Vector-Borne Diseases — MCQs
Vector for Zika virus disease is:
Which of the following diseases has the largest submerged portion in the iceberg model of disease?
Which of the following diseases is transmitted by Mansonia?
A patient hailing from Delhi presents with fever, arthralgia, and extensive petechial rash for 3 days. Lab investigations revealed a hemoglobin of 9 g/ dL, a white blood cell count of 9000 cells/mm3, a platelet count of 20000 cells/mm3, and a prolonged bleeding time. The clotting time was normal. What is the most likely diagnosis?
Which of the following diseases is transmitted by Aedes aegypti?
26-year-old man from Bihar presents with erythematous papules on the face and back of the neck, which are hypopigmented and normoaesthetic, with no nerve thickening. A history of prolonged fever in childhood is present. What is the diagnosis?
Which of the following diseases is spread by mosquitoes?
All are true regarding Japanese encephalitis disease except:
Kala azar is transmitted by:
All following are at-risk group adults meriting Hepatitis B vaccination in low endemic areas except for which of the following?
Vector-Borne Diseases Indian Medical PG Practice Questions and MCQs
Question 1: Vector for Zika virus disease is:
- A. Culex
- B. Aedes Aegypti (Correct Answer)
- C. Phlebotomus
- D. Anopheles stephensi
Explanation: ***Aedes aegypti*** - The **Aedes aegypti mosquito** is the primary vector responsible for transmitting the Zika virus to humans. - This mosquito species is also known to transmit other arboviruses, including **dengue** and **chikungunya** viruses. *Culex* - **Culex mosquitoes** are known vectors for diseases such as **West Nile virus** and **Japanese encephalitis**. - They are generally not considered primary vectors for the Zika virus. *Phlebotomus* - **Phlebotomus (sandflies)** are vectors for parasitic diseases, most notably **leishmaniasis**. - They are not involved in the transmission of viral infections like Zika. *Anopheles stephensi* - **Anopheles mosquitoes**, particularly *Anopheles stephensi*, are the main vectors for **malaria**. - They do not play a role in the transmission of the Zika virus.
Question 2: Which of the following diseases has the largest submerged portion in the iceberg model of disease?
- A. Influenza (Correct Answer)
- B. Chickenpox
- C. Tetanus
- D. Rabies
Explanation: **The Iceberg Model of Disease** represents the concept that for many diseases, only a small portion of cases (the "tip" above water) are clinically apparent and reported, while a much larger portion (the "submerged" part) consists of asymptomatic, subclinical, or undiagnosed cases. ***Influenza*** - Has the **largest submerged portion** among the given options, with **50-75% of infections being asymptomatic or mild** and going undiagnosed - High transmissibility and varied clinical presentation contribute to significant hidden burden - Only severe cases requiring hospitalization typically get reported, representing just the "tip of the iceberg" - Classic example of diseases with large subclinical-to-clinical ratio *Chickenpox* - Most cases are **clinically apparent** with characteristic vesicular rash - Asymptomatic infections are rare due to distinctive clinical features - High visibility of cases reduces the submerged portion significantly *Tetanus* - **Severe, acute neurological condition** with distinct clinical manifestations (trismus, risus sardonicus, opisthotonus) - Almost all cases are diagnosed due to dramatic presentation - Virtually no submerged portion - what exists clinically is recognized *Rabies* - **Nearly uniformly fatal** once symptoms appear, making all symptomatic cases clinically evident - No asymptomatic or mild phase after symptom onset - Minimal to no submerged portion in the iceberg model
Question 3: Which of the following diseases is transmitted by Mansonia?
- A. Chikungunya
- B. Bancroftian filariasis (Correct Answer)
- C. Japanese encephalitis
- D. Dengue
Explanation: ***Bancroftian filariasis*** - **Bancroftian filariasis** (caused by *Wuchereria bancrofti*) is commonly transmitted by three mosquito genera: *Culex*, *Anopheles*, and *Mansonia*. - *Mansonia* mosquitoes are known vectors for the larvae of *Wuchereria bancrofti*, which mature into adult worms in the human lymphatic system. *Chikungunya* - Chikungunya virus is primarily transmitted by mosquitoes of the genus *Aedes*, particularly **_Aedes aegypti_** and **_Aedes albopictus_**. - *Mansonia* mosquitoes are not considered primary or significant vectors for the transmission of Chikungunya. *Japanese encephalitis* - Japanese encephalitis virus is mainly transmitted by mosquitoes of the genus _Culex_, specifically **_Culex tritaeniorhynchus_**. - While *Mansonia* mosquitoes may occasionally carry the virus, they are not primary vectors for its transmission to humans. *Dengue* - Dengue virus is primarily transmitted by **_Aedes aegypti_** and **_Aedes albopictus_** mosquitoes. - *Mansonia* mosquitoes are not implicated in the transmission cycle of Dengue fever.
Question 4: A patient hailing from Delhi presents with fever, arthralgia, and extensive petechial rash for 3 days. Lab investigations revealed a hemoglobin of 9 g/ dL, a white blood cell count of 9000 cells/mm3, a platelet count of 20000 cells/mm3, and a prolonged bleeding time. The clotting time was normal. What is the most likely diagnosis?
