Zoonotic Diseases Practice Questions

Q: Fever of unknown origin in a farmer who raises goats would most likely be caused by which of the following organisms?

Brucella melitensis. ***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.

Q: Mammalian reservoir of Rickettsial pox -

Mice. ***Mice*** - The primary **mammalian reservoir** for *Rickettsia akari*, which causes **rickettsialpox**, is **mice** (specifically the house mouse, *Mus musculus*). - The disease is transmitted to humans by the bite of the **mouse mite** (*Liponyssoides sanguineus*), which is the vector. *Cattle* - **Cattle** are not known reservoirs for *Rickettsia akari* or agents causing **rickettsialpox**. - They are more commonly associated with other zoonotic diseases such as **anthrax** or **Q fever** (*Coxiella burnetii*). *Goat* - **Goats** are not considered reservoirs for *Rickettsia akari* or the transmission of **rickettsialpox**. - They can be reservoirs for diseases like **brucellosis** or **Q fever**, but not for rickettsialpox. *Human* - **Humans** are occasional and **dead-end hosts** for *Rickettsia akari*, meaning they can get the disease but do not typically transmit it further to maintain the natural cycle. - Humans become infected when bitten by an infected **mouse mite** but do not act as the reservoir.

Q: Jail fever is related to

Rickettsia prowazekii. ***Rickettsia prowazekii*** - **Jail fever** is another name for **epidemic typhus**, which is caused by *Rickettsia prowazekii*. - This disease is historically associated with crowded, unsanitary conditions like those found in jails or during wartime. *Rickettsia conorii* - This bacterium causes **Mediterranean spotted fever** (boutonneuse fever), which is characterized by a distinctive skin rash and eschar. - It is transmitted by dog ticks, and is not associated with the term "jail fever." *Rickettsia typhi* - *Rickettsia typhi* is responsible for **murine typhus** (endemic typhus), which is typically transmitted by fleas, mainly from rats. - While it is a rickettsial disease, it is not referred to as jail fever. *Rickettsia akari* - This species causes **rickettsialpox**, a mild rickettsial infection characterized by an initial papule that develops into an eschar, followed by a generalized papulovesicular rash. - It is transmitted by mites found on house mice and is distinct from jail fever.

Q: Rickettsialpox is caused by?

Rickettsia akari. ***Rickettsia akari*** - **Rickettsia akari** is the specific etiologic agent responsible for causing **rickettsialpox**. - This Rickettsia species is transmitted to humans by the bite of the **mouse mite**, particularly *Liponyssoides sanguineus*. *Rickettsia conorii* - **Rickettsia conorii** is the pathogen that causes **Mediterranean spotted fever** (also known as boutonneuse fever), which is distinct from rickettsialpox. - It is typically transmitted by ticks, such as *Rhipicephalus sanguineus*. *Rickettsia rickettsii* - This bacterium is the causative agent of **Rocky Mountain spotted fever**, a severe and potentially fatal tick-borne disease. - It is not associated with rickettsialpox, which presents with different clinical features and epidemiology. *Rickettsia typhi* - **Rickettsia typhi** is the cause of **murine (endemic) typhus**, a flea-borne disease primarily associated with rats. - Murine typhus has different clinical manifestations and epidemiology compared to rickettsialpox.

Q: Rickettsia rickettsii is responsible for which disease -

Rocky mountain spotted fever. ***Rocky mountain spotted fever*** - **Rickettsia rickettsii** is the specific etiologic agent responsible for **Rocky Mountain Spotted Fever (RMSF)**, a severe tick-borne illness. - RMSF is characterized by a distinctive **rash** that typically begins on the ankles and wrists and spreads inwards, affecting the palms and soles. *Endemic typhus* - Endemic typhus, also known as **murine typhus**, is caused by **Rickettsia typhi**, not Rickettsia rickettsii. - It is typically transmitted by fleas, particularly those found on rodents, and is less severe than RMSF. *Scrub typhus* - Scrub typhus is caused by **Orientia tsutsugamushi**, a different rickettsial species. - This disease is transmitted by the bite of infected chiggers (larval mites) and is prevalent in rural Asia and the Pacific. *Epidemic typhus* - Epidemic typhus is caused by **Rickettsia prowazekii** and is transmitted by the human body louse. - It is historically associated with crowded, unsanitary conditions and can cause severe systemic illness.

