Blood and Tissue Protozoa — MCQs
Romana's sign is seen in infection due to:
A woman traveling from Bihar to Delhi is suspected to have Kala-azar. Suitable investigation is?
Tsetse fly transmits:
A patient presents with a headache, high fever and meningismus. Within 3 days he becomes unconscious. Most probable causative agent?
A patient from Bihar is admitted with splenomegaly and clinical features suggestive of leishmaniasis. What is the vector responsible for transmitting this disease?
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 with right upper quadrant tenderness. Peripheral smear was prepared. Diagnosis is?
A blood smear from a patient with cyclic fevers shows Maltese cross formations within red blood cells. Which organism is the likely cause?
A 15-year-old boy returned from a vacation to his relatives' village. He developed a severe headache and purulent nasal discharge and was diagnosed with primary amebic meningoencephalitis (PAM). He died 5 days later. Which is the most likely etiological agent?
A 35 year old man presented with dry cough and rusty colored sputum. He has a history of eating in a Chinese restaurant very often with consumption of crabs. What is the probable causative agent in this condition?
Peripheral blood smear in Plasmodium falciparum infection may show all of the following except -
Blood and Tissue Protozoa Indian Medical PG Practice Questions and MCQs
Question 1: Romana's sign is seen in infection due to:
- A. Trypanosoma cruzi (Correct Answer)
- B. Trypanosoma brucei
- C. Leishmania donovani
- D. Onchocerca volvulus
Explanation: ***Trypanosoma cruzi*** - **Romana's sign** is characteristic of the **acute phase** of **Chagas disease**, caused by *Trypanosoma cruzi*. - It presents as **unilateral periorbital edema** and swelling, indicating the site of parasite entry, often from the bite of a **reduviid bug** near the eye or by rubbing the parasite-laden feces into the eye. *Trypanosoma brucei* - This parasite causes **African trypanosomiasis** (sleeping sickness), which presents with distinct symptoms like **fever**, **headache**, **lymphadenopathy** (winterbottom's sign), and later neurological involvement [2]. - Ocular signs are not typically a primary or diagnostic feature in the way Romana's sign is for Chagas disease. *Leishmania donovani* - *Leishmania donovani* is the causative agent of **visceral leishmaniasis** (**kala-azar**), characterized by **fever**, **splenomegaly**, **hepatomegaly**, and **pancytopenia** [1]. - It does not cause Romana's sign; ocular involvement, if present, is usually different and not a hallmark diagnostic feature. *Onchocerca volvulus* - This filarial nematode causes **onchocerciasis** (river blindness), primarily associated with **subcutaneous nodules**, **dermatitis**, and **ocular lesions** leading to blindness. - While it causes eye pathology, it does not involve the specific periorbital edema known as Romana's sign.
Question 2: A woman traveling from Bihar to Delhi is suspected to have Kala-azar. Suitable investigation is?
- A. P24 antigen
- B. Rk-39 test (Correct Answer)
- C. Combo RDT
- D. HRP-2 antigen
Explanation: ***Rk-39 test*** - The **Rk-39 test** is a rapid diagnostic test highly sensitive and specific for detecting antibodies against the **kinesin-related protein K39** of *Leishmania donovani*, the causative agent of **Kala-azar (visceral leishmaniasis)**. - It is particularly useful in **endemic regions** like Bihar for quick and accurate diagnosis, especially in patients with suspected Kala-azar presenting with fever, splenomegaly, and pancytopenia. *P24 antigen* - **P24 antigen** testing is primarily used for the diagnosis of **HIV infection**. - It detects the **core protein p24** of the HIV virus, which is not relevant for the diagnosis of Kala-azar. *Combo RDT* - A **Combo RDT** (Rapid Diagnostic Test), without further specification, typically refers to tests for **malaria**, which detect antigens like **HRP-2** and **aldolase**. - While RDTs are used for parasitic diseases, this general term does not specifically refer to a test for **Kala-azar**. *HRP-2 antigen* - **HRP-2 (Histidine-rich protein 2) antigen** is a specific marker for **Plasmodium falciparum**, used in the diagnosis of **malaria**. - It is not associated with the diagnosis of **Kala-azar**, which is caused by *Leishmania donovani*.
