Infectious Diseases Practice Questions

Q: What is the current Global strategy for malaria control called?

Roll Back Malaria. **Explanation:** **Roll Back Malaria (RBM)** is the correct answer as it represents the current global strategic framework for addressing malaria. Launched in **1998** by the WHO, UNICEF, UNDP, and the World Bank, its primary goal is to coordinate international action to reduce the malaria burden through evidence-based interventions like Long-Lasting Insecticidal Nets (LLINs), Indoor Residual Spraying (IRS), and Artemisinin-based Combination Therapy (ACT). **Analysis of Incorrect Options:** * **Modified Plan of Operation (MPO):** Launched in India in **1977**, this was a specific national strategy introduced after the resurgence of malaria in the mid-70s. It shifted the focus from total eradication to "effective control." * **Malaria Eradication Programme:** This refers to the **Global Malaria Eradication Programme (GMEP)** launched by the WHO in **1955**. It was eventually abandoned in 1969 due to the emergence of drug resistance (Chloroquine) and insecticide resistance (DDT). * **Malaria Control Programme:** This is a generic term. While India started the National Malaria Control Programme (NMCP) in **1953**, it is not the name of the current "Global Strategy." **High-Yield Clinical Pearls for NEET-PG:** * **National Framework for Malaria Elimination (NFME) 2016–2030:** India’s current roadmap aiming for a malaria-free country by **2030**. * **World Malaria Day:** Observed on **April 25th**. * **Drug of Choice:** ACT is the mainstay for *P. falciparum*; Chloroquine remains the drug of choice for *P. vivax* (provided there is no resistance). * **E-2025 Initiative:** A WHO initiative supporting 25 countries that have the potential to eliminate malaria by 2025.

Q: What is the concentration of potassium in ORS in milliequivalents per liter?

20 meq/L. The correct answer is **20 mEq/L**. This is a high-yield fact based on the **WHO Reduced Osmolarity ORS** formulation, which is the current global standard for managing dehydration due to diarrhea. ### **Educational Explanation** The primary goal of Oral Rehydration Salts (ORS) is to utilize the sodium-glucose cotransport mechanism in the small intestine to facilitate water absorption. Potassium is included to replace the significant fecal losses of potassium that occur during acute watery diarrhea, thereby preventing hypokalemia and associated complications like paralytic ileus. * **Why 20 mEq/L is correct:** The WHO Reduced Osmolarity ORS contains **1.5 g/L of Potassium Chloride**, which provides exactly **20 mEq/L** of potassium. This concentration is optimized to maintain electrolyte balance without causing hyperkalemia. ### **Analysis of Incorrect Options** * **A. 30 mEq/L:** This is not a standard concentration in WHO ORS. However, it is worth noting that ReSoMal (Rehydration Solution for Malnutrition) contains a higher potassium level (40 mEq/L) to address the chronic depletion seen in SAM patients. * **C. 90 mEq/L:** This was the **Sodium** concentration in the "Old" WHO ORS (Standard ORS). It is far too high for potassium. * **D. 60 mEq/L:** This was the **Chloride** concentration in the "Old" WHO ORS. In the current Reduced Osmolarity ORS, the chloride concentration is 65 mEq/L. ### **NEET-PG High-Yield Pearls** | Component | Reduced Osmolarity ORS (Current) | | :--- | :--- | | **Sodium** | 75 mEq/L | | **Chloride** | 65 mEq/L | | **Glucose (Anhydrous)** | 75 mmol/L (13.5 g/L) | | **Potassium** | **20 mEq/L** | | **Citrate** | 10 mmol/L | | **Total Osmolarity** | **245 mOsm/L** | * **Clinical Tip:** Reduced osmolarity ORS (245 mOsm/L) is superior to the older version (311 mOsm/L) because it reduces stool output, decreases vomiting, and reduces the need for unscheduled IV fluids.

Q: What is the drug of choice for Falciparum Malaria?

