One Health Approach to Zoonoses — MCQs
Zoonotic diseases are -
Which of the following diseases has the largest submerged portion in the iceberg model of disease?
Which of the following diseases is primarily monitored under the Integrated Disease Surveillance Program (IDSP)?
Which of the following statements about a primary health centre (PHC) is incorrect?
Four weeks after assisting in several calf deliveries, a farmer develops fever, weakness, muscle aches, and sweats. The fever rises in the afternoon and falls during the night. A Brucella species is isolated. Which Brucella species is a possible bioterrorism agent and is best described by one of the following?
Considering that dogs are the most common carriers of rabies and that the disease predominantly affects children in developing countries, what is the most effective and direct method to significantly reduce the incidence of rabies?
Transition from increased prevalence of infectious and communicable diseases to man-made diseases is known as
What is the most effective natural barrier to rabies?
A veterinary doctor had pyrexia of unknown origin. Blood culture in special laboratory media was positive for Gram-negative, oxidase-positive short bacilli. Which one of the following is the likely organism grown in culture?
A patient presented with pyrexia of unknown origin. Blood culture in special laboratory media was positive for gram-negative short bacilli that were oxidase-positive. Which one of the following is the likely organism grown in culture?
One Health Approach to Zoonoses Indian Medical PG Practice Questions and MCQs
Question 1: Zoonotic diseases are -
- A. Anthrax
- B. Plague
- C. Salmonellosis
- D. All of the options (Correct Answer)
Explanation: ***All of the options*** - **Anthrax**, **Plague**, and **Salmonellosis** are all well-established examples of zoonotic diseases, which are infections naturally transmitted between vertebrate animals and humans. - These diseases represent a diverse spectrum of bacterial infections with significant public health implications worldwide. **Anthrax** - Caused by *Bacillus anthracis*, a spore-forming bacterium naturally found in soil that primarily affects livestock and wild herbivores. - Humans acquire infection through contact with infected animals or contaminated animal products (hides, wool, meat). - Clinical forms include cutaneous (most common), inhalational (most severe), and gastrointestinal anthrax. - Remains an important occupational hazard for veterinarians, farmers, and those handling animal products. **Plague** - Caused by *Yersinia pestis*, maintained in nature through rodent-flea cycles. - Transmission to humans occurs primarily via bites from infected fleas or direct contact with infected animals. - Historically responsible for devastating pandemics including the Black Death. - Clinical manifestations include bubonic (most common), pneumonic (person-to-person transmission possible), and septicemic plague. **Salmonellosis** - Caused by non-typhoidal *Salmonella* species, commonly colonizing the intestines of various animals including poultry, cattle, reptiles, and pets. - Humans typically acquire infection through consumption of contaminated food (undercooked meat, eggs, unpasteurized dairy) or direct animal contact. - Presents as acute gastroenteritis with diarrhea, fever, and abdominal cramps. - One of the most common foodborne zoonotic infections globally.
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 primarily monitored under the Integrated Disease Surveillance Program (IDSP)?
- A. Tuberculosis
- B. HIV
- C. Malaria (Correct Answer)
- D. Diabetes
Explanation: ***Malaria*** - Malaria is a significant public health concern with high incidence and mortality, making its surveillance crucial for **disease control and elimination efforts**. - The IDSP aims for early detection and rapid response to **outbreaks of communicable diseases**, including vector-borne diseases like malaria. *Tuberculosis* - While a major public health issue, **tuberculosis (TB)** is primarily monitored under the **National Tuberculosis Elimination Programme (NTEP)**, which has a dedicated and extensive surveillance system. - The NTEP focuses on active case finding, treatment, and prevention of TB through a specific, robust framework separate from the IDSP's general surveillance. *HIV* - **HIV/AIDS** surveillance is conducted under the **National AIDS Control Organisation (NACO)**, which has a specialized program for monitoring prevalence, incidence, and risk behaviors. - NACO's surveillance includes sentinel surveillance among specific populations and programmatic data collection, distinct from the IDSP's generalized infectious disease monitoring. *Diabetes* - **Diabetes** is a **non-communicable disease** and is not primarily monitored under the IDSP, which focuses on infectious disease outbreaks. - Surveillance for non-communicable diseases like diabetes typically falls under programs dedicated to non-communicable disease prevention and control, focusing on prevalence and risk factors.