Question 3: Tsetse fly transmits:
- A. Trypanosoma brucei (Correct Answer)
- B. T. cruzi
- C. Leishmania donovani
- D. Leishmania tropica
Explanation: ***Trypanosoma brucei*** - The **tsetse fly** (genus *Glossina*) is the biological vector for **African trypanosomiasis**, caused by *Trypanosoma brucei*. - This parasite is responsible for **sleeping sickness** in humans and **nagana** in livestock. *T. cruzi* - *Trypanosoma cruzi* is the causative agent of **Chagas disease** (American trypanosomiasis). - It is primarily transmitted by **reduviid bugs** (also known as kissing bugs or assassin bugs), not tsetse flies. *Leishmania donovani* - *Leishmania donovani* causes **visceral leishmaniasis** (kala-azar), a severe systemic infection. - Its transmission occurs through the bite of infected **sandflies**, specifically of the genus *Phlebotomus*. *Leishmania tropica* - *Leishmania tropica* causes **cutaneous leishmaniasis** (oriental sore), a localized skin infection. - Like *L. donovani*, it is transmitted by the bite of infected **sandflies**.
Question 4: A patient presents with a headache, high fever and meningismus. Within 3 days he becomes unconscious. Most probable causative agent?
- A. Acanthamoeba castellanii
- B. Trypanosoma cruzi
- C. Naegleria fowleri (Correct Answer)
- D. Entamoeba histolytica
Explanation: ***Naegleria fowleri*** - This protozoan causes **Primary Amebic Meningoencephalitis (PAM)**, characterized by rapid onset of headache, high fever, meningismus, and rapid progression to coma and death within days. - The disease is often acquired through **nasal insufflation of contaminated water**, allowing the amoeba to migrate to the brain. *Acanthamoeba castellanii* - This amoeba causes **Granulomatous Amebic Encephalitis (GAE)**, which is typically a chronic or subacute infection, progressing over weeks to months, unlike the rapid onset described. - GAE often occurs in **immunocompromised individuals** and can also cause keratitis or disseminated disease. *Trypanosoma cruzi* - This parasite causes **Chagas disease**, which can involve the central nervous system in acute or chronic stages, but does not typically present as acute fulminant meningoencephalitis with rapid progression to unconsciousness in days. - Neurological manifestations in Chagas disease are more varied and often associated with **cardiomyopathy** or gastrointestinal involvement. *Entamoeba histolytica* - This parasite is primarily known for causing **amebic dysentery** and **liver abscesses**. - While it can rarely cause brain abscesses, this is not the typical presentation of an acute, rapidly progressive meningoencephalitis with meningismus and high fever as described.
Question 5: A patient from Bihar is admitted with splenomegaly and clinical features suggestive of leishmaniasis. What is the vector responsible for transmitting this disease?
- A. Phlebotomus (Correct Answer)
- B. Rat flea
- C. Black fly
- D. Chrysops fly
Explanation: ***Phlebotomus*** - **Phlebotomus** (sandfly), specifically ***Phlebotomus argentipes*** in India, is the principal vector for transmitting **Leishmania donovani** parasites causing **visceral leishmaniasis (kala-azar)**. - Bihar is a highly endemic region for kala-azar in India. - The sandfly transmits the parasite when it takes a blood meal from an infected host and then bites an uninfected individual. *Rat flea* - The **rat flea** (**Xenopsylla cheopis**) is the primary vector for diseases like **bubonic plague** and **murine typhus**, not leishmaniasis. - It transmits bacteria such as *Yersinia pestis* and *Rickettsia typhi*. *Black fly* - **Black flies** (**Simulium species**) are vectors for **onchocerciasis** (river blindness), caused by the parasitic worm *Onchocerca volvulus*. - They transmit the microfilariae when biting humans. *Chrysops fly* - The **Chrysops fly** (deer fly or mango fly) is the vector for **Loa loa filariasis** (African eye worm). - It transmits *Loa loa* eyeworm larvae when it bites humans.
