Zoonotic Diseases Practice Questions

Q: Most common route of infection in pasteurella cellulitis -

Animal bites or scratches. ***Animal bites or scratches*** - *Pasteurella multocida* is a common commensal bacterium in the oral flora of **cats and dogs**. - **Animal bites or scratches** are the primary mode of transmission for *Pasteurella* infections, particularly cellulitis, due to direct inoculation. *Aerosols or dust* - Transmission via **aerosols or dust** is rare for *Pasteurella* infections, which typically require direct contact or inoculation. - While other bacteria can spread this way, *Pasteurella* cellulitis is not commonly acquired through airborne routes. *Contaminated tissue* - While possible in some contexts, **contaminated tissue** is not the most common route of infection for *Pasteurella* cellulitis. - Direct inoculation from an **animal's oral flora** is far more frequent than contact with contaminated environmental tissues. *Human to human* - *Pasteurella* infections are generally **not transmissible from human to human**. - The organism is primarily associated with animals and their bites or scratches.

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

Strains of avian influenza. ***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.

Q: In human infections, the morula form is seen in which of the following organisms?

Ehrlichia. ***Correct: Ehrlichia*** - *Ehrlichia* species are **obligate intracellular bacteria** that replicate in host immune cells, forming distinctive microcolonies known as **morulae** (mulberry-like clusters). - The presence of morulae within the cytoplasm of **white blood cells** (monocytes or granulocytes) is the **key diagnostic feature** for ehrlichiosis. - The term "morula" comes from Latin for "mulberry," describing the characteristic clustered appearance visible on microscopy. *Incorrect: Chlamydiae* - *Chlamydiae* are obligate intracellular parasites with a unique developmental cycle involving elementary bodies (infectious form) and reticulate bodies (replicative form). - They form **intracytoplasmic inclusions** within vacuoles, but these are **not morulae**. *Incorrect: Bartonella quintana* - *Bartonella quintana* is a fastidious gram-negative bacillus associated with **trench fever** and bacillary angiomatosis. - Typically seen as individual or small clusters of bacteria, but **does not form morulae** within host cells. *Incorrect: Mycoplasma hominis* - *Mycoplasma hominis* is a small, **wall-less bacterium** that can cause genitourinary infections. - It is an extracellular pathogen or adheres to host cells but **does not invade or form intracytoplasmic morulae**.

Q: Patient came from Nagaland and shows positive test with OXK antigen. Diagnosis is?

Scrub typhus. ***Scrub typhus*** - A **positive Weil-Felix test** for the **OXK antigen** is highly suggestive of scrub typhus, particularly if the patient is from an endemic region like Nagaland. - Scrub typhus is caused by **_Orientia tsutsugamushi_**, transmitted by **chiggers** (larval mites), often presenting with fever and an **eschar**. *Trench fever* - Caused by **_Bartonella quintana_** and transmitted by the **human body louse**. - It does not typically show a positive Weil-Felix test for the OXK antigen. *Endemic typhus* - Also known as **murine typhus**, it is caused by **_Rickettsia typhi_** and transmitted by **fleas** (e.g., rat flea). - While it causes a positive Weil-Felix test, it usually involves the **OX19 antigen**, not OXK. *Epidemic typhus* - Caused by **_Rickettsia prowazekii_** and transmitted by the **human body louse**. - It yields a positive Weil-Felix test for the **OX19 and OX2 antigens**, but typically not for OXK.

Q: Boutonneuse fever is caused by which of the following?

B. Rickettsia conorii. ***Rickettsia conorii*** - **Boutonneuse fever**, also known as Mediterranean spotted fever, is specifically caused by the bacterium **Rickettsia conorii**. - This zoonotic disease is transmitted to humans through the bite of infected ticks, primarily the **dog tick** (Rhipicephalus sanguineus). *Rickettsia japonica* - **Rickettsia japonica** is the causative agent of **oriental spotted fever**, a tick-borne illness primarily found in Japan. - This Rickettsial disease is distinct from Boutonneuse fever, having a different geographical distribution and primary vector. *Rickettsia sibirica* - **Rickettsia sibirica** is responsible for **Siberian tick typhus** (North Asian tick typhus), which is prevalent in Siberia, Mongolia, and Northern China. - While also a tick-borne Rickettsial infection, its clinical presentation and geographic range differ from Boutonneuse fever. *Rickettsia australis* - **Rickettsia australis** causes **Queensland tick typhus**, an indigenous Rickettsial disease found in Australia. - This pathogen is distinct from Rickettsia conorii and causes a localized form of tick typhus.

