Infectious Diseases — MCQs

You are the DOTS provider for a patient. He has completed his 6 months of treatment. He was sputum +ve to begin with, but after the intensive phase of treatment he became sputum -ve. He was again confirmed to be sputum negative 2 months after starting the continuation phase. This patient can be termed as:

Infectious Diseases Indian Medical PG Practice Questions and MCQs

Question 481: Which of the following is NOT transmitted by soft ticks?

A. KFD in India (Correct Answer)
B. Q fever
C. KFD outside India
D. Relapsing fever

Explanation: ***KFD in India*** - **Kyasanur Forest Disease (KFD)** in India is transmitted by **hard tick** species *Haemaphysalis spinigera*, NOT by soft ticks. - This is a viral hemorrhagic fever endemic to Karnataka and neighboring states in India. - Since it is NOT transmitted by soft ticks, this is the correct answer. *Q fever* - **Q fever** (*Coxiella burnetii*) can be transmitted by both **hard ticks** and **soft ticks**. - Primary transmission occurs through inhalation of contaminated aerosols from infected animals. - Since it CAN be transmitted by soft ticks, this is incorrect. *KFD outside India* - **Alkhurma hemorrhagic fever virus (AHFV)**, a close relative of KFD virus, occurs in the Middle East and is transmitted by **hard ticks** (*Ornithodoros savignyi* and *Hyalomma* species). - Related flaviviruses outside India follow similar hard tick transmission patterns. - This option may cause confusion but generally refers to KFD-like diseases transmitted by hard ticks, not soft ticks. *Relapsing fever* - **Tick-borne relapsing fever** (caused by *Borrelia* species) is classically transmitted by **soft ticks** of the genus *Ornithodoros*. - Since it IS transmitted by soft ticks, this is incorrect. - This differentiates it from Lyme disease, which is transmitted by hard ticks (*Ixodes* species).

Question 482: Crimean-Congo Hemorrhagic Fever is transmitted by?

A. Catfish
B. Mosquitoes
C. Ticks (Correct Answer)
D. Mites

Explanation: ***Ticks*** - Crimean-Congo Hemorrhagic Fever (CCHF) is primarily transmitted to humans through the bite of infected **Hyalomma ticks**. - Transmission can also occur through contact with infected animal blood or tissues, or through contact with infected human body fluids. *Cat fish* - **Catfish** are aquatic animals and are not known vectors for the transmission of viral diseases like CCHF. - Their habitat and interaction with humans do not facilitate the spread of tick-borne illnesses. *Mosquitoes* - **Mosquitoes** are vectors for diseases like dengue, malaria, and Zika, but not for CCHF. - CCHF is caused by a Nairovirus, which typically requires a tick vector for its lifecycle and transmission to humans. *Mites* - While some **mites** can transmit diseases (e.g., scrub typhus), they are not the primary or significant vector for Crimean-Congo Hemorrhagic Fever. - The main vector for CCHF is specified as ticks, particularly the Hyalomma genus.

Question 483: Which of the following acts as a vector of West Nile fever?

A. Tick
B. Culex mosquito (Correct Answer)
C. Mite
D. Flea

Explanation: ***Culex mosquito*** - The **Culex mosquito** genus is the primary vector for West Nile virus transmission to humans. - These mosquitoes commonly acquire the virus by feeding on **infected birds** and then transmit it to other animals and humans. *Tick* - **Ticks** are known vectors for diseases like **Lyme disease** (Borrelia burgdorferi) and **Rocky Mountain spotted fever** (Rickettsia rickettsii). - They are not vectors for West Nile fever. *Mite* - **Mites** can transmit diseases such as **scrub typhus** (Orientia tsutsugamushi) and **rickettsial pox** (Rickettsia akari). - They are not associated with the transmission of West Nile virus. *Flea* - **Fleas** are well-known vectors for diseases like **bubonic plague** (Yersinia pestis) and **murine typhus** (Rickettsia typhi). - They do not transmit West Nile fever.

