[HWTS] W01 - Water Borne Sicknesses | Waste Management Engineering

diseases can reduce the quality of life
- before causing death
- this can mean the years lived mean much less
disability adjusted life years (DALY)
- YLL = number of deaths * life expectancy at age of death
- YLD = number of cases * disability weight * avg duration of case
- DALY = YLL + YLD
DALY is a metric to establish the severity of a disease
- depends on the weight assigned to the disease

diarrheal causes - DALY

in 2008, volgens WHO:

diarrhea causes 52.5 M DALYs/year
- 3.1% of global total
- 9% of child disease burden
india: 13.6 M
china: 3.9 M
nigeria 3.9 M
pakistan 3.3 M
drc 3.3 M
- 10% of all DALYs

2010 study by IHME
IHME: Institute for Health Metrics and Evaluation
- not endorsed by WHO
  - methods not full transparent
  - not given full access to results for evaluation
  - methodological differences
key differences with WHO
- revised disability weights
  - online process and field survey
- no hygiene risk factor
  - data avilable was not string enough to add this meaningfully
- no disease burden from ‘improved’ water and sanitation
link to study:
- https://vizhub.healthdata.org/gbd-compare/
- global disease trends and by country maybe analyzed here
- explore diarrheal disease trends here
burden of disease from poor wash is high
diarrheal disease is a leading cause of mortality and morbidity

there are thousands of organisms that can cause water-borne diseases
broadly categorized as four types of pathogens
- helminthis
- protozoa
- bacteria
- viruses
human hair is 100 microns thick on an average

protozoans are 10-50 microns
they are a one cell eukaryotes
- their cell has a nucleus unlike prokaryotes bacteria
some protozoans form en egg-like cyst to survive in harsh conditions
- exposure to extreme temperature
- chemicals
- long periods without food and water
many protozoans are parasites, and cause diseases like
- malaria
- giardia
entamoeba histolytica and cryptosporidium dysentry cause severe diarrhea
entamoeba causes dysentry or bloody diarrhea
- only 10-20% develop symptoms
- causes 100000 deaths in a year
- affects adults more than children
cryptosporidium forms cysts which are about 5 microns in diamter
- highly resistant to treatment
- major cause of death among HIV/AIDS patients
infectious dose for protozoans is low
- a single cyst causes disease

they are prokaryotic,
- i.e. they have no nucleus
they are everywhere
- soil
- deep ocean
- acidic hot springs
a gram of soil or a mL of water contans several million bacterial cells
they are 1-2 microns in size
a vast mejority of bacteria are harmless
- some are beneficial to humans
- a lot of bacteria in the gut helps process food and deliver nutrients to the human body
- a few of them cause diseases
  - cholera
  - trachoma
  - salmonella
e.coli is universally found in human and animal feces
- not normally pathogenic
- preferred indicator bacteria to identify presence of feces contamination in water
some strains of e.coli cause disease
- one group of these pathogens is the enterotoxigenic e.coli or ETEC
- top five pathogens isolated from children with diarrhea
  - affects small children
shigella is another common bacterial pathogen
- a distant relative of e.coli
vibrio cholera causes cholera
- spreads very rapidly under the right conditions
  - crowding
  - poor sanitation and hygiene
  - after natural disasters
  - refugee camps
  - peri-urban slums
- casues severe diarrhea and if not treated within hours, death
- 3 - 5 million cases every year
- 100000 - 120000 death every year

0.1 microns or smaller
they have no independent metabolism
- they grow or reproduce within a living host cell
- cannot multiply within the environment
most viruses are host specific
- causing disease in humans or specific animals
rotaviruses and hepatitus A and E viruses are the most widespread waterborne viruses
rotavirus: 75 nanometers
- main pathogen causing diarrheal disease
- infected people shed large number of viruses in their feces
  - 10^11 viruses per gram
  - takes only 10-100 virus particles to cause infection
- estimated cause of 500000 deaths in 2004
  - 85% deaths in low-income countries like africa and asia
hepatitis A
- spreads through food and water
- direct contact with infected people
hepatitus E: 30 nanometers
- thousands of hepatitis E viruses lined up
- would still be smaller than human hair
- mainly spread through drinking water
- 50000 deaths related to Hepatitis E
polio
- water borne virus
- 223 cases in 2012, down from 350000 cases in 1988
- only three countries have it
  - pakistan
  - nigeria
  - afghanistan
- even one infected child poses a risk to all other children

transmission is through drinking water
it’s tiny larvae live in fresh water
- are eaten by small aquatic insect called copepods
- copepods are about 1 mm, visible to naked eye
when the copepods are subjected to HCl in the human stomach, it dies and releases the guinea worm larvae
- this larvae grows into adult worms in the stomach
  - usually called a John since it occurs in Johns a lot
- they can reach a length of one meter
  - and can be as wide a spaghetti noodle
the worm migrate through the body and emerge out of the skin, usually near the feet
the worm has to be removed slowly,
- winding it up and pulling it out of the body
- bit by bit over weeks
- is extremely painful
it often creates sores and blisters
- people soak feet in water to relieve pain
- the worm then discharged thousands of larvae into the water
- completing the transmission cycle
number of cases have dropped from 3.5 million in 1986 to 542 in 2012
since copepods are large, they are removed by simple sand filters for drinking water