Q: What is the cause of rabies in wild animals?

Wild-type rabies virus. ***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.

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

Human Monocytic Ehrlichiosis (HME). ***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.

Q: 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?

Microscopic agglutination test. ***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.

Q: Erysipeloid disease is caused by which type of infection?

Erysipelothrix infection. ***Erysipelothrix infection*** - **Erysipeloid disease** is caused by the bacterium **_Erysipelothrix rhusiopathiae_**. - This is a **zoonotic infection** transmitted through contact with infected animals or animal products (fish, shellfish, poultry, swine) via cuts or abrasions. - Clinically presents as a localized, violaceous, non-suppurative skin lesion, typically on the hands and fingers. - The term **"Erysipelothrix infection"** directly identifies the causative organism, making this the most accurate answer. *Fish handler's disease* - This is actually a **synonym for erysipeloid**, not a separate disease entity. - It refers to the same condition caused by **_Erysipelothrix rhusiopathiae_**, named for the occupational exposure common in fish handlers. - While this term describes erysipeloid, it is a **colloquial name** rather than identifying the specific infectious agent. *Seal finger* - **Seal finger** is a distinct infection occurring in seal handlers, causing painful cellulitis of the fingers. - Causative organisms include various bacteria such as **_Mycoplasma phocacerebrale_**, **_Streptococcus_** species, and occasionally **_Erysipelothrix_**. - This is **not synonymous** with erysipeloid disease. *Whale finger* - Similar to seal finger, this refers to infections from handling whale carcasses. - Caused by various marine-associated bacteria, not specifically **_Erysipelothrix rhusiopathiae_**. - This is a **different clinical entity** from erysipeloid.

Q: Glanders is caused by:

Bacteria. ***Bacteria*** - Glanders is a **zoonotic disease** caused by the bacterium *Burkholderia mallei*. - This gram-negative bacterium primarily affects **equids** (horses, mules, donkeys) but can be transmitted to humans and other animals. *Protozoa* - Protozoa are **single-celled eukaryotic organisms** that cause diseases like malaria, Giardiasis, and amoebiasis. - They are distinctly different from bacteria in their cellular structure and mechanisms of infection. *Virus* - Viruses are **acellular infectious agents** that replicate only inside the living cells of an organism. - They cause a wide range of diseases such as influenza, HIV, and COVID-19, but not glanders. *Fungi* - Fungi are **eukaryotic organisms** that include yeasts, molds, and mushrooms. - They cause diseases like candidiasis, aspergillosis, and ringworm, which are distinct from bacterial infections.

Question 1

Most common route of infection in pasteurella cellulitis -

Accepted Answer

Animal bites or scratches

Answer

Aerosols or dust

Answer

Contaminated tissue

Answer

Human to human

Question 2

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

Accepted Answer

Strains of avian influenza

Answer

Frequent endemic infection in man

Answer

Have same frequency of antigenic variation

Answer

None of the options

Question 3

In human infections, the morula form is seen in which of the following organisms?

Accepted Answer

Ehrlichia

Answer

Chlamydiae

Answer

Bartonella quintana

Answer

Mycoplasma hominis

Question 4

Patient came from Nagaland and shows positive test with OXK antigen. Diagnosis is?

Accepted Answer

Scrub typhus

Answer

Trench fever

Answer

Endemic typhus

Answer

Epidemic typhus

Question 5

Boutonneuse fever is caused by which of the following?

Accepted Answer

B. Rickettsia conorii

Answer

A. Rickettsia japonica

Answer

C. Rickettsia sibirica

Answer

D. Rickettsia australis

Question 6

What is the cause of rabies in wild animals?

Accepted Answer

Wild-type rabies virus

Answer

Laboratory passage in rabbits

Answer

Fatal encephalitis within 6 days

Answer

Negri bodies are not observed

Question 7

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

Accepted Answer

Human Monocytic Ehrlichiosis (HME)

Answer

HGE

Answer

Glandular fever

Answer

None of the options

Question 8

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?

Accepted Answer

Microscopic agglutination test

Answer

Widal test

Answer

Paul-Bunnell test

Answer

Weil-Felix reaction

Question 9

Erysipeloid disease is caused by which type of infection?

Accepted Answer

Erysipelothrix infection

Answer

Whale finger

Answer

Fish handler's disease

Answer

Seal finger

Question 10

Glanders is caused by:

Accepted Answer

Bacteria

Answer

Protozoa

Answer

Virus

Answer

Fungi

Zoonotic Diseases — MCQs

Zoonotic Diseases — MCQs

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