Water Quality Interventions to Prevent Diarrhoeal Disease ...

Water Quality Interventions to
Prevent Diarrhoeal Disease:

Effectiveness and Cost-effectiveness

Thomas Clasen
London School of Hygiene & Tropical Medicine
Keppel St., London WC1E 7HT, United Kingdom

[email protected]

Summary

„ Water and the burden of disease
„ Refining the dominant paradigm
„ Cochrane review: water quality

interventions to prevent diarrhoea
„ WHO Cost-effectiveness analysis

Leading Causes of DALYs from Infectious Diseases

2004 World Health Report

DALYs (000s) 100000 94603
90000 84458
80000
70000 61996
60000 46486
50000 34736
40000 21475
30000
20000
10000
0

Respiratory infections
DiarrhoealHIdiVs/eAIasDeSs
TuberMcaullaorsiias
Measles

Leading Causes of Deaths from Infectious Diseases

2004 World Health Report

Deaths (000s) 4500 3963
4000 2777
1798 1566
3500 1271
3000
2500 611

2000
1500
1000

500
0

ReDsiapirrrahtooTreuyalIbHenIrDficVes/ucletAiIaoossDinessSs
Malaria
Measles

Childhood Mortality by Cause

Black RE, Morris SS & Bryce J (2003). Where and why are 10 million children dying every year? Lancet 361:2226-34.

Environmental Barriers
to Faecal-Oral Transmission

„ Primary Barrier

„ Sanitation (proper excreta
disposal)

„ Hygiene (hand washing)

„ Secondary Barriers

„ Water quality (treatment &
safe storage)

„ Water quantity (personal
and domestic hygiene)

„ Hygiene (especially hand
washing)

„ Proper cooking/food
handing practices

Emergence of the
Dominant Paradigm

Percentage reductions in diarrhoeal morbidity rates attributed to

water supply or excreta disposal improvements (Esrey, 1985)

Reduction

Type of Intervention No. Studies Median Range
All Interventions 53 22% 0-100%

Improvements in Water Quality 9 16% 0-90%

Improvements in Water Quantity 17 25% 0-100%

Improvements in Water Quality and Availability 8 37% 0-82%

Improvements in Excreta Disposal 10 22% 0-48%

Reduction in Diarrhoea from
Improvements in Water Quality

Expected reduction in diarrhoeal disease morbidity from improvements in
one or more components of water and sanitation (Esrey, 1991)

Water and Sanitation All Studies Rigorous Studies
Sanitation No. Studies Reduction No. Studies Reduction
Water Quality and Quantity
Water Quality 7 20% 2 30%
Water Quantity 11 22% 5 36%
Hygiene 22 16% 2 17%
7 17% 4 15%
7 27% 5 20%
6 33% 6 33%

Interventions at
Source

Interventions at the Household

What about boiling?

„ Once boiled water begins to cool, it is immediately vulnerable
to recontamination from hands, utensils and added water since
it contains no residual disinfectant and is often stored in open
vessels without a tap.

„ Among 137 households in Pakistan who reported boiling as their only
method for treating water, only 24 (17.5%) of samples from stored water
were free of faecal coliform (Luby 2000).

„ In random sampling of 400 households in Indonesia where
householders were encourage to boil, 47.5% of samples from the

households were positive for E. coli, with 13.3% >101 CFU/100ml (high

risk) and 18.0% <10>100 CFU/100ml (intermediate risk) (Handzel 2005)
„ Another study of water samples from 1027 households in post-tsunami

Indonesia found that neither adequate boiling (maintaining a rolling
boil for at least one minute) nor adequate boiling combined with water
storage in a narrow mouthed container were associated with a decreased
risk of stored water contamination (Gupta 2005).
„ In a six-month study among 216 self-reported boilers in India, treatment
improved water to WHO “safe” level (0 TTC/100ml) in only 49.1% of
monthly samples (Clasen, in preparation)

What about boiling?

„ Boiling water at home has also been associated with higher
levels of burn accidents, especially among young children. In
Sao Paulo, Brazil, boiling water was responsible for 59% of burn
accidents among children under 3 years (Rossi 1998). In Togo,
71.3% of all burn victims admitted to hospital were exposed to
boiling fluids (Houangbevi 1981).

„ A recent cost analysis from India based on both laboratory data
and field observations estimated the annual cost of treating water
by boiling to be US$7.99 per capita for households using LP gas
and US$8.34 for households using wood (McLaughlin 2006).