- A. Dengue (Correct Answer)
- B. Malaria
- C. Scrub typhus
- D. Typhoid
Explanation: Dengue - The combination of **fever, arthralgia, extensive petechial rash**, and severe **thrombocytopenia** (platelet count 20,000/mm³) with **prolonged bleeding time** is highly characteristic of severe dengue infection, especially in an endemic area like Delhi [1]. - While leukocytosis (WBC 9000/mm³) is not typical for dengue (usually causes leukopenia), the other features strongly point to dengue hemorrhagic fever [1]. *Malaria* - Typically presents with **intermittent high fever**, chills, and sweats. While it can cause some thrombocytopenia and anemia, the **extensive petechial rash** is not a characteristic feature. - **Thrombocytopenia** in malaria is usually milder than observed here, and prolonged bleeding time is less common [2]. *Scrub typhus* - Caused by Orientia tsutsugamushi, it is characterized by **fever, headache, myalgia, and a characteristic eschar** (necrotic ulcer) at the bite site, which is not mentioned. - While it can cause rash and some thrombocytopenia, the **petechial rash** and such severe thrombocytopenia with prolonged bleeding time are less typical. *Typhoid* - Presents with **sustained high fever**, headache, bradycardia, and sometimes a **rose spot rash** (maculopapular), which is different from a petechial rash. - Typhoid typically causes **leukopenia** and can lead to gastrointestinal complications like intestinal bleeding, but severe thrombocytopenia and extensive petechiae are not common presenting features.
Question 5: Which of the following diseases is transmitted by Aedes aegypti?
- A. Japanese encephalitis
- B. Filariasis
- C. Malaria
- D. Yellow fever (Correct Answer)
Explanation: ***Yellow fever*** - **Yellow fever** is a viral hemorrhagic disease transmitted primarily by the **Aedes aegypti** mosquito. - This mosquito species is also responsible for transmitting other arboviruses like **Dengue**, **Chikungunya**, and **Zika** viruses. *Japanese encephalitis* - **Japanese encephalitis** is typically transmitted by mosquitoes of the **Culex** genus, particularly **Culex tritaeniorhynchus**. - It is a leading cause of viral encephalitis in Asia, affecting the brain and central nervous system. *Filariasis* - **Lymphatic filariasis** is transmitted by several mosquito genera, including **Culex**, **Anopheles**, and **Aedes**, but it's not exclusively carried by **Aedes aegypti**. - It is caused by parasitic worms and can lead to severe swelling (lymphedema) and elephantiasis. *Malaria* - **Malaria** is transmitted exclusively by infected female **Anopheles mosquitoes**. - The parasite Plasmodium causes malaria, and different species infect humans, leading to cyclical fevers and chills.
Question 6: 26-year-old man from Bihar presents with erythematous papules on the face and back of the neck, which are hypopigmented and normoaesthetic, with no nerve thickening. A history of prolonged fever in childhood is present. What is the diagnosis?
- A. Tuberculoid leprosy
- B. Lepromatous leprosy
- C. Lupus vulgaris
- D. Dermal leishmaniasis (PKDL) (Correct Answer)
Explanation: ***Dermal leishmaniasis (PKDL)*** - PKDL presents with **erythematous papules** on the face and neck, which are **hypopigmented and normoaesthetic** (intact sensation), fitting the patient's description perfectly. - A history of **prolonged fever in childhood** in Bihar is highly suggestive of prior **visceral leishmaniasis (kala-azar)**, after which PKDL typically develops (months to years post-treatment). - The **absence of nerve thickening** and **normal sensation** are key features distinguishing PKDL from leprosy. - Bihar is an **endemic area** for visceral leishmaniasis in India. *Tuberculoid leprosy* - Characterized by **hypopigmented, anaesthetic patches** with **thickened nerves** - both features are absent in this case. - The **normoaesthetic** nature of lesions here rules out tuberculoid leprosy. - Lesions are typically **well-demarcated** and few in number. *Lepromatous leprosy* - Involves widespread, symmetrical lesions that are often **erythematous nodules** or **diffuse infiltrations**, with multiple nerve involvements. - Would show **nerve thickening** and eventual sensory loss, which are not present here. - The clinical picture does not match lepromatous leprosy. *Lupus vulgaris* - A form of **cutaneous tuberculosis** presenting as red-brown plaques with an **"apple-jelly" appearance** on diascopy. - While it can occur on the face, there is no history of fever or connection to visceral leishmaniasis. - The morphology (papules vs plaques) and epidemiological context favor PKDL.
Question 7: Which of the following diseases is spread by mosquitoes?