Question 4: Which of the following statements about a primary health centre (PHC) is incorrect?
- A. Tertiary care surgical procedures (Correct Answer)
- B. Caters about 20,000- 30,000 people
- C. Provide water and sanitation and basic health requirements
- D. There is one medical officer and one staff nurse
Explanation: ***Tertiary care surgical procedures*** - Primary Health Centres (PHCs) are designed to provide **basic and essential healthcare services** at the community level, not advanced surgical interventions. - **Tertiary care procedures**, which involve complex surgeries or specialized treatments, are typically performed at **district hospitals** or super-specialty hospitals. - PHCs focus on **primary healthcare** including outpatient care, basic laboratory services, immunization, maternal and child health services, and health education. *Caters about 20,000-30,000 people* - This statement is **correct** regarding the population coverage of a PHC in rural areas. - According to IPHS norms, a PHC serves **20,000-30,000 population** in plain areas and **30,000 population** in hilly/tribal/difficult areas. - The PHC acts as the **first point of contact** for individuals seeking health services in a defined geographical area. *Provide water and sanitation and basic health requirements* - This is a **correct** statement, as PHCs are responsible for promoting health and preventing disease through community-level interventions. - They ensure access to **safe water, sanitation, and essential primary healthcare**. - PHCs focus on improving **public health determinants** alongside providing clinical services through health education and environmental health activities. *There is one medical officer and one staff nurse* - This statement is **correct** and describes the **minimum staffing pattern** at PHCs according to Indian Public Health Standards (IPHS). - A standard PHC has at least **1 Medical Officer, 1 Staff Nurse, and support staff** including ANMs (Auxiliary Nurse Midwives) who work at sub-centers. - Additional staff may be present depending on whether it's a 4-bedded or 6-bedded PHC.
Question 5: Four weeks after assisting in several calf deliveries, a farmer develops fever, weakness, muscle aches, and sweats. The fever rises in the afternoon and falls during the night. A Brucella species is isolated. Which Brucella species is a possible bioterrorism agent and is best described by one of the following?
- A. Typically infects goats and sheep, grows well in CO2, and is not inhibited by thionine or basic fuchsin dyes (Correct Answer)
- B. Commonly inhabits the canine respiratory tract and is an occasional pathogen for humans; strongly urease-positive
- C. Gram-negative bipolar stained bacilli that cause diarrhea by means of a heat-stable enterotoxin, with abdominal pain that may be mistaken for appendicitis
- D. Pits agar, grows both in carbon dioxide and under anaerobic conditions, and is part of the normal oral cavity flora
Explanation: ***Typically infects goats and sheep, grows well in CO2, and is not inhibited by thionine or basic fuchsin dyes*** - This description is characteristic of ***Brucella melitensis***, which is recognized as the most pathogenic **Brucella** species and a potential **bioterrorism agent** (CDC Category B) due to its high infectivity and severe disease course. - Its specific growth requirements (CO2 preference) and dye resistance patterns (not inhibited by **thionine** or **basic fuchsin**) are key laboratory identifiers that differentiate it from other **Brucella** species (*B. abortus* is inhibited by thionine; *B. suis* is inhibited by basic fuchsin). - Low infective dose (10-100 organisms) and aerosol transmission capability make it a significant bioterrorism threat. *Commonly inhabits the canine respiratory tract and is an occasional pathogen for humans; strongly urease-positive* - This describes ***Bordetella bronchiseptica***, not a **Brucella** species. It is a pathogen primarily associated with animals, especially dogs (kennel cough), and only rarely causes disease in immunocompromised humans. - While it can be urease-positive, it belongs to a different genus and does not fit the clinical or epidemiological context of brucellosis. *Gram-negative bipolar stained bacilli that cause diarrhea by means of a heat-stable enterotoxin, with abdominal pain that may be mistaken for appendicitis* - This description points to ***Yersinia enterocolitica***, not a **Brucella** species. It is a **Gram-negative bacterium** known for causing gastrointestinal infections with symptoms that can mimic **appendicitis** (pseudoappendicitis syndrome). - Its characteristic **bipolar staining** ("safety pin" appearance) and production of **heat-stable enterotoxin** are distinct from **Brucella** species. *Pits agar, grows both in carbon dioxide and under anaerobic conditions, and is part of the normal oral cavity flora* - This description is typical of ***Eikenella corrodens***, not a **Brucella** species. It is a **Gram-negative bacillus** found in the **normal oral flora** that can cause infections related to human bites or dental procedures. - Its ability to "pit" agar and specific atmospheric growth requirements (CO2 and anaerobic) are unique characteristics that differentiate it from **Brucella** species.
