Water-borne diseases 11-12 Flashcards
What is the global distribution of access to clean water and sanitation?
Increase in population –> increased demand for water –> increases waste production –> megacities = concentrated sources of pollution and population
- Water sources are better in urban areas vs rural areas
- Africa, China and India have > 50% of population w/ no access to sanitation - impacts on quality and food that we eat
- 40% of hospital beds occupied by pts w/ enteric infection
Climate change affects water supply
What are the 4 categories of the Bradley Classification of Water-Related Infections?
Water-washed/inadequate water supply for hygiene e.g. trachoma (bacterial infection of the eye)
Water-based e.g. Schistosomiasis
Water-related insect vector - reproduce in aquatic environment e.g. malaria + stagnant water pools or drainage
Water-borne e.g. bacteria, viruses, protozoa and helminth worms
What is a water-washed transmission referring to?
Person-to-person transmission due to inadequate personal + domestic hygiene
What is a water-based transmission referring to?
Transmission of infections via an obligatory aquatic host e.g. snail
1st host = humans
2nd host = snails
What is a water-related insect vector referring to?
Transmission by insects which breed in (or bite near) water
What is a water-borne transmission referring to?
You drink/eat it
Transmitted via faeco-oral route - usually affects the small intestine as nutrients degraded here
Can infect w/ good sanitation –> vector transmission e.g. flies, rodents
Asymptomatic carriers handling food
What is the global impact of enteric water-borne disease?
One third of population, mostly children are infected w/ intestinal worms –> malnutrition, anaemia, malabsorption syndrome, intestinal obstruction
Give 2 examples of enteric diseases
Ascaris Lumbricodes = persistent enteric parasites which produce extremely resistant eggs which can survive several years in soil - to treat, must collect faeces + treat faecal matter
Taenia sagniata = influences economic quality of meat products; has a human host and livestock host. Eggs are in faeces + passed into environment –> cattle + pigs infected by feeding –> humans infected by eating raw or undercooked infected meat
What is the cycle of disease transmission for water-borne diseases?
Infected individual –> Faeces –> Water or crop contamination –> Oral ingestion`
What does a single barrier imply?
‘Complete’ control by disinfection; treatment to eliminate pathogens e.g. pasteurisation, thermophilic digestion, alkaline/lime
What does multiple barriers imply?
Transmission without disinfection/treatment to reduce pathogens + restrictions on land use e.g. avoid application to crops that may be eaten raw
What policy does the UK have to control sludge?
A Code of Practice Agricultural Use of Sewage Sludge
How is sludge treated in developing countries?
Sludge is dried under the sun and stored for more than 6 months
What are wastewater stabilisation ponds?
Reduces the organic content and removes the pathogens from wastewater
Wastewater enters on one side of the waste stabilisation pond + exits as ‘effluent’ after several days in the pond which treatment processes take place
Well managed wastewater and faecal sludge treatment processes are effective in preventing enteric pathogen transmission
What are the advantages of wastewater stabilisation ponds?
V Effective pathogen destruction
Effective design criteria well established
Low cost
No energy expenditure
Simple to operate and maintain
High resilience + buffering
Wide range of industrial, domestic + agricultural wastes treated
What are the disadvantages of wastewater stabilisation ponds?
Large land area restrictive in urban sites
Describe the epidemiology of diarrhoeal disease?
Leading cause of childhood mortality + morbidity - contributed to 15% of all under-5 deaths –> 2nd leading cause of death
Developing countries/LICs carry the largest burden - four fifths of under-5 mortality occur in SSA and S Asia
What is the definition of diarrhoea?
Passage of three or more loose or watery stools per 24 hours or an increase in stool frequency or liquidity
What is WASH?
Water, Sanitation, Hygiene
What are the interventions used to decrease morbidity and mortality?
Time to settle in containers Filtration through cloth or sand Chlorine drops Solar disinfection (SODIS) Storage of household water is just as important; women are the best targets for household water treatment education programmes
SDG 6 - achieve access to adequate and equitable sanitation and hygiene for all; halving the proportion of untreated wastewater; expand international cooperation + capacity-building; participation of local communities
Give an example of a mode of sanitation
Toilets - isolate and treats human waste. Can decrease:
- Faecal-oral infections e.g. diarrhoea
- Helminth infections e.g. hoodworm
- Insect vectors e.g. mosquitoes, flies
- Aquatic intermediate hosts e.g. snails, schistosomiasis
Describe the steps in a sanitation ladder (Butler and Davies, 2004) x4
Covered latrine
Covered + ventilated latrine
Pour flush latrine`
Septic tank
Describe the common methods for treating water at household level in LIC settings
Dry + on-site: pit latrines, VIP latrines, compost
Wet + on-site: Pour flush latrines, septic tank systems
Dry + off-site: Bucket latrines, vault latrines
Wet + off-site: sewerage, constructed wetland
What are the technical factors of low-cost sanitation methods?
Local availability of water Soil infiltration rate Number of users Space available Emptying frequency Other things disposed in toilet
What other factors can affect sanitation apart from technical solutions?
Political, social +/- economic: issues of education, affordability, gender equality
Motivating factors for sanitation
- Improving health
- Personal dignity + privacy
- Urban environment
- Safety
Integrated interventions are needed - behavioural change intervention most crucial
