Infectious Diseases Practice Questions

Q: Most common source of diphtheria transmission is:

Carrier. ***Carrier*** - **Asymptomatic carriers** can harbor and shed *Corynebacterium diphtheriae* for extended periods, making them a significant reservoir. - They often remain undetected, thus facilitating the **silent spread** of the infection within a community. *Both carriers and cases* - While both contribute to transmission, **carriers** are often considered the most common source due to their asymptomatic nature and prolonged shedding, unlike acute cases who are usually identified and isolated. - This option is partially true, but **carriers** are particularly effective at sustaining endemic transmission. *Case* - **Diphtheria cases** do transmit the disease, but they are typically symptomatic, leading to quicker diagnosis and isolation, which limits their overall contribution to widespread transmission compared to unnoticed carriers. - Their period of infectivity is generally shorter than that of chronic carriers. *None of the options* - This option is incorrect as there are clear sources of diphtheria transmission. - **Carriers** specifically play a well-documented and crucial role in the epidemiology of diphtheria.

Q: Under National Vector Borne Diseases Control Programme, operational efficiency of antimalarial measures is assessed by:

Annual Parasite Incidence. ***Annual Parasite Incidence*** - **Annual Parasite Incidence (API)** is a key indicator for assessing the operational efficiency of malaria control measures as it measures the **number of confirmed malaria cases per 1,000 population per year**. - A decrease in API over time suggests that antimalarial measures are effectively reducing the incidence of malaria in the population. *Infant parasite rate* - The **infant parasite rate** specifically focuses on malaria infection prevalence in infants, often reflecting recent transmission. - While important for understanding ongoing transmission, it may not reflect the overall operational efficiency of all antimalarial measures across all age groups. *Slide positivity rate* - The **slide positivity rate (SPR)** indicates the proportion of blood smears examined that are positive for malaria parasites. - SPR reflects the intensity of transmission and diagnostic efficiency, but a high SPR could also indicate poor case detection or treatment, making it less direct for assessing operational efficiency of control over a population. *Annual Blood Examination Rate* - The **Annual Blood Examination Rate (ABER)** indicates the proportion of the population whose blood is examined for malaria parasites within a year. - ABER reflects surveillance efforts and case detection, but a high ABER without a corresponding decrease in malaria cases does not necessarily signify efficient control measures for reducing disease burden.

Q: The arthropod vector BEST KNOWN for transovarian transmission of multiple pathogens is -

Ticks. ***Ticks*** - Ticks are well-known for their diverse modes of pathogen transmission, including **transovarian transmission**, where pathogens are passed from an infected female tick to her offspring through the eggs. - This mechanism is crucial for the maintenance and spread of several tick-borne diseases, such as **Rocky Mountain spotted fever (caused by *Rickettsia rickettsii*)** and **Babesiosis** (caused by *Babesia* species). *Fleas* - Fleas are primarily known for transmitting pathogens such as *Yersinia pestis* (causing **plague**) and *Rickettsia typhi* (causing **murine typhus**) through their bites, but transovarian transmission is not their primary mode. - They typically transmit pathogens through **regurgitation** during feeding or by their **feces** being rubbed into the bite wound. *Sandfly* - Sandflies are vectors for diseases like **leishmaniasis**, caused by parasitic protozoa of the genus *Leishmania*. - They transmit these pathogens through **saliva** during blood meals, but transovarian transmission is not a significant feature of their lifecycle. *Mosquitoes* - Mosquitoes are vectors for a wide range of diseases, including **malaria**, **dengue**, **Zika**, and **West Nile virus**, primarily through the **injection of saliva** during blood feeding. - While some arboviruses can exhibit transovarian transmission in mosquitoes, it is not as prominent or broadly impactful across multiple pathogens as it is in ticks.

Q: Hepatitis B can be transmitted through all EXCEPT:

Stool. ***Stool*** - Hepatitis B virus is primarily transmitted through **blood** and **body fluids**, not via the **fecal-oral route**. - While viral particles might theoretically be present in stool, the concentration is too low to cause an infection. *Milk* - **Breast milk** can contain the hepatitis B virus, allowing for mother-to-child transmission during breastfeeding. - This is a less common route than perinatal transmission at birth but is still possible. *Blood* - **Blood** is a major vehicle for hepatitis B transmission, occurring through shared needles, transfusions (less common now due to screening), or unprotected medical procedures. - Even microscopic amounts of infected blood can transmit the virus. *Semen* - **Semen** is a known bodily fluid that can transmit the hepatitis B virus during unprotected sexual intercourse. - This is a significant mode of transmission for adults.

