Health and Community 8: Water, Microbiology, and Human Health

Water, Microbiology, and Human Health

  • The lecture discusses the relationship between water, microbiology, and human health.
  • The aim is to understand this relationship, appreciate the diversity of organisms causing waterborne diseases, and advocate for clean and safe drinking water.

Water Cleanliness and Health Burdens

  • UK Water Abundance: The UK has an abundance of clean, safe water.
  • Global Disparities: This is not the case worldwide, some depend on insecure surface water sources.
  • Surface water is unreliable and potentially unsafe.

Defining Clean and Safe Water

  • Visual Appeal vs. Safety: Clear water may not be safe, and muddy water may not be harmful.
  • Clean Water: Relates to visual appeal.
  • Safe Water: Water is available, accessible, and free from harmful contaminants.
  • Contaminants include bacteria, viruses, protozoa, chemicals, particulate matter, and sewage.
  • Water isn't sterile, but there are safe levels of contaminants.
  • Fecal bacteria are a major concern for transmitting pathogenic diseases.
  • Safe water is the primary concern, though clean appearance is also desired.

Global Problem

  • Unsafe Water Usage: 1 billion people drink from unsafe water sources, often contaminated with feces.
  • Lack of Basic Water Supply: Millions lack basic water provision (water source within 30 minutes round trip).
  • Surface Water Dependence: 150 million people rely on surface water.
  • Health Impact: 800,000 annual deaths are attributed to unsafe water, inadequate sanitation, and poor hygiene.
  • Almost half of these deaths occur in children under five, often due to diarrheal diseases.
  • Water stress is increasing due to population and climate factors.
  • Good News: Most of the global population (71%) has some basic water service, but there is still room for improvement.

Causative Chain of Infection and Improvements

  • Chain of Infection:
    • Agent (infectious organism).
    • Source (animal reservoir or people).
    • Contamination (introduction of the agent to water).
    • Survival and growth of the pathogen in the water.
    • Consumption of contaminated water.
  • Breaking the Chain: Improvements can be made by breaking any link in the chain.
  • Clean Water Supplies: Developing infrastructure is a huge challenge.
  • Millennium Development Goals: Universal and equitable access to safe water for all by 2030.

Waste Management

  • Lack of Toilets: 4.5 billion people do not have a toilet at home to safely manage waste.
  • Open Defecation: 800 million people defecate in the open.
  • Goal for 2030: Equitable access to safe sanitation for all and an end to open defecation.
  • Access to Water for Hygiene: Access to water for washing is essential.
  • Handwashing Facilities: Only 76% of households in Western Asia and Northern Africa have handwashing facilities, while in Sub-Saharan Africa, only 14% do.
  • Goal for 2030: Handwashing in all homes.
  • Sustainable Development Goal 6: Provides access to WASH (water, sanitation, hygiene) facilities in homes.
  • WHO Target: Aims to prevent child deaths and illnesses from contaminated water, exposure to excreta, and lack of handwashing facilities.
  • No child should miss school due to lack of clean toilets and privacy, and no one should have to defecate in the open.

Areas for Improvement

  • Sub-Saharan Africa needs the most work on drinking water services.
  • Things are slowly improving.

Achieving Clean and Safe Water

  • A multifaceted problem involving infrastructure, money, and political will.
  • Water Filtration: Can be achieved with simple filtration processes.
    • Filtering through different grades of rock and sand to remove particulate matter and bacteria.
    • Filtering through charcoal to remove chemical contaminants.
  • Boiling Water: Not a sustainable long-term solution due to reliance on resources such as wood.
  • Sewage treatment is crucial to prevent water source contamination.

Sewage Treatment

  • Low-Tech Interventions: Excreta is treated and deposited in situ (e.g., pit latrines).
  • Technological Interventions: Waste is stored and transported for treatment elsewhere.
  • Industrial Sewage Treatment (e.g., UK):
    • Raw sewage is screened and macerated.
    • Heavy stuff settles out.
    • Effluent is pumped into clarifying ponds.
    • Primary sludge is tapped off (potentially for fertilizer).
    • Effluent is put into aeration tanks with added bacteria to break down excreta.
    • Secondary effluent is disinfected and discharged into surface water.
  • Release of untreated effluent into rivers is an increasing problem in the UK.

