Water-Borne Diseases Indian Medical PG Practice Questions and MCQs
Practice Indian Medical PG questions for Water-Borne Diseases. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Water-Borne Diseases Indian Medical PG Question 1: 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)
Water-Borne Diseases 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.
Water-Borne Diseases Indian Medical PG Question 2: A frequent traveler presented with 4 days of continuous fever, abdominal pain, and bradycardia. What is the best diagnostic test to confirm the pathogen?
- A. Widal test
- B. Blood culture (Correct Answer)
- C. Urine culture
- D. Stool culture
Water-Borne Diseases Explanation: ***Blood culture***
- **Blood culture** is the most sensitive and specific test for confirming **typhoid fever** in the first week of illness.
- The presence of **continuous fever** (step-ladder pattern), **abdominal pain**, and **relative bradycardia** in a traveler strongly suggests typhoid fever caused by *Salmonella Typhi*.
*Widal test*
- The **Widal test** detects antibodies against *Salmonella Typhi* antigens and is often positive later in the disease course.
- It has **limited sensitivity and specificity**, especially in endemic areas or with prior vaccination, leading to false positives and negatives.
*Urine culture*
- **Urine culture** has a low yield for *Salmonella Typhi*, as bacteria are intermittently shed in urine, usually later in the disease.
- It's primarily useful for diagnosing **urinary tract infections** or in chronic carriers of typhoid.
*Stool culture*
- **Stool culture** yield is higher in the later stages of typhoid fever, as *Salmonella Typhi* is shed in feces.
- Its sensitivity is lower than blood culture in the early acute phase when bacteremia is most prominent.
Water-Borne Diseases Indian Medical PG Question 3: All of the following are helminthic waterborne disease except?
- A. Hydatid cyst
- B. Roundworm
- C. Giardiasis (Correct Answer)
- D. Threadworm
Water-Borne Diseases Explanation: ***Giardiasis***
- **Giardiasis** is caused by the **protozoan parasite** *Giardia lamblia*, not a helminth.
- It is a true waterborne disease, transmitted through contaminated water.
- This is the correct answer as it is NOT a helminthic infection.
*Hydatid cyst*
- **Hydatid cyst disease** is caused by the larval stage of the **tapeworm** *Echinococcus granulosus*, a helminth.
- Primarily transmitted through ingestion of eggs from dog feces (zoonotic), though contaminated water can occasionally serve as a vehicle.
*Roundworm*
- **Roundworm infection** (ascariasis) is caused by the nematode *Ascaris lumbricoides*, a helminth.
- Classified as a soil-transmitted helminth (STH), acquired through ingestion of eggs from contaminated soil; water can occasionally act as a transmission vehicle.
*Threadworm*
- **Threadworm infection** (enterobiasis/pinworm) is caused by the nematode *Enterobius vermicularis*, a helminth.
- Primarily transmitted person-to-person via the fecal-oral route through contaminated hands and fomites; water transmission is uncommon but possible in poor sanitation conditions.
Water-Borne Diseases Indian Medical PG Question 4: Which disease is characterized by severe watery diarrhea and is associated with a toxin-producing bacterium?
- A. Gastroenteritis
- B. Cholera (Correct Answer)
- C. Dysentery
- D. Typhoid fever
Water-Borne Diseases Explanation: ***Cholera***
- Cholera is known for causing **severe, watery diarrhea** (often described as "rice water stools") due to the action of **cholera toxin** produced by *Vibrio cholerae* [1], [2].
- The toxin stimulates excessive fluid and electrolyte secretion in the small intestine, leading to rapid **dehydration** and electrolyte imbalance [2].
*Gastroenteritis*
- This is a general term for **inflammation of the stomach and intestines**, which can be caused by various pathogens (viruses, bacteria, parasites) and toxins.
- While it often presents with diarrhea, it doesn't specifically imply the **severe watery diarrhea** linked to a specific toxin as seen in cholera.
*Dysentery*
- Dysentery is characterized by **bloody diarrhea**, often accompanied by **fever and abdominal cramps**, indicating inflammation and damage to the intestinal lining [3].
- It is typically caused by bacteria like *Shigella* or *entamoeba histolytica*, distinct from the purely watery diarrhea of cholera [3].
*Typhoid fever*
- Typhoid fever is a systemic illness caused by *Salmonella typhi*, characterized by **sustained fever, headache, malaise**, and can include **constipation or mild diarrhea**.
- It does not primarily present with **severe watery diarrhea** induced by a specific toxin, unlike cholera.
