Infectious Diseases Practice Questions

Q: Schistosomiasis is an example of which type of zoonosis that requires an intermediate host?

Meta-zoonoses. ***Meta-zoonoses*** - **Meta-zoonoses** are defined as zoonotic diseases that require an **intermediate invertebrate host** for the completion of the parasite's life cycle. - **Schistosomiasis** fits this definition as it involves fresh water snails acting as an intermediate host, where the parasite undergoes essential developmental stages. *Cyclo-zoonoses* - **Cyclo-zoonoses** require **more than one vertebrate host species** but no invertebrate host for the completion of the infectious agent's life cycle. - An example would be **Taeniasis**, which involves humans and cattle or pigs, but not an invertebrate. *Direct-zoonoses* - **Direct-zoonoses** are transmitted directly from an **infected vertebrate host to a susceptible vertebrate host** without the need for an intermediate host or vector. - Examples include **rabies** or **brucellosis**, which are passed directly from animals to humans. *Sporo-zoonoses* - **Sporo-zoonoses** are zoonoses where the infectious agent undergoes **sporogonic development in an invertebrate host**, but this term is not a standard or widely recognized category in the same way as direct, cyclo-, or meta-zoonoses. - The more appropriate term for diseases involving an invertebrate intermediate host is **meta-zoonoses**.

Q: Which of the following is the primary transmission route for Hepatitis E?

Contaminated water. ***Contaminated water*** - **Hepatitis E virus (HEV)** is primarily transmitted through the **fecal-oral route**, with contaminated drinking water being the most common vehicle. - This mode of transmission is particularly prevalent in regions with poor sanitation and hygiene, leading to **waterborne outbreaks**. - HEV is responsible for **epidemic hepatitis** in developing countries, especially during floods and monsoons. *Blood and bodily fluids* - This is the primary transmission route for other hepatitis viruses like **Hepatitis B** and **Hepatitis C**, but not for Hepatitis E. - While rare cases of **transfusion-transmitted HEV** have been reported in endemic areas, it is not the main mode of spread. *Vertical transmission (mother to child)* - Vertical transmission can occur but is **not the primary route** for HEV. - When it does occur in pregnant women (especially in third trimester), it can lead to **severe outcomes** including fulminant hepatitis with high mortality (15-25%). *Airborne transmission* - **Hepatitis E** is not an **airborne disease**; it is not spread through respiratory droplets or aerosols. - This route of transmission is associated with respiratory infections, not enteric viruses like HEV.

Q: Which of the following is a zoonotic disease?

Hydatid cyst. ***Hydatid cyst*** - This disease is caused by the larval stage of the tapeworm **Echinococcus granulosus**, which completes its life cycle in dogs and sheep. - Humans can become infected by ingesting material contaminated with **Echinococcus eggs**, typically from contact with infected dogs or contaminated food/water, making it a zoonotic disease. *Malaria* - Malaria is transmitted by the **Anopheles mosquito** biting infected humans and then uninfected humans. - While it involves a vector, its primary reservoir is humans and it is not typically considered zoonotic as there is no animal-to-human transmission from a non-human primary reservoir. *Filariasis* - Filariasis is spread by various mosquito vectors (e.g., **Culex, Anopheles, Aedes**) that transmit parasitic worms to humans. - The life cycle primarily involves humans and mosquitos, and it is not classified as a zoonotic disease. *Dengue fever* - Dengue fever is a viral infection transmitted by **Aedes mosquitoes** (primarily *Aedes aegypti* and *Aedes albopictus*) between humans. - Similar to malaria, while it involves a vector, the primary reservoir is humans, and it is not considered zoonotic.

Q: What is the recommended Aedes Aegypti index for preventing Yellow Fever transmission?

