Infectious Diseases — MCQs

Disease caused by a virus of the family of RNA paramyxovirus, with an incubation period of 14-21 days, high secondary attack rate, and the most common complication being aseptic meningitis. A live, attenuated vaccine is available for the disease, with the Jeryl Lynn strain. What is the name of this disease?

Q736

Walter Reed is associated with which disease?

Q737

Transovarian transmission is seen in which infection?

Q738

Which of the following diseases is MOST characteristically associated with Aedes aegypti transmission globally?

Q739

A cook prepares sandwiches for 10 people going for a picnic. Eight out of them develop severe gastroenteritis within 4-6 hours of consuming the sandwiches. It is likely that on investigation, the cook is found to be the carrier of -

Q740

Which disease is primarily associated with soil as both a source and a reservoir for infection?

Infectious Diseases Indian Medical PG Practice Questions and MCQs

Question 731: Which of the following diseases does not have healthy carriers?

A. Diphtheria
B. Salmonellosis
C. Measles (Correct Answer)
D. Poliomyelitis

Explanation: ***Measles*** - Measles is a highly contagious viral disease that typically presents with a characteristic **rash**, **fever**, **cough**, **coryza**, and **conjunctivitis**. - Individuals infected with measles are usually symptomatic and contagious during the **prodromal phase** and until several days after the rash appears; asymptomatic carriage is generally not observed. *Diphtheria* - Healthy carriers of **Corynebacterium diphtheriae** can exist, particularly in the pharynx or skin, without showing overt disease symptoms. - These carriers can still **transmit the bacteria** to susceptible individuals, making them a public health concern. *Salmonellosis* - Individuals infected with **Salmonella Typhi** (which causes typhoid fever) can become asymptomatic chronic carriers, shedding bacteria in their stool for years. - While other Salmonella species can cause acute gastroenteritis, chronic asymptomatic carriage is most notable with **typhoid fever**. *Poliomyelitis* - Many individuals infected with the **poliovirus** can be asymptomatic and shed the virus in their stool. - These healthy carriers play a significant role in the **transmission of the virus** within communities, making eradication challenging.

Question 732: According to DOTS-PLUS guidelines 2013, which of the following statements about the treatment of multidrug-resistant TB is incorrect?

A. Total duration 24-27 months
B. Intensive phase 6-9 months
C. Continuation phase - 2 drugs (Correct Answer)
D. Intensive phase - 6 drugs

Explanation: ***Continuation phase - 2 drugs*** - According to DOTS-PLUS guidelines (2013), the continuation phase for multidrug-resistant TB (MDR-TB) should include at least **three to four effective drugs**, not two. - Using only two drugs in the continuation phase would be grossly inadequate and would likely lead to treatment failure and the development of extensively drug-resistant TB (XDR-TB). - This statement is **clearly incorrect** and represents a major deviation from standard treatment protocols. *Total duration 24-27 months* - According to DOTS-PLUS 2013 guidelines, the total treatment duration for MDR-TB is typically **18-24 months** (at least 18 months after culture conversion). - In complex cases, treatment may be extended beyond 24 months, though 24-27 months falls within acceptable parameters for difficult cases. - This statement is essentially correct for the upper range of treatment duration. *Intensive phase 6-9 months* - The intensive phase for MDR-TB treatment is indeed typically **6-9 months** or until culture conversion is documented. - This phase includes daily injectable agents and multiple oral drugs to rapidly reduce bacterial load. - This statement is **correct**. *Intensive phase - 6 drugs* - The 2013 DOTS-PLUS guidelines recommend an intensive phase regimen comprising **at least 4 effective drugs including an injectable agent**. - A 5-6 drug regimen may be used in complex cases or when drug susceptibility is uncertain. - While not the minimum standard, using 6 drugs is within acceptable practice, making this statement **generally correct**.

Question 733: How do hookworms infect humans?

A. Contaminated soil (Correct Answer)
B. Water
C. Food
D. Human feces

Explanation: ***Contaminated soil*** - Hookworm larvae (filariform larvae) present in **contaminated soil** can penetrate unbroken human skin, typically through the feet. - This penetration is the primary mode of infection for humans in endemic areas. *Water* - While some parasitic protozoa are transmitted through contaminated water, hookworms primarily infect via **skin penetration** from soil. - Ingestion of contaminated water is not a common or direct route for hookworm infection. *Food* - Hookworm infection is generally not acquired through the ingestion of **contaminated food**. - Infections spread via food usually involve other parasitic organisms like *Taenia* species or *Ascaris lumbricoides* eggs. *Human feces* - Human feces contain hookworm eggs, which hatch into rhabditiform larvae and then mature into infectious filariform larvae in the soil. - However, direct contact with **feces** itself is not the immediate infective route; the larvae in the soil are the infective stage.