Artemisinin-based Combination Therapy (ACT). **Explanation:** The current National Drug Policy for Malaria in India (NVBDCP guidelines) mandates **Artemisinin-based Combination Therapy (ACT)** as the first-line treatment for all cases of *Plasmodium falciparum* malaria. The underlying medical concept is to combat widespread drug resistance and ensure rapid parasite clearance. ACTs combine a fast-acting artemisinin derivative (which reduces the parasite biomass quickly) with a long-acting partner drug (which eliminates remaining parasites and prevents recrudescence). **Analysis of Options:** * **Chloroquine (A):** While it remains the drug of choice for *P. vivax* in most regions, it is no longer used for *P. falciparum* due to high levels of chloroquine resistance (CQR) globally and across India. * **Mefloquine (B):** This is primarily used for chemoprophylaxis in travelers or as a partner drug within an ACT (e.g., Artesunate + Mefloquine). It is not used as a monotherapy for treatment due to neuropsychiatric side effects and resistance. * **Proguanil (C):** This is a folate antagonist used mainly for prophylaxis (often in combination with Atovaquone) rather than the acute treatment of falciparum malaria. **High-Yield Clinical Pearls for NEET-PG:** 1. **ACT Regimen in India:** The standard ACT used is **Artesunate (3 days) + Sulphadoxine-Pyrimethamine (1 day)**. 2. **North-East Exception:** In North-Eastern states (where SP resistance is high), the recommended ACT is **Artemether + Lumefantrine**. 3. **Gametocidal Action:** A single dose of **Primaquine (0.75 mg/kg)** is added on Day 2 to all *P. falciparum* cases to prevent transmission (except in pregnancy/infancy). 4. **Severe Malaria:** The drug of choice is **Intravenous (IV) Artesunate** for at least 24 hours, regardless of the species.

Q: What is the best disinfectant for cholera stool?

Cresol. ### Explanation In the management of a Cholera outbreak, the immediate disinfection of excreta (stool and vomit) is a critical step in breaking the chain of transmission. **Why Cresol is the Correct Answer:** **Cresol (5% solution)** is considered the disinfectant of choice for cholera stool. The primary reason is its high efficacy in the presence of **organic matter**. Cholera stools are voluminous and contain significant organic debris; while many disinfectants are neutralized by organic loads, Cresol retains its germicidal activity. It requires a contact time of approximately **1 hour** for complete disinfection. **Analysis of Incorrect Options:** * **Bleaching Powder (Calcium Hypochlorite):** While excellent for water disinfection, it is less effective for bulk stool because the organic matter rapidly consumes the free chlorine, rendering it ineffective unless used in very high, impractical concentrations. * **Phenol:** Although a standard antiseptic, it is generally less potent than its derivative, Cresol (which has a higher phenol coefficient). Cresol is preferred in public health practice for crude disinfection tasks. * **Lime (Slaked Lime):** Historically used for disinfecting gutters or feces in pits, it is less reliable and slower-acting compared to chemical germicides like Cresol for immediate bedside disinfection. **High-Yield Clinical Pearls for NEET-PG:** * **Best disinfectant for Cholera stool:** Cresol (5%). * **Best disinfectant for Water (Cholera):** Bleaching powder (Chlorine). * **Contact time for stool disinfection:** Minimum 1 hour. * **Concurrent Disinfection:** This refers to the immediate disinfection of all infectious excreta and soiled articles (linen) during the course of the illness. * **Terminal Disinfection:** Disinfection of the patient’s environment after they have recovered or died.

Q: Which of the following diseases involves a transmission chain with birds, arthropods, and humans?

Japanese encephalitis. **Explanation:** **Japanese Encephalitis (JE)** is the correct answer because it follows a complex **zoonotic transmission cycle** involving three key components: 1. **Birds:** Ardeid birds (herons and egrets) act as the **natural reservoir** hosts. 2. **Arthropods:** The primary vector is the **Culex tritaeniorhynchus** mosquito, which breeds in stagnant water like rice fields. 3. **Humans:** Humans act as **accidental, dead-end hosts** because the viremia in humans is insufficient to infect a biting mosquito. *Note: Pigs are the most important "amplifier hosts" in this cycle, but the bird-arthropod-human chain is a classic description of JE ecology.* **Why the other options are incorrect:** * **Malaria:** Involves an **Anopheles** mosquito and **Humans** only. There is no avian (bird) reservoir involved in human malaria. * **Paragonimus (Lung Fluke):** A parasitic infection involving a complex cycle with snails (1st intermediate host), crustaceans/crabs (2nd intermediate host), and humans/mammals. It does not involve birds or arthropod vectors. * **Plague:** Primarily involves **Rodents** (rats) and the **Rat Flea** (*Xenopsylla cheopis*). While birds are not part of the cycle, humans are accidental hosts. **High-Yield NEET-PG Pearls:** * **Vector:** *Culex tritaeniorhynchus* (Night biter, rice field breeder). * **Amplifier Host:** Pig (shows no symptoms but produces high viral titers). * **Dead-end Hosts:** Humans and Horses. * **Vaccine:** Live attenuated **SA-14-14-2** is commonly used in the Universal Immunization Programme (UIP) in endemic districts of India. * **Seasonality:** Peak incidence coincides with the rainy season and post-harvest periods.

Q: Which mosquito species is recognized as the principal secondary vector for Zika virus transmission globally?

