Wildlife Reservoirs of Zoonotic Pathogens — MCQs

10 questions

A man with chills, fever, and headache is thought to have "atypical" pneumonia. History reveals that he raises chickens, and that approximately 2 weeks ago he lost a large number of them to an undiagnosed disease. Which of the following is the most likely diagnosis of this man's condition?

Which of the following diseases has the largest submerged portion in the iceberg model of disease?

Zoonoses are all except-

Zoonotic diseases are all except -

Which of the following statements about viral diseases is true?

What term describes an infection or infectious disease that is transmissible under natural conditions from vertebrate animals to humans?

All are true regarding Japanese encephalitis disease except:

Following are examples of human "dead end" diseases except -

Which of the following statements is true regarding the epidemiology of influenza?

Q10

A farmer presents to the emergency department with painful inguinal lymphadenopathy and a history of fever and flu-like symptoms. Clinical examination reveals an ulcer on the leg. Which of the following stains should be used to detect suspected bipolar-stained organisms?

Wildlife Reservoirs of Zoonotic Pathogens Indian Medical PG Practice Questions and MCQs

Question 1: A man with chills, fever, and headache is thought to have "atypical" pneumonia. History reveals that he raises chickens, and that approximately 2 weeks ago he lost a large number of them to an undiagnosed disease. Which of the following is the most likely diagnosis of this man's condition?

A. Leptospirosis
B. Relapsing fever
C. Anthrax
D. Ornithosis (Correct Answer)

Explanation: ***Ornithosis*** - The patient's symptoms of **chills, fever, headache, and atypical pneumonia**, combined with a history of **raising chickens** that recently died from an undiagnosed disease, are highly suggestive of ornithosis (also known as **psittacosis** or **parrot fever**). [2], [3] - This zoonotic infection is caused by **Chlamydophila psittaci** and is transmitted to humans through inhalation of contaminated aerosols from infected birds (poultry, parrots, pigeons). [2] *Leptospirosis* - **Leptospirosis** is typically associated with exposure to **contaminated water or soil** with animal urine, not direct contact with sick poultry. - While it can cause fever and headache, it often presents with **jaundice, renal failure, and hemorrhagic manifestations**, which are not mentioned here. *Relapsing fever* - **Relapsing fever** is characterized by **recurrent episodes of fever** separated by afebrile periods, caused by **Borrelia** species transmitted by lice or ticks. - The clinical presentation does not align with the typical course or epidemiological link to sick chickens. *Anthrax* - **Inhalational anthrax** can cause severe respiratory symptoms and fever but is primarily associated with exposure to **Bacillus anthracis spores**, often from infected livestock (cattle, sheep) or bioweapon exposure. [1] - The rapid death of a large number of chickens and the patient's "atypical pneumonia" do not fit the typical presentation or common transmission routes of anthrax. [1]

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: 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 4: 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 5: Which of the following statements about viral diseases is true?

A. Hanta virus pulmonary syndrome is caused by inhalation of rodent urine and feces (Correct Answer)
B. Lyssa virus is transmitted by ticks
C. None of the options
D. Kyasanur forest disease is caused by bite of wild animal

Explanation: ***Hanta virus pulmonary syndrome is caused by inhalation of rodent urine and feces*** - **Hantavirus pulmonary syndrome (HPS)** is a severe, often fatal, respiratory disease in humans. - Humans can contract the disease when they breathe in **aerosolized virus** particles from **rodent urine, droppings, or saliva**. *Kyasanur forest disease is caused by bite of wild animal* - **Kyasanur Forest Disease (KFD)** is primarily transmitted by the bite of infected ticks, specifically **Haemaphysalis spinigera**, not directly by wild animal bites. - While wild animals (like monkeys and rodents) can be hosts for the ticks, the direct transmission to humans is via the **tick vector**. *Lyssa virus is transmitted by ticks* - **Lyssaviruses** (which include the rabies virus) are primarily transmitted to humans through the bite or scratch of an infected mammal, most commonly a **rabid animal**. - **Ticks** are not known vectors for Lyssaviruses.