Question 734: Which of the following diseases is primarily transmitted by soft ticks?

A. Tick typhus
B. Relapsing fever (Correct Answer)
C. Hemorrhagic fever
D. Tularemia

Explanation: ***Relapsing fever*** - **Relapsing fever** is primarily caused by **spirochete bacteria** (Borrelia species) transmitted by **soft ticks** (Ornithodoros species). - The disease is characterized by recurrent episodes of **fever** separated by afebrile periods. *Hemorrhagic fever* - **Hemorrhagic fevers** are caused by various viruses (e.g., Ebola, Marburg, Dengue, Lassa) and are typically transmitted by **mosquitoes**, **rodents**, or direct contact, not primarily soft ticks. - While some tick-borne diseases can cause hemorrhagic symptoms, the term "hemorrhagic fever" is not specific to soft tick transmission. *Tick typhus* - **Tick typhus** (Rocky Mountain spotted fever, etc.) is caused by **Rickettsia bacteria** and is transmitted by **hard ticks** (Ixodidae family), not soft ticks. - Symptoms include fever, rash, and headache. *Tularemia* - **Tularemia** is caused by the bacterium **Francisella tularensis** and can be transmitted by various means including **hard ticks**, deer flies, direct contact with infected animals, or inhalation. - While ticks can transmit tularemia, it is not primarily associated with **soft ticks** in the same way relapsing fever is.

Question 735: Disease caused by a virus of the family of RNA paramyxovirus, with an incubation period of 14-21 days, high secondary attack rate, and the most common complication being aseptic meningitis. A live, attenuated vaccine is available for the disease, with the Jeryl Lynn strain. What is the name of this disease?

A. Measles
B. Mumps (Correct Answer)
C. Rubella
D. Chicken pox

Explanation: ***Mumps*** - Mumps is caused by an **RNA paramyxovirus** and has a typical incubation period of **14-21 days**. - It is known for its **high secondary attack rate** and **aseptic meningitis** as the most common complication, aligning perfectly with the provided description. - The vaccine is developed from the **Jeryl Lynn strain**, which is the hallmark identifying feature of mumps vaccine. *Measles* - While also caused by an **RNA paramyxovirus** with a high attack rate, measles is primarily characterized by a **maculopapular rash** and respiratory symptoms, not aseptic meningitis as its most common complication. - The incubation period for measles is typically shorter, around **7-14 days**, and the vaccine strain is usually **Edmonston-Zagreb or Schwarz**, not Jeryl Lynn. *Rubella* - Rubella is caused by an **RNA togavirus**, not a paramyxovirus, and is characterized by a milder rash and lymphadenopathy. - The incubation period is typically **12-23 days**, but the viral family and common complications do not match the description. - Complications such as arthritis or encephalitis are rare. *Chicken pox* - Chickenpox is caused by the **varicella-zoster virus**, which is a **DNA herpesvirus**, not an RNA paramyxovirus. - It is characterized by a **vesicular rash** and can lead to complications like pneumonia or encephalitis, but not aseptic meningitis as its most common complication.

Question 736: Walter Reed is associated with which disease?

A. Yellow Fever (Correct Answer)
B. Typhoid Fever
C. Plague
D. Malaria

Explanation: ***Yellow Fever*** - **Walter Reed** led the US Army Yellow Fever Commission in **Cuba** in 1900. - His team definitively proved that **Aedes aegypti mosquitoes** transmit **yellow fever**. *Typhoid Fever* - While significant medical advancements were made in understanding **typhoid fever** around the same time, Walter Reed's primary focus was not on this disease. - The mode of transmission for typhoid (contaminated food and water) was established by others, notably **Robert Koch** and **George Soper**. *Plague* - **Plague**, caused by the bacterium **Yersinia pestis**, is primarily transmitted by fleas from rodents to humans. - Walter Reed's research did not involve **plague**. *Malaria* - **Malaria** is transmitted by **Anopheles mosquitoes**, and its causative agent, **Plasmodium**, was identified by **Alphonse Laveran**. - Although also a mosquito-borne illness, Walter Reed's specific groundbreaking work was on **yellow fever**.

Question 737: Transovarian transmission is seen in which infection?

