Viral Zoonoses — MCQs
Which of the following statements about rabies is true?
Patient: fever, joint pain, rash. Recent history of mosquito bite. Most likely diagnosis in urban area?
The tick-borne hemorrhagic fever found in Karnataka state is:
Which of the following is best for ante-mortem diagnosis of rabies?
Which of the following statements regarding classical Dengue fever is FALSE?
Which of the following diseases is not included in the National Vector Borne Disease Control Program?
Zoonotic disease of viral etiology includes -
Which of the following viral diseases is least commonly reported in India?
Most effective preventive measure against rabies
Antemortem diagnosis of rabies is made with:
Viral Zoonoses Indian Medical PG Practice Questions and MCQs
Question 1: Which of the following statements about rabies is true?
- A. Presence of meningitis suggests against the diagnosis of rabies
- B. Convulsions are generally not seen in a patient with rabies
- C. Incubation period is approximately 20 to 80 days
- D. Intracytoplasmic eosinophilic inclusion bodies are seen in brain cells (Correct Answer)
Explanation: ***Intracytoplasmic eosinophilic inclusion bodies are seen in brain cells*** - **Negri bodies** are pathognomonic **intracytoplasmic eosinophilic inclusion bodies** found in rabies infection [1] - They are seen in **neurons (nerve cells) of the brain**, particularly in the **hippocampus (Ammon's horn)**, **cerebellum (Purkinje cells)**, and **brainstem** [1] - Neurons are brain cells, making this statement **correct and accurate** - Negri bodies are found in approximately **50-80% of rabies cases** and are diagnostic when present *Incubation period is approximately 20 to 80 days* - The incubation period for rabies is highly variable and typically ranges from **1-3 months (30-90 days)** - The range can extend from **as short as 5 days to several years** in rare cases - The statement "20 to 80 days" is **too narrow** and doesn't capture the typical range accurately - Variability depends on bite location, viral load, and host factors *Presence of meningitis suggests against the diagnosis of rabies* - This is **incorrect** - rabies primarily causes **encephalitis**, but meningeal signs can be present - Rabies can present with **meningismus and CSF pleocytosis** - The presence of meningeal symptoms does **not rule out rabies** *Convulsions are generally not seen in a patient with rabies* - This is **false** - **seizures and convulsions are common** in rabies, especially in the **furious form** - Neurological manifestations include **muscle spasms**, **seizures**, **hydrophobia**, and **aerophobia** - The severe CNS inflammation leads to frequent convulsive episodes **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1279-1280.
Question 2: Patient: fever, joint pain, rash. Recent history of mosquito bite. Most likely diagnosis in urban area?
- A. Dengue
- B. Japanese Encephalitis
- C. Malaria
- D. Chikungunya (Correct Answer)
Explanation: ***Chikungunya*** - **Chikungunya** is a viral disease transmitted by mosquitoes that commonly presents with **fever**, severe **joint pain** (polyarthralgia), and a **rash**, fitting the patient's symptoms. - Its high prevalence in **urban areas** and recent history of **mosquito bites** make it a strong diagnostic consideration. *Dengue* - While Dengue also causes **fever** [1] and a **rash**, it is more typically associated with **severe muscle and bone pain** ("breakbone fever"), and **hemorrhagic manifestations** or shock, which are not mentioned. - **Joint pain** in dengue is usually less debilitating than in chikungunya. *Japanese Encephalitis* - This is a serious **neurological infection** characterized by **fever**, **headache**, seizures, and altered mental status, rather than prominent joint pain and rash. - It primarily affects the **brain** and is less likely to present with this specific symptom triad. *Malaria* - Malaria is characterized by **cyclic fevers**, chills, sweating, and fatigue, but typically **does not present with a rash** [1] or significant joint pain. - It is caused by a **parasite** transmitted by *Anopheles* mosquitoes, and its clinical picture differs from the described symptoms.
Question 3: The tick-borne hemorrhagic fever found in Karnataka state is:
- A. Japanese encephalitis
- B. Kyasanur forest disease (Correct Answer)
- C. Epidemic nephrosonephritis
- D. Lassa fever
Explanation: Kyasanur forest disease - **Kyasanur Forest Disease (KFD)** is a **tick-borne hemorrhagic fever** endemic to **Karnataka, India**, particularly in the Shivamogga district. - The disease is caused by the **Kyasanur Forest Disease virus (KFDV)**, a member of the *Flaviviridae* family, transmitted to humans through the bite of infected ticks, primarily *Haemaphysalis spinigera*. *Japanese encephalitis* - **Japanese encephalitis** is a **mosquito-borne viral disease** that can cause encephalitis, but it is not typically characterized as a hemorrhagic fever and is not specifically linked to ticks in Karnataka. - While it can cause neurological symptoms, the primary vector is **mosquitoes**, not ticks, and its epidemiology differs from KFD. *Epidemic nephrosonephritis* - **Epidemic nephrosonephritis** (also known as **Hemorrhagic Fever with Renal Syndrome - HFRS**) is caused by **Hantaviruses** and is typically transmitted through contact with rodent urine, feces, or saliva. - It primarily affects the kidneys and can cause hemorrhagic manifestations, but it is **not tick-borne** and is not the specific hemorrhagic fever found in Karnataka. *Lassa fever* - **Lassa fever** is an **acute viral hemorrhagic illness** caused by the Lassa virus, which is endemic to West Africa and is primarily transmitted to humans through contact with food or household items contaminated with the urine and feces of **multimammate rats (Mastomys natalensis)**. - It is **not found in India** and is not transmitted by ticks.