Q: The most important sandfly-transmitted disease in India is-

Kala azar. ***Kala azar*** - **Kala azar**, or **visceral leishmaniasis**, is a severe parasitic disease endemic to India, transmitted primarily by *Phlebotomus argentipes* sandflies. - It is characterized by fever, **splenomegaly**, hepatomegaly, and can be fatal if untreated, making it a major public health concern. *Typhus* - **Typhus** is caused by Rickettsial bacteria and is typically transmitted by lice or fleas, not sandflies. - Symptoms include fever, rash, and headache, differing significantly from the visceral symptoms of Kala azar. *Relapsing fever* - **Relapsing fever** is caused by *Borrelia* bacteria and is transmitted by ticks or lice, not sandflies. - It is characterized by recurring episodes of fever, distinct from the progressive symptoms of Kala azar. *Plague* - **Plague** is caused by *Yersinia pestis* and is primarily transmitted by **fleas** carried by rodents. - It presents with buboes, fever, and sepsis, which are different from the clinical manifestations of sandfly-borne diseases.

Q: Following diseases are transmitted by mosquito except?

Plague. ***Plague*** - **Plague** is primarily transmitted by the bite of infected **fleas**, which are often found on rodents like rats. - While humans can contract plague through contact with infected animals or respiratory droplets from pneumonic plague patients, **mosquitoes are not vectors** for its transmission. *Dengue fever* - **Dengue fever** is a well-known **mosquito-borne** viral infection, transmitted primarily by **Aedes aegypti** and **Aedes albopictus** mosquitoes. - These mosquitoes bite during the daytime and are responsible for spreading the dengue virus in tropical and subtropical regions. *Yellow fever* - **Yellow fever** is another significant **mosquito-borne viral disease**, primarily transmitted by infected **Aedes aegypti** mosquitoes. - It circulates in urban, savanna, and jungle environments, with mosquitoes acting as the primary vector for human infection. *Japanese encephalitis* - **Japanese encephalitis** is a serious **mosquito-borne viral infection** of the brain, transmitted mainly by **Culex mosquitoes**, particularly **Culex tritaeniorhynchus**. - These mosquitoes typically breed in rice paddies and feed on birds and pigs, which act as amplifying hosts, before transmitting the virus to humans.

Q: Diseases associated with rodents include all except

Oriental sore. ***Oriental sore*** - **Oriental sore** is a form of **cutaneous leishmaniasis**, caused by Leishmania parasites transmitted by the bite of **sandflies**, not rodents. - This disease is characterized by chronic skin lesions that can develop into ulcers. *Leptospirosis* - **Leptospirosis** is a bacterial disease spread through the urine of infected animals, including **rodents**, often via contaminated water or soil. - Symptoms can range from mild flu-like illness to severe conditions like **Weil's disease**, affecting the liver and kidneys. *Tularemia* - **Tularemia**, also known as **rabbit fever**, is a bacterial disease that can be transmitted by **rodents**, rabbits, and other animals. - Transmission occurs through insect bites (ticks, deer flies), contact with infected animal carcasses, or contaminated food/water. *Rat Bite fever* - **Rat Bite fever** is caused by bacteria (usually *Streptobacillus moniliformis* or *Spirillum minus*) transmitted through a **rat bite** or scratch. - It is directly associated with rodent exposure and can cause fever, rash, and arthritis.

Q: Sputum positive TB is diagnosed when:

2 out of 3 sputum sample +ve. **2 out of 3 sputum sample +ve** - The diagnosis of sputum-positive **tuberculosis (TB)** typically requires at least two out of three sputum samples to be positive for **acid-fast bacilli (AFB)** on smear microscopy [1]. - This criterion helps to ensure the presence of active, transmissible disease and to minimize false positives. *Mantoux test positive* - A positive Mantoux test (or tuberculin skin test) indicates **latent TB infection** or prior exposure to *Mycobacterium tuberculosis*, not necessarily active disease [2]. - It does not confirm active, sputum-positive TB and can be positive even in individuals who have received the BCG vaccine. *1 out of 2 sputum sample +ve* - While one positive sputum sample is highly suspicious, the standard diagnostic criteria for sputum-positive TB usually require **at least two positive samples** to establish a definitive diagnosis [1]. - Relying on only one positive sample might lead to an increased risk of false positives or inadequate classification for public health reporting. *BACTEC +ve* - **BACTEC** is a rapid culture method for *Mycobacterium tuberculosis* and a positive result indicates the presence of viable bacteria. - While BACTEC culture positivity confirms active TB, sputum-positive TB specifically refers to the presence of **AFB on smear microscopy**, which indicates high bacillary load and contagiousness [1].

