Global Impact of Zoonotic Diseases — MCQs
Most common widespread zoonotic disease in the world is -
All of the following are zoonosis, except:
Which of the following statements is incorrect regarding the strategic plan for malaria control 2012-2017?
Zoonoses are all except-
Which diseases are infectious but not communicable?
Which of the following is the true statement regarding measures to prevent typhoid transmission in the community?
Fever of unknown origin in a farmer who raises goats would most likely be caused by which of the following organisms?
Following are examples of human "dead end" diseases except -
Which of the following statements is TRUE regarding Disability-Adjusted Life Year (DALY)?
Which organism does not require a vector for transmission?
Global Impact of Zoonotic Diseases Indian Medical PG Practice Questions and MCQs
Question 1: Most common widespread zoonotic disease in the world is -
- A. Leptospirosis (Correct Answer)
- B. Brucellosis
- C. Rabies
- D. Anthrax
Explanation: ***Leptospirosis*** - **Leptospirosis** is considered the most common widespread **zoonotic disease** globally, with an estimated 1.03 million cases per year. - It is caused by **spirochetes** of the genus *Leptospira* and is transmitted to humans through contact with urine from infected animals or contaminated water/soil. *Brucellosis* - **Brucellosis** is a significant zoonotic disease but is generally less widespread than leptospirosis, particularly in regions with effective control programs for livestock. - It is transmitted through direct contact with infected animals or consumption of unpasteurized dairy products, often causing **undulant fever**. *Rabies* - **Rabies** is a severe and nearly universally fatal zoonotic disease, but its global incidence is lower than leptospirosis, largely due to successful vaccination campaigns in animals. - Transmission occurs primarily through the bite of an infected animal, leading to **neurological symptoms**. *Anthrax* - **Anthrax** is a serious bacterial disease, but its occurrence is relatively rare and often localized to specific regions or outbreak events. - It is caused by *Bacillus anthracis* and is typically acquired through contact with infected animals or their products, presenting in **cutaneous**, **inhalational**, **gastrointestinal**, or **injectional** forms.
Question 2: All of the following are zoonosis, except:
- A. Japanese Encephalitis
- B. Plague
- C. Tuberculosis
- D. HIV (Correct Answer)
Explanation: ***HIV*** - While HIV originated from **simian immunodeficiency virus (SIV)** in non-human primates, it is **no longer considered a zoonosis** because transmission now occurs exclusively **human-to-human**. - The virus has fully adapted to **human hosts**, and there is **no ongoing animal reservoir** contributing to the current epidemic. - Zoonotic diseases require **active animal-to-human transmission**, which does not apply to HIV in its current form. *Japanese Encephalitis* - This is a **mosquito-borne viral disease** that primarily circulates between **mosquitoes, pigs, and birds**. - Humans are **accidental dead-end hosts**, making this a true **zoonotic disease**. *Plague* - Caused by **Yersinia pestis**, which naturally infects **small mammals (rodents)** and their fleas. - Humans become infected through **flea bites** or direct contact with infected animals, making it a **classic zoonosis**. *Tuberculosis* - While most human TB is caused by **M. tuberculosis** (human-to-human), **M. bovis** causes **zoonotic TB**. - Transmitted from **infected cattle** to humans via **unpasteurized dairy products** or close contact with infected animals. - This animal-to-human transmission qualifies TB as a **zoonotic disease**.
Question 3: Which of the following statements is incorrect regarding the strategic plan for malaria control 2012-2017?