Q: All are true about scrub typhus, except:

Adult female feeds on vertebrate hosts. ***Adult female feeds on vertebrate hosts*** - This statement is incorrect because the **larval stage** (chiggers) of the trombiculid mite is the one that feeds on vertebrate hosts (including humans) and transmits *Orientia tsutsugamushi*. - **Adult and nymphal mites** are free-living and feed on vegetation or small invertebrates, not vertebrate blood. *Causative organism is O. tsutsugamushi* - This statement is true; **scrub typhus** is caused by the obligate intracellular bacterium *Orientia tsutsugamushi*. - *O. tsutsugamushi* is transmitted to humans through the bite of infected larval mites. *Vector is trombiculid mite* - This statement is true; **trombiculid mites**, specifically their larval stage (chiggers), are the **vectors** for *Orientia tsutsugamushi*. - These mites are often found in areas with dense vegetation, making **scrubland** a risk factor for exposure. *Tetracycline is the drug of choice* - This statement is true; **tetracyclines**, such as **doxycycline**, are the drugs of choice for treating scrub typhus. - **Chloramphenicol** is an alternative in cases where tetracyclines are contraindicated, though often associated with side effects.

Q: Which of the following is transmitted by mites:

Scrub typhus. **Scrub typhus** - This disease is caused by the bacterium *Orientia tsutsugamushi* and is transmitted to humans through the bite of infected **larval mites** (chiggers). - The mites are found in rural areas, particularly in parts of Asia, and their bite often leaves a characteristic **eschar** at the inoculation site. *Endemic typhus* - Also known as murine typhus, this condition is caused by *Rickettsia typhi* and is transmitted by the **rat flea**, not mites. - It is typically associated with rodent populations. *Trench fever* - This disease is caused by *Bartonella quintana* and is transmitted by the human **body louse**, not mites. - It was historically prevalent during wartime due to crowded, unsanitary conditions. *Epidemic typhus* - Caused by *Rickettsia prowazekii*, this form of typhus is transmitted by the human **body louse**, not mites. - It is often associated with outbreaks in areas with poor hygiene and crowded living conditions.

Q: Cat scratch disease is caused by

Bartonella. ***Correct: Bartonella*** - **Cat scratch disease** is caused by the bacterium **Bartonella henselae**, which is transmitted through the scratch or bite of an infected cat. - The infection primarily manifests as **lymphadenopathy** (swollen lymph nodes) near the site of inoculation. *Incorrect: Moraxella* - **Moraxella** species, particularly *Moraxella catarrhalis*, are common causes of upper and lower respiratory tract infections, such as **otitis media** and **bronchitis**. - They are not associated with cat scratch disease. *Incorrect: Pseudomonas* - **Pseudomonas aeruginosa** is a ubiquitous bacterium known for causing opportunistic infections in immunocompromised individuals, such as **pneumonia**, **urinary tract infections**, and **wound infections**. - It is a common cause of healthcare-associated infections but not cat scratch disease. *Incorrect: Francisella* - **Francisella tularensis** is the causative agent of **tularemia**, a zoonotic disease typically transmitted by contact with infected animals (e.g., rabbits, rodents) or vectors (e.g., ticks, flies). - Its clinical presentation involves fever, skin ulcers, and lymphadenopathy, but it is distinct from cat scratch disease and not transmitted by cats.

