Infectious Diseases Practice Questions

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

Measles. ***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.

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

Continuation phase - 2 drugs. ***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**.

Q: Walter Reed is associated with which disease?

Yellow Fever. ***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**.

Q: Which of the following statements about the Mantoux test is NOT true?

Result is seen after 3 weeks. Result is seen after 3 weeks - The results of a Mantoux test, indicating the induration size, are read **48 to 72 hours** after the injection, not three weeks. - Waiting three weeks would lead to a missed or inaccurate reading, as the immune response would have waned. *PPD RT-23 with tween 80 used as strain* - The Mantoux test uses a **Purified Protein Derivative (PPD)**, often designated as **PPD RT-23**, derived from Mycobacterium tuberculosis. - **Tween 80** is commonly added to PPD preparations to stabilize the protein and prevent it from adhering to the container, ensuring accurate dosing. * > 9mm induration is taken as positive* - An induration of **greater than 9mm** (often 10mm or more, depending on risk factors) is generally considered a **positive result** in the Mantoux test. - The interpretation of induration size varies based on the individual's risk factors for tuberculosis and exposure history. *Type IV Hypersensitivity* - The Mantoux test elicits a **Type IV hypersensitivity reaction**, also known as a **delayed-type hypersensitivity (DTH)** reaction. - This reaction involves T-cells and macrophages, which migrate to the injection site, causing induration and erythema within 48 to 72 hours.

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

Dengue fever. ***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*.

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

Tetanus. ***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.

Q: The Roll Back Malaria programme focused mainly on

Insecticide treated bed nets. ***Insecticide treated bed nets*** - The **Roll Back Malaria (RBM)** program, launched in 1998, focused significantly on key interventions including the promotion and distribution of **insecticide-treated nets (ITNs)**. - ITNs are highly effective in **preventing mosquito bites**, thus reducing malaria transmission, especially in vulnerable populations. *IEC campaigns for community awareness* - While **Information, Education, and Communication (IEC)** campaigns are crucial for health programs, they were a supportive component rather than the primary focus of RBM's core intervention strategy. - RBM emphasized **tangible interventions** with direct impact on disease transmission. *Development of larvivorous fishes for eradication of larvae* - The use of **larvivorous fish** is a form of biological control, which is typically part of **integrated vector management** but not the central pillar of RBM's strategy. - RBM prioritized interventions with **broad, immediate impact** across larger populations. *Presumptive treatment of malaria case* - **Presumptive treatment** (treating based on symptoms without laboratory confirmation) was an important aspect of early malaria control but not the main strategic thrust of the RBM initiative. - RBM's primary focus was on **prevention and rapid diagnosis/treatment** using effective antimalarials, and vector control strategies.

Q: Which of the following is a distinguishing feature of Aedes mosquitoes compared to Anopheles mosquitoes?

Wings unspotted. ***Wings unspotted*** - **Aedes mosquitoes have unspotted wings**, which is a key distinguishing feature for adult identification. - *Anopheles* mosquitoes characteristically have **spotted wings** with patches of dark and pale scales, making this a reliable diagnostic criterion. - This is one of the most practical features for field identification of adult mosquitoes. *Pupa has a narrow siphon* - This is **incorrect** - *Aedes* pupae actually have a **broad and short respiratory siphon (trumpet)**. - *Anopheles* pupae have a **narrow and long siphon**, which is the opposite of what this option states. - Pupal characteristics are useful but require microscopic examination. *Pupa has broad siphon* - While *Aedes* pupae do have a **broader siphon** compared to *Anopheles*, this is less commonly used for routine identification. - The broad siphon refers to the respiratory trumpet structure at the cephalothorax. - However, **wing spotting pattern** remains the preferred adult identification method. *Eggs are oval shaped* - *Aedes* eggs are **oval/elongated and laid singly**, often on moist surfaces above the waterline. - *Anopheles* eggs are also **boat-shaped with lateral floats** and laid singly on the water surface. - Both genera have oval-shaped eggs, making this a less reliable distinguishing feature alone.

