Infectious Diseases Practice Questions

Q: Following are examples of human "dead end" diseases except -

Bubonic plague. ***Bubonic plague (Plague)*** - The question refers to **plague in general**, which includes multiple clinical forms. - While **bubonic plague** (the most common form) is transmitted via **flea bites** from infected rodents and humans are typically dead-end hosts for this form, **pneumonic plague** (secondary complication or primary infection) allows **human-to-human transmission** via respiratory droplets. - This makes plague the **exception** among the listed diseases, as humans can serve as a source of infection to others in the pneumonic form, unlike true dead-end host situations. *Japanese encephalitis* - Humans are **dead-end hosts** for Japanese encephalitis virus. - Infected humans do not develop sufficient **viremia** to infect feeding mosquitoes. - The virus maintains its cycle between **Culex mosquitoes**, **pigs** (amplifying hosts), and **wading birds**, with humans being incidental hosts. *Hydatid disease* - Humans are **definitive dead-end hosts** for *Echinococcus granulosus* (causing cystic echinococcosis/hydatid disease). - The normal life cycle requires **definitive hosts** (dogs, canids) and **intermediate hosts** (sheep, cattle). - Humans develop **hydatid cysts** but cannot transmit the infection further as the parasite cannot complete its life cycle in humans. *Leishmaniasis* - In most forms of leishmaniasis, humans are considered **dead-end or accidental hosts**, particularly in **zoonotic cutaneous leishmaniasis** where animal reservoirs (rodents, dogs) maintain transmission. - However, in **anthroponotic visceral leishmaniasis** (*Leishmania donovani* in the Indian subcontinent), humans can serve as reservoir hosts. - For the purpose of this question, leishmaniasis is generally classified with dead-end diseases as the majority of leishmaniasis forms have zoonotic cycles where humans are incidental hosts with limited onward transmission.

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 most commonly reported bacterial sexually transmitted infection?

Chlamydia. ***Correct: Chlamydia*** - **Chlamydia trachomatis** is the most frequently reported bacterial STI in many countries, often being **asymptomatic** and thus easily spread - Its high prevalence is due to efficient transmission and the widespread use of sensitive diagnostic tests that detect infections in asymptomatic individuals - Accounts for the majority of reported bacterial STI cases globally *Incorrect: HSV* - **Herpes Simplex Virus (HSV)** is a **viral STI**, not bacterial, and is characterized by recurrent outbreaks of **genital ulcers** or sores - While common, it does not qualify as a bacterial infection and is often not laboratory-confirmed due to mild or subclinical presentations *Incorrect: HIV* - **Human Immunodeficiency Virus (HIV)** is also a **viral STI**, not bacterial, that attacks the immune system leading to AIDS - Although highly impactful, HIV is not a bacterial infection and has lower incidence rates compared to Chlamydia *Incorrect: Syphilis* - **Syphilis**, caused by the bacterium **Treponema pallidum**, is a serious bacterial STI that can have long-term complications if untreated - While its incidence has been increasing in some regions, it is significantly less common than **Chlamydia** in terms of overall reported cases

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: What is the osmolarity of the new Oral Rehydration Solution (ORS)?

245. ***245*** - The **new ORS (reduced osmolarity ORS)** has an osmolarity of **245 mOsmol/L**. - This reduced osmolarity formulation has been shown to be more effective in reducing stool output, vomiting, and duration of diarrhea compared to the standard ORS. *270* - While 270 mOsmol/L is closer to the target, it is not the exact osmolarity of the **new ORS formulation**. - The precise osmolarity of the new ORS is specifically designed for optimal water and electrolyte absorption. *290* - The **standard (or traditional) ORS** had an osmolarity of **310 mOsmol/L**, which is higher than 290 mOsmol/L. - An osmolarity of 290 mOsmol/L does not correspond to a recognized standard or new ORS formulation. *310* - The **standard (or traditional) ORS** formulation had an osmolarity of **310 mOsmol/L**. - The move to a new ORS with reduced osmolarity was to improve efficacy and reduce the risk of hypernatremia in some patients.

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: Which disease is classified as 'multibacillary'?

Leprosy. **Leprosy** - Leprosy, caused by *Mycobacterium leprae*, is classified by the **WHO** into **paucibacillary (PB)** and **multibacillary (MB)** forms based on bacterial load and number of skin lesions. - **Multibacillary leprosy** is defined as having more than 5 skin lesions with positive skin smears, requiring a longer treatment regimen (12 months of multidrug therapy with rifampicin, dapsone, and clofazimine). - This classification is specific to **leprosy** and is crucial for determining appropriate treatment duration and drug combinations. *Tuberculosis* - Tuberculosis is classified by **anatomical location** (pulmonary vs. extrapulmonary), **drug susceptibility** (drug-sensitive vs. drug-resistant), or **smear status** (smear-positive vs. smear-negative). - The term **'multibacillary'** is not used in TB classification, making this an incorrect option. *Trachoma* - Trachoma is a chronic **keratoconjunctivitis** caused by *Chlamydia trachomatis*, classified by **clinical stages** (TF, TI, TS, TT, CO) according to the WHO simplified grading system. - The paucibacillary/multibacillary classification does **not apply** to trachoma. *Tetanus* - Tetanus is a **toxin-mediated disease** caused by *Clostridium tetani*, manifesting as muscle spasms and lockjaw. - Classification is based on **clinical severity** (localized, generalized, cephalic, neonatal), not bacterial load, making the term 'multibacillary' inapplicable.

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: Vector of scrub typhus in man?

Leptotrombidium deliense. ***Leptotrombidium deliense*** - This is the **chigger mite** species primarily responsible for transmitting **scrub typhus** to humans. - **Larval mites (chiggers)** of this species feed on human skin and transmit the bacterium *Orientia tsutsugamushi*. *O. tsutsugamushi* - This is the **causative agent** of scrub typhus, not the vector. - It is a **rickettsial bacterium** transmitted by infected chiggers. *Lice* - **Lice** (e.g., *Pediculus humanus corporis*) are vectors for diseases like **epidemic typhus** (caused by *Rickettsia prowazekii*) and **relapsing fever**, but not scrub typhus. - They are **blood-sucking insects** distinct from mites. *Pediculus humanus* - This refers to **human lice**, specifically *Pediculus humanus capitis* (head louse) or *Pediculus humanus corporis* (body louse). - As mentioned, lice transmit diseases like epidemic typhus, not **scrub typhus**.

Question 1

Following are examples of human "dead end" diseases except -

Accepted Answer

Bubonic plague

Answer

Hydatid disease

Answer

Japanese encephalitis

Answer

Leishmaniasis

Question 2

Which of the following is a zoonotic disease?

Accepted Answer

Hydatid cyst

Answer

Malaria

Answer

Filariasis

Answer

Dengue fever

Question 3

What is the most commonly reported bacterial sexually transmitted infection?

Accepted Answer

Chlamydia

Answer

HSV

Answer

HIV

Answer

Syphilis

Question 4

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 5

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 6

What is the osmolarity of the new Oral Rehydration Solution (ORS)?

Accepted Answer

245

Answer

270

Answer

290

Answer

310

Question 7

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

Accepted Answer

> 50

Answer

> 200

Answer

> 100

Answer

> 300

Question 8

Which disease is classified as 'multibacillary'?

Accepted Answer

Leprosy

Answer

Tuberculosis

Answer

Trachoma

Answer

Tetanus

Question 9

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 10

Vector of scrub typhus in man?

Accepted Answer

Leptotrombidium deliense

Answer

O. tsutsugamushi

Answer

Lice

Answer

Pediculus humanus

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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