Infectious Diseases — MCQs
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Which of the following diseases is transmitted by Aedes aegypti?
According to DOTS strategy, what is the criterion for diagnosis of tuberculosis?
The most common way in which tuberculosis is acquired is via the
Culex mosquito transmits:
Under the original International Health Regulations, the internationally quarantinable diseases were -
A patient who was initially smear positive, who began the treatment and who remained or became smear positive again at five months or later during the course of treatment is called as:
In dengue surveillance, indices that are commonly used to monitor Aedes aegypti infestation levels are all, EXCEPT:
Indicator for outbreak of Plague epidemic is
Leprosy commonly spreads by:
Which of the following diseases is spread by mosquitoes?
Infectious Diseases Indian Medical PG Practice Questions and MCQs
Question 281: Which of the following diseases is transmitted by Aedes aegypti?
- A. Japanese encephalitis
- B. Filariasis
- C. Malaria
- D. Yellow fever (Correct Answer)
Explanation: ***Yellow fever*** - **Yellow fever** is a viral hemorrhagic disease transmitted primarily by the **Aedes aegypti** mosquito. - This mosquito species is also responsible for transmitting other arboviruses like **Dengue**, **Chikungunya**, and **Zika** viruses. *Japanese encephalitis* - **Japanese encephalitis** is typically transmitted by mosquitoes of the **Culex** genus, particularly **Culex tritaeniorhynchus**. - It is a leading cause of viral encephalitis in Asia, affecting the brain and central nervous system. *Filariasis* - **Lymphatic filariasis** is transmitted by several mosquito genera, including **Culex**, **Anopheles**, and **Aedes**, but it's not exclusively carried by **Aedes aegypti**. - It is caused by parasitic worms and can lead to severe swelling (lymphedema) and elephantiasis. *Malaria* - **Malaria** is transmitted exclusively by infected female **Anopheles mosquitoes**. - The parasite Plasmodium causes malaria, and different species infect humans, leading to cyclical fevers and chills.
Question 282: According to DOTS strategy, what is the criterion for diagnosis of tuberculosis?
- A. 3 out of 3 samples positive
- B. 1 out of 2 samples positive
- C. 2 out of 3 samples positive (Correct Answer)
- D. None of the options
Explanation: ***2 out of 3 samples positive*** - Under the **DOTS (Directly Observed Treatment, Short-course) strategy**, a diagnosis of **pulmonary tuberculosis** is confirmed when at least **two out of three sputum smear samples** are positive for acid-fast bacilli (AFB). - This criterion aims to balance diagnostic accuracy with the feasibility of rapid and efficient diagnosis in resource-limited settings. *3 out of 3 samples positive* - Requiring all three samples to be positive would be more stringent and might lead to **delayed diagnosis** or **missed cases**, especially in individuals with lower bacillary loads. - While highly specific, it is not the standard criterion for initial diagnosis under DOTS, which prioritizes timely treatment. *1 out of 2 samples positive* - This criterion would be **less specific** and could result in a higher rate of **false positives**, leading to unnecessary treatment and potential side effects. - The DOTS strategy aims for a reliable diagnosis with a reasonable level of certainty before initiating a lengthy and potent drug regimen. *None of the options* - This option is incorrect because there is a specific, well-established criterion within the DOTS strategy for diagnosing pulmonary tuberculosis based on sputum smear microscopy results. - The framework provides clear guidelines for diagnosis and treatment to ensure effective control of the disease globally.
Question 283: The most common way in which tuberculosis is acquired is via the
- A. Genital tract
- B. Gastrointestinal tract
- C. Respiratory tract (Correct Answer)
- D. Skin
Explanation: ***Respiratory tract*** - **Tuberculosis (TB)** is primarily transmitted through **airborne droplets** generated when an infected person coughs, sneezes, or speaks. - Inhalation of these droplets containing **Mycobacterium tuberculosis** leads to infection, making the respiratory tract the most common route. *Genital tract* - While TB can affect the genital tract (e.g., **genital tuberculosis**), it is a rare manifestation and not the primary mode of transmission. - Genital tract involvement usually occurs via **hematogenous spread** from a primary pulmonary focus, not direct acquisition. *Gastrointestinal tract* - **Gastrointestinal TB** can occur through ingestion of contaminated milk (historically **Mycobacterium bovis**) or sputum containing **Mycobacterium tuberculosis**. - However, this is far less common than respiratory transmission, especially in modern settings with pasteurization. *Skin* - **Cutaneous TB** can occur through direct inoculation of the skin, but this is a very rare form of transmission. - It usually presents as specific skin lesions and is not the predominant way in which TB is acquired by the general population.
