Emerging Parasitic Infections — MCQs
Rat flea transmits:
Which of the following amoebae does not have a neuropathogenic effect?
A patient presents with a headache, high fever and meningismus. Within 3 days he becomes unconscious. Most probable causative agent?
Tropical pulmonary eosinophilia is most characteristically seen due to which of the following infections?
A 46-year-old woman with HIV presents with severe persistent diarrhea. Histological investigation reveals the presence of oocysts. Identify the organism causing diarrhea in this HIV patient.
Nitazoxanide is specifically indicated for the treatment of which opportunistic infection in AIDS patients?
A 15-year-old boy came back to his village after a vacation to his relatives where he went swimming in a local freshwater lake. He developed severe headache and purulent nasal discharge and was diagnosed with acute meningoencephalitis. He died 5 days later. Which of the following is the most likely etiological agent?
Which of the following conditions is NOT typically associated with eosinophilic meningitis?
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 24-year-old patient presents with a high-grade fever, headache, and weakness since 5 days. He gives a history of blood transfusion 4 months back. The microscopic examination of the thin blood smear is given below. What is the most probable causative agent?
Emerging Parasitic Infections Indian Medical PG Practice Questions and MCQs
Question 1: Rat flea transmits:
- A. Lassa fever
- B. Trachoma
- C. Endemic typhus (Correct Answer)
- D. Rabies
Explanation: ***Endemic typhus*** - **Endemic typhus**, also known as **murine typhus**, is transmitted by the **rat flea (Xenopsylla cheopis)**, which carries the bacterium **Rickettsia typhi**. - The flea bites humans after feeding on infected rats, transmitting the bacteria. *Lassa fever* - **Lassa fever** is a **viral hemorrhagic fever** transmitted to humans primarily through contact with food or household items contaminated with urine or feces of **infected multimammate rats**. - It is not transmitted by fleas. *Trachoma* - **Trachoma** is a chronic infectious eye disease caused by the bacterium **Chlamydia trachomatis**. - It is transmitted through direct or indirect contact with eye and nose discharge of infected individuals, often via **flies (Musca sorbens)** that land on the eyes. *Rabies* - **Rabies** is a **viral disease** that is transmitted to humans through the saliva of infected animals, most commonly via a **bite** from an infected mammal such as a **dog, bat, or fox**. - It is not transmitted by fleas.
Question 2: Which of the following amoebae does not have a neuropathogenic effect?
- A. Naegleria
- B. Acanthamoeba
- C. Dientamoeba (Correct Answer)
- D. Balamuthia
Explanation: ***Dientamoeba*** - *Dientamoeba fragilis* is an intestinal flagellate (often mistakenly classified as an amoeba) that causes **gastrointestinal symptoms** like diarrhea and abdominal pain. - It has **no known neuropathogenic effects** and does not invade the central nervous system. *Naegleria* - *Naegleria fowleri* is a highly virulent amoeba that causes **primary amoebic meningoencephalitis (PAM)**, a rapidly fatal infection of the central nervous system. - It typically invades the brain after **nasal insufflation** of contaminated water. *Acanthamoeba* - *Acanthamoeba* species can cause **granulomatous amoebic encephalitis (GAE)**, a subacute to chronic central nervous system infection, particularly in immunocompromised individuals. - They are also known to cause **amoebic keratitis**, a severe eye infection. *Balamuthia* - *Balamuthia mandrillaris* causes **granulomatous amoebic encephalitis (GAE)**, similar to *Acanthamoeba*, but often in both immunocompetent and immunocompromised individuals. - It can also lead to **skin lesions** and has a tropism for the brain, causing severe neurological damage.
Question 3: 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 4: Tropical pulmonary eosinophilia is most characteristically seen due to which of the following infections?
- A. Roundworm
- B. Trichinella
- C. Ancylostoma
- D. Filaria (Correct Answer)
Explanation: *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].
Question 5: A 46-year-old woman with HIV presents with severe persistent diarrhea. Histological investigation reveals the presence of oocysts. Identify the organism causing diarrhea in this HIV patient.
- A. Cryptosporidium (Correct Answer)
- B. Staphylococcus aureus
- C. Salmonella
- D. Clostridium botulinum
Explanation: ***Cryptosporidium*** - **Cryptosporidium** is a common cause of **severe, persistent diarrhea** in immunocompromised individuals, particularly those with **HIV/AIDS**. - Its presence is confirmed by identifying **oocysts in stool samples** through histological investigation or acid-fast staining. *Staphylococcus aureus* - **Staphylococcus aureus** typically causes **food poisoning** characterized by rapid onset of nausea, vomiting, and non-bloody diarrhea. - It is a bacterial infection and **does not produce oocysts**. *Salmonella* - **Salmonella** species are bacteria that cause **gastroenteritis**, typhoid fever, or bacteremia, often characterized by fever, abdominal cramps, and diarrhea. - Like other bacteria, they **do not form oocysts**; diagnosis is made by stool culture. *Clostridium botulinum* - **Clostridium botulinum** causes **botulism**, a neurologic illness resulting from toxin ingestion, leading to flaccid paralysis. - It is not associated with **diarrhea** and **does not produce oocysts**.
Question 6: Nitazoxanide is specifically indicated for the treatment of which opportunistic infection in AIDS patients?