Q: Nipah virus is transmitted by

Fruit bats. ***Fruit bats*** - **Fruit bats**, particularly those of the *Pteropus* genus (flying foxes), are the **natural reservoir** for Nipah virus. - The virus is shed in their **urine**, **feces**, and **saliva**, which can then contaminate fruit and other food sources. *Pigs* - **Pigs** can act as **intermediate hosts** and amplify the Nipah virus, transmitting it to humans. - However, they are not the natural reservoir; they become infected by consuming contaminated plant products or interacting with infected bats. *Cattle* - While other livestock, such as **horses** and **goats**, have been shown to be susceptible to Nipah virus infection, **cattle are not typically primary transmitters** to humans. - Their role in Nipah virus epidemiology is generally considered minor compared to bats and pigs. *Mosquitoes* - Nipah virus is **not transmitted by mosquitoes** or other insect vectors. - It is primarily spread through direct contact with infected animals or their bodily fluids, or through contaminated food.

Q: Ehrlichia chaffeensis is the causative agent of -

HME. ***HME (Human Monocytic Ehrlichiosis)*** - **Ehrlichia chaffeensis** is the primary causative agent of **Human Monocytic Ehrlichiosis**, a tick-borne illness. - This bacterium primarily infects **monocytes** and macrophages, leading to characteristic intracellular inclusions called **morulae**. *Glandular fever* - Glandular fever, also known as **infectious mononucleosis**, is predominantly caused by the **Epstein-Barr virus (EBV)**. - It is characterized by fever, sore throat, lymphadenopathy, and fatigue, and is not caused by bacteria. *HGE (Human Granulocytic Ehrlichiosis)* - **Human Granulocytic Ehrlichiosis (HGE)** is caused by **Anaplasma phagocytophilum**, not *Ehrlichia chaffeensis*. - HGE primarily targets **neutrophils** (granulocytes), differentiating it from HME which targets monocytes. *None of the options* - This option is incorrect because *Ehrlichia chaffeensis* is indeed the causative agent of HME, as described above.

Question 1

Fever of unknown origin in a farmer who raises goats would most likely be caused by which of the following organisms?

Accepted Answer

Brucella melitensis

Answer

T. pallidum

Answer

Histoplasma capsulatum

Answer

Clostridium novyi

Question 2

Mammalian reservoir of Rickettsial pox -

Accepted Answer

Mice

Answer

Cattle

Answer

Goat

Answer

Human

Question 3

Jail fever is related to

Accepted Answer

Rickettsia prowazekii

Answer

Rickettsia conorii

Answer

Rickettsia typhi

Answer

Rickettsia akari

Question 4

Rickettsialpox is caused by?

Accepted Answer

Rickettsia akari

Answer

Rickettsia conorii

Answer

Rickettsia rickettsii

Answer

Rickettsia typhi

Question 5

Rickettsia rickettsii is responsible for which disease -

Accepted Answer

Rocky mountain spotted fever

Answer

Endemic typhus

Answer

Scrub typhus

Answer

Epidemic typhus

Question 6

All are true about scrub typhus, except:

Accepted Answer

Adult female feeds on vertebrate hosts

Answer

Causative organism is O. tsutsugamushi

Answer

Vector is trombiculid mite

Answer

Tetracycline is the drug of choice

Question 7

Which of the following is transmitted by mites:

Accepted Answer

Scrub typhus

Answer

Endemic typhus

Answer

Trench fever

Answer

Epidemic typhus

Question 8

Cat scratch disease is caused by

Accepted Answer

Bartonella

Answer

Moraxella

Answer

Pseudomonas

Answer

Francisella

Question 9

Nipah virus is transmitted by

Accepted Answer

Fruit bats

Answer

Pigs

Answer

Cattle

Answer

Mosquitoes

Question 10

Ehrlichia chaffeensis is the causative agent of -

Accepted Answer

HME

Answer

Glandular fever

Answer

HGE

Answer

None of the options

Zoonotic Diseases — MCQs

Zoonotic Diseases — MCQs

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