Question 284: Culex mosquito transmits:
- A. Dengue fever
- B. Tularemia
- C. Yellow fever
- D. Japanese encephalitis (Correct Answer)
Explanation: ***Japanese encephalitis*** * **Culex mosquitoes** are the primary vectors for the **Japanese encephalitis virus** (JEV), a flavivirus. * JEV is a significant cause of **viral encephalitis** in Asia, largely transmitted by Culex species such as *Culex tritaeniorhynchus*. *Dengue fever* * Dengue fever is primarily transmitted by mosquitoes of the genus ***Aedes***, particularly *Aedes aegypti* and *Aedes albopictus*. * These mosquitoes are known for biting during the **daytime** and are common in urban and semi-urban areas. *Tularemia* * Tularemia is caused by the bacterium *Francisella tularensis* and is primarily transmitted by **ticks**, deer flies, or direct contact with infected animals. * Mosquitoes are **not a primary vector** for the transmission of tularemia. *Yellow fever* * Yellow fever is primarily transmitted by mosquitoes of the genus ***Aedes***, particularly *Aedes aegypti*. * This viral hemorrhagic fever is common in tropical and subtropical regions of South America and Africa.
Question 285: Under the original International Health Regulations, the internationally quarantinable diseases were -
- A. Cholera
- B. All of the above (Correct Answer)
- C. Plague
- D. Yellow fever
Explanation: ***All of the above*** - **Cholera**, **plague**, and **yellow fever** were the three diseases designated as internationally quarantinable under the **original International Health Regulations (IHR)** before the 2005 revision. - These diseases were selected due to their potential for rapid international spread and serious public health impact, requiring coordinated global surveillance and response. - **Note:** The IHR (2005), which came into force in 2007, replaced this fixed list with a framework for assessing **Public Health Emergencies of International Concern (PHEIC)** using a decision algorithm. *Cholera* - **Cholera** is an acute diarrheal illness caused by *Vibrio cholerae* that can cause severe dehydration and death if untreated, with high potential for **epidemic spread**, particularly in areas with poor sanitation. - It was designated as quarantinable due to its rapid transmission via contaminated water and food. *Plague* - **Plague**, caused by the bacterium *Yersinia pestis*, has historically caused devastating pandemics and remains a concern due to its high fatality rate and potential for spread through **vector transmission** (fleas) or **person-to-person transmission via pneumonic plague**. - Its inclusion reflected its capacity to cause widespread morbidity and mortality. *Yellow fever* - **Yellow fever** is a viral hemorrhagic disease transmitted by *Aedes* mosquitoes, posing risk in tropical and subtropical regions of Africa and South America. - Its quarantinable status stemmed from its potential for rapid spread into non-endemic areas by infected travelers and the presence of **competent mosquito vectors globally**.
Question 286: A patient who was initially smear positive, who began the treatment and who remained or became smear positive again at five months or later during the course of treatment is called as:
- A. Treatment failure (Correct Answer)
- B. Relapse
- C. Defaulter
- D. None of the options
Explanation: ***Treatment failure*** - This definition accurately describes a patient who was initially **smear positive**, began treatment, and remained or became **smear positive again at five months or later** during the course of treatment. - It indicates that the current anti-tuberculosis regimen is insufficient to clear the bacterial load, often due to **drug resistance** or poor adherence. *Relapse* - A relapse refers to a patient who successfully completed their anti-tuberculosis treatment, was declared cured, but subsequently developed **tuberculosis again**. - The key differentiator is the prior completion of treatment and declaration of cure, which is not the case in the scenario described. *Defaulter* - A defaulter is a patient who has **interrupted their treatment for two consecutive months or more** after having been on treatment for at least one month. - This definition focuses on the interruption of treatment, not the persistent or recurrent smear positivity while actively undergoing treatment. *None of the options* - This option is incorrect because "Treatment failure" accurately describes the scenario presented.
