer

Nematodes

Answer

None of the options

Question 10

Who discovered the malarial parasite?

Accepted Answer

Charles Louis Alphonse Laveran

Answer

Ronald Ross

Answer

Paul Muller

Answer

Pampania

Parasitology — MCQs

Parasitology — MCQs

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