Zoonotic Diseases Practice Questions

Q: Q fever is caused by:

C. burnetii. ***C. burnetii*** - **Coxiella burnetii** is the causative agent of **Q fever**, a zoonotic disease - Transmission typically occurs through **inhalation of contaminated aerosols** from infected animals, particularly livestock (cattle, sheep, goats) - Presents with **acute febrile illness**, pneumonia, and hepatitis; can cause chronic endocarditis - Unique among rickettsial organisms: does **not cause a rash** *R. quintana* - **Rochalimaea quintana** (now **Bartonella quintana**) causes **trench fever** - Transmitted by **body lice**, not aerosols - Characterized by recurrent fevers, headaches, and leg pain *R. typhi* - **Rickettsia typhi** causes **murine typhus** (endemic typhus) - Transmitted by **fleas of rodents**, primarily rats - Presents with fever, headache, and **maculopapular rash** *R. akari* - **Rickettsia akari** causes **rickettsialpox**, a mild rickettsial infection - Transmitted by **mites of house mice** - Characterized by distinctive **eschar** followed by papulovesicular rash

Q: Which organism is detected using ELISA for virulence marker antigen (VMA)?

Yersinia pestis. ***Yersinia pestis*** - **Virulence marker antigen (VMA)** specifically refers to the **F1 antigen** of *Yersinia pestis*, the causative agent of plague. - **ELISA detection of F1 antigen** (VMA) is a rapid and specific diagnostic method for plague, particularly useful in endemic areas and for early diagnosis. - The F1 capsular antigen is a key virulence factor that protects the bacterium from phagocytosis and is highly specific to *Y. pestis*. - VMA ELISA is recommended by WHO for plague diagnosis and has high sensitivity and specificity. *Enteroinvasive Escherichia coli* - EIEC is diagnosed primarily through **stool culture**, **Sereny test**, or **PCR for invasion plasmid genes** (ipaH). - While EIEC has virulence factors related to invasion, it is **not associated with VMA detection by ELISA**. - EIEC causes dysentery-like illness but does not produce the specific VMA used in diagnostic testing. *Haemophilus influenzae* - Detection relies on **culture**, **Gram stain**, and **capsular polysaccharide antigen detection** (latex agglutination or immunochromatography). - **Not associated with VMA** as a diagnostic marker. *Streptococcus pneumoniae* - Commonly detected by **culture**, **Gram stain**, **optochin sensitivity**, and **urinary antigen tests** for capsular polysaccharides. - **VMA is not used** for *S. pneumoniae* detection.

Q: Which organism does not require a vector for transmission?

Coxiella burnetii. ***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.

Q: Wool-sorter's disease is caused by which of the following?

Bacillus anthracis. **Bacillus anthracis** - **Wool-sorter's disease** is the historical name for the **inhalational form of anthrax**, caused by inhaling spores of *Bacillus anthracis*. - This form of anthrax primarily affects the lungs and can lead to severe, often fatal, pneumonia. - The disease was named after workers in the wool industry who developed anthrax from handling contaminated animal hides and wool. *Pseudomonas aeruginosa* - *Pseudomonas aeruginosa* is a common opportunistic pathogen associated with **hospital-acquired infections**, especially in immunocompromised individuals. - It causes a wide range of infections, including pneumonia, but is not linked to wool-sorter's disease. *Vibrio cholerae* - *Vibrio cholerae* is the bacterium responsible for **cholera**, an acute diarrheal illness. - It is transmitted through **contaminated water or food** and causes severe dehydration, not respiratory disease. *Coxiella burnetii* - *Coxiella burnetii* causes **Q fever**, which is primarily transmitted through inhalation of aerosols from infected animals. - While it can cause pneumonia, it is a distinct disease from anthrax and is not referred to as wool-sorter's disease.

Q: A 36-year-old man presents to his primary care physician's office complaining of fever and headache. On examination, he has leucopenia, increased liver enzymes, and inclusion bodies are seen in his monocytes. Given his history of removing a tick from his leg, which of the following is the most likely diagnosis?

Ehrlichiosis. ***Ehrlichiosis*** - This diagnosis is strongly supported by the patient's history of a **tick bite**, presenting symptoms of **fever** and **headache**, and laboratory findings of **leukopenia** and **elevated liver enzymes**. - The presence of **inclusion bodies (morulae) in monocytes** is a classic diagnostic feature of ehrlichiosis, as *Ehrlichia chaffeensis* specifically infects monocytes and macrophages [1]. *Lyme disease* - While Lyme disease is also a **tick-borne illness**, it typically presents with an **erythema migrans rash** (bull's-eye rash), which is not mentioned in this case [1]. - Unlike ehrlichiosis, Lyme disease is caused by *Borrelia burgdorferi* and does not commonly feature **leukopenia** or **monocytic inclusion bodies** [1]. *Q fever* - Q fever is caused by *Coxiella burnetii* and is usually transmitted through **inhalation of aerosols** from infected animals, not typically by tick bites. - Although it can cause **fever** and **headache**, it is not associated with **monocytic inclusion bodies** or the specific leukopenia profile seen here. *Rocky Mountain spotted fever* - This **tick-borne illness** is caused by *Rickettsia rickettsii* and is characterized by a **rash** that typically starts on the ankles and wrists and spreads centrally. - While it can cause **fever** and **headache**, it does not involve **monocytic inclusion bodies**; instead, it affects endothelial cells.