Question 4: Which of the following is best for ante-mortem diagnosis of rabies?
- A. Immunofluorescence of corneal impressions
- B. Isolation of virus from saliva
- C. Immunofluorescence of skin biopsy (Correct Answer)
- D. Antirabies antibodies in blood
Explanation: ***Immunofluorescence of skin biopsy*** - This method involves taking a **skin biopsy** from the **nuchal area** (nape of the neck) and staining it with **fluorescently labeled antibodies** to detect **rabies viral antigens** in cutaneous nerves. - It is considered the most reliable ante-mortem diagnostic test for rabies due to its high specificity and sensitivity in detecting viral nucleocapsid protein. *Immunofluorescence of corneal impressions* - While this method can detect rabies antigens, it generally has **lower sensitivity** compared to skin biopsy. - The procedure can be technically challenging and may yield **false negatives**, especially in early stages of the disease. *Isolation of virus from saliva* - **Viral isolation from saliva** is a possible method, but it is **less sensitive** and **more time-consuming** than immunological detection. - The shedding of rabies virus in saliva can be **intermittent**, leading to potential false negatives. *Antirabies antibodies in blood* - The presence of **antirabies antibodies in the blood** usually indicates either prior vaccination or a late stage of infection where the immune system has begun to respond. - These antibodies are often **undetectable in the early stages** of rabies infection, making this test unreliable for early ante-mortem diagnosis.
Question 5: Which of the following statements regarding classical Dengue fever is FALSE?
- A. Positive tourniquet test (Correct Answer)
- B. Low case fatality rate
- C. Self limiting disease
- D. Transmitted by Aedes aegypti
Explanation: **CRITICAL ISSUE:** This question as currently written is problematic because **all four statements are TRUE** about classical dengue fever, making it impossible to identify a FALSE statement. ***Analysis of Each Statement:*** **Positive tourniquet test** (Currently marked as answer) - This is actually a **TRUE statement** about classical dengue fever - The tourniquet test is **positive in classical dengue fever** and is used as a diagnostic criterion by WHO - A positive tourniquet test indicates capillary fragility and is seen in both classical dengue and DHF - **This should NOT be the answer** to a FALSE question **Low case fatality rate** - TRUE statement: Classical dengue fever has a very low case fatality rate (<1%) with proper supportive care - Mortality is primarily associated with severe dengue/DHF/DSS **Self limiting disease** - TRUE statement: Classical dengue is typically self-limiting, resolving within 7-10 days with symptomatic treatment - Characterized by fever, headache, retro-orbital pain, myalgia, and rash **Transmitted by Aedes aegypti** - TRUE statement: **Aedes aegypti** is the primary vector for dengue transmission - Also transmitted by Aedes albopictus in some regions - Day-biting mosquitoes found in urban/semi-urban areas **RECOMMENDATION:** This question needs revision as it currently has no correct answer. All options are true statements about classical dengue fever.
Question 6: Which of the following diseases is not included in the National Vector Borne Disease Control Program?
- A. Tuberculosis (Correct Answer)
- B. Japanese encephalitis
- C. Malaria
- D. Dengue
Explanation: ***Tuberculosis*** - **Tuberculosis** is a bacterial infection primarily affecting the lungs and is not transmitted by a vector. - It is controlled under the **National TB Elimination Programme (NTEP)**, a separate national health program. *Japanese encephalitis* - **Japanese encephalitis** is a viral disease transmitted by mosquitoes, making it a vector-borne disease. - It is one of the diseases specifically targeted by the **National Vector Borne Disease Control Program (NVBDCP)**. *Malaria* - **Malaria** is a parasitic disease transmitted by Anopheles mosquitoes, clearly categorizing it as vector-borne. - It is a primary focus of the **NVBDCP** due to its significant public health impact. *Dengue* - **Dengue** is a viral disease transmitted by Aedes mosquitoes, hence a vector-borne disease. - **Dengue control and prevention** are key objectives of the **NVBDCP**.
