Infectious Diseases Practice Questions

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**.

Q: A 25-year-old female has been diagnosed to be suffering from tuberculosis categorized as category II (sputum +ve) case of relapse. According to the previous RNTCP (Revised National Tuberculosis Control Programme) guidelines, the treatment regimen recommended under DOTS was:

2(HRSZE)3 + 1(HRZE)3 + 5(HRE)3. ***2(HRSZE)3 + 1(HRZE)3 + 5(HRE)3*** - This regimen reflects the standard **Category II DOTS regimen** under the **previous RNTCP guidelines** for **sputum-positive relapse cases**, which was an 8-month treatment protocol. - The intensive phase consisted of **2 months of daily Streptomycin, Isoniazid, Rifampicin, Pyrazinamide, and Ethambutol (HRSZE)**, followed by **1 month of daily Isoniazid, Rifampicin, Pyrazinamide, and Ethambutol (HRZE)**, and a continuation phase of **5 months of Isoniazid, Rifampicin, and Ethambutol (HRE)** given three times weekly. - **Note:** Under current NTEP (National TB Elimination Programme) guidelines, previously treated cases undergo drug susceptibility testing, and fixed Category II regimens are no longer the standard approach. *3(HRZE)3 + 2(HRE)3 + 4(HR)3* - This is an incorrect combination of drugs and durations that does not match any standard DOTS category under previous RNTCP guidelines. - Category II relapse cases required a five-drug intensive phase including Streptomycin, not a four-drug regimen. *3(HRSZE)3 + 1(HRZE)3 + 6(HRE)3* - While this option includes the correct five-drug intensive phase, the duration is incorrect—the intensive phase with Streptomycin should be **2 months, not 3 months**. - The continuation phase of 6 months (instead of 5 months) also makes the total treatment duration longer than the standard 8-month Category II protocol. *2(HRZE)3 + 5(HR)3* - This regimen represents the **Category I (new cases) regimen** under previous RNTCP guidelines, which used only four drugs in the intensive phase. - It **lacks Streptomycin**, which was essential for Category II (relapse/failure/treatment after default) cases, and the continuation phase lacks Ethambutol, which was included in Category II continuation.

Q: Not true about Aedes mosquito

Larvae has siphon tube. ***Larvae has siphon tube*** - Aedes larvae do not possess a long **siphon tube** for respiration; instead, they have a short, broad siphon or no siphon at all. - The presence of a long siphon tube is characteristic of **Culex mosquito** larvae, which helps them breathe by piercing the water surface. *Boat shaped eggs* - **Aedes mosquito** eggs are typically oval and laid singly on damp surfaces, not boat-shaped. - **Anopheles mosquitos** are known for laying boat-shaped eggs with floats. *Has stripes on body* - **Aedes aegypti** and **Aedes albopictus** (the tiger mosquito) are known for their distinct black and white stripes or bands on their legs and body. - This characteristic "striped" appearance is a key identification feature of adult Aedes mosquitoes. *Also known as tiger mosquito* - One of the most prevalent species, **Aedes albopictus**, is indeed widely known as the **Asian tiger mosquito** due to its distinctive striped appearance. - This common name helps differentiate it from other mosquito species and reflects its aggressive biting habits during the day.

Question 1

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

Accepted Answer

Ticks

Answer

Fleas

Answer

Sandfly

Answer

Mosquitoes

Question 2

Hepatitis B can be transmitted through all EXCEPT:

Accepted Answer

Stool

Answer

Milk

Answer

Blood

Answer

Semen

Question 3

The most important sandfly-transmitted disease in India is-

Accepted Answer

Kala azar

Answer

Typhus

Answer

Relapsing fever

Answer

Plague

Question 4

Following diseases are transmitted by mosquito except?

Accepted Answer

Plague

Answer

Dengue fever

Answer

Yellow fever

Answer

Japanese encephalitis

Question 5

Diseases associated with rodents include all except

Accepted Answer

Oriental sore

Answer

Leptospirosis

Answer

Tularemia

Answer

Rat Bite fever

Question 6

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 7

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 8

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

Question 9

A 25-year-old female has been diagnosed to be suffering from tuberculosis categorized as category II (sputum +ve) case of relapse. According to the previous RNTCP (Revised National Tuberculosis Control Programme) guidelines, the treatment regimen recommended under DOTS was:

Accepted Answer

2(HRSZE)3 + 1(HRZE)3 + 5(HRE)3

Answer

3(HRZE)3 + 2(HRE)3 + 4(HR)3

Answer

3(HRSZE)3 + 1(HRZE)3 + 6(HRE)3

Answer

2(HRZE)3 + 5(HR)3

Question 10

Not true about Aedes mosquito

Accepted Answer

Larvae has siphon tube

Answer

Boat shaped eggs

Answer

Has stripes on body

Answer

Also known as tiger mosquito

Infectious Diseases — MCQs

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