Question 6: 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 with right upper quadrant tenderness. Peripheral smear was prepared. Diagnosis is?
- A. Plasmodium vivax
- B. Infectious mononucleosis
- C. Plasmodium falciparum (Correct Answer)
- D. Amoebic liver abscess
Explanation: ***Plasmodium falciparum*** - **High-grade fever with chills and rigors** is a classic presentation of malaria, often more severe with *P. falciparum* [1]. - **Splenomegaly** and **right upper quadrant tenderness** can occur in severe malaria due to liver and spleen involvement, especially with *P. falciparum*'s ability to cause profound organ dysfunction [1]. *Plasmodium vivax* - While *P. vivax* causes fever, chills, and rigors, it typically presents with a **tertian fever pattern** (fever every 48 hours), and severe complications like significant right upper quadrant tenderness are less common than with *P. falciparum* [1]. - **Splenomegaly** can be present, but the overall severity and potential for complications are higher in *P. falciparum* [1]. *Infectious mononucleosis* - Characterized by **fever, fatigue, pharyngitis**, and **lymphadenopathy**, often with splenomegaly. - However, **right upper quadrant tenderness** and the acute, severe presentation with prominent chills and rigors described are less typical of infectious mononucleosis. *Amoebic liver abscess* - This typically presents with **fever** and **right upper quadrant pain**, often with a tender hepatomegaly. - However, **prominent chills and rigors** are less common, and it is usually not associated with a palpable, firm spleen as a primary feature.
Question 7: A blood smear from a patient with cyclic fevers shows Maltese cross formations within red blood cells. Which organism is the likely cause?
- A. Leishmania donovani
- B. Plasmodium vivax
- C. Plasmodium falciparum
- D. Babesia microti (Correct Answer)
Explanation: ***Babesia microti*** - The presence of **Maltese cross formations** (tetrads of merozoites) within red blood cells on a blood smear is a **pathognomonic sign** of *Babesia microti* infection. - *Babesia microti* causes **babesiosis**, a tick-borne illness known to cause **cyclic fevers**, hemolytic anemia, and can be particularly severe in asplenic individuals. *Leishmania donovani* - *Leishmania donovani* is the causative agent of **visceral leishmaniasis** (kala-azar), which is characterized by irregular fever, hepatosplenomegaly, and pancytopenia. - Diagnosis involves finding **amastigotes** within macrophages in bone marrow, spleen, or lymph nodes, not Maltese cross formations in red blood cells. *Plasmodium vivax* - *Plasmodium vivax* causes **tertian malaria**, characterized by fevers recurring every 48 hours, and infects **young red blood cells**, leading to their enlargement with **Schüffner's dots**. - While it infects red blood cells and causes fever, it does not form Maltese cross structures; instead, ring forms, trophozoites, schizonts, and gametocytes are observed. *Plasmodium falciparum* - *Plasmodium falciparum* causes the **most severe form of malaria**, characterized by irregular fevers and the presence of **crescent-shaped gametocytes** and small, delicate ring forms in red blood cells. - It does not produce Maltese cross formations; its characteristic morphology and severe clinical presentation differentiate it from babesiosis.
Question 8: A 15-year-old boy returned from a vacation to his relatives' village. He developed a severe headache and purulent nasal discharge and was diagnosed with primary amebic meningoencephalitis (PAM). He died 5 days later. Which is the most likely etiological agent?
