Prevention and Control of Zoonoses — MCQs
What is the first step an epidemiologist takes in an epidemic investigation?
Zoonotic diseases are all except -
A single disease control strategy implemented by a program is known as?
A boy got unprovoked bite from a neighbour's dog. The animal control authority caught the dog and it was found to be healthy. What will be the next step?
Which of the following diseases is not covered under the Integrated Disease Surveillance Project (IDSP)?
All of the following are true about the Herd immunity for infectious diseases except -
A child has received full rabies vaccination in December 2023 and now presented with an oozing wound on the great toe and the pet was also vaccinated. Next line of management is
Silicosis can be controlled by:
What is the most effective natural barrier to rabies?
Schistosomiasis is an example of which type of zoonosis?
Prevention and Control of Zoonoses Indian Medical PG Practice Questions and MCQs
Question 1: What is the first step an epidemiologist takes in an epidemic investigation?
- A. Confirm the diagnosis (Correct Answer)
- B. Identify the prone people
- C. Identify the causative factors
- D. Identify the cases
Explanation: ***Confirm the diagnosis*** - The initial and most crucial step is to **confirm the diagnosis** of the disease in question to ensure that the reported cases are indeed suffering from the same condition. - This step helps to avoid misclassification and ensures the investigation focuses on a specific, confirmed health problem. *Identify the cases* - While essential, **identifying cases** usually follows initial diagnostic confirmation, as you need a clear case definition based on a confirmed diagnosis to correctly identify who is a case. - This involves defining who is considered a case based on symptoms, laboratory results, and epidemiological links. *Identify the prone people* - **Identifying prone people** refers to determining the population at risk, which is a subsequent step after understanding the confirmed disease and its initial pattern. - This step typically falls under characterizing the distribution of the disease (person, place, time) in the investigation. *Identify the causative factors* - **Identifying causative factors** is a later stage in the investigation, often involving analytical studies to test hypotheses, which can only occur effectively once the diagnosis is confirmed and cases are clearly defined and counted. - This step aims to understand *why* the epidemic is occurring, after establishing *what* is occurring.
Question 2: Zoonotic diseases are all except -
- A. Q fever
- B. Typhoid (Correct Answer)
- C. Anthrax
- D. Rabies
Explanation: ***Typhoid*** - Typhoid fever is a **bacterial infection** caused by *Salmonella Typhi*, which is spread through contaminated food and water, primarily from human waste. - It is an exclusively **human disease**, meaning there is no animal reservoir involved in its transmission to humans. *Q fever* - Q fever is a **zoonotic disease** caused by the bacterium *Coxiella burnetii*, primarily spread from livestock (cattle, sheep, goats) to humans. - Transmission generally occurs through inhalation of contaminated aerosols from animal excreta or birth products. *Anthrax* - Anthrax is a serious **zoonotic disease** caused by the bacterium *Bacillus anthracis*, which can affect both animals and humans. - Humans usually contract anthrax through contact with infected animals or contaminated animal products. *Rabies* - Rabies is a fatal **viral zoonotic disease** that is transmitted to humans through the saliva of infected animals, most commonly from dog bites. - Wild animals like bats, raccoons, and foxes are important reservoirs for the rabies virus.
Question 3: A single disease control strategy implemented by a program is known as?
- A. Horizontal program
- B. Interventional program
- C. Volunteer program
- D. Vertical program (Correct Answer)
Explanation: ***Vertical program*** - A **vertical program** focuses on the specific control or eradication of a **single disease** or a highly integrated group of diseases. - These programs often operate with a dedicated infrastructure, resources, and personnel, distinct from the broader health system, to achieve their targeted objectives. *Horizontal program* - A **horizontal program** integrates multiple health services and diseases under a single, overarching health system. - It emphasizes strengthening the **primary healthcare infrastructure** and delivering comprehensive care rather than targeting individual diseases. *Interventional program* - An **interventional program** is a broad term that could apply to any health program designed to intervene in the progression or incidence of a disease. - It doesn't specifically define whether the intervention targets a single disease or multiple health issues; its focus is on the act of intervention itself. *Volunteer program* - A **volunteer program** refers to initiatives where individuals offer their time and services without receiving monetary compensation. - While volunteers can be part of any type of health program (vertical or horizontal), the term itself describes the nature of the labor force rather than the program's strategic approach to disease control.
