Infectious Diseases — MCQs

Infectious Diseases Indian Medical PG Practice Questions and MCQs

Question 451: Lyme disease is transmitted by

A. Mosquito
B. Tick (Correct Answer)
C. Mite
D. Rat flea

Explanation: ***Tick*** - Lyme disease is caused by the bacterium **_Borrelia burgdorferi_** and is primarily transmitted through the bite of infected **black-legged ticks** (also known as deer ticks). - The tick must be attached for at least 36-48 hours for the bacteria to be transmitted, leading to symptoms like a **bullseye rash (erythema migrans)**, fever, and joint pain. *Mosquito* - Mosquitoes are vectors for diseases such as **malaria**, **Dengue fever**, **Zika virus**, and **West Nile virus**, but not Lyme disease. - They transmit pathogens through their bite but are not involved in the **_Borrelia burgdorferi_** life cycle. *Mite* - Mites are responsible for diseases like **scabies** and act as vectors for scrub typhus, but they do not transmit Lyme disease. - While ticks are also arachnids like mites, they belong to different families and transmit different pathogens. *Rat flea* - Rat fleas are primarily known for transmitting **_Yersinia pestis_**, the bacterium that causes **bubonic plague**. - They are not associated with the transmission of Lyme disease.

Question 452: Tuberculous pericarditis is included in which treatment category of DOTS strategy?

A. Category IV
B. Category II
C. Category I (Correct Answer)
D. Category III

Explanation: ***Correct Option: Category I*** - **Tuberculous pericarditis** is classified as a **severe form of extra-pulmonary tuberculosis (EPTB)**. - Category I includes new cases of **smear-positive pulmonary TB**, **severe smear-negative pulmonary TB**, and **severe forms of EPTB**. - Severe EPTB includes: **TB meningitis, TB pericarditis, intestinal TB, genitourinary TB, spinal TB, and disseminated/miliary TB**. - Tuberculous pericarditis is considered severe due to potential complications like **cardiac tamponade** and **constrictive pericarditis**, requiring intensive treatment. *Incorrect Option: Category II* - Category II is reserved for **retreatment cases** including relapse, treatment failure, or treatment after default. - This is not applicable to a **newly diagnosed case** of tuberculous pericarditis. *Incorrect Option: Category III* - Category III (now largely phased out) was for **less severe forms of EPTB** such as lymph node TB or pleural TB. - Also included new smear-negative pulmonary TB without extensive involvement. - **Tuberculous pericarditis is too severe** to be classified under Category III. *Incorrect Option: Category IV* - Category IV is for **multi-drug resistant tuberculosis (MDR-TB)** and extensively drug-resistant TB (XDR-TB). - Requires specialized, longer treatment regimens. - Not applicable to drug-sensitive tuberculous pericarditis.

Question 453: Most common vector of Japanese encephalitis is:

A. Aedes
B. Anopheles
C. Culex (Correct Answer)
D. Ixodes

Explanation: **Culex** - **Culex mosquitoes**, particularly species like *Culex tritaeniorhynchus*, are the primary vectors responsible for transmitting **Japanese encephalitis virus** to humans. - These mosquitoes typically breed in stagnant water, such as rice paddies, and are most active during dusk and dawn. *Aedes* - **Aedes mosquitoes** are well-known vectors for diseases such as **dengue fever**, **Zika virus**, and **chikungunya virus**. - While they can transmit a range of arboviruses, they are not the primary vectors for Japanese encephalitis. *Anopheles* - **Anopheles mosquitoes** are the primary vectors for **malaria**, transmitting the *Plasmodium* parasite. - They are not associated with the transmission of Japanese encephalitis. *Ixodes* - **Ixodes ticks** are the primary vectors for **Lyme disease**, transmitting the bacterium *Borrelia burgdorferi*. - They are not insects and are not involved in the transmission of viral diseases such as Japanese encephalitis.

Question 454: After the appearance of rash, prophylactic isolation of measles case is necessary for a minimum of:

A. 2 days
B. 5 days (Correct Answer)
C. 7 days
D. 9 days

Explanation: ***5 days*** - Measles patients are infectious from **4 days before** to **4 days after** the rash appears, making them infectious for approximately 8-9 days total. - Standard isolation guidelines recommend isolation for **at least 4 days after rash onset**, and the 5-day option represents a **conservative approach** ensuring complete coverage of the infectious period. - This timeframe is crucial for controlling the spread of the **highly contagious measles virus** in community and healthcare settings, and the minimum of 5 days ensures no residual transmission risk. *2 days* - Isolating for only 2 days after the rash appears is **insufficient** as the patient remains infectious for at least 4 days post-rash. - This period does not cover the full duration of infectivity, leading to potential **onward transmission** and outbreak continuation. *7 days* - While 7 days would effectively cover the infectious period, it is **longer than medically necessary** for standard measles isolation after rash onset. - This extended isolation may impose **unnecessary burden** on patients, caregivers, and healthcare facilities without additional public health benefit. *9 days* - Isolating for 9 days is **excessive** and not required for measles, as the infectivity period after rash onset ends by day 4-5. - Prolonged isolation beyond the recommended period provides **no additional public health benefit** and can have significant social, psychological, and economic impacts on patients and families.

