Water-borne diseases 11-12

Question 1

What is the global distribution of access to clean water and sanitation?

Answer 1

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

Question 2

What are the 4 categories of the Bradley Classification of Water-Related Infections?

Answer 2

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

Question 3

What is a water-washed transmission referring to?

Answer 3

Person-to-person transmission due to inadequate personal + domestic hygiene

Question 4

What is a water-based transmission referring to?

Answer 4

Transmission of infections via an obligatory aquatic host e.g. snail
1st host = humans
2nd host = snails

Question 5

What is a water-related insect vector referring to?

Answer 5

Transmission by insects which breed in (or bite near) water

Question 6

What is a water-borne transmission referring to?

Answer 6

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

Question 7

What is the global impact of enteric water-borne disease?

Answer 7

One third of population, mostly children are infected w/ intestinal worms –> malnutrition, anaemia, malabsorption syndrome, intestinal obstruction

Question 8

Give 2 examples of enteric diseases

Answer 8

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

Question 9

What is the cycle of disease transmission for water-borne diseases?

Answer 9

Infected individual –> Faeces –> Water or crop contamination –> Oral ingestion`

Question 10

What does a single barrier imply?

Answer 10

‘Complete’ control by disinfection; treatment to eliminate pathogens e.g. pasteurisation, thermophilic digestion, alkaline/lime

Question 11

What does multiple barriers imply?

Answer 11

Transmission without disinfection/treatment to reduce pathogens + restrictions on land use e.g. avoid application to crops that may be eaten raw

Question 12

What policy does the UK have to control sludge?

Answer 12

A Code of Practice Agricultural Use of Sewage Sludge

Question 13

How is sludge treated in developing countries?

Answer 13

Sludge is dried under the sun and stored for more than 6 months

Question 14

What are wastewater stabilisation ponds?

Answer 14

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

Question 15

What are the advantages of wastewater stabilisation ponds?

Answer 15

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

Question 16

What are the disadvantages of wastewater stabilisation ponds?

Answer 16

Large land area restrictive in urban sites

Question 17

Describe the epidemiology of diarrhoeal disease?

Answer 17

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

Question 18

What is the definition of diarrhoea?

Answer 18

Passage of three or more loose or watery stools per 24 hours or an increase in stool frequency or liquidity

Question 19

What is WASH?

Answer 19

Water, Sanitation, Hygiene

Question 20

What are the interventions used to decrease morbidity and mortality?

Answer 20

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

Question 21

Give an example of a mode of sanitation

Answer 21

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

Question 22

Describe the steps in a sanitation ladder (Butler and Davies, 2004) x4

Answer 22

Covered latrine
Covered + ventilated latrine
Pour flush latrine`
Septic tank

Question 23

Describe the common methods for treating water at household level in LIC settings

Answer 23

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

Question 24

What are the technical factors of low-cost sanitation methods?

Answer 24

Local availability of water
Soil infiltration rate
Number of users
Space available
Emptying frequency
Other things disposed in toilet

Question 25

What other factors can affect sanitation apart from technical solutions?

Answer 25

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