Question 7: Zoonotic disease of viral etiology includes -
- A. Q fever
- B. Rickettsial disease
- C. Rubella
- D. Rabies (Correct Answer)
Explanation: ***Rabies*** - Rabies is a classic example of a **zoonotic disease** caused by the **rabies virus**, transmitted to humans primarily through the bite of an infected animal. - The virus affects the **central nervous system** and is almost invariably fatal once clinical symptoms appear. *Q fever* - Q fever is a **zoonotic disease**, but it is caused by the bacterium **Coxiella burnetii**, not a virus. - It is often transmitted from farm animals and can cause acute or chronic illness. *Rickettsial disease* - Rickettsial diseases are caused by various species of **Rickettsia bacteria**, which are spread by arthropod vectors like ticks, fleas, and lice. - These are bacterial infections and not viral in origin. *Rubella* - Rubella, also known as German measles, is a **viral disease** caused by the rubella virus, but it is typically spread directly from person to person through respiratory droplets. - It is **not considered a zoonotic disease** as it does not primarily originate in animals and transmit to humans.
Question 8: Which of the following viral diseases is least commonly reported in India?
- A. Japanese B encephalitis
- B. Lassa fever (Correct Answer)
- C. KFD
- D. Dengue
Explanation: ***Lassa fever*** - **Lassa fever** is endemic to West Africa, with the **multimammate rat** being its primary reservoir. - Cases of Lassa fever are **extremely rare** in India, primarily limited to travel-related instances due to the geographical distribution of the disease and its vector. *Japanese B encephalitis* - **Japanese B encephalitis (JBE)** is a significant public health concern in India, particularly in endemic regions. - It is a mosquito-borne viral disease, and **vaccination programs** are ongoing to control its spread. *KFD* - **Kyasanur Forest Disease (KFD)** is an endemic viral hemorrhagic fever primarily found in the **Karnataka state of India**. - It is transmitted by **ticks**, making it a regionally significant but recognized viral disease within India. *Dengue* - **Dengue** is one of the most commonly reported and widespread viral diseases in India. - It is a **mosquito-borne** illness with frequent outbreaks occurring across various parts of the country.
Question 9: Most effective preventive measure against rabies
- A. Heat
- B. Humidity
- C. Avoiding contact with infected animals and vaccination (Correct Answer)
- D. None of the options
Explanation: ***Avoiding contact with infected animals and vaccination*** ✓ - The most effective preventive measure against rabies is to **avoid contact with potentially infected animals**, especially wild animals and unvaccinated domestic animals. - **Vaccination** (pre-exposure prophylaxis) is crucial for individuals at high risk of exposure (veterinarians, animal handlers, laboratory workers) and for domestic animals, forming the cornerstone of rabies prevention. - Post-exposure prophylaxis (PEP) with immunoglobulin and vaccine series is highly effective when administered promptly after exposure. *Heat* - While high temperatures can inactivate the rabies virus in a laboratory setting, it is **not a practical or effective preventive measure** against rabies in real-world scenarios. - The virus is transmitted through bites, scratches, and mucous membrane contact with infected saliva; environmental heat does not prevent transmission or infection. *Humidity* - **Humidity does not play a significant role** in the prevention or transmission of rabies. - The rabies virus is labile outside of a host and does not survive long in the environment, regardless of humidity levels. *None of the options* - This option is incorrect because there are highly effective preventive measures against rabies, as detailed in the correct option. - Rabies prevention is well-established through public health interventions (animal vaccination programs, post-exposure prophylaxis) and individual precautions.
Question 10: Antemortem diagnosis of rabies is made with:
- A. Inoculation in culture media
- B. Negri bodies in hippocampus
- C. Corneal impression smear (Correct Answer)
- D. Rabies virus specific antibodies
Explanation: ***Corneal impression smear*** - A **corneal impression smear** can detect viral antigens in the cornea using fluorescent antibody staining, a method that can be performed on living patients. - This technique provides a relatively rapid and non-invasive way to diagnose rabies **antemortem**. *Inoculation in culture media* - Rabies virus is notoriously difficult to culture in standard cell culture media, making this method impractical and unreliable for **antemortem diagnosis**. - While viral isolation is possible in specialized research settings, it is not a routine diagnostic tool for rabies in living patients. *Negri bodies in hippocampus* - **Negri bodies** are eosinophilic inclusions found in the cytoplasm of neurons, particularly in the hippocampus, which are pathognomonic for rabies. - However, their detection requires **postmortem brain tissue biopsy**, making this a **postmortem diagnostic** method, not antemortem. *Rabies virus specific antibodies* - While the presence of **rabies virus-specific antibodies** (particularly in CSF) can indicate exposure and infection, they often appear late in the disease course. - The detection of antibodies may not be reliable for early **antemortem diagnosis**, especially in naive individuals whose immune response has not yet fully developed.
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