Question 287: In dengue surveillance, indices that are commonly used to monitor Aedes aegypti infestation levels are all, EXCEPT:
- A. Street index (Correct Answer)
- B. House index
- C. Breteau index
- D. Pupae index
Explanation: ***Street index*** - The **Street index** is not a standard entomological index used for monitoring *Aedes aegypti* infestation levels or density in dengue surveillance. - Surveillance efforts typically focus on household-level indices to assess mosquito breeding sites. *House index* - The **House index** (HI) measures the percentage of houses infested with *Aedes* larvae and/or pupae. - It provides an indication of the proportion of dwellings in an area that serve as mosquito breeding sites. *Breteau index* - The **Breteau index** (BI) calculates the number of positive containers per 100 houses inspected. - It reflects the density of breeding containers and is considered a more sensitive indicator of mosquito population density than the House index. *Pupae index* - The **Pupae index** (PI) measures the average number of pupae per person or per house. - This index is highly correlated with adult mosquito density and is considered the most accurate indicator of potential dengue transmission risk.
Question 288: Indicator for outbreak of Plague epidemic is
- A. Rat burrow index
- B. Total flea
- C. Cheopis index (Correct Answer)
- D. Specific flea index
Explanation: ***Cheopis index*** - The **Cheopis index** (or **flea index**) measures the average number of *Xenopsylla cheopis* (oriental rat flea) per rat, which is the primary vector for **bubonic plague**. - A Cheopis index of **1 or more** indicates a high risk of a plague outbreak, as it suggests a significant number of infected fleas are present on the rat population. *Rat burrow index* - The **rat burrow index** indicates the density of rat activity by counting active burrows, but it does not directly measure the **flea burden** or infection risk. - While high rat density can indirectly increase risk, it's not as specific an indicator for **plague transmission** as the Cheopis index. *Total flea* - **Total flea count** refers to the absolute number of fleas collected, but it doesn't account for the **rat population size** or the specific vector species (*Xenopsylla cheopis*). - A high total flea count might simply reflect a large rat population rather than an elevated risk of **plague transmission**. *Specific flea index* - The term **specific flea index** is less commonly used in the context of plague surveillance compared to the **Cheopis index**, which specifically targets the primary vector. - It could be interpreted as similar to the Cheopis index but lacks the precise and globally recognized definition used for **plague risk assessment**.
Question 289: Leprosy commonly spreads by:
- A. Water
- B. Milk
- C. Mosquitoes
- D. Droplet (Correct Answer)
Explanation: ***Droplet*** - Leprosy is primarily transmitted through **respiratory droplets** expelled during coughing or sneezing by an untreated person with **multibacillary leprosy**. - **Prolonged, close contact** with an infected individual is typically required for transmission due to the slow growth rate of *Mycobacterium leprae*. *Water* - Diseases spread through water, such as **cholera** or **typhoid**, are often caused by the ingestion of contaminated water containing pathogens. - Leprosy is not a **waterborne disease**; its transmission route is different. *Milk* - **Milk-borne diseases** are typically contracted by consuming raw or unpasteurized milk contaminated with bacteria like *Listeria* or *Brucella*. - Leprosy is not transmitted via **ingestion of milk** or dairy products. *Mosquitoes* - Mosquitoes are vectors for diseases such as **malaria**, **dengue**, and **Zika virus**, transmitting pathogens through bites. - Leprosy is not an **arthropod-borne disease** and is not spread by insect bites.
Question 290: Which of the following diseases is spread by mosquitoes?
- A. Dengue (Correct Answer)
- B. Listeriosis
- C. Kala azar
- D. Trypanosomiasis
Explanation: ***Dengue*** is the correct answer. - **Dengue fever** is a **mosquito-borne** viral disease transmitted primarily by **Aedes aegypti** and **Aedes albopictus** mosquitoes. - Symptoms range from mild flu-like illness to severe dengue hemorrhagic fever or dengue shock syndrome. *Listeriosis* - Caused by **Listeria monocytogenes**, transmitted through contaminated food consumption. - **Not spread by mosquitoes** but through foodborne routes or contact with infected animals. *Kala azar* - Visceral leishmaniasis caused by **Leishmania parasites**, transmitted by infected **sandflies**, not mosquitoes. - Affects internal organs including spleen, liver, and bone marrow. *Trypanosomiasis* - Includes **African sleeping sickness** (transmitted by **tsetse flies**) and **Chagas disease** (transmitted by **reduviid bugs/kissing bugs**). - Neither vector is a mosquito.
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