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?
Nitazoxanide is specifically indicated for the treatment of which opportunistic infection in AIDS patients?
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?
All are ophthalmological emergencies except -
What should be the minimum value of HbA1c to safely carry out a surgical procedure in an emergency setting?
A patient is having gastrointestinal problems including abdominal pain and distension, bloody or mucus-filled diarrhea, and tenesmus, with rectal prolapse. A stool, ova and parasites exam reveals the presence of typical Barrel-shaped eggs, possible causative agent is?
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: 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 6: 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 7: 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.
Question 8: All are ophthalmological emergencies except -
- A. Endophthalmitis
- B. CRVO (Correct Answer)
- C. Acute congestive glaucoma
- D. CRAO
Explanation: ***CRVO*** - Central Retinal Vein Occlusion (CRVO) is characterized by painless **vision loss** due to retinal hemorrhage and edema, but it is generally *not* considered an immediate, vision-threatening emergency in the same vein as the other options. - While it requires prompt evaluation and management to preserve vision, CRVO allows for a less urgent intervention compared to conditions that can lead to permanent vision loss within hours. *Endophthalmitis* - **Endophthalmitis** is a severe inflammation of the intraocular fluids and tissues, typically caused by infection, and can lead to rapid and irreversible vision loss if not treated urgently. - It presents with pain, redness, reduced vision, and hypopyon (pus in the anterior chamber), necessitating immediate antibiotic treatment and surgical intervention. *Acute congestive glaucoma* - **Acute congestive glaucoma** (acute angle-closure glaucoma) involves a sudden increase in intraocular pressure, causing severe pain, redness, corneal edema, and profound vision loss. - If left untreated, the high pressure can cause irreversible damage to the optic nerve within hours, making it a true ocular emergency. *CRAO* - **Central Retinal Artery Occlusion (CRAO)** is a sudden, painless loss of vision in one eye due to blockage of the central retinal artery, leading to retinal ischemia. - It is an ocular emergency because irreversible retinal damage and vision loss can occur within 90-120 minutes of the occlusion, requiring immediate intervention to restore blood flow.
Question 9: What should be the minimum value of HbA1c to safely carry out a surgical procedure in an emergency setting?
- A. <7
- B. <8
- C. <10 (Correct Answer)
- D. <8
Explanation: ***<10*** - In an **emergency setting**, the priority is to proceed rapidly with surgery; current guidelines suggest that an **HbA1c <10%** is acceptable to proceed without significant delay for optimization. - While lower HbA1c is ideal, delaying an emergency procedure to achieve an HbA1c below 10% is generally **not recommended**, as the benefits of urgent surgery outweigh the risks associated with this level of glycemic control [1]. *<7* - An HbA1c of **<7% is the general target** for optimal glycemic control in most diabetic patients, especially in an elective setting. - Achieving this level in an emergency would likely require **delaying surgery**, which is not feasible or safe when immediate intervention is needed. *<8* - An HbA1c of **<8%** represents good control for many individuals, particularly older adults or those with comorbidities. - While better than 10%, it is not the absolute minimum required to proceed with an **emergency surgery**, as timely intervention is paramount. *<8* - An HbA1c of **<8%** represents good control for many individuals, particularly older adults or those with comorbidities. - While better than 10%, it is not the absolute minimum required to proceed with an **emergency surgery**, as timely intervention is paramount.
Question 10: A patient is having gastrointestinal problems including abdominal pain and distension, bloody or mucus-filled diarrhea, and tenesmus, with rectal prolapse. A stool, ova and parasites exam reveals the presence of typical Barrel-shaped eggs, possible causative agent is?
- A. Campylobacter
- B. Clostridium difficile
- C. Giardia lamblia
- D. Trichuris (Correct Answer)
Explanation: ***Trichuris*** - The presence of **barrel-shaped eggs** in a stool sample is highly characteristic of *Trichuris trichiura*, also known as **whipworm**. - **Bloody or mucus-filled diarrhea**, abdominal pain, tenesmus, and rectal prolapse (especially in heavy infections) are classic symptoms of **trichuriasis**. *Campylobacter* - *Campylobacter* is a bacterium that causes **bacterial gastroenteritis**, characterized by sudden onset of **diarrhea (often bloody)**, abdominal cramps, and fever. - It would not be identified by **barrel-shaped eggs** in a stool ova and parasite exam. *Clostridium difficile* - *Clostridium difficile* causes **antibiotic-associated diarrhea** and **pseudomembranous colitis**, presenting with watery diarrhea, abdominal pain, and fever. - Diagnosis involves detecting **toxins** or the organism's DNA, not eggs in stool. *Giardia lamblia* - *Giardia lamblia* causes **giardiasis**, typically presenting with **greasy, foul-smelling stools**, bloating, and malabsorption. - The diagnostic stage in stool is **cysts** or **trophozoites**, which are not barrel-shaped.
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