Which of the following statements about pathogenic mosquitoes is correct?
Which of the following statements about Culex larvae is correct?
Horrock's apparatus is used to measure?
Which indicator is used in Horroch's apparatus?
In water testing from a well using Horrock's apparatus, blue color appears from the 4th cup onwards. What is the amount of bleaching powder required to disinfect 75000 litres of water?
Waste Sharps should be disposed in ?
Pneumonic plague is spread by:
What is the most common mode of transmission of HIV?
Which of the following is not a recognized transmission route for amoebiasis?
What is the range of values for the Physical Quality of Life Index (PQLI)?
NEET-PG 2015 - Community Medicine NEET-PG Practice Questions and MCQs
Question 51: Which of the following statements about pathogenic mosquitoes is correct?
- A. Mansonia mosquitoes lay their eggs in rafts.
- B. Culex mosquitoes are primarily vectors for West Nile virus.
- C. Aedes mosquitoes are known for their distinctive black and white striped markings.
- D. Anopheles mosquitoes are known for transmitting malaria. (Correct Answer)
Explanation: ***Correct: Anopheles mosquitoes are known for transmitting malaria.*** - **Anopheles mosquitoes** are the **primary and only vectors** for **malaria**, a parasitic disease caused by Plasmodium parasites. - They transmit the parasite through their **saliva** when they bite humans, typically during **dusk and dawn**. - This is the most significant pathogenic association among the options. *Incorrect: Mansonia mosquitoes lay their eggs in rafts.* - **Mansonia mosquitoes** lay their eggs in **clusters attached to underwater parts of aquatic plants**, not in rafts. - **Culex mosquitoes** are the ones that lay their eggs in **raft-like formations** on water surfaces. *Incorrect: Culex mosquitoes are primarily vectors for West Nile virus.* - While **Culex mosquitoes** can transmit West Nile virus, in the **Indian context** they are primarily known as vectors for **lymphatic filariasis** (Wuchereria bancrofti) and **Japanese encephalitis**. - West Nile virus is more relevant in Western countries and is not the primary disease association for Culex in India. *Incorrect: Aedes mosquitoes are known for their distinctive black and white striped markings.* - While **Aedes aegypti** and **Aedes albopictus** do have **black and white striped markings**, this is a **morphological characteristic** rather than a primary **pathogenic association**. - The question asks about pathogenic mosquitoes, and Aedes is better characterized by its **disease transmission** (dengue, Zika, chikungunya, yellow fever) rather than its appearance. - As a pathogenic mosquito, its **daytime biting behavior** and **urban breeding habits** are more relevant than its markings.
Question 52: Which of the following statements about Culex larvae is correct?
- A. Rest parallel to surface water
- B. Long Palmate hair
- C. Siphon tube present (Correct Answer)
- D. All are false
Explanation: ***Siphon tube present*** - **Culex larvae** possess a prominent **siphon tube** at their posterior end, which is used for breathing by extending to the water surface. - This **siphon tube** is a key morphological feature that helps distinguish them from *Anopheles* larvae. *Rest parallel to surface water* - **Anopheles larvae** typically rest parallel to the water surface because they lack a long siphon and obtain oxygen directly through spiracles on their dorsal surface. - **Culex larvae**, due to their siphon tube, hang head-down at an angle from the water surface. *Long Palmate hair* - **Palmate hairs** are characteristic structures found on the abdomen of **Anopheles larvae** that help them float horizontally at the water surface. - **Culex larvae** do not possess well-developed palmate hairs. *All are false* - This statement is incorrect because the presence of a **siphon tube** is a defining characteristic of **Culex larvae**.
Question 53: Horrock's apparatus is used to measure?
- A. Wind velocity
- B. Humidity
- C. Chlorine demand (Correct Answer)
- D. Cooling power
Explanation: ***Chlorine demand*** - Horrock's apparatus is specifically designed for determining the **chlorine demand** of water, which is the amount of **chlorine** consumed by impurities before a **free chlorine residual** is established. - This apparatus is crucial in **water treatment processes** to ensure effective **disinfection** by adjusting chlorine dosages. *Wind velocity* - **Wind velocity** is typically measured using an **anemometer**, a device with rotating cups or a propeller that spins in response to wind. - Horrock's apparatus has no components or mechanisms for detecting or quantifying wind movement. *Humidity* - **Humidity** is measured by instruments such as **hygrometers** or **psychrometers**, which assess the amount of water vapor in the air. - These devices utilize properties like **condensation** or changes in **electrical resistance**, which are unrelated to the function of Horrock's apparatus. *Cooling power* - **Cooling power** refers to the rate at which heat can be removed from a system and is measured using devices like **catathermometers** or specialized **calorimeters**. - Horrock's apparatus is a **chemical testing device** and does not have the capability to measure thermal properties or cooling rates.