Question 4: A boy got unprovoked bite from a neighbour's dog. The animal control authority caught the dog and it was found to be healthy. What will be the next step?
- A. Test antibody level in the dog
- B. Perform euthanasia for the dog
- C. Start post-exposure prophylaxis
- D. Observe the dog for 10 days for signs of rabies (Correct Answer)
Explanation: ***Observe the dog for 10 days for signs of rabies*** - According to **WHO and ICDCDR guidelines**, when a biting domestic dog/cat is captured and appears healthy, the standard protocol is to **observe the animal for 10 days** for signs of rabies. - If the dog remains **healthy throughout the 10-day observation period**, it confirms that rabies virus was not present in its saliva at the time of bite, as rabies virus appears in saliva only **2-3 days before clinical signs develop**. - During observation, **post-exposure prophylaxis (PEP) may be initiated** and can be discontinued if the animal remains healthy after 10 days, or withheld pending observation results depending on local protocols. *Test antibody level in the dog* - **Antibody testing** does not determine whether the animal is currently **shedding rabies virus in saliva**, which is the key factor for transmission risk assessment. - Antibodies may be present due to **previous vaccination** without indicating active infection or current infectivity, making this test irrelevant for immediate post-bite management decisions. *Perform euthanasia for the dog* - **Euthanasia and brain examination** is reserved for animals showing **clinical signs of rabies**, those unavailable for observation, or when **observation is not feasible** (e.g., wild animals, stray animals that cannot be confined). - Since the dog is **healthy and available for observation**, euthanasia is not indicated and would be unnecessary and unethical given the availability of safer monitoring options. *Start post-exposure prophylaxis* - While **human PEP initiation** is recommended for Category II/III exposures, the question asks for the **next step regarding the animal** after it has been caught and found healthy. - The key management decision is to **observe the animal**, which then guides whether PEP can be discontinued (if started) or needs to be initiated (if withheld).
Question 5: Which of the following diseases is not covered under the Integrated Disease Surveillance Project (IDSP)?
- A. Tuberculosis
- B. Cholera
- C. Herpes zoster (Correct Answer)
- D. Meningococcal disease
Explanation: ***Herpes zoster*** - **Herpes zoster** (shingles) is not included in the Integrated Disease Surveillance Project (IDSP) as it is neither an epidemic-prone disease nor a notifiable disease under the program. - IDSP focuses on diseases with significant public health impact, epidemic potential, or those requiring immediate public health response. - While herpes zoster can cause morbidity in immunocompromised individuals, it does not pose a widespread public health threat requiring national surveillance. *Tuberculosis* - **Tuberculosis (TB)** is explicitly covered under IDSP as a major notifiable disease due to its high burden in India and significant public health importance. - TB surveillance under IDSP helps monitor disease trends, detect outbreaks, and evaluate the effectiveness of the National Tuberculosis Elimination Programme. - Regular reporting and surveillance are essential for achieving TB elimination goals. *Cholera* - **Cholera** is a priority disease under IDSP as an epidemic-prone disease with potential for rapid outbreaks and high mortality if untreated. - It is part of the core surveillance list due to its ability to cause severe dehydration and waterborne epidemics. - Early detection through IDSP enables timely implementation of control measures including safe water supply and oral rehydration therapy. *Meningococcal disease* - **Meningococcal disease** (acute bacterial meningitis) is covered under IDSP due to its high case fatality rate, epidemic potential, and need for urgent public health response. - Surveillance is critical for early outbreak detection and implementation of preventive measures such as mass vaccination and chemoprophylaxis. - Close monitoring helps identify circulating serotypes and guide vaccination strategies.