Less than 1%. ***Less than 1%*** - An **Aedes Aegypti index** of **less than 1%** is the recommended threshold by WHO to effectively prevent Yellow Fever transmission. - Maintaining the vector index (House Index) below this critical level significantly reduces the chances of epidemic transmission. - This stringent target is essential for breaking the transmission cycle in endemic areas. *Less than 5%* - While an index of less than 5% represents moderate control, it is insufficient for reliable Yellow Fever prevention. - This threshold may be acceptable for the Breteau Index (measured differently), but for the House Index, 1% is the standard. - At this level, there remains significant risk of transmission during favorable conditions. *Less than 10%* - An index of **less than 10%** is considered inadequate for prevention of Yellow Fever transmission. - This level carries a substantial risk of outbreaks, as the vector population remains high enough to support sustained transmission. - Urgent vector control interventions are needed at this level. *Less than 20%* - An **Aedes Aegypti index** of less than 20% indicates a high-risk environment for Yellow Fever transmission. - This level is far above the recommended threshold and suggests a critical need for immediate and aggressive vector control measures. - At this level, epidemic transmission is highly likely if the virus is introduced.

Q: Pediculosis is caused by?

Louse. ***Louse*** - **Pediculosis** is a parasitic infestation of the skin by blood-feeding insects called **lice**. - There are different types of lice, including head lice (Pediculus humanus capitis), body lice (Pediculus humanus humanus), and pubic lice (Pthirus pubis), all of which cause pediculosis. *Mite* - **Mites** are responsible for infestations like **scabies**, which is caused by Sarcoptes scabiei. - While both lice and mites are arthropods, they cause distinct parasitic conditions with different clinical presentations and treatments. *Tick* - **Ticks** are known vectors for various diseases, including **Lyme disease** (Borrelia burgdorferi), **Rocky Mountain spotted fever** (Rickettsia rickettsii), and **tick-borne encephalitis**. - Ticks are arachnids, not insects, and their bites can cause localized reactions but not pediculosis. *Black Fly* - **Black flies** (Simulium species) are vectors for **onchocerciasis** (river blindness), caused by the parasitic nematode Onchocerca volvulus. - Their bites are typically painful and can cause localized swelling and allergic reactions, but they do not transmit pediculosis.

Q: Which vector is MOST commonly associated with transovarial transmission in diseases like Kyasanur Forest Disease and Crimean-Congo Hemorrhagic Fever?

Ticks. ***Ticks*** - Ticks are the primary **vectors** for transmitting **Kyasanur Forest Disease** (KFD virus) and **Crimean-Congo Hemorrhagic Fever** (CCHF virus), both relevant to India. - **Transovarial transmission** is a key mechanism where pathogens are passed from an infected female tick to her offspring via eggs, perpetuating the disease cycle within tick populations. - KFD is endemic to **Karnataka** (Western Ghats), while CCHF has been reported from various parts of India including Gujarat, Rajasthan, and Uttar Pradesh. *Mosquitoes* - Mosquitoes are known vectors for diseases like **malaria**, **dengue fever**, and **chikungunya**, but not for KFD or CCHF. - They primarily transmit pathogens through **salivary injection** during blood feeding, not typically via transovarial transmission for these specific tick-borne illnesses. *Fleas* - Fleas are vectors for diseases such as the **plague** (Yersinia pestis) and **murine typhus** (Rickettsia typhi). - They do not transmit KFD or CCHF, and their mode of transmission is typically through flea bites rather than transovarial mechanisms for these conditions. *Mites* - Mites can cause various skin conditions (e.g., **scabies**) and transmit **scrub typhus** (Orientia tsutsugamushi), which is relevant in India. - However, they are not associated with the transmission of KFD or CCHF.

Q: What is the Chandler's Index for Hookworm that indicates a significant health problem?