Water-Borne Diseases Indian Medical PG Question 5: A 17 year old adolescent, presented with fever since one week which is step-ladder in pattern. He also has loose stools which are "pea-soup" in consistency. Rose spots are seen on his body. He is most probably infected with:
- A. Salmonella typhi (Correct Answer)
- B. Adenovirus
- C. Rotavirus
- D. Vibrio cholerae
Water-Borne Diseases Explanation: ***Salmonella typhi***
- The combination of **step-ladder fever**, **"pea-soup" diarrhea**, and **rose spots** is a classic presentation of **typhoid fever**, caused by *Salmonella typhi* [1].
- This bacterial infection predominantly affects the gastrointestinal tract and can lead to systemic symptoms [1].
*Adenovirus*
- **Adenovirus** typically causes **respiratory tract infections**, **conjunctivitis**, or **gastroenteritis**, but not with the specific symptom profile of step-ladder fever or rose spots.
- While it can cause diarrhea, it's usually not described as "pea-soup" and lacks the other systemic features.
*Rotavirus*
- **Rotavirus** is a common cause of **severe gastroenteritis** in infants and young children, characterized by **watery diarrhea** and vomiting.
- It does not present with step-ladder fever or rose spots, which are pathognomonic for typhoid.
*Vibrio cholerae*
- **Vibrio cholerae** causes **cholera**, an acute diarrheal illness characterized by **profuse watery diarrhea** (often described as "rice-water stools") and rapid dehydration.
- It does not typically cause step-ladder fever or skin manifestations like rose spots.
Water-Borne Diseases Indian Medical PG Question 6: What is the name of the defluoridation process of drinking water developed by the NEERI?
- A. Activated sludge process
- B. Recarbonation process
- C. Nalgonda process (Correct Answer)
- D. Double pot method
Water-Borne Diseases Explanation: ***Nalgonda process***
- The **Nalgonda technique** is a defluoridation method developed by the **National Environmental Engineering Research Institute (NEERI)** in India.
- It utilizes **aluminum salts**, **lime**, and **bleaching powder** for fluoride removal through precipitation and adsorption.
*Activated sludge process*
- This is a **wastewater treatment method** that uses microorganisms to consume organic pollutants, primarily for sewage treatment, not defluoridation.
- It involves aeration of wastewater with a flocculated biological growth of bacteria and other microorganisms.
*Recarbonation process*
- **Recarbonation** is a step in **water softening**, specifically after lime-soda ash treatment, to lower the pH and stabilize the water by converting excess calcium hydroxide to calcium carbonate.
- It is used to prevent scale formation and is not a defluoridation method.
*Double pot method*
- The **double pot method** is a technique for **household water purification**, often used in rural areas, that typically involves filtration and disinfection, but not specific defluoridation.
- It usually consists of two pots, one placed inside the other, with a filter medium or coagulant treatment.
Water-Borne Diseases Indian Medical PG Question 7: Which of the following pathogens are associated with watery diarrhea after an incubation period of 8 to 14 hours?
- A. Rotavirus and Norwalk virus
- B. Shigella and Salmonella
- C. S. aureus and Bacillus cereus
- D. Bacillus cereus and Clostridium perfringens (Correct Answer)
Water-Borne Diseases Explanation: **Bacillus cereus and Clostridium perfringens**
- Both *Bacillus cereus* diarrheal type and *Clostridium perfringens* are known to cause **watery diarrhea** after an incubation period of **8 to 14 hours**.
- This longer incubation period is typical for toxins produced in the gut after ingestion of spores or large numbers of bacteria.
*Rotavirus and Norwalk virus*
- **Rotavirus** typically has an incubation period of 1-3 days and causes **severe watery diarrhea**, especially in infants and young children.
- **Norwalk virus** (norovirus) usually has an incubation period of 12-48 hours and causes **acute gastroenteritis** with vomiting and watery diarrhea.
*Shigella and Salmonella*
- **Shigella** causes **dysentery** (bloody diarrhea) with a shorter incubation period (1-2 days) rather than watery diarrhea.
- **Salmonella** can cause **inflammatory diarrhea** (salmonellosis) with an incubation period ranging from 6 hours to 6 days, often shorter than 8-14 hours for typical infections.
*S. aureus and Bacillus cereus*
- **Staphylococcus aureus** causes vomiting and diarrhea due to preformed toxin, with a very short incubation period of **1-6 hours**.
- While *Bacillus cereus* can cause emetic (vomiting) or diarrheal type illness, the emetic form has a 1-6 hour incubation period, which is not consistent with the 8-14 hour window.
Water-Borne Diseases Indian Medical PG Question 8: A person returns to Delhi from Bangladesh after 2 days and has diarrhea. Stool examination shows RBC's in stool. The likely organism causing is ?