A. Plague
B. Filarial
C. Guinea
D. Rocky Mountain spotted fever (Correct Answer)

Explanation: ***Rocky Mountain spotted fever*** - Transovarian transmission is a key characteristic of the **Rickettsia rickettsii** bacteria, the causative agent of Rocky Mountain spotted fever. - This mechanism ensures that the pathogen is passed from an infected female tick to her offspring, thereby maintaining the infection in the **tick population**. *Plague* - Plague (caused by **Yersinia pestis**) is primarily transmitted to humans through the bite of infected **fleas** or contact with infected animals. - It does not demonstrate transovarian transmission within its vector (fleas) as a common mode of perpetuation. *Filarial* - Filarial infections are caused by **nematodes** and are transmitted by insect vectors like mosquitoes or blackflies. - While these vectors transmit the larvae, they do not typically pass the parasitic infection to their offspring via transovarian transmission. *Guinea* - Guinea worm disease (**Dracunculus medinensis**) is transmitted when people drink water contaminated with copepods (water fleas) infected with **Guinea worm larvae**. - There is no transovarian transmission involved in the life cycle of the Guinea worm or its intermediate host.

Question 738: Which of the following diseases is MOST characteristically associated with Aedes aegypti transmission globally?

A. Dengue fever (Correct Answer)
B. Japanese encephalitis
C. Chikungunya
D. Yellow fever

Explanation: ***Dengue fever*** - *Aedes aegypti* is the **primary vector** for dengue fever globally, making it the most characteristic association. - This mosquito species is prevalent in tropical and subtropical regions where dengue is endemic. *Japanese encephalitis* - Japanese encephalitis is primarily transmitted by **Culex mosquitoes**, particularly *Culex tritaeniorhynchus*, not *Aedes aegypti*. - It is prevalent in Asia and typically associated with rural agricultural areas. *Yellow fever* - While *Aedes aegypti* can transmit yellow fever, it is not the **most characteristic association globally** as other *Aedes* species and *Haemagogus* species are also significant vectors, especially in sylvatic cycles. - Yellow fever's geographical distribution is more restricted to parts of Africa and South America. *Chikungunya* - Chikungunya is transmitted by both **Aedes aegypti** and **Aedes albopictus**. - While *Aedes aegypti* is a vector, *Aedes albopictus* has also played a significant role in recent outbreaks, and its characteristic association is with both species rather than exclusively *Aedes aegypti*.

Question 739: A cook prepares sandwiches for 10 people going for a picnic. Eight out of them develop severe gastroenteritis within 4-6 hours of consuming the sandwiches. It is likely that on investigation, the cook is found to be the carrier of -

A. Salmonella typhi
B. Vibrio cholerae
C. Entamoeba histolytica
D. Staphylococcus aureus (Correct Answer)

Explanation: ***Staphylococcus aureus*** - The rapid onset of symptoms (4-6 hours) and the development of severe gastroenteritis in multiple individuals after consuming common food items (sandwiches) strongly suggest a **preformed toxin ingestion**. - **_Staphylococcus aureus_** is a common cause of food poisoning due to its ability to produce enterotoxins that are heat-stable and cause rapid onset of nausea, vomiting, and diarrhea. *Salmonella typhi* - **_Salmonella typhi_** causes typhoid fever, which typically has an incubation period of **1-3 weeks**, much longer than the 4-6 hours seen in this case. - The symptoms of typhoid fever are also more systemic, including high fever, headache, and abdominal pain, rather than acute gastroenteritis with rapid onset. *Vibrio cholerae* - **_Vibrio cholerae_** causes cholera, characterized by **profuse watery diarrhea** with a typical incubation period of **1-5 days**. - The rapid onset of symptoms in this scenario (4-6 hours) does not align with the incubation period of cholera. *Entamoeba histolytica* - **_Entamoeba histolytica_** causes amoebiasis, which has an incubation period ranging from **several days to weeks or even months**. - It typically presents with **bloody diarrhea** and abdominal pain, and its slow onset is inconsistent with the acute event described.

Question 740: Which disease is primarily associated with soil as both a source and a reservoir for infection?

A. Rabies
B. Tetanus (Correct Answer)
C. Typhoid
D. Measles

Explanation: ***Correct: Tetanus*** - The causative agent, *Clostridium tetani*, forms **spores** that are widespread in **soil** and animal feces. - Soil acts as both a **source** for the bacteria to enter wounds and a **reservoir** where it can persist for long periods. - Spores are highly resistant and can survive in soil for years. *Incorrect: Rabies* - Primarily transmitted through the **saliva of infected animals**, usually via bites. - Animals (dogs, bats, etc.), not soil, serve as the primary **reservoir** for the rabies virus. *Incorrect: Typhoid* - Caused by *Salmonella Typhi*, which is transmitted through **contaminated food and water** via fecal-oral routes. - **Humans are the only known reservoir** for *Salmonella Typhi*, with chronic carriers shedding the bacteria in their feces. *Incorrect: Measles* - A highly contagious viral disease spread through **respiratory droplets** from an infected person. - **Humans are the only natural reservoir** for the measles virus.

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