Question 6: What term describes an infection or infectious disease that is transmissible under natural conditions from vertebrate animals to humans?

A. Epizootic
B. Epornithic
C. Zoonoses (Correct Answer)
D. Exotic

Explanation: ***Zoonoses*** - A **zoonosis** is an infectious disease that can be **transmitted naturally from vertebrate animals to humans**. - Examples include rabies, Lyme disease, and influenza, where animals act as natural hosts or reservoirs for the pathogen. *Epizootic* - **Epizootic** refers to a disease event in an **animal population** that is analogous to an **epidemic in humans**, indicating a sudden and widespread outbreak. - It describes the prevalence pattern of a disease within an animal population, not the transmission across species to humans. *Epornithic* - **Epornithic** is a term specifically used for an outbreak of disease within a **bird population**, similar to how epizootic refers to animals in general. - This term does not describe the transmission of disease from animals to humans, but rather the incidence within birds. *Exotic* - **Exotic** refers to something originating in or characteristic of a distant foreign country, often implying something unusual or introduced from outside. - It does not specifically describe a type of infectious disease or its transmissibility from animals to humans.

Question 7: 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 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 the epidemiology of influenza?

A. Pandemics cannot occur with influenza viruses.
B. Incubation period is typically 7-10 days.
C. Humans are the only reservoir for influenza.
D. Asymptomatic cases can occur and may contribute to transmission. (Correct Answer)

Explanation: ***Asymptomatic cases can occur and may contribute to transmission.*** - Asymptomatic or mildly symptomatic individuals can shed the virus, contributing to the silent spread of influenza within a community. - This characteristic makes **influenza control** challenging, as not all infected individuals seek medical attention or are easily identified. *Incubation period is typically 7-10 days.* - The typical incubation period for influenza is much shorter, usually **1 to 4 days**, with an average of 2 days. - A 7-10 day incubation period is more characteristic of infections like **measles** or **mumps**, not influenza. *Pandemics cannot occur with influenza viruses.* - Influenza viruses are well-known for their potential to cause **pandemics** through antigenic shifts, leading to novel strains against which the population has little to no immunity. - Historically, there have been several major influenza pandemics, such as the **1918 Spanish Flu** and the 2009 H1N1 pandemic. *Humans are the only reservoir for influenza.* - While humans are a significant reservoir, influenza viruses also circulate in **animal reservoirs** such as birds (especially wild aquatic birds) and pigs. - These animal reservoirs can serve as sources for new human strains through **inter-species transmission** and genetic reassortment.

Question 10: A farmer presents to the emergency department with painful inguinal lymphadenopathy and a history of fever and flu-like symptoms. Clinical examination reveals an ulcer on the leg. Which of the following stains should be used to detect suspected bipolar-stained organisms?

A. Albe's stain
B. McFadyean's stain
C. Wayson's stain (Correct Answer)
D. Ziehl-Neelsen stain

Explanation: ***Wayson's stain*** - This stain is specifically used for the detection of **Yersinia pestis**, the causative agent of **plague**, which often presents with **bipolar staining**. - Clinical features like **painful inguinal lymphadenopathy** (buboes), fever, flu-like symptoms, and an ulcer (possibly an inoculation site) are highly suggestive of **plague**. *Albe's stain* - **Albe's stain** is used for demonstrating **bacterial capsules**, not for bipolar-stained organisms. - It would not specifically identify **Yersinia pestis** in this context. *Mc Fayden's stain* - **McFadyen's stain** is primarily used to detect the capsule of **Bacillus anthracis** (anthrax) from smears. - While helpful for anthrax, it is not the specific stain for bipolar staining of **Yersinia pestis**. *Ziehl Nelson stain* - **Ziehl-Neelsen stain** is an **acid-fast stain** used to identify organisms with high mycolic acid content in their cell walls, such as **Mycobacterium tuberculosis**. - It is not suitable for visualizing gram-negative bacteria like **Yersinia pestis** or their bipolar staining characteristics.

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