Zoonotic Diseases — MCQs

Zoonotic Diseases Indian Medical PG Practice Questions and MCQs

Question 41: A bird seller developed fever with chills and severe body pain. Investigation confirms the disease as ornithosis. Causative agent is:

A. Coxiella burnetii
B. Borrelia
C. Burkholderia pseudomallei
D. Chlamydia psittaci (Correct Answer)

Explanation: ***Chlamydia psittaci*** - **Ornithosis**, also known as psittacosis, is caused by *C. psittaci* and is transmitted to humans through contact with infected birds (e.g., parrots, parakeets, pigeons). The patient's occupation as a **bird seller** is a key clue. - Clinical manifestations include **fever, chills, and severe body pain**, mimicking severe influenza or atypical pneumonia. *Coxiella burnetii* - This bacterium causes **Q fever**, primarily transmitted from livestock (cattle, sheep, goats) through aerosols from birth products. - While Q fever can cause similar flu-like symptoms and atypical pneumonia, the patient's **bird exposure** points away from this diagnosis. *Borrelia* - Different species of *Borrelia* cause diseases such as **Lyme disease** (*B. burgdorferi*) and **relapsing fever** (*B. recurrentis*, *B. hermsii*). - These infections are typically transmitted by ticks or lice and are not associated with avian exposure or ornithosis. *Burkholderia pseudomallei* - This bacterium causes **melioidosis**, an infection prevalent in tropical and subtropical regions, particularly Southeast Asia and northern Australia. - It is acquired through contact with contaminated soil or water, not typically through avian exposure, and often presents with pneumonia, abscesses, or septicemia.

Question 42: A 28-year-old patient presents with high-grade fever, severe cough, and progressive dyspnea. The patient lives near a poultry farm where there has been a recent bird flu outbreak. What is the most appropriate diagnostic test?

A. Virus isolation
B. Rapid antigen test
C. RT-PCR (Correct Answer)
D. Antibody detection

Explanation: ***RT-PCR*** - **Reverse transcription polymerase chain reaction (RT-PCR)** is the gold standard for diagnosing avian influenza (bird flu) due to its high sensitivity and specificity. - It directly detects the **viral RNA** and can confirm active infection, which is crucial given the recent bird flu outbreak and the patient's symptoms. *Virus isolation* - **Virus isolation** is a highly specific method but is time-consuming and requires specialized laboratory facilities, making it less suitable for rapid diagnosis in an acute clinical setting. - It is often used for **viral characterization** and surveillance rather than initial patient diagnosis. *Rapid antigen test* - **Rapid antigen tests** for influenza generally have lower sensitivity for avian influenza compared to RT-PCR, leading to a higher risk of false negatives. - While quick, their reduced accuracy might delay appropriate patient management, especially in a potential outbreak scenario. *Antibody detection* - **Antibody detection** (serology) indicates past exposure or infection, as antibodies typically take several days to weeks to develop. - It is not suitable for diagnosing an **acute, active infection** like the current presentation of fever, headache, and rash due to the lag in antibody production.

Question 43: A patient presents with a bullseye rash after a tick bite. Which organism is most likely responsible for this condition?

A. Borrelia burgdorferi (Correct Answer)
B. Rickettsia rickettsii
C. Treponema pallidum
D. Leptospira interrogans

Explanation: ***Correct: Borrelia burgdorferi*** - **Lyme disease**, caused by *Borrelia burgdorferi*, is classically characterized by an **erythema migrans** rash, which is often described as a **"bullseye"** or target-like lesion, developing after a tick bite. - This **spirochete** is transmitted to humans through the bite of infected *Ixodes* ticks and is the most common cause of vector-borne disease in the United States. *Incorrect: Rickettsia rickettsii* - This organism causes **Rocky Mountain spotted fever**, which typically presents with a **maculopapular rash** that begins on the ankles and wrists and spreads centrally. - While also transmitted by ticks, it does not typically cause a bullseye-shaped erythema migrans rash. *Incorrect: Treponema pallidum* - This bacterium is the causative agent of **syphilis** and is transmitted through sexual contact, not tick bites. - The primary lesion of syphilis is a **chancre**, a painless ulcer, which is distinct from a bullseye rash. *Incorrect: Leptospira interrogans* - This spirochete is responsible for **leptospirosis**, contracted through contact with contaminated water or animal urine. - It can cause severe systemic symptoms, including fever, headache, muscle pain, and jaundice, but it does not produce a bullseye rash.