- A. Enteropathogenic E. Coli
- B. Salmonella typhi
- C. Enterotoxigenic E. Coli
- D. Shigella dysenteriae (Correct Answer)
Water-Borne Diseases Explanation: ***Shigella dysenteriae***
- This organism causes **bacillary dysentery**, characterized by fever, abdominal cramps, and frequent, small-volume stools containing **blood and mucus (RBCs)**, which fits the clinical picture of a traveler experiencing diarrhea with RBCs in stool.
- The rapid onset (within 2 days of return) and the presence of **RBCs in stool** are highly suggestive of an invasive bacterial pathogen like *Shigella*.
*Enteropathogenic E. Coli*
- **EPEC** typically causes **watery diarrhea**, particularly in infants, by disrupting intestinal microvilli.
- It does **not usually cause bloody stools** or significant red blood cells in the stool.
*Salmonella typhi*
- While *Salmonella typhi* causes **typhoid fever**, its initial presentation is typically with fever, headache, and constipation, followed by a **pea-soup diarrhea** in later stages, which is usually not bloody.
- The rapid onset of bloody diarrhea within 2 days is less characteristic of typhoid fever, which has a longer incubation period.
*Enterotoxigenic E. Coli*
- **ETEC** is a common cause of **traveler's diarrhea**, but it produces toxins that lead to **watery, non-bloody diarrhea**.
- The presence of **RBCs in the stool** makes ETEC an unlikely cause in this scenario.
Water-Borne Diseases Indian Medical PG Question 9: All are zoonotic disease except -
- A. Leptospirosis
- B. Rabies
- C. Scabies (Correct Answer)
- D. Brucellosis
Water-Borne Diseases Explanation: ***Scabies***
- **Scabies** is a parasitic skin infestation caused by the **Sarcoptes scabiei mite**, which typically spreads from person to person through direct skin contact.
- While animal scabies exists, human scabies is primarily a **human-to-human transmission** disease and is not generally considered a zoonosis in the context of common human infections.
*Leptospirosis*
- **Leptospirosis** is a bacterial disease transmitted through contact with urine from infected animals or contaminated water/soil.
- It is a classic example of a **zoonotic disease** affecting a wide range of mammals, including rodents, livestock, and pets.
*Rabies*
- **Rabies** is a viral disease primarily transmitted to humans through the bite of an infected animal, usually a mammal.
- It is a well-known and fatal **zoonotic disease** worldwide, with dogs being the most common source of human infection in many regions.
*Brucellosis*
- **Brucellosis** is a bacterial infection transmitted to humans through contact with infected animals (e.g., cattle, goats, sheep) or consumption of contaminated unpasteurized dairy products.
- It is a prominent **zoonotic disease** resulting in fever, sweating, and weakness, among other symptoms.
Water-Borne Diseases Indian Medical PG Question 10: All following are at-risk group adults meriting Hepatitis B vaccination in low endemic areas except for which of the following?
- A. Medical/nursing personnel
- B. Patients with chronic liver disease
- C. Diabetics on insulin (Correct Answer)
- D. Patients on chronic hemodialysis
Water-Borne Diseases Explanation: ***Diabetics on insulin***
- This is the correct answer as the exception based on **guidelines at the time of this exam (2012)**.
- At that time, diabetics were **not routinely listed** as a standard at-risk group for hepatitis B vaccination in low endemic areas, though the ACIP was beginning to recognize increased risk in this population.
- **Current Update (Post-2012):** The **CDC/ACIP now recommends** hepatitis B vaccination for all previously unvaccinated adults with diabetes aged 19-59 years, due to documented increased risk of HBV infection associated with:
- Shared blood glucose monitoring devices
- Assisted blood glucose monitoring in healthcare settings
- Outbreak investigations showing higher transmission rates
- For the purpose of this historical exam question, diabetics were the exception among the listed groups.
*Medical/nursing personnel*
- Healthcare workers are at **high occupational risk** due to frequent exposure to blood and body fluids.
- This has been a **standard, long-standing recommendation** for HBV vaccination regardless of endemic status.
- The risk remains present even in low endemic areas due to potential exposure to infected patients.
*Patients with chronic liver disease*
- Individuals with pre-existing chronic liver disease are at risk of **severe outcomes** if they acquire hepatitis B infection.
- Superimposed acute HBV infection can lead to:
- Rapid progression to cirrhosis
- Acute-on-chronic liver failure
- Hepatocellular carcinoma
- Vaccination is **crucial for prevention** and has been a standard recommendation.
*Patients on chronic hemodialysis*
- Hemodialysis patients face **elevated risk** of HBV acquisition due to:
- Frequent vascular access procedures
- Prolonged time in healthcare settings
- Potential for nosocomial transmission in dialysis units
- Their **immunocompromised state** increases risk of chronic infection and complications.
- Vaccination is a **standard preventive measure** in this population.
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