- A. Dengue (Correct Answer)
- B. Listeriosis
- C. Kala azar
- D. Trypanosomiasis
Explanation: ***Dengue*** is the correct answer. - **Dengue fever** is a **mosquito-borne** viral disease transmitted primarily by **Aedes aegypti** and **Aedes albopictus** mosquitoes. - Symptoms range from mild flu-like illness to severe dengue hemorrhagic fever or dengue shock syndrome. *Listeriosis* - Caused by **Listeria monocytogenes**, transmitted through contaminated food consumption. - **Not spread by mosquitoes** but through foodborne routes or contact with infected animals. *Kala azar* - Visceral leishmaniasis caused by **Leishmania parasites**, transmitted by infected **sandflies**, not mosquitoes. - Affects internal organs including spleen, liver, and bone marrow. *Trypanosomiasis* - Includes **African sleeping sickness** (transmitted by **tsetse flies**) and **Chagas disease** (transmitted by **reduviid bugs/kissing bugs**). - Neither vector is a mosquito.
Question 8: All are true regarding Japanese encephalitis disease except:
- A. Man acts as reservoir (Correct Answer)
- B. Pig vaccination control transmission
- C. Vector is Culex vishnui
- D. None of the options are true
Explanation: ***Man acts as reservoir*** - Humans are considered **dead-end hosts** for Japanese encephalitis; they do not develop sufficiently high viremia to transmit the virus back to mosquitoes. - The primary reservoirs for the Japanese encephalitis virus are **pigs** and **wading birds**. *Pig vaccination control transmission* - **Vaccinating pigs** is an effective strategy to control Japanese encephalitis transmission because pigs are significant amplifier hosts, producing high levels of viremia. - By reducing the viral load in the pig population, pig vaccination helps **break the transmission cycle** between mosquitoes and humans. *Vector is Culex vishnui* - The primary vector involved in the transmission of Japanese encephalitis is indeed **Culex mosquitoes**, with **Culex vishnui complex** being a significant group responsible for its spread in many endemic regions. - These mosquitoes primarily breed in **rice paddies** and other stagnant water sources, which are common in areas where the disease is prevalent. *None of the options are true* - This option is incorrect because the statements regarding **pig vaccination** and the **Culex vishnui** vector are true in the context of Japanese encephalitis. - The initial premise that "Man acts as reservoir" is the false statement, making it the correct answer to the "except" question.
Question 9: Kala azar is transmitted by:
- A. Tse tse fly
- B. Sandfly (Correct Answer)
- C. Hard tick
- D. Culex mosquito
Explanation: ***Sandfly*** - **Kala azar**, also known as **visceral leishmaniasis**, is a severe parasitic disease caused by **Leishmania donovani**. - This parasite is transmitted to humans through the bite of an infected female **phlebotomine sandfly**. *Tse tse fly* - The **tse tse fly** is the vector for **African trypanosomiasis**, also known as **sleeping sickness**. - It transmits **Trypanosoma brucei**, a different parasitic organism than the one causing kala azar. *Hard tick* - **Hard ticks** are vectors for several diseases, including **Lyme disease** (Borrelia burgdorferi), **Rocky Mountain spotted fever** (Rickettsia rickettsii), and **anaplasmosis**. - They are not associated with the transmission of leishmaniasis. *Culex mosquito* - The **Culex mosquito** is a common vector for diseases such as **West Nile virus**, **Japanese encephalitis**, and **filariasis**. - It does not transmit the **Leishmania parasite** responsible for kala azar.
Question 10: All following are at-risk group adults meriting Hepatitis B vaccination in low endemic areas except for which of the following?
- A. Medical/nursing personnel
- B. Patients with chronic liver disease
- C. Diabetics on insulin (Correct Answer)
- D. Patients on chronic hemodialysis
Explanation: ***Diabetics on insulin*** - This is the correct answer as the exception based on **guidelines at the time of this exam (2012)**. - At that time, diabetics were **not routinely listed** as a standard at-risk group for hepatitis B vaccination in low endemic areas, though the ACIP was beginning to recognize increased risk in this population. - **Current Update (Post-2012):** The **CDC/ACIP now recommends** hepatitis B vaccination for all previously unvaccinated adults with diabetes aged 19-59 years, due to documented increased risk of HBV infection associated with: - Shared blood glucose monitoring devices - Assisted blood glucose monitoring in healthcare settings - Outbreak investigations showing higher transmission rates - For the purpose of this historical exam question, diabetics were the exception among the listed groups. *Medical/nursing personnel* - Healthcare workers are at **high occupational risk** due to frequent exposure to blood and body fluids. - This has been a **standard, long-standing recommendation** for HBV vaccination regardless of endemic status. - The risk remains present even in low endemic areas due to potential exposure to infected patients. *Patients with chronic liver disease* - Individuals with pre-existing chronic liver disease are at risk of **severe outcomes** if they acquire hepatitis B infection. - Superimposed acute HBV infection can lead to: - Rapid progression to cirrhosis - Acute-on-chronic liver failure - Hepatocellular carcinoma - Vaccination is **crucial for prevention** and has been a standard recommendation. *Patients on chronic hemodialysis* - Hemodialysis patients face **elevated risk** of HBV acquisition due to: - Frequent vascular access procedures - Prolonged time in healthcare settings - Potential for nosocomial transmission in dialysis units - Their **immunocompromised state** increases risk of chronic infection and complications. - Vaccination is a **standard preventive measure** in this population.
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