Question 6: All of the following are true about the Herd immunity for infectious diseases except -
- A. It is more easily achieved for infections that do not have a sub-clinical phase (Correct Answer)
- B. In the case of tetanus it does not protect the individual
- C. It is affected by the presence and distribution of alternative animal hosts
- D. It refers to group protection beyond what is afforded by the protection of immunized individuals
Explanation: ***It is more easily achieved for infections that do not have a sub-clinical phase*** - This statement is incorrect because infections with a **sub-clinical phase** (asymptomatic carriers) can still contribute to transmission, making herd immunity harder to achieve. - The presence of asymptomatic but infectious individuals means that a higher percentage of the population needs to be immune to protect the unimmunized. *In the case of tetanus it does not protect the individual* - **Tetanus** is caused by a toxin produced by *Clostridium tetani*, which is ubiquitous in the environment and does not spread person-to-person. - Therefore, **herd immunity** (protection from indirect transmission) is irrelevant for tetanus; individual vaccination is the only way to prevent the disease. *It is affected by the presence and distribution of alternative animal hosts* - For **zoonotic diseases**, such as rabies or influenza, the presence of **animal reservoirs** can make achieving herd immunity in the human population more challenging. - These animal hosts can maintain the pathogen's circulation, allowing for reintroduction into the human population. *It refers to group protection beyond what is afforded by the protection of immunized individuals* - **Herd immunity** occurs when a sufficiently high proportion of the population is immune to an infectious disease, indirectly protecting non-immune individuals. - This collective immunity reduces the likelihood of an outbreak and limits disease transmission within the population.
Question 7: A child has received full rabies vaccination in December 2023 and now presented with an oozing wound on the great toe and the pet was also vaccinated. Next line of management is
- A. RIG + 5 doses of vaccine
- B. 5 doses of vaccines only
- C. No vaccine required
- D. 2 doses of Rabies vaccine (Correct Answer)
Explanation: ***2 doses of Rabies vaccine*** - For individuals who have received **previous full rabies vaccination** (either pre-exposure or post-exposure prophylaxis), a subsequent exposure requires only **two booster doses of vaccine on days 0 and 3**, regardless of wound category. - Even though this is a **Category III exposure** (oozing wound with break in skin), **no RIG is required** for previously immunized individuals as per WHO and APCRI guidelines. - The pre-existing immunity from the prior vaccination provides a **rapid anamnestic (memory) response**, eliminating the need for passive immunization or a full primary series. *RIG + 5 doses of vaccine* - This regimen is for individuals with **no prior vaccination history** and represents the full post-exposure prophylaxis for Category III exposures (transdermal bites, oozing wounds). - The child has been previously vaccinated, rendering this extensive protocol unnecessary and potentially harmful due to **immune complex formation** if RIG is given to an immune individual. *5 doses of vaccines only* - This approach is suitable for **previously unvaccinated individuals** with Category II exposure (nibbling, minor scratches without bleeding) where RIG may not be available. - However, in a previously vaccinated individual, the full 5-dose series is **excessive and not indicated** as immunity is already established. *No vaccine required* - Even with a previously vaccinated child and a vaccinated pet, there is still a **potential risk of exposure** to rabies, especially with a Category III wound (oozing wound). - Omitting vaccination entirely would be **negligent** and violates standard guidelines, as vaccine efficacy is not 100% and animal vaccination status can be uncertain or lapsed.
Question 8: Silicosis can be controlled by:
- A. BCG vaccination
- B. Rigorous dust control (Correct Answer)
- C. Adequate personal hygiene
- D. Effective implementation of factories act
Explanation: ***Rigorous dust control*** - **Silicosis** is a lung disease caused by inhaling **crystalline silica dust**, making dust control the primary preventive measure - This includes **engineering controls** such as ventilation, wet methods, local exhaust systems, and enclosure to minimize airborne dust levels - **Primary prevention** through environmental control is the most effective strategy *BCG vaccination* - **BCG vaccination** is used to prevent **tuberculosis**, not silicosis - While patients with silicosis have increased risk for tuberculosis, BCG does not directly prevent or control silicosis development *Adequate personal hygiene* - Good **personal hygiene** is important for overall health but does not prevent inhalation of **silica dust** in occupational settings - Does not address the fundamental environmental exposure that causes silicosis *Effective implementation of factories act* - The **Factories Act** provides legal frameworks for worker safety and encompasses broad measures - However, the specific control of silicosis depends directly on technical measures of **rigorous dust control**, which are implemented through but not synonymous with such legislation
Question 9: What is the most effective natural barrier to rabies?
