Non-Communicable Diseases — MCQs

Non-Communicable Diseases Indian Medical PG Practice Questions and MCQs

Question 191: The time required for the development of a parasite from the gametocyte to the sporozoite stage in a mosquito is called as:

A. Extrinsic incubation period (Correct Answer)
B. Intrinsic incubation period
C. Generation time
D. Median incubation period

Explanation: ### Explanation **Correct Answer: A. Extrinsic incubation period** The **Extrinsic Incubation Period (EIP)** is the time interval required for a pathogen to develop or multiply within an arthropod vector (like a mosquito) before it becomes infective to a vertebrate host. In the context of Malaria, this represents the duration from the ingestion of **gametocytes** by the mosquito to the appearance of **sporozoites** in its salivary glands. This period is highly temperature-dependent; for *Plasmodium vivax*, it is approximately 8–10 days at 25°C. **Analysis of Incorrect Options:** * **B. Intrinsic incubation period:** This is the time interval between the entry of the pathogen into the **human host** and the onset of the first clinical sign or symptom. * **C. Generation time:** This refers to the interval between the receipt of infection by a host and the maximum infectivity of that host. In malaria, it is the time from the entry of sporozoites into a human until the peak production of gametocytes. * **D. Median incubation period:** This is a statistical measure representing the time required for 50% of an exposed population to develop the disease. **High-Yield Facts for NEET-PG:** * **Serial Interval:** The time gap between the onset of the primary case and the onset of the secondary case in a transmission chain. * **Pre-patent Period:** The time between the entry of the parasite and its first demonstration in the blood or excreta (e.g., 8 days for *P. falciparum*). * **Environmental Impact:** If the extrinsic incubation period exceeds the lifespan of the mosquito, transmission of the disease cannot occur. This is a key principle in vector control strategies.

Question 192: The DPT vaccine is administered via which route?

A. Intramuscular (Correct Answer)
B. Subcutaneous
C. Intradermal
D. Intravenous

Explanation: **Explanation:** The **DPT (Diphtheria, Pertussis, and Tetanus)** vaccine is a combination vaccine administered via the **Intramuscular (IM)** route. In infants, the preferred site is the **anterolateral aspect of the mid-thigh**, as this area has the largest muscle mass (vastus lateralis) and avoids potential injury to the sciatic nerve. **Why Intramuscular?** DPT contains **adjuvants** (like aluminum salts) designed to enhance the immune response. These adjuvants are highly irritating to the skin and subcutaneous tissues. Injecting deep into the muscle ensures slow absorption and minimizes local reactions. **Analysis of Incorrect Options:** * **Subcutaneous:** This route is avoided for DPT because the adjuvants can cause **sterile abscesses**, localized tissue necrosis, and severe irritation if deposited in the fatty layer. (Note: Measles and Yellow Fever vaccines are typically subcutaneous). * **Intradermal:** This route is used for vaccines requiring a slow release and specific immune cell interaction, such as **BCG** or the **Rabies** vaccine (IDRV). DPT would cause significant skin damage if given this way. * **Intravenous:** Vaccines are never administered intravenously as they need to be processed by local immune cells and can cause systemic anaphylaxis if injected directly into the bloodstream. **High-Yield Clinical Pearls for NEET-PG:** * **Site:** Anterolateral thigh (Infants); Deltoid (Older children/Adults). * **Angle:** 90 degrees. * **Storage:** DPT is **heat-stable but freeze-sensitive**. It must be stored at +2°C to +8°C. If frozen, it loses potency (perform the **Shake Test** to check for damage). * **Pentavalent Vaccine:** In the National Immunization Schedule, DPT is now part of the Pentavalent vaccine (DPT + Hep B + Hib), also given IM.

Question 193: In which year was the Rubella virus first isolated?

A. 1862
B. 1912
C. 1932
D. 1962 (Correct Answer)

Explanation: **Explanation:** The correct answer is **1962**. While Rubella (German Measles) was clinically described as a distinct disease as early as the 18th century, the virus itself remained elusive for decades. In 1962, two independent groups of researchers—**Parkman and Wegman** at the Walter Reed Army Institute of Research, and **Weller and Neva** at Harvard—successfully isolated the Rubella virus using tissue culture techniques. This breakthrough was pivotal as it paved the way for the development of the first Rubella vaccines in the late 1960s. **Analysis of Incorrect Options:** * **1862 (Option A):** This predates the "Golden Age of Microbiology." At this time, the germ theory was still being established, and viruses (which are much smaller than bacteria) could not yet be isolated. * **1912 (Option B):** While the viral etiology of Rubella was suspected in the early 20th century, the technology for viral cell culture (necessary for isolation) was not yet sufficiently advanced. * **1932 (Option C):** This was around the time researchers were beginning to differentiate viral exanthems, but the definitive isolation of the Rubella virus had not yet occurred. **NEET-PG High-Yield Pearls:** * **Gregg’s Phenomenon (1941):** Norman Gregg, an Australian ophthalmologist, first linked maternal Rubella infection to congenital cataracts, establishing the concept of **Congenital Rubella Syndrome (CRS)**. * **Virus Family:** Rubella belongs to the *Togaviridae* family (Genus: *Rubivirus*). * **Incubation Period:** 14–21 days (Average 18 days). * **Infectivity:** Most infectious from 7 days before to 7 days after the onset of the rash. * **Vaccine:** It is a **Live Attenuated Vaccine** (RA 27/3 strain is most commonly used). It is contraindicated in pregnancy.