> 50. ***> 50*** - A Chandler's Index of **> 50** indicates a significant public health problem due to **hookworm infection**. - **Chandler's Index** is calculated as the **average egg count per person in a community** (total hookworm eggs counted ÷ number of persons examined), used to assess the population-level burden of hookworm infection. - A value **> 50** suggests that the community has a significant hookworm problem requiring public health intervention. *> 300* - This value is significantly higher than the threshold for a significant public health problem and would indicate an **extremely severe burden of infection**. - While this represents a very high Chandler's Index, it's not the standard cut-off for defining a "significant" health problem (which is the lower threshold of >50). *> 200* - A Chandler's Index of **> 200** would denote a very high intensity of hookworm infection in the community. - However, this is not the standard threshold used to define when hookworm becomes a "significant" public health issue - the threshold is lower at >50. *> 100* - A Chandler's Index of **> 100** represents a substantial level of hookworm infection within a population. - However, the widely recognized cutoff for a "significant health problem" is **> 50**, indicating public health concern even at this moderate level of community infection burden.

Q: The primary reservoir for leptospirosis transmission is:

Rat. ***Correct Answer: Rat*** - **Rats** (and other rodents) are considered the primary natural reservoir for *Leptospira* bacteria worldwide and are **asymptomatic carriers**. - They excrete the bacteria in their urine, contaminating water and soil, which serves as the main source of human infection. *Incorrect: Cat* - While cats can become infected with *Leptospira*, they are **not typically considered significant reservoirs** for human transmission. - Their role in the epidemiologic cycle of leptospirosis is generally minor compared to rodents and some other mammals. *Incorrect: Dog* - **Dogs** can contract leptospirosis and excrete the bacteria in their urine, posing a risk to humans, but they are generally considered **incidental hosts or secondary reservoirs**, not the primary one. - Vaccination in dogs helps reduce their role in transmission. *Incorrect: Fish* - **Fish are not known to be reservoirs** for *Leptospira* bacteria. - Leptospirosis is primarily transmitted through contact with infected animal urine, not aquatic life like fish.

Question 1

Schistosomiasis is an example of which type of zoonosis that requires an intermediate host?

Accepted Answer

Meta-zoonoses

Answer

Cyclo-zoonoses

Answer

Direct-zoonoses

Answer

Sporo-zoonoses

Question 2

What is the significance of a 2-year post-treatment surveillance period in paucibacillary leprosy?

Accepted Answer

To identify relapses, reactions, and neurological complications after treatment completion

Answer

To monitor for treatment compliance during active therapy

Answer

To assess the effectiveness of multibacillary leprosy treatment protocols

Answer

To detect early signs of drug resistance in ongoing treatment

Question 3

Which of the following is the primary transmission route for Hepatitis E?

Accepted Answer

Contaminated water

Answer

Blood and bodily fluids

Answer

Airborne transmission

Answer

Vertical transmission (mother to child)

Question 4

Which of the following is a zoonotic disease?

Accepted Answer

Hydatid cyst

Answer

Malaria

Answer

Filariasis

Answer

Dengue fever

Question 5

What is the recommended Aedes Aegypti index for preventing Yellow Fever transmission?

Accepted Answer

Less than 1%

Answer

Less than 5%

Answer

Less than 10%

Answer

Less than 20%

Question 6

Pediculosis is caused by?

Accepted Answer

Louse

Answer

Mite

Answer

Tick

Answer

Black Fly

Question 7

Which vector is MOST commonly associated with transovarial transmission in diseases like Kyasanur Forest Disease and Crimean-Congo Hemorrhagic Fever?

Accepted Answer

Ticks

Answer

Mosquitoes

Answer

Fleas

Answer

Mites

Question 8

What is the Chandler's Index for Hookworm that indicates a significant health problem?

Accepted Answer

> 50

Answer

> 200

Answer

> 100

Answer

> 300

Question 9

The primary reservoir for leptospirosis transmission is:

Accepted Answer

Rat

Answer

Cat

Answer

Dog

Answer

Fish

Question 10

Which of the following is not an indicator for malaria surveillance in a population?

Accepted Answer

Hemoglobin level

Answer

Annual parasite index

Answer

Annual parasite incidence

Answer

Annual falciparum incidence

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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