- A. Heat
- B. Humidity
- C. Water (Correct Answer)
- D. None of the above
Explanation: **Explanation:** The correct answer is **Water**. This question refers to the ecological and behavioral transmission of rabies rather than a physiological barrier within the human body. **Why Water is the Correct Answer:** Rabies is primarily transmitted through the bites of terrestrial mammals (dogs, foxes, raccoons). Large bodies of water, such as wide rivers, lakes, and oceans, act as the most effective **natural geographic barriers** to the spread of the virus. These barriers limit the migration and interaction of infected animal populations, effectively "quarantining" specific regions. For example, island nations like the UK, Japan, and Australia have historically maintained a rabies-free status largely due to the surrounding water acting as a physical deterrent to infected terrestrial vectors. **Analysis of Incorrect Options:** * **Heat & Humidity:** While the Rabies virus (*Lyssavirus*) is thermolabile (easily destroyed by heat and desiccation outside the host), environmental temperature and humidity do not stop the spread of the disease. Rabies thrives in both tropical (India) and arctic (Arctic fox) climates. These factors affect the survival of the virus on surfaces but do not act as a barrier to the movement of the vectors. **NEET-PG High-Yield Pearls:** * **Virus Type:** Negative-sense, single-stranded RNA virus; Bullet-shaped (Rhabdoviridae family). * **Pathognomonic Feature:** **Negri bodies** (intracytoplasmic eosinophilic inclusions) found most commonly in the Hippocampus (Ammon’s horn) and Cerebellum (Purkinje cells). * **Centripetal Spread:** The virus travels from the site of the bite to the CNS via **retrograde axonal transport** (dynein motors). * **Hydrophobia:** A clinical hallmark caused by forceful spasms of the accessory respiratory muscles and diaphragm when attempting to swallow water. * **Post-Exposure Prophylaxis (PEP):** Includes wound washing (most important initial step), Rabies vaccine (Days 0, 3, 7, 14, 28), and Human Rabies Immunoglobulin (HRIG).
Question 10: Schistosomiasis is an example of which type of zoonosis?
- A. Meta-zoonoses (Correct Answer)
- B. Cyclo-zoonoses
- C. Direct-zoonoses
- D. Sporo-zoonoses
Explanation: ### Explanation **Correct Answer: A. Meta-zoonoses** **Concept:** Zoonoses are classified based on the life cycle of the infecting organism. **Meta-zoonoses** are infections transmitted to humans via **invertebrate vectors**, in which the agent multiplies, develops, or both. There is always an extrinsic incubation period before transmission to a vertebrate host. **Schistosomiasis** (Bilharziasis) is a classic meta-zoonosis because the parasite requires an intermediate host—**freshwater snails** (invertebrates)—to complete its life cycle. The miracidia develop into cercariae within the snail before becoming infectious to humans. --- **Analysis of Incorrect Options:** * **B. Cyclo-zoonoses:** These require **more than one vertebrate host** but no invertebrate host to complete the life cycle. Examples include *Taenia solium* (pork tapeworm) and *Echinococcus granulosus* (hydatid cyst). * **C. Direct-zoonoses:** These are maintained in nature by a single vertebrate species and are transmitted from one vertebrate to another by direct contact or mechanical vectors. Examples include **Rabies**, Anthrax, and Brucellosis. * **D. Sapro-zoonoses:** (Often confused with Sporo-zoonoses) These require a **non-animal site** (soil, water, or decaying organic matter) for development. Examples include Tetanus and Histoplasmosis. --- **High-Yield Clinical Pearls for NEET-PG:** * **Vector for Schistosomiasis:** *Biomphalaria* (S. mansoni), *Bulinus* (S. haematobium), and *Oncomelania* (S. japonicum). * **Infective Stage:** Cercaria (penetrates unbroken skin during swimming/wading). * **Diagnostic Hallmark:** *S. haematobium* is associated with **terminal hematuria** and **Squamous Cell Carcinoma of the bladder**. * **Drug of Choice:** Praziquantel is the gold standard for all Schistosoma species.
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