- A. 50% reduction in mortality by 2017
- B. Objective is API < 1 per 10,000 (Correct Answer)
- C. Complete treatment to 100% of patients
- D. Annual incidence < 1 per 1000 by 2017
Explanation: ***Objective is API < 1 per 10,000*** - The correct objective for the **Annual Parasite Incidence (API)** in the 2012-2017 strategic plan for malaria control was to reduce it to **less than 1 per 1,000 population**, not 1 per 10,000, making this statement incorrect. - This metric measures the number of new malaria cases per 1,000 people per year. *50% reduction in mortality by 2017* - A key objective of the **National Framework for Malaria Elimination in India** (which this strategic plan aimed to contribute to) was indeed to achieve a significant reduction in malaria-related mortality. - Specifically, aiming for a **50% reduction in mortality** by 2017 was a stated goal to lessen the disease burden. *Annual incidence < 1 per 1000 by 2017* - One of the primary goals of the **Malaria Control Strategic Plan 2012-2017** was to reduce the annual parasite incidence (API) to **less than 1 per 1,000 population** in all endemic areas. - This target focused on decreasing the occurrence of new malaria cases. *Complete treatment to 100% of patients* - A core component of malaria control strategies emphasizes ensuring that **all confirmed malaria cases** receive complete and effective treatment. - Achieving **100% complete treatment adherence** is crucial to prevent drug resistance and eliminate the parasite reservoir.
Question 4: Zoonoses are all except-
- A. Plague
- B. Guinea worm infestation (Correct Answer)
- C. Rabies
- D. Hydatid cyst
Explanation: ***Guinea worm infestation*** - **Dracunculiasis (Guinea worm disease)** is exclusively a human disease (anthroponosis), meaning humans are the only definitive hosts. - The life cycle involves humans as the primary host and **copepods** (small crustaceans) as intermediate hosts; there is no animal reservoir or transmission to/from other vertebrate animals. - This is **NOT a zoonosis** because it does not involve animal-to-human transmission. *Plague* - **Plague** is a classic zoonosis caused by *Yersinia pestis*, primarily affecting rodents and transmitted to humans via **flea bites**. - Rodents (especially rats) serve as natural reservoirs, making this a clear example of animal-to-human disease transmission. *Rabies* - **Rabies** is a viral zoonotic disease transmitted to humans through the saliva of infected animals, most commonly via **bites from infected animals**. - The main reservoirs are **carnivorous mammals** such as dogs, foxes, bats, and raccoons, making it a classic zoonosis. *Hydatid cyst* - **Hydatid disease (echinococcosis)** is a zoonosis caused by the larval stage of *Echinococcus* tapeworms. - Definitive hosts are **carnivores** (e.g., dogs, wolves), and humans are accidental intermediate hosts who acquire infection through contact with infected animal feces or contaminated food/water.
Question 5: Which diseases are infectious but not communicable?
- A. Tetanus (Correct Answer)
- B. Mumps
- C. Scarlet fever
- D. Measles
Explanation: **Key Concept:** Infectious diseases are caused by microorganisms, while communicable diseases can spread from person to person. Some diseases are infectious but NOT communicable. ***Correct: Tetanus*** - Tetanus is caused by toxins produced by *Clostridium tetani*, which typically enters the body through **wounds contaminated with soil or feces** - It is **infectious** because a microorganism causes the disease - It is **NOT communicable** as it **cannot be spread directly from person to person** - the bacteria must enter through environmental contamination - Classic example of infectious but non-communicable disease *Incorrect: Mumps* - Mumps is a **communicable disease** caused by the mumps virus, primarily spread through **respiratory droplets** from person to person - Leads to inflammation of **salivary glands**, especially the parotid glands - Both infectious AND communicable *Incorrect: Scarlet fever* - Scarlet fever is a **communicable bacterial infection** caused by group A *Streptococcus*, spread through **respiratory droplets** from person to person - Presents with a characteristic **red rash**, sore throat, and fever - Both infectious AND communicable *Incorrect: Measles* - Measles is a **highly communicable viral disease** transmitted through **airborne droplets** from person to person - Characterized by a distinctive **rash, fever, cough, coryza, and conjunctivitis** - Both infectious AND communicable
Question 6: Which of the following is the true statement regarding measures to prevent typhoid transmission in the community?
- A. Typhoid vaccine administration is the best method of preventing transmission.
- B. Person-to-person transmission is the primary mode of spread.
- C. Drug resistance in typhoid is not as big a problem as in TB.