Question 194: What is the usual incubation period of pertussis?

A. 7-14 days (Correct Answer)
B. 3-5 days
C. 21-25 days
D. Less than 3 days

Explanation: **Explanation:** **1. Why Option A is Correct:** Pertussis (Whooping Cough), caused by the bacterium *Bordetella pertussis*, typically has an incubation period of **7 to 14 days** (with an upper limit of 21 days). This is the time required for the bacteria to colonize the ciliated epithelium of the respiratory tract and produce toxins (like pertussis toxin) that trigger the initial catarrhal symptoms. **2. Why Other Options are Incorrect:** * **Option B (3-5 days):** This is too short for Pertussis but is characteristic of infections like **Diphtheria** or **Meningococcal meningitis**. * **Option C (21-25 days):** This is longer than the typical range. While the incubation period can occasionally extend to 21 days, it rarely exceeds it. This range is more typical for **Mumps** (14–21 days) or **Rubella**. * **Option D (Less than 3 days):** This very short incubation period is seen in **Influenza**, **Cholera**, or **Staphylococcal food poisoning**. **3. High-Yield Clinical Pearls for NEET-PG:** * **Infectivity:** Pertussis is most infectious during the **Catarrhal stage** (the first 1-2 weeks). * **Drug of Choice:** **Erythromycin** (or other Macrolides like Azithromycin) is the treatment of choice. It reduces communicability but has limited impact on clinical symptoms if started late. * **Vaccination:** The vaccine is part of the National Immunization Schedule (Pentavalent/DPT). Note that the immunity (both natural and vaccine-induced) is **not lifelong**. * **Secondary Attack Rate (SAR):** It is very high, approximately **90%** in susceptible household contacts.

Question 195: Apart from dengue hemorrhagic fever, Aedes aegypti is a vector for the transmission of which disease?

A. Filaria
B. Japanese encephalitis
C. Kyasanur forest disease
D. Yellow fever (Correct Answer)

Explanation: ### Explanation **Correct Answer: D. Yellow fever** **1. Why Yellow Fever is Correct:** *Aedes aegypti* is a highly efficient urban vector known for its "nervous biting" habit (biting multiple people to complete one blood meal). While it is the primary vector for **Dengue**, it is also the principal vector for **Yellow Fever**, **Chikungunya**, and **Zika virus**. In the context of Yellow Fever, *Aedes aegypti* facilitates the "Urban Cycle" of transmission between humans, whereas *Haemagogus* species are involved in the "Sylvatic (Jungle) Cycle." **2. Analysis of Incorrect Options:** * **A. Filaria:** In India, the primary vector for Lymphatic Filariasis (*Wuchereria bancrofti*) is the **Culex quinquefasciatus** mosquito, which breeds in dirty, stagnant water. * **B. Japanese Encephalitis (JE):** This is transmitted primarily by **Culex tritaeniorhynchus** and *Culex vishnui* group mosquitoes. They typically breed in irrigated rice fields. * **C. Kyasanur Forest Disease (KFD):** This is a viral hemorrhagic fever transmitted by **Hard Ticks** (*Haemaphysalis spinigera*), not mosquitoes. It is endemic to specific regions in Karnataka, India. **3. NEET-PG High-Yield Pearls:** * **Aedes aegypti Characteristics:** Known as the "Tiger Mosquito" (due to white stripes), it is a **daytime biter**, breeds in **artificial collections of clean water** (coolers, tires, flower pots), and has a flight range of usually less than 100 meters. * **Yellow Fever in India:** Although the vector (*Aedes aegypti*) is abundant in India, Yellow Fever is **not present** in India. This is a classic "vulnerable but not receptive" scenario. * **The "Aedes" Rule:** Remember the triad: **Dengue, Chikungunya, and Zika** are all transmitted by *Aedes*.

Question 196: All of the following are true about malaria, except?

