Epidemiology Practice Questions

Q: Which of the following drugs is most effective for the radical cure of Plasmodium vivax malaria?

Chloroquine + Primaquine. **Explanation:** The treatment of *Plasmodium vivax* malaria requires a dual approach to address different stages of the parasite’s life cycle. This is known as **Radical Cure**, which aims to achieve both clinical cure (clearing blood stages) and prevention of relapse (clearing liver stages). 1. **Why Option C is Correct:** * **Chloroquine** is a potent schizonticide that eliminates the erythrocytic (blood) stages of the parasite, thereby relieving clinical symptoms. * **Primaquine** is a tissue schizonticide that targets the **hypnozoites** (dormant forms) in the liver. Without Primaquine, these hypnozoites can reactivate, causing a relapse. * The combination is essential because neither drug alone can achieve a complete cure and prevent recurrence. 2. **Why Other Options are Incorrect:** * **Option A (Chloroquine):** While it treats the acute attack, it has no effect on liver hypnozoites. Using it alone leads to high relapse rates. * **Option B (Primaquine):** While it kills liver stages, it is a weak blood schizonticide and is not used alone to treat an acute clinical attack of malaria. **High-Yield Clinical Pearls for NEET-PG:** * **Standard Regimen (NVBDCP India):** Chloroquine (25 mg/kg over 3 days) + Primaquine (0.25 mg/kg daily for **14 days**). * **G6PD Deficiency:** Before administering Primaquine, patients must be screened for G6PD deficiency, as the drug can trigger **acute hemolysis**. * **Pregnancy:** Primaquine is **contraindicated** in pregnancy and infants under 6 months due to the risk of neonatal hemolysis. * **Relapse vs. Recrudescence:** Relapse is unique to *P. vivax* and *P. ovale* due to hypnozoites; recrudescence occurs in *P. falciparum* due to incomplete clearance of blood stages.

Q: Which of the following considerations regarding Dracunculosis eradication is NOT true?

DDT. **Explanation:** Dracunculiasis (Guinea Worm Disease) is a parasitic infection caused by *Dracunculus medinensis*. It is unique because it is transmitted solely through drinking water contaminated with **Cyclops** (water fleas) harboring the infective larvae. India was declared Dracunculiasis-free by the WHO in February 2000. **Why DDT is the correct answer (NOT true):** DDT is a residual insecticide used primarily for controlling adult mosquitoes (vectors for Malaria) or sandflies. Since Dracunculiasis is **not** transmitted by an insect vector but by a crustacean (Cyclops) in water, DDT has no role in its eradication. The chemical of choice for killing Cyclops in drinking water is **Abate (Temephos)**. **Analysis of other options:** * **Drinking piped water/Hand pumps:** This is a primary prevention strategy. Providing safe water sources eliminates the need for people to use open "step-wells" or ponds where transmission occurs. * **Health education:** Crucial for behavioral change, such as teaching communities to filter water using fine cloth (nylon mesh) and preventing infected individuals from entering water bodies. * **Control of Cyclops:** This is the mainstay of environmental control. It involves chemical treatment of water (Temephos) or biological control (introducing larvivorous fish like Gambusia). **High-Yield Facts for NEET-PG:** * **Intermediate Host:** Cyclops (Water flea). * **Infective Stage:** 3rd stage L3 larva. * **Definitive Host:** Humans (No animal reservoir). * **Incubation Period:** 10–14 months. * **Eradication Strategy:** India used the "Guinea Worm Eradication Programme" (GWEP) launched in 1983-84. * **Last Case in India:** Reported in July 1996 (Jodhpur, Rajasthan).

Q: What are the minimum and maximum values established for the calculation of the Life Expectancy index in the Human Development Index (HDI)?

25 years and 85 years. **Explanation:** The **Human Development Index (HDI)** is a composite statistic used to rank countries based on three dimensions: health, education, and standard of living. The health dimension is assessed by **Life Expectancy at Birth**. To transform these raw indicators into a dimension index ranging from 0 to 1, the UNDP establishes specific **goalposts** (minimum and maximum values): 1. **Why Option D is Correct:** For the Life Expectancy Index, the **minimum value is 20 years** (revised from 25 in older reports, but 20-25 remains the standard academic benchmark for exams) and the **maximum value is 85 years**. The value of 20-25 years is chosen as a "natural zero," representing the minimum life expectancy required for a society to survive, while 85 years is an observed aspirational ceiling. 2. **Why Options A, B, and C are Incorrect:** * **0 years** is not used as a minimum because no human population has ever functioned with a life expectancy of zero. * **65 or 100 years** are not used as maximums because 65 is too low (many countries exceed this) and 100 is currently unrealistic as a national average. **High-Yield Facts for NEET-PG:** * **HDI Components:** 1. Life Expectancy Index (Health), 2. Education Index (Mean years and Expected years of schooling), 3. GNI per capita (Standard of Living). * **Calculation:** HDI is the **Geometric Mean** of these three dimension indices. * **India’s Status:** India typically falls in the **"Medium Human Development"** category. * **PQLI vs. HDI:** Do not confuse HDI with the Physical Quality of Life Index (PQLI). PQLI includes Infant Mortality Rate, Life Expectancy at age 1, and Literacy, but *excludes* income.

Q: A country in Africa has shown improvement in death rate, but the birth rate is yet to be controlled and thus remains high. The country is most likely to be in which stage of the demographic cycle?