Q: The rodent that is the primary natural reservoir of plague in the Indian subcontinent is

Tatera indica. ***Tatera indica*** - *Tatera indica*, also known as the **Indian gerbil**, is recognized as a significant **natural reservoir** for plague, specifically *Yersinia pestis*, in the Indian subcontinent. - These rodents play a crucial role in maintaining the **enzootic cycle** of plague in the region. *House mouse* - While **house mice** (*Mus musculus*) can be infected with plague, they are generally not considered the **primary natural reservoir** in endemic regions. - Their role in plague transmission is typically more peripheral compared to other rodent species. *Black rat* - The **black rat** (*Rattus rattus*) was historically a major vector for **epidemic plague** due to its close association with human dwellings. - However, it is primarily an **amplifying host** rather than a consistent natural reservoir maintaining the enzootic cycle in the **wild**. *Brown rat* - The **brown rat** (*Rattus norvegicus*) is also known to carry plague, but its ecological niche and geographical distribution make it less prominent as the **primary natural reservoir** in the Indian subcontinent compared to *Tatera indica*. - It is often associated with urban and suburban environments but is not the main long-term reservoir species in the wild.

Q: Which of the following is NOT a measure to prevent vertical transmission of HIV?

Administration of vitamin A. ***Administration of vitamin A*** - **Vitamin A supplementation** is important for general maternal and child health during pregnancy and lactation. - However, there is **no evidence** that vitamin A administration has any role in preventing **vertical transmission of HIV**. - It is **NOT part of PMTCT (Prevention of Mother-to-Child Transmission) protocols**. *Vaginal delivery* - **Vaginal delivery increases the risk** of HIV transmission compared to elective cesarean section. - **Elective cesarean section** (not vaginal delivery) is the preventive measure recommended for mothers with high or unknown viral loads. - Vaginal delivery may be acceptable only in mothers with **undetectable viral loads** on effective ART. *Stop breast feeding* - **Avoiding breastfeeding** (using replacement feeding) is a recognized strategy to prevent **postnatal HIV transmission** in resource-rich settings. - In resource-limited settings, WHO recommends **exclusive breastfeeding with maternal ART** as the safest option. - This is part of the comprehensive **PMTCT strategy**. *Treatment with zidovudine* - **Zidovudine (AZT)** is a cornerstone of **PMTCT protocols**. - Administration during pregnancy, labor, and to the newborn **significantly reduces vertical transmission risk**. - Now often part of combination **antiretroviral therapy (ART)** regimens for pregnant women with HIV.

Question 1

Which of the following diseases does not have healthy carriers?

Accepted Answer

Measles

Answer

Diphtheria

Answer

Salmonellosis

Answer

Poliomyelitis

Question 2

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

Accepted Answer

Continuation phase - 2 drugs

Answer

Total duration 24-27 months

Answer

Intensive phase 6-9 months

Answer

Intensive phase - 6 drugs

Question 3

Walter Reed is associated with which disease?

Accepted Answer

Yellow Fever

Answer

Typhoid Fever

Answer

Plague

Answer

Malaria

Question 4

Which of the following statements about the Mantoux test is NOT true?

Accepted Answer

Result is seen after 3 weeks

Answer

> 9mm induration is taken as positive

Answer

Type IV Hypersensitivity

Answer

PPD RT-23 with tween 80 used as strain

Question 5

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

Accepted Answer

Dengue fever

Answer

Japanese encephalitis

Answer

Chikungunya

Answer

Yellow fever

Question 6

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

Accepted Answer

Tetanus

Answer

Rabies

Answer

Typhoid

Answer

Measles

Question 7

The Roll Back Malaria programme focused mainly on

Accepted Answer

Insecticide treated bed nets

Answer

IEC campaigns for community awareness

Answer

Development of larvivorous fishes for eradication of larvae.

Answer

Presumptive treatment of malaria case

Question 8

Which of the following is a distinguishing feature of Aedes mosquitoes compared to Anopheles mosquitoes?

Accepted Answer

Wings unspotted

Answer

Pupa has broad siphon

Answer

Pupa has a narrow siphon

Answer

Eggs are oval shaped

Question 9

The rodent that is the primary natural reservoir of plague in the Indian subcontinent is

Accepted Answer

Tatera indica

Answer

House mouse

Answer

Black rat

Answer

Brown rat

Question 10

Which of the following is NOT a measure to prevent vertical transmission of HIV?

Accepted Answer

Administration of vitamin A

Answer

Stop breast feeding

Answer

Vaginal delivery

Answer

Treatment with zidovudine

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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