A. Infant parasite rate is a poor indicator of malaria occurrence in a community. (Correct Answer)
B. The vector for transmission is the Anopheles mosquito.
C. Newborns are resistant to P. falciparum infection.
D. Anopheles culicifacies is common in rural areas.

Explanation: ### Explanation **1. Why Option A is the Correct Answer (The "Except" Statement):** In malariology, the **Infant Parasite Rate (IPR)** is considered the **most sensitive index** for measuring the transmission of malaria in a community. It specifically measures the presence of parasites in infants (0–12 months). Since infants have not lived through multiple seasons, a positive blood smear indicates **recent transmission** within the locality. If the IPR is zero for three consecutive years, it signifies the interruption of malaria transmission. Therefore, stating it is a "poor indicator" is factually incorrect. **2. Analysis of Other Options:** * **Option B:** This is a basic fact. The female **Anopheles mosquito** is the definitive host and the primary vector for human malaria. * **Option C:** Newborns possess a temporary biological resistance to *P. falciparum*. This is attributed to the presence of **high levels of Fetal Hemoglobin (HbF)**, which inhibits parasite growth, and the transfer of **maternal antibodies (IgG)** across the placenta. * **Option D:** *Anopheles culicifacies* is the most important vector of **rural malaria** in India. It breeds in clean standing water like irrigation channels, pools, and borrow pits. **3. NEET-PG High-Yield Pearls:** * **Spleen Rate:** Used to measure endemicity in children (2–10 years). * **Annual Parasite Incidence (API):** The most common index used under the National Framework for Malaria Elimination in India to classify areas for intervention. * **Vector Habitats:** *A. stephensi* is the primary vector for **urban malaria**, while *A. fluviatilis* is the vector in **hilly/forest areas**. * **Quinine** remains the drug of choice for malaria in the first trimester of pregnancy.

Question 197: In a study, a new treatment resulted in 36 deaths or treatment failures out of a sample of 120. With an alternative treatment, 26 treatment failures were reported from a sample size of 130. How many patients should be treated with the first treatment to avert one death?

A. 100
B. 10 (Correct Answer)
C. 250
D. 160

Explanation: ### Explanation The question asks for the number of patients needed to be treated with the first treatment to avert one death, which is the definition of **Number Needed to Treat (NNT)**. **1. Calculation of the Correct Answer (B):** * **Event Rate in Group 1 (EER):** 36/120 = 0.3 (30%) * **Event Rate in Group 2 (CER):** 26/130 = 0.2 (20%) * **Absolute Risk Reduction (ARR):** This is the arithmetic difference between the two event rates. * ARR = |EER – CER| = |0.3 – 0.2| = **0.1** * **Number Needed to Treat (NNT):** This is the inverse of ARR. * NNT = 1 / ARR = 1 / 0.1 = **10** * Therefore, 10 patients must be treated with the first treatment to prevent one additional death compared to the second treatment. **2. Why other options are incorrect:** * **Option A (100):** This is a common calculation error where the decimal point is misplaced (1/0.01 instead of 1/0.1). * **Option C (250):** This value does not correlate with the mathematical relationship between the provided sample sizes and outcomes. * **Option D (160):** This might result from incorrectly adding the total number of failures (36+26) or misapplying the formula. **3. Clinical Pearls & High-Yield Facts for NEET-PG:** * **NNT Formula:** $1 / \text{Absolute Risk Reduction (ARR)}$. * **Interpretation:** The lower the NNT, the more effective the treatment. An NNT of 1 means every single patient treated benefits. * **Number Needed to Harm (NNH):** Calculated similarly ($1 / \text{Absolute Risk Increase}$), it indicates how many patients must be exposed to a risk factor to cause one adverse event. * **Relative Risk Reduction (RRR):** Unlike ARR, RRR does not account for the baseline risk and can often make a treatment's effect look more impressive than it is.

Question 198: Which of the following statements about Pulse Polio immunization is false?

A. Mop-up immunization is conducted in restricted geographical areas.
B. It is carried out in all children less than 5 years of age.
C. Mopping-up is done in areas where wild poliovirus is found.
D. AFP surveillance is performed in all children less than 5 years of age. (Correct Answer)