Second stage. ### Explanation The demographic cycle describes the transition of a population from high birth and death rates to low birth and death rates as a country develops. **Why the Correct Answer is Right:** The **Second Stage (Early Expanding)** is characterized by a **decline in the death rate** due to improvements in food supply, sanitation, and healthcare. However, the **birth rate remains high** because social norms and lack of family planning take longer to change. This gap between a high birth rate and a falling death rate leads to a "population explosion." The scenario described (improved death rate but uncontrolled birth rate) is the hallmark of this stage. **Analysis of Incorrect Options:** * **A. First Stage (High Stationary):** Characterized by both high birth and high death rates, resulting in a stable but small population. (e.g., isolated tribes). * **C. Third Stage (Late Expanding):** The death rate continues to decline or stabilizes, but the **birth rate begins to fall**. The population still grows, but at a slower pace. (e.g., India is currently in this stage). * **D. Fourth Stage (Low Stationary):** Characterized by both low birth and low death rates, leading to zero population growth. (e.g., many European countries). **High-Yield NEET-PG Pearls:** * **India’s Status:** India is currently in the **Late Expanding (Third) Stage**. * **Fifth Stage (Declining):** A theoretical stage where the birth rate falls below the death rate, leading to a population decrease (e.g., Germany, Japan). * **Key Driver:** The transition from Stage 1 to Stage 2 is usually triggered by medical and sanitary advances, while the transition from Stage 2 to Stage 3 is driven by socio-economic changes and contraception.

Q: What is the period of isolation for Salmonella infection?

3 consecutive stool cultures are negative. ### Explanation The correct answer is **C: 3 consecutive stool cultures are negative.** **Why it is correct:** Salmonella (specifically *Salmonella Typhi* and *Paratyphi*) is primarily transmitted via the fecal-oral route. Clinical recovery does not always coincide with the cessation of pathogen shedding. To ensure a patient is no longer infectious and to prevent the development of a "carrier state," public health guidelines require microbiological evidence of clearance. Isolation or exclusion from high-risk activities (like food handling) is maintained until **three consecutive stool cultures**, taken at least 24 hours apart, are negative. **Analysis of Incorrect Options:** * **A. 72 hours after chemotherapy:** While symptoms may improve shortly after starting antibiotics (chemotherapy), the patient can still shed the bacteria in feces, posing a transmission risk. * **B. Widal test negative:** The Widal test measures antibodies (H and O agglutinins), not the presence of the bacteria itself. Titers can remain high long after the infection has cleared, making it an invalid tool for determining the end of isolation. * **D. Urine culture is negative twice:** While *S. Typhi* can be found in urine (especially in cases associated with Schistosomiasis), stool culture is the gold standard for confirming the end of the communicable period. **High-Yield Facts for NEET-PG:** * **Carrier State:** Defined as the excretion of *S. Typhi* in stool/urine for **more than one year**. * **Chronic Carrier Site:** The **Gallbladder** is the most common site for chronic fecal carriage (often associated with gallstones). * **Urinary Carrier Site:** Associated with **Schistosoma haematobium** infection in the bladder. * **Culture Timing:** Stool cultures are most likely to be positive in the **2nd and 3rd weeks** of illness, whereas blood cultures are best in the **1st week**.

Question 1

Which of the following drugs is most effective for the radical cure of Plasmodium vivax malaria?

Accepted Answer

Chloroquine + Primaquine

Answer

Chloroquine

Answer

Primaquine

Answer

None of the above

Question 2

In an area with an annual parasite index of less than 2, what is the recommended course of action?

Accepted Answer

Monthly blood smears for all positive cases

Answer

Passive surveillance only

Answer

Two rounds of DDT application annually

Answer

Entomological surveillance

Question 3

A Chandler's index of 250 - 300 eggs/gm of stool indicates which of the following regarding public health significance?

Accepted Answer

A minor public health program

Answer

Potential danger

Answer

An important public health program

Answer

Not of much significance

Question 4

What is surveillance?

Accepted Answer

Continuous monitoring of occurrence and distribution of a disease

Answer

Monitoring of activity of health workers

Answer

Monitoring of trends of a disease

Answer

Related to the virulence of the organism

Question 5

What is true about Dengue fever?

Accepted Answer

Is the most common arboviral infection

Answer

Can be both epidemic as well as endemic

Answer

Can survive in ambient temperature

Answer

Incidence is decreasing in India in last 2-3 decades

Question 6

Which of the following considerations regarding Dracunculosis eradication is NOT true?

Accepted Answer

DDT

Answer

Drinking piped water and installation of hand pumps

Answer

Health education and awareness of the public

Answer

Control of Cyclops

Question 7

What are the minimum and maximum values established for the calculation of the Life Expectancy index in the Human Development Index (HDI)?

Accepted Answer

25 years and 85 years

Answer

0 years and 65 years

Answer

0 years and 85 years

Answer

0 years and 100 years

Question 8

A country in Africa has shown improvement in death rate, but the birth rate is yet to be controlled and thus remains high. The country is most likely to be in which stage of the demographic cycle?

Accepted Answer

Second stage

Answer

First stage

Answer

Third stage

Answer

Fourth stage

Question 9

What is the period of isolation for Salmonella infection?

Accepted Answer

3 consecutive stool cultures are negative

Answer

72 hours after chemotherapy

Answer

Widal test negative

Answer

Urine culture is negative twice

Question 10

When selecting a screening test for a disease, which of the following factors should NOT be considered?

Accepted Answer

Cost of the test

Answer

Efficiency of the treatment

Answer

Knowledge of the physician about the disease

Answer

Suffering caused by the disease to the population

Epidemiology — MCQs

Epidemiology — MCQs

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