Question 54: Which indicator is used in Horroch's apparatus?
- A. Potassium permanganate
- B. Bleaching powder
- C. Soda-lime
- D. Starch iodine (Correct Answer)
Explanation: ***Starch iodine*** - Horroch's apparatus is specifically designed for testing the **sterilizing efficiency of hypochlorite solutions** in dairies. - **Starch iodine** (starch-iodide paper) is used as an indicator because it reacts with residual free chlorine to produce a **blue-black color**, which confirms that adequate free chlorine is present for effective sterilization. - The principle: Free chlorine oxidizes iodide to iodine, which then reacts with starch to give the characteristic blue color. *Bleaching powder* - **Bleaching powder** (calcium hypochlorite) is the active ingredient in hypochlorite sterilizing solutions being tested, not an indicator itself. - It's the substance whose sterilizing efficacy is being evaluated using the apparatus. *Soda-lime* - **Soda-lime** is primarily used as an absorbent for **carbon dioxide (CO2)** and other acidic gases in various laboratory and anesthetic applications. - It has no role as an indicator in Horroch's apparatus for testing hypochlorite solutions. *Potassium permanganate* - **Potassium permanganate** is a strong oxidizing agent often used as an indicator in redox titrations, as its deep purple color disappears when reduced. - It is not suitable for indicating residual chlorine in Horroch's test, which specifically relies on the starch-iodine reaction.
Question 55: In water testing from a well using Horrock's apparatus, blue color appears from the 4th cup onwards. What is the amount of bleaching powder required to disinfect 75000 litres of water?
- A. 1600 gm
- B. 2000 gm
- C. 1300 gm
- D. 100 gm (Correct Answer)
Explanation: ***100 gm*** - In **Horrock's apparatus** test, blue color appearing from the 4th cup indicates a **chlorine demand of 0.4 ppm (0.4 mg/L)** for the water sample. - **Total chlorine required** = 0.4 mg/L × 75,000 L = **30,000 mg = 30 gm** of pure chlorine. - Standard bleaching powder contains **30% available chlorine**, so: **Bleaching powder needed = 30 gm ÷ 0.30 = 100 gm**. - This is the scientifically accurate amount for disinfecting 75,000 liters of water with 0.4 ppm chlorine demand. *1000 gm* - This represents a **10-fold excess** over the actual requirement of 100 gm based on the measured chlorine demand. - Using 1000 gm would result in severe **over-chlorination** (4 ppm instead of 0.4 ppm), causing strong unpleasant taste, odor, and potential health concerns. *1600 gm* - This amount represents **16 times the required dose**, leading to dangerously high chlorine levels in the water. - Such excessive chlorination would make the water unpalatable and potentially toxic to consumers. *2000 gm* - This represents a **20-fold excess**, providing extreme and harmful over-disinfection. - Such excessive amounts could lead to **chlorine toxicity** and would be wasteful and harmful to consumers. *1300 gm* - This amount exceeds the calculated requirement by **13 times**, providing unnecessary and harmful over-disinfection. - The precise calculation based on **0.4 ppm chlorine demand** and **75,000 L volume** yields exactly **100 gm**, not 1300 gm.
Question 56: Waste Sharps should be disposed in ?
- A. Black bag
- B. Yellow bag (Correct Answer)
- C. None of the options
- D. Blue bag
Explanation: ***Yellow bag (Historical answer per BMW Rules 1998)*** - Under the **Biomedical Waste Management Rules 1998** (applicable at the time of NEET-PG 2015), **sharps waste** including needles, syringes, and scalpels were disposed in **yellow puncture-proof containers**. - This was the correct answer when this question was asked in the 2015 examination. - **Current Guidelines (BMW Rules 2016):** Sharps are now disposed in **white/translucent puncture-proof containers**, NOT yellow bags. Yellow bags are currently used for soiled infectious waste like dressings and body fluid-contaminated materials. *Black bag* - **Black bags** are used for **general non-hazardous waste** that poses no biological risk. - Disposing of sharps in black bags creates serious **risk of needlestick injuries** and potential transmission of bloodborne pathogens. *None of the options* - This is incorrect because there is a specific, regulated method for disposing of sharps in healthcare settings. - Proper waste segregation is **mandatory** for safety and regulatory compliance. *Blue bag* - **Blue bags** (per BMW Rules 2016) are used for disposal of **glassware** (broken or discarded) and **metallic body implants**. - Under older guidelines, blue bags were for certain pharmaceutical waste. - They are not designated for sharps disposal.