Question 455: You are explaining to your patient about epidemic typhus. He wants to know how he could have gotten infected with the disease. All the following are TRUE regarding transmission of epidemic typhus, EXCEPT:

A. It may be transmitted by getting bitten by an infected louse (Correct Answer)
B. It may be transmitted by self-inoculation due to an infected louse being crushed due to scratching
C. It may be transmitted by inhalation of infected louse feces
D. It may be transmitted by self-inoculation of infected louse feces while scratching

Explanation: ***Correct Answer: It may be transmitted by getting bitten by an infected louse*** - This is **FALSE** and therefore the correct answer to this EXCEPT question - Epidemic typhus (*Rickettsia prowazekii*) is NOT transmitted by the louse bite itself - Transmission occurs through **louse feces contaminating abraded skin**, not through the bite - The body louse (*Pediculus humanus corporis*) is the vector, but the bacteria are in its feces, not its saliva *Incorrect: It may be transmitted by self-inoculation due to an infected louse being crushed due to scratching* - This is TRUE, so incorrect for an EXCEPT question - Crushing an infected louse releases *Rickettsia prowazekii* from its body - The bacteria can then enter through **skin abrasions** caused by scratching - This is a recognized transmission mechanism in epidemic typhus *Incorrect: It may be transmitted by inhalation of infected louse feces* - This is TRUE, so incorrect for an EXCEPT question - **Aerosolized dried louse feces** containing *Rickettsia prowazekii* can be inhaled - This mode is less common but documented, especially in crowded or confined environments - Respiratory transmission can occur without direct skin contact *Incorrect: It may be transmitted by self-inoculation of infected louse feces while scratching* - This is TRUE, so incorrect for an EXCEPT question - This is the **PRIMARY mode of transmission** for epidemic typhus - Louse feces containing bacteria contaminate **scratched or abraded skin** - The bacteria enter the bloodstream through these breaks in the skin barrier

Question 456: Which of the following is the most peripheral laboratory under RNTCP?

A. Intermediate Reference laboratory
B. Peripheral Reference laboratory
C. Tuberculosis unit
D. Designated microscopy centre (Correct Answer)

Explanation: ***Designated microscopy centre*** - The **Designated Microscopy Centre (DMC)** is the most peripheral laboratory under the **Revised National Tuberculosis Control Programme (RNTCP)**, responsible for initial **sputum smear microscopy**. - These centers are established at the **primary healthcare level** to ensure widespread access to basic tuberculosis diagnostic services. *Intermediate Reference laboratory* - An **Intermediate Reference Laboratory (IRL)** is a higher-level facility that provides **advanced diagnostic services** and quality assurance for multiple DMCs. - They are not the most peripheral but serve as a **referral center** for smaller labs and perform drug susceptibility testing. *Peripheral Reference laboratory* - The term **"Peripheral Reference Laboratory"** is not a standard designation within the RNTCP structure for a distinct laboratory tier at the most peripheral level. - The hierarchy typically includes DMCs, IRLs, and National Reference Laboratories. *Tuberculosis unit* - A **Tuberculosis Unit (TU)** is essentially an administrative and programmatic unit within the RNTCP responsible for **managing TB control activities** for a specific population. - While TUs coordinate laboratory services, they are not themselves laboratories or the most peripheral diagnostic facility.

Question 457: 1st case of which of the following was found in Shimoga district of Karnataka -

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

Explanation: ***KFD*** - **Kyasanur Forest Disease (KFD)** is an endemic viral hemorrhagic fever whose first human cases were identified in the Shimoga district of Karnataka, India, in 1957. - The disease is caused by the **Kyasanur Forest disease virus (KFDV)**, a member of the *Flaviviridae* family, transmitted by ticks. *Japanese encephalitis* - While Japanese encephalitis is prevalent in parts of India, its initial discovery and identification are not associated with the Shimoga district of Karnataka. - The disease is caused by the **Japanese encephalitis virus (JEV)** and is primarily transmitted by mosquitoes. *Yellow fever* - **Yellow fever** is primarily widespread in tropical and subtropical areas of South America and Africa. - There are no historical records indicating the first case of yellow fever was discovered in the Shimoga district of Karnataka. *Dengue fever* - **Dengue fever** is a mosquito-borne tropical disease found globally, but its initial discovery is not linked to the Shimoga district of Karnataka. - Its outbreaks are common in many parts of India, but the first documented case of dengue fever did not originate there.