Question 484: In an epidemic of plague, within 48 hours of application of insecticides by spraying, the X. cheopis index should fall to:

A. 5
B. 2
C. 1
D. 0 (Correct Answer)

Explanation: ***Correct Answer: 0*** - In an epidemic of plague, the immediate goal of insecticide spraying is to rapidly eliminate the **flea vectors**, primarily *Xenopsylla cheopis*. - A successful intervention aims for a rapid reduction to **zero live fleas** within 48 hours to halt transmission as quickly as possible. *Incorrect: 5* - An X. cheopis index of 5 would still indicate a significant presence of fleas, suggesting **ineffective vector control** and continued risk of plague transmission. - This level is far above the desired target for emergency plague control. *Incorrect: 2* - While lower than 5, an X. cheopis index of 2 still signifies the presence of live fleas capable of transmitting the disease, indicating an **incomplete elimination effort**. - The objective in a plague epidemic is complete disruption of the transmission chain, which requires a zero index. *Incorrect: 1* - An X. cheopis index of 1, though very low, still means there is at least one active flea per rodent on average, which poses an **ongoing risk of disease transmission**. - The critical nature of plague control necessitates achieving an index of zero to ensure complete cessation of vector-borne spread within 48 hours.

Question 485: SARS is most commonly seen in which of the following groups?

A. Coal miners
B. School kids
C. Pregnancy
D. Health care workers (Correct Answer)

Explanation: ***Health care workers*** - **SARS (Severe Acute Respiratory Syndrome)** is a viral respiratory illness known to spread easily, particularly in close-contact environments where aerosol-generating procedures might be performed. - Due to their direct exposure to infected patients and potential involvement in diagnostic and therapeutic procedures, **healthcare workers** are at a significantly higher risk of contracting and transmitting SARS compared to the general population. *Coal miners* - **Coal miners** are primarily at risk for respiratory diseases like **coal worker's pneumoconiosis** (black lung disease) due to chronic exposure to coal dust, not viral infections like SARS. - This group's occupational hazards are related to particulate matter, not infectious agents commonly associated with SARS outbreaks. *School kids* - While respiratory viruses can spread in schools, **SARS outbreaks** were not primarily characterized by widespread infection in children, largely due to differences in exposure patterns and potentially milder disease presentation in younger populations. - The initial outbreaks and severe cases of SARS predominantly impacted adults, especially in healthcare settings. *Pregnancy* - **Pregnancy** itself does not make individuals inherently more susceptible to contracting SARS; rather, if a pregnant individual contracts SARS, they may experience more severe outcomes. - While important for maternal and fetal health, this group is not identified as the most common demographic for initial SARS acquisition.

Question 486: Most important strategy for control of malaria in an endemic area:

A. Vector control (Correct Answer)
B. Chemoprophylaxis
C. Early treatment of cases
D. Elimination of plasmodium

Explanation: ***Vector control*** - **Vector control** strategies, such as **insecticide-treated bed nets (ITNs)** and **indoor residual spraying (IRS)**, are the most effective in reducing malaria transmission by targeting the Anopheles mosquito - By reducing the mosquito population and their biting rates, vector control significantly cuts down the number of infected bites, leading to a substantial decrease in malaria incidence - This is the **cornerstone of WHO's Global Malaria Programme** and has proven most cost-effective for endemic areas *Incorrect: Chemoprophylaxis* - Chemoprophylaxis involves taking antimalarial drugs to prevent infection, which is effective for individuals or travelers but not sustainable or scalable for mass control in endemic populations - Widespread use would be cost-prohibitive and could accelerate **antimalarial drug resistance** *Incorrect: Early treatment of cases* - Early treatment with effective antimalarials reduces disease severity and prevents onward transmission, which is crucial for managing the disease burden - However, it does not directly prevent new infections or interrupt the transmission cycle as effectively as vector control at a population level - This is a **secondary strategy** that complements but does not replace vector control *Incorrect: Elimination of plasmodium* - Elimination of Plasmodium refers to eradication of the parasite, which is the ultimate goal, but it is not a direct "strategy" in itself but rather the **outcome** of successful control measures - Complete eradication is ambitious and challenging; current efforts focus on breaking the transmission cycle through vector control and effective case management

Question 487: All are true about scrub typhus, except:

A. Causative organism is O. tsutsugamushi
B. Adult female feeds on vertebrate hosts (Correct Answer)
C. Vector is trombiculid mite
D. Tetracycline is the drug of choice

Explanation: ***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.