Natural Water Purification

  • Hydrological Cycle: Relies on evaporation and rainfall to separate waste from clean water.
  • Reservoirs: Retain water.
  • Aquifers: Surface water slowly drains into aquifers, filtering over years, decades, or millennia.

Industrial Methods for Cleaning Water

  • Bottled Water Production:
    • Source water is exposed to ozone.
    • Goes through a series of filters.
    • Undergoes reverse osmosis.
    • Minerals added back in for taste.

Monitoring Water Quality

  • UK Guidance: Acceptable limits for fecal bacteria.
    • E. coli: Zero per 100 ml.
    • Faecal coliforms: Zero per 100 ml.
    • Viable counts: Limits on colony forming units per ml.
    • Indicator organisms: If found, water is deemed unsafe.
  • River water sampling shows levels of fecal coliforms and E. coli exceed safe limits.
  • Sewage release associated with flooding is an issue in the UK.

Waterborne Diseases

  • Bacterial Examples: Cholera (Vibrio cholerae), toxin-producing E. coli.
  • Viral Examples: Norovirus, rotavirus.
  • Eukaryotic Parasites: Cryptosporidium, giardia.

Vector-Borne Diseases

  • Mosquitoes can breed in unsanitary water and transmit diseases.
  • Culex quinquefasciatus: Mosquito breeds in dirty water and carries West Nile Virus and Wuchereria bancrofti.
  • Malaria is also influenced by water management.

UK Water Park Outbreak Example

  • A diarrheal bug outbreak was linked to a water park.
  • Initially suspected to be cryptosporidium, later identified as norovirus.
  • Similar presentation but different epidemiology.

Norovirus

  • A non-enveloped RNA virus, moderate danger to human health.
  • Affects the young (under fives) the most.
  • Global issue, including the UK (lots of infections).
  • Strong winter seasonality.
  • Small genome with three open reading frames.
    • First ORF for replication.
    • Second and third ORFs for structural components (antigens).
  • Antigenic Variation:
    • RNA virus mutates quickly.
    • Diverging populations with different antigens.
    • Immune system selects for better-transmitting viruses.
    • Results in cycles of infection with different genotypes.
    • Re-infection cycles due to outer domain variability.
  • PHE reports weekly on norovirus infections and outbreaks (hospital ward closures).
  • Endemic with seasonal epidemics.

Cryptosporidium

  • A eukaryotic parasite, different from norovirus.
  • Species associated with human infection: Cryptosporidium parvum and hominis.
  • Moderate danger, global concern.
  • UK transmission patterns: Recreational risks (swimming pools, petting zoos), young age.
  • Symptomatic episodes of severe diarrhea contribute to virulence.
  • Complex life cycle: Oocysts are released and ingested by the host.
  • Parasite exits oocyst and develops through stages.
  • Sexual stages lead to oocyst development and release.
  • Larger genome and more virulence factors than norovirus.
  • Critical stages: Excision, adherence to epithelium, invasion, multiplication.
  • Sporadic outbreaks in the UK from water parks and petting zoos.
  • Contamination of water supply (dead animal in the reservoir in Bristol).
  • Associations in transmission due to seasonality and things like field trips, school returns and children of susceptible ages.
  • Outbreaks often seen in swimming pools and petting zoos.
  • Age and sex distribution: Affects under fours and women in their 20s and 30s.

Conclusion

  • Many bacterial diseases are transmitted via water.
  • Access to safe water and sanitation are sustainable development goals.
  • Monitoring is needed to capture outbreaks.
  • Revisions should include.
  • Relationship between microbiology and water.
  • Organisms that cause waterborne diseases.
  • The necessity and practicality of clean and safe drinking water.
  • The balance between the health and disease of populations.