Question 57: Pneumonic plague is spread by:
- A. Direct contact with infected tissue
- B. Bite of infected flea
- C. Ingestion of contaminated food
- D. Droplet infection (Correct Answer)
Explanation: ***Correct: Droplet infection*** - Pneumonic plague is a severe form of plague that affects the **lungs** and is transmitted through **respiratory droplets** expelled by an infected person or animal during coughing or sneezing. - This direct person-to-person transmission distinguishes it from other forms of plague. - It is the **only form of plague** that can spread directly from human to human without an animal or flea vector. *Incorrect: Bite of infected flea* - This is the primary mode of transmission for **bubonic plague**, where the bacterium *Yersinia pestis* is transmitted from rodents to humans via infected fleas. - While bubonic plague can progress to pneumonic plague, the initial transmission route for the pneumonic form itself is not flea bites. *Incorrect: Direct contact with infected tissue* - Direct contact with infected tissues or fluids can lead to **septicemic plague** or sometimes bubonic plague, especially in cases where there is a break in the skin. - This is not the typical or primary route for the spread of pneumonic plague, which is respiratory. *Incorrect: Ingestion of contaminated food* - Ingestion of contaminated food or water is a route for various **gastrointestinal infections** and diseases like salmonella or cholera. - It is not a known or common method for the transmission of any form of plague, including pneumonic plague.
Question 58: What is the most common mode of transmission of HIV?
- A. Occupational exposure (needle stick injury)
- B. Perinatal transmission (mother to child)
- C. Sexual contact (Correct Answer)
- D. Transmission via blood and blood products
Explanation: ***Sexual contact*** - **Unprotected sexual intercourse**, both heterosexual and homosexual, is overwhelmingly the most common way HIV is transmitted globally. - The virus can be exchanged through **bodily fluids** such as semen, vaginal fluids, and rectal fluids during sexual activity. - Accounts for approximately **80% of new HIV infections** worldwide. *Occupational exposure (needle stick injury)* - While a recognised mode of transmission, **needle stick injuries** account for a very small percentage of total HIV infections, primarily affecting healthcare workers. - The risk of transmission per exposure is relatively low (approximately **0.3%**), especially compared to sexual contact. *Perinatal transmission (mother to child)* - **Mother-to-child transmission** can occur during pregnancy, childbirth, or breastfeeding. - Although significant, especially in resource-limited settings, global efforts and **PMTCT programs** have resulted in a significant reduction in this type of transmission. *Transmission via blood and blood products* - This mode was once a major concern but is now extremely rare in countries with robust **blood screening programs**. - While sharing contaminated needles among **intravenous drug users** remains a risk, transfusion-related HIV is largely controlled.
Question 59: Which of the following is not a recognized transmission route for amoebiasis?
- A. Sexual transmission
- B. Blood and blood products
- C. Vector transmission (Correct Answer)
- D. Fecal-oral route
Explanation: ***Vector transmission*** - Amoebiasis, caused by *Entamoeba histolytica*, is primarily an **intestinal infection** transmitted through the **fecal-oral route**. - Its life cycle **does not involve any arthropod vector** (e.g., mosquito, tick, fly) for transmission. - This is the **only route among the options that is definitively NOT recognized** for amoebiasis transmission. *Sexual transmission* - Amoebiasis **can be transmitted** through **oral-anal sexual contact**, particularly documented in men who have sex with men (MSM). - This represents an **indirect fecal-oral transmission** route and is a recognized mode of spread. *Blood and blood products* - While *E. histolytica* can disseminate to cause **amoebic liver abscesses** and rarely systemic disease, transmission via blood transfusion is **extremely rare and not well-documented**. - However, theoretically possible in cases of parasitemia during invasive disease. - Unlike vector transmission, this cannot be definitively ruled out as "not recognized." *Fecal-oral route* - This is the **primary and most important transmission route** for amoebiasis. - Infection occurs through ingestion of **cysts** from contaminated food, water, or through direct person-to-person contact with poor hand hygiene.
Question 60: What is the range of values for the Physical Quality of Life Index (PQLI)?
- A. 0 to 10
- B. 0 to 50
- C. 0 to 100 (Correct Answer)
- D. 100 to 200
Explanation: ***0 to 100*** - The **Physical Quality of Life Index (PQLI)** is an index that measures the quality of life or well-being of a country, with values ranging from **0 (worst)** to **100 (best)**. - This standardized range allows for easy comparison of living standards and societal progress across different nations. *0 to 10* - This range is too small and does not accurately represent the comprehensive scoring system used for the **PQLI**, which aggregates multiple indicators. - While some individual metrics might use a 0-10 scale, the composite PQLI itself uses a broader range. *0 to 50* - This range is insufficient to capture the full spectrum of development indicators factored into the **PQLI**. - A maximum value of 50 would compress the data too much, making fine distinctions between countries less apparent. *100 to 200* - The **PQLI** is capped at 100, which signifies the highest possible quality of life; therefore, values above 100 are not possible. - This range suggests an overly optimistic or unstandardized index, which is not the case for PQLI.