Q: Not true about aedes mosquito-

Eggs cannot survive more than 1 week without water. ***Eggs cannot survive more than 1 week without water*** - This statement is incorrect because **Aedes eggs** are known for their ability to survive long periods (months to even a year) of **desiccation** (drying out) in the absence of water. - This characteristic allows the eggs to **withstand dry seasons** and hatch when conditions become favorable with water. *Transmits dengue fever* - **Aedes aegypti** and **Aedes albopictus** are the primary vectors for **dengue virus**. - The mosquito acquires the virus by biting an infected person and then transmits it to other individuals through subsequent bites. *Are recurrent day time biters* - **Aedes mosquitoes** are primarily active and feed during the **daylight hours**, particularly in the early morning and late afternoon. - They are known for taking **multiple blood meals** from different individuals in a single gonotrophic cycle, making them efficient disease transmitters. *Prefer breeding in stagnant water* - **Aedes mosquitoes** lay their eggs in small collections of **stagnant water**, often in artificial containers around human dwellings. - Examples include water storage containers, discarded tires, flower pots, and gutters, which highlights their **domestic breeding habits**.

Q: Anopheles species responsible for the transmission of malaria in urban areas is

Anopheles stephensi. **Anopheles stephensi** - **Anopheles stephensi** is recognized as the primary vector for malaria transmission in **urban areas** of the Indian subcontinent due to its ability to breed in man-made water containers and adaptation to urban environments. - It exhibits **endophilic** (resting indoors) and **anthropophilic** (preferring human blood) behaviors, increasing its efficiency in transmitting malaria in human-dense urban settings. *Anopheles sundaicus* - **Anopheles sundaicus** is primarily found in **coastal saline water** and brackish water environments, making it a significant vector in coastal regions rather than typical urban settings. - It is known for transmitting malaria in **swampy and estuarine areas**, which are not characteristic of most urban landscapes. *Anopheles fluviatilis* - **Anopheles fluviatilis** is a major vector in **hilly and forested areas** of India, breeding in clean, flowing water like streams and rivulets. - Its breeding habitats and geographical distribution are typically associated with **rural and foothill regions**, not major urban centers. *Anopheles culicifacies* - **Anopheles culicifacies** is the most important vector for malaria in **rural areas** of India, breeding in a variety of rural water sources such as agricultural fields, wells, and ponds. - While it can be found on the outskirts of urban areas, it is not the primary urban vector and is more strongly associated with **agricultural and village environments**.

Question 1

Most common source of diphtheria transmission is:

Accepted Answer

Carrier

Answer

Both carriers and cases

Answer

Case

Answer

None of the options

Question 2

Under National Vector Borne Diseases Control Programme, operational efficiency of antimalarial measures is assessed by:

Accepted Answer

Annual Parasite Incidence

Answer

Infant parasite rate

Answer

Slide positivity rate

Answer

Annual Blood Examination Rate

Question 3

The arthropod vector BEST KNOWN for transovarian transmission of multiple pathogens is -

Accepted Answer

Ticks

Answer

Fleas

Answer

Sandfly

Answer

Mosquitoes

Question 4

Hepatitis B can be transmitted through all EXCEPT:

Accepted Answer

Stool

Answer

Milk

Answer

Blood

Answer

Semen

Question 5

The most important sandfly-transmitted disease in India is-

Accepted Answer

Kala azar

Answer

Typhus

Answer

Relapsing fever

Answer

Plague

Question 6

Following diseases are transmitted by mosquito except?

Accepted Answer

Plague

Answer

Dengue fever

Answer

Yellow fever

Answer

Japanese encephalitis

Question 7

Diseases associated with rodents include all except

Accepted Answer

Oriental sore

Answer

Leptospirosis

Answer

Tularemia

Answer

Rat Bite fever

Question 8

Sputum positive TB is diagnosed when:

Accepted Answer

2 out of 3 sputum sample +ve

Answer

Mantoux test positive

Answer

1 out of 2 sputum sample +ve

Answer

BACTEC +ve

Question 9

Not true about aedes mosquito-

Accepted Answer

Eggs cannot survive more than 1 week without water

Answer

Transmits dengue fever

Answer

Are recurrent day time biters

Answer

Prefer breeding in stagnant water

Question 10

Anopheles species responsible for the transmission of malaria in urban areas is

Accepted Answer

Anopheles stephensi

Answer

Anopheles sundaicus

Answer

Anopheles fluviatilis

Answer

Anopheles culicifacies

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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