Aedes albopictus. ***Aedes albopictus*** - This mosquito, commonly known as the **Asian tiger mosquito**, is recognized as the **principal secondary vector** for Zika virus transmission globally. - It is a competent vector capable of transmitting **Zika**, **Dengue**, and **Chikungunya** viruses across multiple continents including Asia, Europe, Africa, and the Americas. - While *Aedes aegypti* remains the primary vector, *Aedes albopictus* plays a significant role in Zika transmission, particularly in temperate regions where *Ae. aegypti* is less prevalent. - Its adaptability to diverse climates and ability to breed in natural and artificial water containers make it epidemiologically important. *Aedes polynesiensis* - This species is primarily known as a vector for **lymphatic filariasis** (*Wuchereria bancrofti*) in Pacific islands. - While it was involved in Zika virus transmission during the **French Polynesia outbreak (2013-2014)**, it is geographically restricted and not considered a principal vector for global Zika transmission. - Its role is limited to specific Pacific island populations. *Aedes australis* - This species is endemic to Australia and transmits **Ross River virus** and other Australian arboviruses. - It is **not** a recognized vector for Zika virus transmission. - Its geographical distribution and host preferences exclude it from the Zika transmission cycle. *Aedes mitchellae* - This species is not documented in major public health literature as a vector for Zika virus. - It belongs to a mosquito species complex with no established role in arboviral transmission to humans. - Epidemiologically insignificant for Zika virus transmission.

Q: What is the usual method of collecting a sample of urine to detect UTI?

Midstream catch. ***Midstream catch*** - This technique is the *standard, non-invasive method* for routine urine culture as it minimizes **contamination** from bacteria residing in the distal urethra and periurethral area. - By discarding the initial urine (starting stream) and collecting the middle portion, the sample is more representative of the urine contained within the **bladder**. *Early morning sample* - While an early morning sample is often preferred for optimal concentration (e.g., detecting **proteinuria** or **casts**), it is not the methodology for *minimizing contamination*. - The collection technique (midstream) is more critical than the time of day for ensuring a reliable sample for **UTI culture**. *Suprapubic catheter* - Suprapubic aspiration (SPA) provides an **uncontaminated specimen** (often considered the gold standard), but it is an invasive procedure requiring a needle insertion into the bladder. - It is reserved for specific situations, such as neonates or patients with ambiguous results, and is not the **usual** collection method. *Starting stream collection* - The starting stream is most likely to be contaminated with **urethral flora** (e.g., *Staphylococcus epidermidis* or environmental organisms). - Collecting the starting stream significantly increases the chance of **false positive** culture results, confusing the diagnosis of a true **UTI**.

Q: Identify A and B in the image of the mosquito larvae given

A-Anopheles, B-Culex. ***A-Anopheles, B-Culex*** - Larva A is identified as **Anopheles** because it rests **parallel** to the water surface and lacks a respiratory **siphon**, breathing through palmate hairs on its abdominal segments. - Larva B is identified as **Culex** as it hangs at an **angle** to the water surface and breathes through a long, narrow respiratory **siphon**. *A-Culex, B-Aedes* - This is incorrect as larva A exhibits the characteristics of **Anopheles** (no siphon, parallel resting), not **Culex**. - While **Aedes** larvae also hang at an angle, larva B's long siphon is more typical of **Culex**; **Aedes** larvae usually have a shorter, stouter siphon. *A-Culex, B-Anopheles* - This option incorrectly reverses the identities. Larva A is **Anopheles** and larva B is **Culex** based on their distinct resting postures and respiratory structures. - The key differentiating feature is the presence of a **siphon** in B (**Culex**) and its absence in A (**Anopheles**). *A-Anopheles, B-Mansonia* - Although the identification of A as **Anopheles** is correct, larva B is not **Mansonia**. - **Mansonia** larvae are unique as they attach to the roots of aquatic plants to obtain oxygen and do not hang from the surface, unlike the larva shown in B.

Q: The SAFE strategy given by WHO forms the mainstream of the management of Trachoma. What does the S in the acronym represent?

Surgery. ***Surgery*** - The 'S' in the WHO's SAFE strategy for Trachoma management stands for **Surgery**, which is essential for correcting **trichiasis** (in-turned eyelashes). - Surgery prevents irreversible vision loss by stopping the eyelashes from rubbing against and scarring the **cornea**. *Symptom* - Management of specific **symptoms** is generally an element of clinical treatment but does not represent a component of the comprehensive population-level intervention strategy known as SAFE. - The SAFE approach focuses on addressing the **infectious agent** (Antibiotics) and transmission factors (Facial cleanliness, Environmental improvement) for elimination. *Spectacles* - **Spectacles** are used for correcting refractive errors (like myopia or hyperopia) and are not a therapeutic measure for active **Chlamydia trachomatis** infection or trichiasis. - The goal of SAFE is elimination of the infectious cause and treatment of the blinding sequelae, not visual **refractive correction**. *Symbol* - A **symbol** is an abstract representation and does not constitute a concrete public health or clinical intervention necessary for the elimination of trachoma. - The other components (**Antibiotics**, **Facial cleanliness**, **Environmental improvement**) are tangible actions aimed at disease control and prevention.