Q: Lyme disease is caused by:

B. burgdorferi. ***Correct: B. burgdorferi*** - **Lyme disease** is a **tick-borne illness** caused by the spirochete *Borrelia burgdorferi*. - This bacterium is transmitted to humans through the bite of infected ticks, primarily the **black-legged tick** (*Ixodes scapularis*). *Incorrect: B. vincenti* - *Borrelia vincenti* is associated with **Vincent's angina** (fusospirochetal disease), a severe gingivitis, and periodontitis. - It is not implicated in Lyme disease but rather in an oro-dental infection. *Incorrect: B. recurrentis* - *Borrelia recurrentis* is the causative agent of **epidemic relapsing fever**. - This disease is transmitted by the **human body louse** and is characterized by recurring episodes of fever. *Incorrect: T. pertenue* - *Treponema pertenue* is the bacterium responsible for **yaws**, a chronic, disfiguring skin infection. - It is a related spirochete to *Treponema pallidum* (syphilis) but causes a non-venereal disease primarily in tropical regions.

Q: What is the causative agent of scrub typhus?

Orientia tsutsugamushi. ***Orientia tsutsugamushi*** - This is the **causative agent** of **scrub typhus**, an acute febrile illness transmitted by the bite of infected larval mites (chiggers). - Previously classified as *Rickettsia tsutsugamushi*, it was **reclassified** to the genus *Orientia* in 1995 due to its unique genetic and antigenic characteristics differentiating it from other rickettsiae. - Scrub typhus is endemic in the Asia-Pacific region and presents with fever, eschar at the bite site, and lymphadenopathy. *R. prowazekii* - This bacterium is responsible for **epidemic typhus**, which is typically transmitted by the **human body louse**. - It causes a more severe disease compared to scrub typhus, often associated with Brill-Zinsser disease in recurrent cases. *R. rickettsii* - This is the etiologic agent of **Rocky Mountain spotted fever (RMSF)**, a severe tick-borne disease in the Americas. - RMSF is characterized by a maculopapular rash that often involves the palms and soles. *R. akari* - This bacterium causes **rickettsialpox**, a mild febrile illness transmitted by the bite of the **house mouse mite**. - Rickettsialpox is characterized by an initial papulovesicular rash and an eschar at the bite site.

Q: Which disease does not have a known animal reservoir?

Bordetella pertussis. ***Bordetella pertussis*** - **Bordetella pertussis**, the causative agent of whooping cough, is unique among these options as it has **no known animal reservoir**. It is exclusively a human pathogen. - Transmission occurs directly from person to person via respiratory droplets, highlighting its **anthroponotic** nature. *Brucella melitensis* - **Brucella melitensis** is primarily associated with **goats and sheep**, acting as a significant animal reservoir. - Humans typically acquire brucellosis through contact with infected animals or consumption of unpasteurized dairy products. *Pasteurella multocida* - **Pasteurella multocida** is a common commensal bacterium found in the oral flora of various animals, including **cats and dogs**. - Human infections usually result from **animal bites or scratches**, demonstrating clear zoonotic transmission. *Francisella tularensis* - **Francisella tularensis**, which causes **tularemia**, has numerous animal reservoirs, including **rabbits, rodents, and ticks**. - Humans can contract tularemia through direct contact with infected animals, insect bites, or inhalation of contaminated aerosols.

Question 1

Q fever is caused by:

Accepted Answer

C. burnetii

Answer

R. quintana

Answer

R. typhi

Answer

R. akari

Question 2

Which organism is detected using ELISA for virulence marker antigen (VMA)?

Accepted Answer

Yersinia pestis

Answer

Enteroinvasive Escherichia coli

Answer

Haemophilus influenzae

Answer

Streptococcus pneumoniae

Question 3

Which organism does not require a vector for transmission?

Accepted Answer

Coxiella burnetii

Answer

Rickettsia rickettsii

Answer

Borrelia recurrentis

Answer

Rickettsia prowazekii

Question 4

Which of the following statements about Q fever is true?

Accepted Answer

The mode of transmission is by inhalation of contaminated aerosols.

Answer

It commonly presents with a characteristic rash and local lesion at the site of inoculation.

Answer

Ticks are the primary vector for human transmission.

Answer

It is primarily a disease of humans with occasional animal involvement.

Question 5

Wool-sorter's disease is caused by which of the following?

Accepted Answer

Bacillus anthracis

Answer

Vibrio cholerae

Answer

Pseudomonas aeruginosa

Answer

Coxiella burnetii

Question 6

A 36-year-old man presents to his primary care physician's office complaining of fever and headache. On examination, he has leucopenia, increased liver enzymes, and inclusion bodies are seen in his monocytes. Given his history of removing a tick from his leg, which of the following is the most likely diagnosis?

Accepted Answer

Ehrlichiosis

Answer

Lyme disease

Answer

Q fever

Answer

Rocky Mountain spotted fever

Question 7

Which of the following statements about viral diseases is true?

Accepted Answer

Hanta virus pulmonary syndrome is caused by inhalation of rodent urine and feces

Answer

Lyssa virus is transmitted by ticks

Answer

None of the options

Answer

Kyasanur forest disease is caused by bite of wild animal

Question 8

Lyme disease is caused by:

Accepted Answer

B. burgdorferi

Answer

T. pertenue

Answer

B. vincenti

Answer

B. recurrentis

Question 9

What is the causative agent of scrub typhus?

Accepted Answer

Orientia tsutsugamushi

Answer

R. prowazekii

Answer

R. rickettsii

Answer

R. akari

Question 10

Which disease does not have a known animal reservoir?

Accepted Answer

Bordetella pertussis

Answer

Brucella melitensis

Answer

Francisella tularensis

Answer

Pasteurella multocida

Zoonotic Diseases — MCQs

Zoonotic Diseases — MCQs

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