Question 458: Color of box containing drugs for treatment of category I of TB -

A. Yellow
B. Red (Correct Answer)
C. Blue
D. Green

Explanation: ***Red*** - In the Revised National Tuberculosis Control Programme (RNTCP), the **red box** contains drugs for **Category I TB**, which includes new smear-positive pulmonary TB, new smear-negative pulmonary TB with extensive parenchymal involvement, and severe forms of extrapulmonary TB. - This color-coding system facilitated appropriate drug distribution and adherence to standardized treatment regimens in the category-based approach. *Yellow* - The **yellow box** in the RNTCP was designated for **Category II TB** drugs, used for retreatment cases such as relapse, treatment failure, or treatment after default. - These cases required a longer and more intensive treatment regimen with additional drugs including streptomycin in the intensive phase. *Blue* - The **blue box** contained drugs for **Category III TB**, which included new smear-negative pulmonary TB cases that did not meet Category I criteria and less severe forms of extrapulmonary TB. - This category received a shorter treatment regimen compared to Categories I and II. *Green* - Green was **not a standard color** in the RNTCP category-based treatment color-coding system. - The RNTCP primarily used red, yellow, and blue boxes for Categories I, II, and III respectively, while MDR-TB treatment followed separate protocols outside this color-coding system.

Question 459: Case finding in RNTCP is based on -

A. Sputum culture
B. Sputum microscopy (Correct Answer)
C. X-ray chest
D. Mantoux test

Explanation: ***Sputum microscopy*** - Within the **Revised National Tuberculosis Control Programme (RNTCP)**, sputum microscopy for **acid-fast bacilli (AFB)** was established as the primary method for initial **case finding and diagnosis** of pulmonary TB, particularly in peripheral health facilities. - It is a **cost-effective and rapid test** that can identify individuals who are likely to be infectious and transmit the disease. - Under RNTCP guidelines, this remained the cornerstone diagnostic approach for widespread case finding. *Sputum culture* - While **sputum culture** is the **gold standard** for TB diagnosis due to its higher sensitivity, it is more time-consuming (weeks) and expensive, and thus was not used for initial widespread case finding in RNTCP settings. - It is mainly employed for **drug susceptibility testing (DST)** and in cases where microscopy is negative but TB is strongly suspected. *X-ray chest* - **Chest X-ray** can indicate lung abnormalities consistent with TB, but it is **not specific for active TB infection** and cannot confirm the presence of Mycobacterium tuberculosis. - It is used as a **screening tool** or to assess the extent of disease, but requires further microbiological confirmation for diagnosis. *Mantoux test* - The **Mantoux test** (tuberculin skin test) indicates **TB exposure or latent TB infection**, not active disease, and is not a case-finding tool for active TB patients. **Note:** Under the current **National Tuberculosis Elimination Programme (NTEP)**, which succeeded RNTCP, **CBNAAT/GeneXpert** (a molecular PCR-based test) has become the first-line diagnostic test for all presumptive TB cases, representing a shift from sputum microscopy to universal drug susceptibility testing.

Question 460: Every TB sputum positive patient can infect up to

A. 1-2 persons per year
B. 10-15 persons per year (Correct Answer)
C. 5-6 persons per year
D. 100-200 persons per year

Explanation: ***10-15 persons per year*** - Each **sputum smear-positive** tuberculosis patient can infect a substantial number of close contacts annually due to the highly contagious nature of **Mycobacterium tuberculosis** via airborne transmission. - This high infectivity rate underscores the importance of prompt diagnosis and treatment to limit disease spread in the community. *1-2 persons per year* - This number is significantly **too low** for a sputum-positive TB patient, who is actively shedding viable bacilli and poses a much higher risk of transmission. - Such a low rate might be associated with less contagious forms of TB, but not sputum-positive pulmonary TB. *5-6 persons per year* - While higher than 1-2, this number still **underestimates the typical infectivity** of an active, sputum-positive TB case. - The potential for infection is greater, especially in conditions of close contact and poor ventilation. *100-200 persons per year* - This figure represents an **overestimation** of the average number of people infected by a single TB patient. - While TB can spread rapidly in specific high-risk settings, such a high general transmission rate is not commonly observed.

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