Question 488: The case fatality rate of untreated typhoid fever is:

A. 10% (Correct Answer)
B. 20%
C. 30%
D. 40%

Explanation: ***10%*** - The **case fatality rate** of untreated typhoid fever is approximately **10-20%**, with **10%** being the commonly cited average figure. - Without antibiotic treatment, complications like **intestinal perforation**, **hemorrhage**, **myocarditis**, and **encephalopathy** contribute to mortality. - This high fatality rate emphasizes the critical importance of early diagnosis and treatment. *20%* - While 20% represents the upper limit of the range for untreated typhoid, **10%** is the more commonly used average estimate in epidemiological studies. - The actual rate can vary based on **host factors** (age, nutritional status, immunity), **strain virulence**, and **supportive care availability**. *30%* - A 30% case fatality rate exceeds the typical range for untreated typhoid fever. - Even in the pre-antibiotic era and resource-limited settings, the rate rarely reached this level. *40%* - A 40% case fatality rate is far higher than observed for untreated typhoid fever. - Such high mortality would be characteristic of other severe infections like **untreated plague** or **severe viral hemorrhagic fevers**, not typhoid. **Note:** With appropriate antibiotic treatment, the case fatality rate of typhoid fever drops to **<1-2%**, highlighting the dramatic impact of modern therapeutics.

Question 489: All of the following statements regarding Dracunculiasis are true except -

A. The disease is limited to tropical and subtropical regions
B. India has eradicated this disease
C. No animal reservoir has been identified
D. Niridazole is effective in treating the disease. (Correct Answer)

Explanation: ***Niridazole is effective in treating the disease.*** - There are currently **no effective antiparasitic drugs** to treat Dracunculiasis. - Treatment focuses on **manual extraction of the worm** and symptom management, not chemotherapy. - Niridazole and other antiparasitic agents have been tried but are **not effective** for curing the infection. *The disease is limited to tropical and subtropical regions* - Dracunculiasis is predominantly found in **arid and semi-arid regions** of Africa, particularly those with poor access to safe drinking water. - Its geographical distribution is indeed restricted to **tropical and subtropical areas**, matching the environmental needs of its lifecycle. *India has eradicated this disease* - India successfully **eradicated Dracunculiasis in 2000**, a significant public health achievement. - This demonstrates that elimination is possible through sustained public health interventions focused on providing safe drinking water and community education. *No animal reservoir has been identified* - Humans have traditionally been considered the **primary definitive host** for *Dracunculus medinensis*. - While dogs and other animals can occasionally be infected, they play a **minimal role in transmission**, and the disease is primarily sustained through the human-cyclops-human cycle. - The statement is essentially **correct** from a classical epidemiological perspective where humans are the main reservoir.

Question 490: You are the DOTS provider for a patient. He has completed his 6 months of treatment. He was sputum +ve to begin with, but after the intensive phase of treatment he became sputum -ve. He was again confirmed to be sputum negative 2 months after starting the continuation phase. This patient can be termed as:

A. Transfer out
B. Cured (Correct Answer)
C. Defaulted
D. Treatment completed

Explanation: ***Cured*** - According to **RNTCP guidelines**, a patient is classified as **cured** when they are initially sputum smear-positive, complete the full course of treatment, and have **negative sputum smear results on at least two occasions** - one at the end of treatment and another on a previous occasion. - This patient was initially **sputum positive**, became **sputum negative after the intensive phase**, and was confirmed **sputum negative 2 months into the continuation phase**, meeting the criteria for cured status. - With documented negative sputum on multiple occasions during treatment, this represents successful bacteriological cure. *Treatment completed* - This category is used for TB patients who have **completed their full course of treatment** but do NOT have sputum smear results available at the end of treatment (either not done or results unavailable). - Since this patient has **documented negative sputum results** on multiple occasions, the appropriate classification is "cured" rather than "treatment completed". - Treatment completed is reserved for cases where bacteriological confirmation of cure is absent. *Transfer out* - This classification is for patients who are **transferred to another treatment unit** and whose treatment outcome is **unknown to the original reporting unit**. - The patient completed treatment under the same DOTS provider without transfer, making this classification incorrect. *Defaulted* - A patient is classified as having **defaulted** if they interrupt their treatment for **two consecutive months or more** after registration. - This patient completed the full 6-month treatment course without interruption, making defaulting an incorrect classification.

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