Explanation: ### Explanation **1. Why Option D is the Correct Answer (False Statement):** Acute Flaccid Paralysis (AFP) surveillance is the gold standard for detecting polio. However, the age criteria for AFP surveillance is **all children less than 15 years of age**, not 5 years. In some cases, surveillance may even include adults if polio is strongly suspected. The goal is to detect every case of AFP to ensure no wild poliovirus (WPV) circulation is missed. **2. Analysis of Incorrect Options (True Statements):** * **Option A & C:** **Mop-up immunization** is a "house-to-house" vaccination campaign conducted in restricted geographical areas where WPV is detected or where there is a high risk of transmission (e.g., low routine immunization coverage, poor sanitation). It is the final stage of polio eradication. * **Option B:** The **Pulse Polio Immunization (PPI)** program targets all children **0–5 years of age**, regardless of their previous immunization status. This "pulse" (simultaneous vaccination) aims to replace wild virus with vaccine virus in the community. **3. High-Yield Clinical Pearls for NEET-PG:** * **AFP Surveillance Criteria:** 1) All children <15 years with AFP, and 2) Any person of any age with paralytic illness if polio is suspected. * **Surveillance Indicators:** A sensitive system must detect at least **2 non-polio AFP cases per 100,000** children under 15 years. * **Stool Sampling:** Two "adequate" stool samples must be collected **24 hours apart** within **14 days** of onset of paralysis. * **Zero Dose:** The dose of OPV given at birth is called the "Zero Dose." * **India Status:** India was declared Polio-free by the WHO on **March 27, 2014** (last case reported in Jan 2011, Howrah, West Bengal).

Question 199: What is the vector responsible for the transmission of Kyasanur Forest Disease (KFD)?

A. Soft tick
B. Hard tick (Correct Answer)
C. Louse
D. Bug

Explanation: **Explanation:** **Kyasanur Forest Disease (KFD)**, commonly known as "Monkey Fever," is a viral hemorrhagic fever endemic to South India (primarily Karnataka). It is caused by the KFD virus, a member of the *Flaviviridae* family. 1. **Why Option B is Correct:** The primary vector for KFD is the **Hard tick**, specifically species belonging to the genus ***Haemaphysalis*** (most notably *Haemaphysalis spinigera*). Ticks act as both the vector and the reservoir for the virus. Humans usually contract the disease through a tick bite or via contact with an infected animal, most commonly monkeys (Langurs and Bonnet macaques), which act as amplifier hosts. 2. **Why Other Options are Incorrect:** * **A. Soft tick:** These are vectors for diseases like Tick-borne Relapsing Fever (TBRF), but not KFD. * **C. Louse:** Body lice are responsible for transmitting Epidemic Typhus, Relapsing Fever, and Trench Fever. * **D. Bug:** Reduviid bugs (Triatomine) transmit Chagas disease, while Bed bugs are not known vectors for major systemic human diseases. **High-Yield Clinical Pearls for NEET-PG:** * **Reservoirs:** Wild rodents and monkeys. Monkeys are "sentinel" animals; their death in a forest often signals a KFD outbreak. * **Seasonality:** Most cases occur during the dry season (January to June) when human activity in forests increases. * **Clinical Presentation:** Characterized by sudden onset high fever, severe headache, myalgia, and hemorrhagic manifestations. A "biphasic" fever pattern is sometimes seen. * **Prevention:** A **formalin-inactivated vaccine** is available and used in endemic areas for individuals aged 7–65 years.

Question 200: Which formula is denoted by (Weight = Height - 100)?

A. Corpulence index
B. Broca index (Correct Answer)
C. Lorentz's formula
D. Quetelet's index

Explanation: **Explanation:** The **Broca Index** is a simple, historical method used to estimate a person’s **Ideal Body Weight (IBW)** in kilograms based on their height in centimeters. The formula is: **Ideal Weight (kg) = Height (cm) – 100** While easy to calculate bedside, it is less precise than modern methods because it does not account for age, gender, or frame size. However, it remains a high-yield concept in Community Medicine for rapid nutritional assessment. **Analysis of Incorrect Options:** * **A. Corpulence Index:** Also known as the Ponderal Index or Rohrer's Index, it is calculated as $Weight (kg) / Height (m)^3$. It is primarily used in pediatrics to assess fetal growth and neonates. * **C. Lorentz’s Formula:** This is a more refined version of the Broca Index that accounts for gender. * *Males:* $Height – 100 – [(Height – 150) / 4]$ * *Females:* $Height – 100 – [(Height – 150) / 2]$ * **D. Quetelet’s Index:** This is the formal name for the **Body Mass Index (BMI)**, calculated as $Weight (kg) / Height (m)^2$. It is the current gold standard for classifying overweight and obesity. **High-Yield Clinical Pearls for NEET-PG:** * **BMI Classifications (WHO):** Underweight (<18.5), Normal (18.5–24.9), Overweight (25–29.9), Obese (≥30). * **Asian-Indian BMI Cut-offs:** Normal (18–22.9), Overweight (23–24.9), Obese (≥25). * **Ponderal Index:** Useful for identifying "thinness" in newborns (SGA vs. IUGR). * **Waist-Hip Ratio:** A better predictor of metabolic risk than BMI; significant if **>0.9 in men** or **>0.85 in women**.

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