Question 44: Indian tick typhus is caused by:

A. R typhi
B. R conorii (Correct Answer)
C. R akari
D. C burnetii

Explanation: ***R conorii*** - *Rickettsia conorii* is the causative agent of **Indian tick typhus**, also known as **Mediterranean spotted fever** or boutonneuse fever. - This bacterial infection is transmitted to humans through the bite of **infected ticks**. *R typhi* - *Rickettsia typhi* is the causative agent of **murine typhus**, which is transmitted by **fleas**, usually from rodents. - Its clinical presentation is generally milder than that of tick-borne rickettsial diseases and often does not involve a prominent rash. *R akari* - *Rickettsia akari* causes **rickettsialpox**, which is transmitted by the **house mouse mite**. - Key features include a primary eschar (black scab) at the bite site followed by a vesicular rash. *C burnetii* - *Coxiella burnetii* is the bacterium responsible for **Q fever**, a systemic infection often transmitted by **inhaling aerosols from infected animals** (e.g., cattle, sheep, goats). - It typically causes an acute flu-like illness, pneumonia, or hepatitis, without a characteristic rash or tick vector in most cases.

Question 45: What is a common characteristic of the H5N1 and H7N7 strains of influenza?

A. Frequent endemic infection in man
B. Have same frequency of antigenic variation
C. Strains of avian influenza (Correct Answer)
D. None of the options

Explanation: ***Strains of avian influenza*** - Both **H5N1** and **H7N7** are well-known subtypes of the **influenza A virus** that primarily infect birds. - While they can infect humans, their natural reservoir and main hosts are **avian species**. *Frequent endemic infection in man* - These strains are not endemic in humans; human infections are typically **sporadic** and associated with close contact with infected birds. - They lack efficient **human-to-human transmission**, which prevents them from becoming endemic in the human population. *Have same frequency of antigenic variation* - Although both undergo **antigenic variation**, the specific frequency and patterns can differ between strains and are influenced by various factors, including their host range and circulation dynamics. - It is inaccurate to assume identical frequencies of **antigenic drift** and **shift** for different viral subtypes. *None of the options* - This option is incorrect because "Strains of avian influenza" is a correct and common characteristic shared by both H5N1 and H7N7.

Question 46: What is the causative agent of Izumi fever?

A. Yersinia pseudotuberculosis (Correct Answer)
B. Yersinia enterocolitica
C. Pseudomonas aeruginosa
D. Pasteurella multocida

Explanation: ***Yersinia pseudotuberculosis*** - Izumi fever (also called **Far East scarlet-like fever**) is caused by Yersinia pseudotuberculosis, particularly referring to outbreaks that occurred in Japan. - This infection presents with **fever, abdominal pain, and a scarlet fever-like rash**, often mimicking appendicitis due to mesenteric lymphadenitis. - Y. pseudotuberculosis is transmitted through **contaminated food and water**, and the Izumi fever variant is characterized by systemic manifestations including erythema and desquamation. *Yersinia enterocolitica* - While this is a closely related species that also causes **gastroenteritis and mesenteric adenitis**, it is NOT the causative agent of Izumi fever. - Y. enterocolitica typically presents with diarrhea, abdominal pain, and fever, but lacks the distinctive scarlet fever-like rash seen in Izumi fever. *Pseudomonas aeruginosa* - This bacterium is an **opportunistic pathogen** often associated with nosocomial infections, especially in immunocompromised individuals. - It causes **pneumonia**, urinary tract infections, and wound infections, but not Izumi fever. *Pasteurella multocida* - This bacterium is common in the **respiratory tracts of animals**, especially cats and dogs, and is a frequent cause of wound infections from animal bites or scratches. - It typically causes localized cellulitis, abscesses, and occasionally severe infections like meningitis or osteomyelitis, not Izumi fever.

Question 47: What is the cause of rabies in wild animals?

A. Wild-type rabies virus (Correct Answer)
B. Laboratory passage in rabbits
C. Fatal encephalitis within 6 days
D. Negri bodies are not observed

Explanation: ***Wild-type rabies virus*** - Rabies in wild animals is caused by infection with the **wild-type rabies virus (Lyssavirus)**, which is maintained in specific wildlife reservoirs. - Rabies virus is a **neurotropic RNA virus** belonging to the family *Rhabdoviridae*. - This virus is transmitted through the saliva of an infected animal, typically via a **bite**. *Laboratory passage in rabbits* - **Laboratory passage in animals**, particularly rabbits, was a historical *method for attenuating the rabies virus* to develop vaccines (e.g., Pasteur's vaccine), not a cause of infection in wild animals. - Attenuated viruses are **less virulent** and do not represent the primary cause of naturally occurring rabies in wildlife. *Fatal encephalitis within 6 days* - This statement describes a **rapid progression of the disease**, which can occur, but it is a *consequence of infection*, not the cause itself. - The incubation period for rabies can vary significantly in animals, from days to months, depending on the **site of the bite** and **viral load**. *Negri bodies are not observed* - **Negri bodies** are *pathognomonic microscopic inclusions* found in the brain cells of animals infected with rabies. - Their *absence* would generally suggest that the animal does not have rabies, making this an incorrect statement about the disease's characteristics.