- A. Plasmodium falciparum
- B. Entamoeba histolytica
- C. Naegleria fowleri (Correct Answer)
- D. Toxoplasma
Explanation: ***Naegleria fowleri*** - This free-living amoeba is the causative agent of **Primary Amebic Meningoencephalitis (PAM)**, a rapidly fatal infection acquired through nasal exposure to contaminated warm freshwater. - The rapid progression from symptom onset (headache, purulent nasal discharge) to death within 5 days is characteristic of PAM caused by **_Naegleria fowleri_**. *Plasmodium falciparum* - This parasite causes **falciparum malaria**, which can lead to cerebral malaria, but its presentation involves cyclic fevers, chills, and typically a longer disease course and different diagnostic markers than PAM. - While it affects the brain, it does not cause purulent nasal discharge or the rapid, fulminant meningoencephalitis seen in PAM. *Entamoeba histolytica* - This amoeba causes **amebic dysentery** and, in rare cases, extraintestinal amebiasis like liver abscesses; it does not typically cause PAM. - Central nervous system involvement by _Entamoeba histolytica_ is usually secondary to systemic spread and manifests as abscesses, not a fulminant meningoencephalitis acquired via nasal passages. *Toxoplasma* - _Toxoplasma gondii_ causes toxoplasmosis, which can lead to toxoplasmic encephalitis, especially in immunocompromised individuals. - _Toxoplasma_ infection typically has a slower onset, different risk factors (e.g., raw meat, cat feces), and does not present with a rapid, purulent meningoencephalitis following swimming exposure.
Question 9: A 35 year old man presented with dry cough and rusty colored sputum. He has a history of eating in a Chinese restaurant very often with consumption of crabs. What is the probable causative agent in this condition?
- A. Pneumocystis jirovecii
- B. Paragonimus westermani (Correct Answer)
- C. Strongyloides stercoralis
- D. Diphyllobothrium latum
Explanation: ***Paragonimus westermani*** - The key clinical features are **dry cough**, **rusty-colored sputum**, and a history of consuming **crabs**. These are classic indicators of **paragonimiasis**. - *Paragonimus westermani* is a **lung fluke** acquired by eating undercooked freshwater crabs or crayfish. *Pneumocystis jirovecii* - This fungus typically causes pneumonia in **immunocompromised individuals**, like those with HIV/AIDS. - While it can cause a dry cough, **rusty-colored sputum** is not a characteristic sign, and there's no mention of immunocompromise. *Strongyloides stercoralis* - This parasite primarily causes **gastrointestinal symptoms** (e.g., abdominal pain, diarrhea) and can lead to cutaneous manifestations (larva currens). - While lung involvement can occur in severe cases (hyperinfection), it does not typically present with **rusty sputum** or a direct association with crab consumption. *Diphyllobothrium latum* - This is the **fish tapeworm**, acquired by eating undercooked freshwater fish. - It primarily causes **gastrointestinal symptoms** such as abdominal pain and diarrhea, and is known for causing **vitamin B12 deficiency** leading to megaloblastic anemia, not pulmonary symptoms.
Question 10: Peripheral blood smear in Plasmodium falciparum infection may show all of the following except -
- A. Schizont (Correct Answer)
- B. Female gametocyte
- C. Trophozoite
- D. Male gametocyte
Explanation: ***Schizont*** - While schizonts are a stage in the *Plasmodium falciparum* life cycle, **mature schizonts** (containing merozoites) are typically not seen in peripheral blood smears of infected patients. - They tend to **sequester in deep capillaries** of organs, making their detection in circulating blood extremely rare. *Female gametocyte* - **Crescent-shaped gametocytes** (both male and female) are a characteristic feature of *Plasmodium falciparum* infection that are readily identified in peripheral blood smears. - These forms are responsible for transmission to the mosquito vector. *Trophozoite* - **Ring-form trophozoites** are the most commonly seen stage of *P. falciparum* in peripheral blood smears. - They are typically thin, delicate rings, often with **double chromatin dots** or appliqué forms. *Male gametocyte* - Similar to female gametocytes, **crescent-shaped male gametocytes** are routinely observed in peripheral blood smears of *Plasmodium falciparum* infected individuals. - They are essential for sexual reproduction within the mosquito.
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