Q: Which of the following is correctly matched for vectors and diseases? Vector: A. Louse, B. Mite, C. Flea, D. Tick. Disease: I. Scrub typhus, II. Endemic typhus, III. Rocky Mountain spotted fever, IV. Epidemic typhus.

A-IV, B-I, C-II, D-III. ***A-IV, B-I, C-II, D-III (Correct)*** - **Louse (A)** transmits **Epidemic typhus (IV)**, caused by *Rickettsia prowazekii*, typically occurring in overcrowded, unhygienic environments. - **Mite (B)** (chigger) transmits **Scrub typhus (I)**, caused by *Orientia tsutsugamushi*. - **Flea (C)** (rat flea) transmits **Endemic typhus (II)**, caused by *Rickettsia typhi*. - **Tick (D)** transmits **Rocky Mountain spotted fever (III)**, caused by *Rickettsia rickettsii*. *A-I, B-III, C-IV, D-II (Incorrect)* - Incorrectly matches Louse (A) with Scrub typhus (I); scrub typhus is transmitted by **mites** (chiggers), not lice. - Incorrectly matches Mite (B) with Rocky Mountain spotted fever (III); RMSF is transmitted by **ticks**, not mites. *A-II, B-III, C-IV, D-I (Incorrect)* - Incorrectly matches Louse (A) with Endemic typhus (II); endemic typhus is transmitted by **fleas** (rat flea), not lice. - Incorrectly matches Flea (C) with Epidemic typhus (IV); epidemic typhus is transmitted by **lice**, not fleas. *A-IV, B-III, C-I, D-II (Incorrect)* - While A-IV is correct (Louse-Epidemic typhus), this option incorrectly matches Mite (B) with Rocky Mountain spotted fever (III), which is transmitted by **ticks**. - Incorrectly matches Flea (C) with Scrub typhus (I); scrub typhus is transmitted by **mites**, not fleas.

Question 1

What is the current Global strategy for malaria control called?

Accepted Answer

Roll Back Malaria

Answer

Modified plan of operation

Answer

Malaria Eradication Programme

Answer

Malaria Control Programme

Question 2

What is the concentration of potassium in ORS in milliequivalents per liter?

Accepted Answer

20 meq/L

Answer

30 meq/L

Answer

90 meq/L

Answer

60 meq/L

Question 3

What is the drug of choice for Falciparum Malaria?

Accepted Answer

Artemisinin-based Combination Therapy (ACT)

Answer

Chloroquine

Answer

Mefloquine

Answer

Proguanil

Question 4

What is the best disinfectant for cholera stool?

Accepted Answer

Cresol

Answer

Bleaching powder

Answer

Phenol

Answer

Lime

Question 5

Which of the following diseases involves a transmission chain with birds, arthropods, and humans?

Accepted Answer

Japanese encephalitis

Answer

Malaria

Answer

Paragonimus

Answer

Plague

Question 6

Which mosquito species is recognized as the principal secondary vector for Zika virus transmission globally?

Accepted Answer

Aedes albopictus

Answer

Aedes polynesiensis

Answer

Aedes australis

Answer

Aedes mitchellae

Question 7

What is the usual method of collecting a sample of urine to detect UTI?

Accepted Answer

Midstream catch

Answer

Starting stream collection

Answer

Early morning sample

Answer

Suprapubic catheter

Question 8

Identify A and B in the image of the mosquito larvae given

Accepted Answer

A-Anopheles, B-Culex

Answer

A-Culex, B-Anopheles

Answer

A-Culex, B-Aedes

Answer

A-Anopheles, B-Mansonia

Question 9

The SAFE strategy given by WHO forms the mainstream of the management of Trachoma. What does the S in the acronym represent?

Accepted Answer

Surgery

Answer

Spectacles

Answer

Symbol

Answer

Symptom

Question 10

Which of the following is correctly matched for vectors and diseases? Vector: A. Louse, B. Mite, C. Flea, D. Tick. Disease: I. Scrub typhus, II. Endemic typhus, III. Rocky Mountain spotted fever, IV. Epidemic typhus.

Accepted Answer

A-IV, B-I, C-II, D-III

Answer

A-II, B-III, C-IV, D-I

Answer

A-IV, B-III, C-I, D-II

Answer

A-I, B-III, C-IV, D-II

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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