Question 48: Which disease is caused by Ehrlichia chaffeensis, a bacterium transmitted through the bite of an infected lone star tick?

A. HGE
B. Glandular fever
C. Human Monocytic Ehrlichiosis (HME) (Correct Answer)
D. None of the options

Explanation: ***Human Monocytic Ehrlichiosis (HME)*** - **Human Monocytic Ehrlichiosis (HME)** is specifically caused by the bacterium **Ehrlichia chaffeensis**. - This bacterium is primarily transmitted to humans through the bite of an infected **lone star tick (Amblyomma americanum)**. *HGE* - **Human Granulocytic Ehrlichiosis (HGE)**, now known as **Anaplasmosis**, is caused by **Anaplasma phagocytophilum**. - While also a tick-borne illness, HGE is transmitted by the **deer tick (Ixodes scapularis)**, not the lone star tick, and affects granulocytes. *Glandular fever* - **Glandular fever**, also known as **infectious mononucleosis**, is typically caused by the **Epstein-Barr virus (EBV)**. - It is transmitted through saliva and is not a bacterial infection or tick-borne disease. *None of the options* - This option is incorrect because **Human Monocytic Ehrlichiosis (HME)** is directly caused by **Ehrlichia chaffeensis** and is listed as an option. - The other options describe different diseases with distinct causative agents and modes of transmission.

Question 49: A 20-year-old boy has been admitted with a history of fever, icterus, conjunctival suffusion, and hematuria for 20 days. Which of the following serological tests can be of diagnostic utility?

A. Widal test
B. Microscopic agglutination test (Correct Answer)
C. Paul-Bunnell test
D. Weil-Felix reaction

Explanation: ***Microscopic agglutination test*** - The patient's symptoms (fever, **icterus**, conjunctival suffusion, and hematuria) are classic for **leptospirosis**, a zoonotic spirochetal infection. - The **Microscopic Agglutination Test (MAT)** is considered the **gold standard** for diagnosing leptospirosis, detecting antibodies to *Leptospira* serovars. *Widal test* - The **Widal test** is used to diagnose **typhoid fever**, caused by *Salmonella Typhi*. - While typhoid fever presents with fever, it does not typically include prominent **icterus**, conjunctival suffusion, or hematuria. *Paul-Bunnell test* - The **Paul-Bunnell test** is a heterophile antibody test used to diagnose **infectious mononucleosis**, caused by the **Epstein-Barr virus**. - Infectious mononucleosis typically presents with fever, pharyngitis, and lymphadenopathy, not the specific constellation of symptoms described. *Weil-Felix reaction* - The **Weil-Felix reaction** is an agglutination test for diagnosing certain **rickettsial infections**, such as typhus fevers and scrub typhus. - While rickettsial infections cause fever, they do not typically present with the pronounced icterus, conjunctival suffusion, and hematuria seen in this case.

Question 50: Erysipeloid is transmitted by which route?

A. Droplet
B. Mosquito bite
C. Fecal-oral
D. Direct contact (Correct Answer)

Explanation: ***Direct contact*** - Erysipeloid, caused by *Erysipelothrix rhusiopathiae*, is transmitted through direct contact with **infected animal products**, especially fish, shellfish, and raw meat. - The bacteria typically enter through a **break in the skin**, such as a cut or abrasion, making occupational exposure common among butchers and fishmongers. *Droplet* - **Droplet transmission** involves the spread of respiratory droplets through coughing or sneezing, which is characteristic of airborne diseases like influenza. - Erysipeloid is primarily a **skin infection** and is not transmitted via the respiratory route. *Mosquito bite* - **Mosquito bites** are vectors for diseases like malaria, dengue, and West Nile virus, where the pathogen is injected directly into the bloodstream. - Erysipeloid is a bacterial infection acquired through **skin contact with contaminated materials**, not insect vectors. *Fecal-oral* - The **fecal-oral route** involves ingesting pathogens from contaminated food or water, often associated with gastrointestinal infections like cholera or giardiasis. - Erysipeloid is a **cutaneous infection** and does not involve the gastrointestinal tract as its primary mode of transmission.

Practice by Chapter

Principles of Zoonotic Transmission

Practice Questions

Viral Zoonoses

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Bacterial Zoonoses

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Parasitic Zoonoses

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Vector-Borne Zoonoses

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Foodborne Zoonoses

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Emerging Zoonotic Diseases

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One Health Approach to Zoonoses

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Prevention and Control of Zoonoses

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Occupational Exposure to Zoonoses

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Wildlife Reservoirs of Zoonotic Pathogens

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Global Impact of Zoonotic Diseases

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