- D. Hygiene practice and clean sanitation control are more important than the typhoid vaccine. (Correct Answer)
Explanation: ***Hygiene practice and clean sanitation control is more important than the typhoid vaccine.*** - **Improved sanitation**, safe water supplies, and adequate hygiene practices are fundamental in controlling the spread of **typhoid fever**, as the disease is primarily transmitted through the **oral-fecal route**. - While vaccines are an important tool, they offer only partial protection and must be combined with **robust public health infrastructure** and **sanitation measures** for effective prevention. *Typhoid vaccine administration is the best method of preventing transmission.* - Typhoid vaccines offer protection, but their effectiveness is not 100%, and they typically require **booster doses** - **Vaccination campaigns** are most effective when implemented alongside improvements in **water and sanitation infrastructure**, as vaccines alone cannot fully prevent transmission in areas with poor hygiene. *Person-to-person transmission is the primary mode of spread.* - While person-to-person transmission can occur, especially in settings with poor hygiene, the primary mode of spread for typhoid is through the **ingestion of food or water contaminated** with the feces of an infected person or carrier. - This emphasizes the crucial role of **water and food safety** rather than just focusing on direct person-to-person contact. *Drug resistance in typhoid is not as big a problem as in TB.* - **Antimicrobial resistance (AMR)** in typhoid fever, particularly to fluoroquinolones and extended-spectrum beta-lactamase (ESBL) producing strains, is a **significant and growing global health concern**, complicating treatment. - While TB also faces serious drug resistance issues, the escalating problem of **extensively drug-resistant (XDR)** and **multi-drug resistant (MDR)** typhoid strains makes it a substantial threat, impacting treatment options and increasing morbidity and mortality.
Question 7: Fever of unknown origin in a farmer who raises goats would most likely be caused by which of the following organisms?
- A. T. pallidum
- B. Histoplasma capsulatum
- C. Clostridium novyi
- D. Brucella melitensis (Correct Answer)
Explanation: ***Brucella melitensis*** - **Brucellosis** is a zoonotic infection commonly acquired through contact with infected animals or consumption of unpasteurized dairy products. - ***Brucella melitensis* is specifically associated with goats and sheep**, making it the most likely organism in this clinical scenario. - It classically presents as **fever of unknown origin (FUO)** due to its varied and non-specific clinical manifestations, including undulating fever, malaise, myalgia, arthralgia, and hepatosplenomegaly. *T. pallidum* - *Treponema pallidum* is the causative agent of **syphilis**, a sexually transmitted infection. - While syphilis can cause fever, its primary modes of transmission (sexual contact, vertical transmission) and clinical manifestations (e.g., chancres, rash, mucous patches) are distinct from the scenario described. - Not associated with occupational goat exposure. *Histoplasma capsulatum* - *Histoplasma capsulatum* causes **histoplasmosis**, a fungal infection associated with exposure to **bird or bat droppings**, particularly in endemic areas (e.g., Ohio and Mississippi River valleys). - Although it can cause disseminated disease and fever, the epidemiological context (exposure to goats, not birds/bats) makes it unlikely in this scenario. *Clostridium novyi* - *Clostridium novyi* is an anaerobic bacterium known to cause **gas gangrene** (clostridial myonecrosis) and occasionally **black disease** in livestock. - It is not typically associated with human fever of unknown origin in the context of occupational animal contact described. - More relevant to wound infections or animal disease rather than systemic FUO in farmers.