- A. Cryptococcosis
- B. Cryptosporidiosis (Correct Answer)
- C. Histoplasmosis
- D. Candidiasis
Explanation: ***Cryptosporidiosis*** - **Nitazoxanide** is an **antiprotozoal agent** specifically indicated for treating **cryptosporidiosis**, particularly in immunocompromised patients like those with AIDS. - It works by inhibiting the **pyruvate ferredoxin oxidoreductase enzyme pathway** in *Cryptosporidium parvum*, disrupting their energy metabolism. *Cryptococcosis* - **Cryptococcosis** is a fungal infection usually treated with **amphotericin B** and **flucytosine**, followed by fluconazole. - Nitazoxanide has **no significant activity** against *Cryptococcus neoformans*. *Histoplasmosis* - **Histoplasmosis** is a fungal infection primarily treated with **amphotericin B** for severe disease or **itraconazole** for milder forms. - Nitazoxanide is an **antiprotozoal** medication and is not effective against *Histoplasma capsulatum*. *Candidiasis* - **Candidiasis** is a fungal infection commonly treated with **fluconazole**, topical azoles, or other antifungal agents depending on the site and severity. - Nitazoxanide is **not indicated** for the treatment of **Candida infections**.
Question 7: A 15-year-old boy came back to his village after a vacation to his relatives where he went swimming in a local freshwater lake. He developed severe headache and purulent nasal discharge and was diagnosed with acute meningoencephalitis. He died 5 days later. Which of the following is the most likely etiological agent?
- A. Acanthamoeba species
- B. Balamuthia mandrillaris
- C. Naegleria fowleri (Correct Answer)
- D. Trypanosoma brucei
Explanation: ***Naegleria fowleri*** - This free-living amoeba causes **Primary Amoebic Meningoencephalitis (PAM)**, which presents as **acute hemorrhagic necrotizing encephalitis** with rapid progression to death within 5-7 days. - The **purulent nasal discharge** and **severe headache** followed by rapid deterioration in a previously healthy adolescent are characteristic features of PAM. *Acanthamoeba species* - Causes **Granulomatous Amoebic Encephalitis (GAE)**, which typically has a **subacute to chronic course** over weeks to months, not the rapid 5-day progression seen here. - Primarily affects **immunocompromised individuals** and often presents with **skin lesions** and **keratitis** before CNS involvement. *Balamuthia mandrillaris* - Also causes **Granulomatous Amoebic Encephalitis (GAE)** with a **chronic progressive course** over weeks to months, inconsistent with the rapid fatality. - Typically presents with **skin lesions** and **chronic neurological symptoms** rather than the acute fulminant presentation described. *Trypanosoma brucei* - Causes **African Trypanosomiasis** (sleeping sickness) with a **biphasic illness** including hemolymphatic and neurological stages over months. - Requires **tsetse fly vector** for transmission and presents with **lymphadenopathy** and **sleep disturbances**, not acute meningoencephalitis.
Question 8: Which of the following conditions is NOT typically associated with eosinophilic meningitis?
- A. Leptomeningeal metastasis (Correct Answer)
- B. Cryptococcal meningitis
- C. Coccidiomycosis
- D. Helminthic infections
Explanation: ***Leptomeningeal metastasis*** - This condition involves the spread of **malignant cells** to the leptomeninges, causing inflammation and neurological symptoms. - While it can cause inflammatory changes in the cerebrospinal fluid, it typically does not lead to a prominent **eosinophilic pleocytosis**. *Coccidiomycosis* - **Coccidioides immitis**, a dimorphic fungus, can cause **meningitis** and is a known cause of **eosinophilic meningitis**, particularly in endemic areas. - The fungal infection triggers a robust immune response that often involves an **eosinophil accumulation** in the CSF. *Cryptococcal meningitis* - Caused by **Cryptococcus neoformans** or **Cryptococcus gattii**, this fungal infection usually presents with **lymphocytic pleocytosis** or can have a normal cell count initially, especially in immunocompromised individuals. - Although it is a fungal infection, **eosinophilia** in the CSF is not a characteristic finding and is quite rare. *Helminthic infections* - Parasitic infections such as those caused by **Angiostrongylus cantonensis** (rat lungworm), **Gnathostoma spinigerum**, or **Taenia solium** (cysticercosis) are common causes of eosinophilic meningitis. - The immune response to the presence of these **helminths** in the central nervous system often involves a significant influx of eosinophils into the CSF.
Question 9: 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 10: A 24-year-old patient presents with a high-grade fever, headache, and weakness since 5 days. He gives a history of blood transfusion 4 months back. The microscopic examination of the thin blood smear is given below. What is the most probable causative agent?
- A. Leishmania donovani
- B. Plasmodium vivax
- C. Plasmodium falciparum
- D. Babesia microti (Correct Answer)
Explanation: ***Babesia microti*** - The image displays **intraerythrocytic pleomorphic ring forms** and classic **tetrad formations (Maltese cross)**, which are pathognomonic for **Babesia microti** infection. - The patient's history of **blood transfusion** 4 months prior is highly suggestive, as babesiosis can be transmitted through contaminated blood products with an incubation period fitting this timeline. - Clinical features include high-grade fever, headache, and weakness, consistent with babesiosis. *Leishmania donovani* - This parasite exists as **amastigotes within macrophages** and does not infect red blood cells or form ring structures as seen in the image. - While it causes fever and weakness (**visceral leishmaniasis/kala-azar**), its microscopic appearance on blood smear shows amastigotes in macrophages, not intraerythrocytic forms. *Plasmodium vivax* - While *P. vivax* infects red blood cells and forms ring stages, it is typically characterized by **enlarged infected RBCs with Schüffner's dots**, which are not seen here. - The **tetrad formations (Maltese cross)** seen in the image are pathognomonic for Babesia, not Plasmodium species. *Plasmodium falciparum* - This parasite typically presents with **multiple small ring forms per RBC** and **applique or "accole" forms** at the periphery of red blood cells. - While *P. falciparum* can cause high fever and severe disease, the specific **tetrad configuration (Maltese cross)** is characteristic of Babesia, not Plasmodium.
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