Water-Borne Diseases

Water-Borne Diseases: Overview - Splashy Intruders

• Diseases caused by pathogenic microbes transmitted through contaminated water.
• Primarily spread via fecal-oral route (📌 4 Fs: Fingers, Flies, Fomites, Fields).
• Classified by etiological agent:
  • Bacterial: Cholera, Typhoid, Bacillary dysentery, E. coli infections.
  • Viral: Hepatitis A & E, Polio, Rotavirus.
  • Protozoal: Amoebiasis, Giardiasis, Cryptosporidiosis.
  • Helminthic: Ascariasis, Trichuriasis, Dracunculiasis.

⭐ Most common cause of acute diarrheal disease outbreaks globally is contaminated water, often with Vibrio cholerae or Rotavirus being key culprits in India.

Bacterial Water-Borne Diseases - Gut Wreckers

• Cholera
  • Pathogen: Vibrio cholerae (O1, O139).
  • Clinical: Profuse "rice-water" stools, severe dehydration.
  • Dx: Stool culture (TCBS agar).
  • Rx: ORS, IV fluids. Antibiotics (Doxycycline 300mg single dose, Azithromycin) reduce duration.
• Typhoid Fever (Enteric Fever)
  • Pathogen: Salmonella Typhi.
  • Clinical: Step-ladder fever, rose spots, relative bradycardia (Faget's sign). Constipation early, then pea-soup diarrhea.
  • Complications: Intestinal perforation.
  • Dx: Blood culture (1st week), Widal test (2nd week).
  • Rx: Ceftriaxone, Azithromycin.
• Oral Rehydration Solution (ORS) - WHO Low Osmolarity
  • Composition (mmol/L): Na+ 75, K+ 20, Cl- 65, Citrate 10, Glucose 75. Total Osmolarity: 245 mOsm/L.
  • 📌 Mnemonic: "Good Old Standard KCl" (Glucose, Osmolarity, Sodium, K, Cl, Citrate).

⭐ Blood culture is the diagnostic gold standard for Typhoid fever in the first week of illness.

Viral & Protozoal Water-Borne Diseases - Microscopic Invaders

• Viral Agents:
  • Hepatitis A (Picornavirus): RNA virus. Feco-oral (water/food). Incubation 2-6 wks. Jaundice, fever. Dx: Anti-HAV IgM (acute). No chronic state. Vaccine preventable.
  • Hepatitis E (Hepevirus): RNA virus. Feco-oral (water). Incubation 2-10 wks. Similar to Hep A. Genotypes 1&2 epidemic.

    ⭐ High mortality (20-25%) in pregnant women (3rd trimester).

  • Poliomyelitis (Enterovirus): RNA virus. Feco-oral. Incubation 7-14 days. <1% paralytic (anterior horn cells). OPV (live)/IPV (killed). India polio-free.
• Protozoal Agents:
  • Amoebiasis (Entamoeba histolytica): Feco-oral (cysts). Asymptomatic common. Amoebic dysentery (blood/mucus), liver abscess (most common extra-intestinal). Flask-shaped ulcers.
  • Giardiasis (Giardia lamblia): Feco-oral (cysts). "Backpacker's diarrhea". Non-bloody, foul, greasy stools (steatorrhea), malabsorption. 📌 Giardia: Greasy, Gassy, Gross.

Prevention & Control of Water-Borne Diseases - Safe Sips Shield

• WASH: Safe water, sanitation, hygiene.
• I. Water Purification:
  • A. Household: Boiling (rolling boil 1-3 min); Chemical (Chlorine tablets, Iodine); Filtration (Ceramic filters, UV).
  • B. Municipal (Large Scale):
    • Steps: Storage → Coagulation/Flocculation → Sedimentation → Filtration (SSF/RSF) → Disinfection.
    • Slow Sand Filters (SSF): Schmutzdecke (biological layer); Rate 0.1-0.4 m³/hr/m²; 99.9% bacteria removal.
    • Rapid Sand Filters (RSF): Needs backwashing; Rate 5-15 m³/hr/m².
    • Chlorination: Break-point chlorination ensures free residual chlorine (0.5 mg/L for 1 hr contact). Orthotolidine-Arsenite (OTA) test for free/combined chlorine.
• II. Sanitation & Hygiene:
  • Safe Excreta Disposal: Sanitary latrines (RCA, Septic tank, VIP latrine) prevent contamination.
  • Handwashing: With soap at critical times. 📌 F-diagram (Faeces→Fluids/Fields/Flies/Fingers→Food→Future Host).
• III. National Health Programs:
  • Swachh Bharat Mission (SBM): Focus on Open Defecation Free (ODF) status.
  • Jal Jeevan Mission (JJM): Aims for Functional Household Tap Connections (FHTC) by 2024.
• IV. Surveillance:
  • Integrated Disease Surveillance Programme (IDSP): For early outbreak detection & water quality monitoring.

⭐ Horrock's Apparatus is used to estimate the correct dose of bleaching powder (chlorinated lime) required for disinfecting 100 gallons of well water. The target free residual chlorine is 0.5 mg/L after 1 hour contact time for safe water.

High‑Yield Points - ⚡ Biggest Takeaways

• Cholera: "rice-water" stools, severe dehydration; ORS is life-saving.
• Typhoid fever: "step-ladder" pyrexia, rose spots; Widal test aids diagnosis.
• Hepatitis A & E: viral, fecal-oral transmission, cause acute jaundice.
• Poliomyelitis: fecal-oral, can cause irreversible flaccid paralysis; vaccination is key.
• Amoebiasis: E. histolytica causes bloody dysentery and liver abscess.
• Giardiasis: G. lamblia causes greasy, foul-smelling stools, leading to malabsorption.
• Chlorination: vital for safe drinking water; residual chlorine testing is essential.