Question 8: Following are examples of human "dead end" diseases except -
- A. Hydatid disease
- B. Japanese encephalitis
- C. Leishmaniasis
- D. Bubonic plague (Correct Answer)
Explanation: ***Bubonic plague (Plague)*** - The question refers to **plague in general**, which includes multiple clinical forms. - While **bubonic plague** (the most common form) is transmitted via **flea bites** from infected rodents and humans are typically dead-end hosts for this form, **pneumonic plague** (secondary complication or primary infection) allows **human-to-human transmission** via respiratory droplets. - This makes plague the **exception** among the listed diseases, as humans can serve as a source of infection to others in the pneumonic form, unlike true dead-end host situations. *Japanese encephalitis* - Humans are **dead-end hosts** for Japanese encephalitis virus. - Infected humans do not develop sufficient **viremia** to infect feeding mosquitoes. - The virus maintains its cycle between **Culex mosquitoes**, **pigs** (amplifying hosts), and **wading birds**, with humans being incidental hosts. *Hydatid disease* - Humans are **definitive dead-end hosts** for *Echinococcus granulosus* (causing cystic echinococcosis/hydatid disease). - The normal life cycle requires **definitive hosts** (dogs, canids) and **intermediate hosts** (sheep, cattle). - Humans develop **hydatid cysts** but cannot transmit the infection further as the parasite cannot complete its life cycle in humans. *Leishmaniasis* - In most forms of leishmaniasis, humans are considered **dead-end or accidental hosts**, particularly in **zoonotic cutaneous leishmaniasis** where animal reservoirs (rodents, dogs) maintain transmission. - However, in **anthroponotic visceral leishmaniasis** (*Leishmania donovani* in the Indian subcontinent), humans can serve as reservoir hosts. - For the purpose of this question, leishmaniasis is generally classified with dead-end diseases as the majority of leishmaniasis forms have zoonotic cycles where humans are incidental hosts with limited onward transmission.
Question 9: Which of the following statements is TRUE regarding Disability-Adjusted Life Year (DALY)?
- A. Years lost due to disability (YLD) are not considered in DALY.
- B. DALY only measures mortality and does not include morbidity.
- C. DALY does not account for both YLD and YLL.
- D. DALY includes both Years of Life Lost (YLL) and Years Lived with Disability (YLD). (Correct Answer)
Explanation: ***DALY includes both Years of Life Lost (YLL) and Years Lived with Disability (YLD).*** - This statement is **correct**. The fundamental formula is **DALY = YLL + YLD**. - **YLL (Years of Life Lost)** quantifies the burden of premature mortality by measuring years of potential life lost due to early death. - **YLD (Years Lived with Disability)** quantifies the burden of morbidity by measuring time lived in states of less than full health. - **DALY** is a comprehensive health metric designed to capture the total burden of disease by integrating both mortality and morbidity components. - This unified metric allows comparison of disease burden across different conditions and populations. *Years of Life Lost (YLL) is not included in DALY calculations.* - This is **incorrect**. YLL is a core component of DALY calculations, representing the mortality burden. *Years lost due to disability (YLD) are not considered in DALY.* - This is **incorrect**. YLD is an essential component of DALY, representing the morbidity burden. *DALY only measures mortality and does not include morbidity.* - This is **incorrect**. DALY explicitly measures both mortality (through YLL) and morbidity (through YLD), making it a comprehensive burden of disease measure.
Question 10: Which organism does not require a vector for transmission?
- A. Rickettsia rickettsii
- B. Borrelia recurrentis
- C. Rickettsia prowazekii
- D. Coxiella burnetii (Correct Answer)
Explanation: ***Coxiella burnetii*** - This organism causes **Q fever** and does not require an arthropod vector; it is primarily transmitted via **aerosols** from infected animals. - Humans usually acquire the infection by inhaling **contaminated aerosols** from infected livestock (cattle, sheep, goats). *Rickettsia prowazekii* - This bacterium is the causative agent of **epidemic typhus** and is transmitted by the **human body louse** (*Pediculus humanus corporis*). - The louse acts as a **biological vector**, acquiring the organism from an infected human and transmitting it through its feces, which are then scratched into the skin. *Rickettsia rickettsii* - This organism causes **Rocky Mountain Spotted Fever (RMSF)** and is transmitted by **ticks**, primarily the American dog tick (*Dermacentor variabilis*) and the Rocky Mountain wood tick (*Dermacentor andersoni*). - Ticks serve as both **vectors** and **reservoirs** for *Rickettsia rickettsii*. *Borrelia recurrentis* - This spirochete causes **louse-borne relapsing fever** and is transmitted by the **human body louse** (*Pediculus humanus corporis*). - Transmission occurs when the louse is crushed and its hemolymph, containing the bacteria, comes into contact with broken skin or mucous membranes.
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