Question 6: Considering that dogs are the most common carriers of rabies and that the disease predominantly affects children in developing countries, what is the most effective and direct method to significantly reduce the incidence of rabies?
- A. Conduct rabies testing for all dogs
- B. Control the stray dog population and vaccinate all dogs (Correct Answer)
- C. Enhance laboratory testing capabilities
- D. Improve healthcare worker training for disease surveillance
Explanation: ***Control the stray dog population and vaccinate all dogs*** - As dogs are the primary reservoirs of rabies, controlling their population, coupled with widespread **dog vaccination**, is the most direct and effective strategy to break the transmission cycle to humans. - This approach tackles the root cause of the disease in areas where dog-mediated transmission is endemic, leading to a significant reduction in human rabies cases. *Conduct rabies testing for all dogs* - While testing identifies infected animals, it is **resource-intensive** and impractical for large dog populations, especially in low-resource settings, and does not prevent future infections. - This strategy is reactive rather than **proactive** in preventing the spread of rabies. *Enhance laboratory testing capabilities* - Improving laboratory testing capabilities is crucial for **surveillance** and accurate diagnosis but does not directly prevent rabies transmission at the source. - It's a supportive measure that helps monitor disease burden but isn't the most effective **primary intervention** for incidence reduction. *Improve healthcare worker training for disease surveillance* - Training healthcare workers enhances case detection and reporting, which is vital for **epidemiological monitoring** and timely post-exposure prophylaxis (PEP). - However, it does not address the fundamental issue of rabies transmission from dogs to humans and is not a direct prevention method for reducing disease incidence.
Question 7: Transition from increased prevalence of infectious and communicable diseases to man-made diseases is known as
- A. Demographic transition
- B. Paradoxical transition
- C. Epidemiological transition (Correct Answer)
- D. Reversal of transition
Explanation: ***Epidemiological transition*** - This term describes the shift in **disease patterns** observed in many populations, moving from a predominance of **infectious and communicable diseases** to an increased prevalence of **chronic, non-communicable diseases** (often described as "man-made" due to their association with lifestyle and environmental factors). - This transition is typically linked to advancements in **public health**, sanitation, medicine, and changes in socioeconomic status. *Demographic transition* - This concept describes the historical shift from high **birth rates** and **death rates** to low birth rates and death rates as a country develops from a pre-industrial to an industrialized economic system. - While related to disease patterns through changes in population structure, it directly focuses on **population growth** and age distribution, not specific disease prevalence. *Paradoxical transition* - This is not a recognized or standard public health or demographic term for the described phenomenon. - The term "paradoxical" would imply a contradictory or unexpected outcome, which is not the primary descriptor for the shift in disease patterns. *Reversal of transition* - This term would imply a return to previous patterns, such as an increase in **infectious diseases** after a period of decline. - While possible in specific contexts (e.g., due to antibiotic resistance or weakened public health systems), it does not describe the initial shift from infectious to man-made diseases.
Question 8: 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 9: A veterinary doctor had pyrexia of unknown origin. Blood culture in special laboratory media was positive for Gram-negative, oxidase-positive short bacilli. Which one of the following is the likely organism grown in culture?
- A. Pasteurella spp.
- B. Francisella spp.
- C. Bartonella spp.
- D. Brucella spp. (Correct Answer)
Explanation: ### Explanation The clinical presentation of **Pyrexia of Unknown Origin (PUO)** in a high-risk professional (veterinary doctor) strongly suggests **Brucellosis**, a classic zoonotic infection. **1. Why Brucella spp. is correct:** * **Occupational Risk:** Veterinarians, farmers, and slaughterhouse workers are at high risk through contact with infected animals or unpasteurized dairy. * **Microbiology:** *Brucella* are small, Gram-negative coccobacilli (short bacilli) that are **oxidase-positive** and catalase-positive. * **Culture:** They are fastidious and require **special media** (e.g., Castaneda’s biphasic medium) for growth. They are notorious for causing "culture-negative" endocarditis if standard media are used or if incubation is too short. **2. Why the other options are incorrect:** * **Pasteurella spp.:** While Gram-negative and oxidase-positive, it is typically associated with **animal bites** (cats/dogs) causing cellulitis, not prolonged PUO. * **Francisella spp.:** Causes Tularemia. While it is a Gram-negative coccobacillus, it is typically **oxidase-negative** and requires cysteine-enriched media (BCYE agar). * **Bartonella spp.:** Causes Cat Scratch Disease or Trench Fever. It is a fastidious Gram-negative rod but is **oxidase-negative**. **3. High-Yield Clinical Pearls for NEET-PG:** * **Gold Standard Diagnosis:** Bone marrow culture (higher yield than blood culture). * **Standard Serology:** Standard Agglutination Test (SAT); titers >1:160 are significant. * **Rose Bengal Plate Test:** Used as a rapid screening tool. * **Treatment:** WHO recommends **Rifampicin + Doxycycline** for 6 weeks. * **Complication:** Osteoarticular involvement (sacroiliitis) is the most common complication.
Question 10: A patient presented with pyrexia of unknown origin. Blood culture in special laboratory media was positive for gram-negative short bacilli that were oxidase-positive. Which one of the following is the likely organism grown in culture?
- A. Pasteurella spp.
- B. Francisella spp.
- C. Bartonella spp.
- D. Brucella spp. (Correct Answer)
Explanation: ### Explanation **Correct Answer: D. Brucella spp.** **Why Brucella is the correct answer:** Brucellosis is a classic cause of **Pyrexia of Unknown Origin (PUO)**, often presenting as "undulant fever." The organism is a small, **Gram-negative coccobacillus** (short bacilli) that is **oxidase-positive** and catalase-positive. A key diagnostic feature is its growth characteristics: it is a fastidious aerobe that requires **special laboratory media** (e.g., Castaneda’s biphasic medium) and often takes prolonged incubation (up to 2-4 weeks) to grow. **Analysis of Incorrect Options:** * **A. Pasteurella spp.:** While these are Gram-negative, oxidase-positive bacilli, they are typically associated with **animal bites** (cats/dogs) and cause acute cellulitis or abscesses rather than chronic PUO. * **B. Francisella spp.:** *Francisella tularensis* (Tularemia) is a Gram-negative coccobacillus, but it is characteristically **oxidase-negative**. It also requires cysteine-enriched media (like BCYE) for growth. * **C. Bartonella spp.:** These are Gram-negative bacilli but are typically **oxidase-negative**. They cause Cat Scratch Disease or Bacillary Angiomatosis and are extremely difficult to culture on standard blood media. **High-Yield Clinical Pearls for NEET-PG:** * **Gold Standard Diagnosis:** Bone marrow culture (higher yield than blood culture). * **Culture Media:** **Castaneda’s Medium** is the traditional biphasic medium used to reduce the risk of laboratory-acquired infections. * **Serology:** The **Standard Agglutination Test (SAT)** detects antibodies; a titer >1:160 is significant. * **Treatment:** The WHO recommends **Rifampicin + Doxycycline** for 6 weeks. * **Occupational Hazard:** It is the most common laboratory-acquired infection; samples must be handled in Biosafety Level 3 (BSL-3) cabinets.
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