„ Gillman and Skillicorn (1985) investigated the affordability of
boiling in a village in Bangladesh. Families in the lowest income
quartile would have had to spend 22% of their yearly income on
fuel; even those in the highest income bracket would have spent
10%. For a typical family in the lowest income quartiles, boiling
of drinking water would require an 11% increase in household
budget.

Systematic Reviews—Wright et al.*

„ Systematic review and meta-
analysis of 57 studies measuring
bacteria counts for source water
and stored water in the home.

„ Results: The bacteriological
quality of drinking water
significantly declined after
collection in many settings.

„ Conclusion: Policies that aim to
improve water quality through
source improvements may be
compromised by post-collection
contamination. Safer household
water storage and treatment is
recommended to prevent this,
together with point-of-use water
quality monitoring.

*Wright J, Gundry S, Conroy R (2004). Household
drinking water in developing countries: a systematic
review of microbiological contamination between
source and point-of-use. Tropical Med. Int’l Health
9(1): 106-117

“The encouraging results
from studies of improved
household water
management provide a
sufficient impetus for re-
examining the potential
health impact of
interventions to improve
drinking water quality. . . .
This type of analysis should
ultimately help refine the
dominant paradigm, and
lead to more focused
guidance on the potential
health impact of water
quality interventions.”

Clasen T & Cairncross S (2004).
Household water management:
refining the dominant paradigm.
Trop. Med. Int’l Health 9(2):1-5

Esrey Update: Fewtrell et al.

Fewtrell L, Kaufmann R, Kay D, Enanoria W, Haller L, Colford J (2005). Water, sanitation, and
hygiene interventions to reduce diarrhoea in developing countries: a systematic review and meta-
analysis. Lancet Infect. Dis 5: 42-52.

Effectiveness Data:
Cochrane Review

Clasen T, Roberts I, Rabie T, Schmidt
W, Cairncross S. Interventions to
improve water quality for preventing
diarrhoea (A Cochrane Review). In: The
Cochrane Library, Issue 3, 2006.

Protocol for Cochrane Review*

„ Objective: To assess the effectiveness of interventions to improve the microbiological
quality of drinking water for preventing endemic diarrhoea (note that cholera is excluded)

„ Studies: RCTs and Quasi-RCTs only “A design that randomly allocates groups either to receive the
„ Extracted data includes: intervention or to serve as the control is the ideal and should

„ Age group be utilized when feasible.” (Esrey, 1986)

„ Type of water source, access to water, amount of water, type of sanitation facilities,
hygiene instruction

„ Compliance with intervention

„ Meta-analysis

„ Subgroup Analysis:

„ Type of water quality intervention

„ Simple vs combined (w/ sanitation, hygiene, supply) interventions

„ Source vs household-based interventions

„ Compliance with intervention

„ Ambient water quality

„ Like all Cochrane reviews, results will be updated continuously to reflect new studies that
meet the review’s inclusion criteria

*Clasen T, Roberts I, Rabie T, Cairncross S. Interventions to improve water quality for preventing diarrhoea
(Protocol for a Cochrane Review). In: The Cochrane Library, Issue 2, 2004. Chichester, UK: John Wile & Sons,

Ltd.

No. Studies in Review

40

35

No. Studies 30
Household

25
Source

20

15

10

5

0 Esrey 1991* Fewtrell 2005* Clasen 2005
Esrey 1985*

Review

*Includes observational studies

Effectiveness: Intervention Type (all age)

Effectiveness: Intervention Point (< 5s)

Summary of Effectiveness—All ages

Intervention Type Estimate % Δ 95% CI of Heterogeneity*
(no. trials) (random) (1-RR) Estimate (Chi-square)

Source (6) 0.73 27% 0.53 to 1.01 p<0.00001

Household (32) 0.53 47% 0.39 to 0.73 p<0.00001

Filtration (6) 0.37 63% 0.28 to 0.49 p=0.56

Chlorination (16) 0.63 37% 0.52 to 0.75 p<0.00001

Solar Disinf (2) 0.69 31% 0.63 to 0.74 p=0.73
Flocc/Disinf (7) 0.48 52% 0.20 to 1.16 p<0.0001
Flocc/Disinf (ex Doocy) 0.69 31% 0.58 to 0.82 p=0.08

Impr. Storage (1) 0.79 21% 0.61 to 1.03 n.a.

*Note that in a test for heterogeneity, a low p-value (eg <0.10) suggests an actual underlying
difference in effect between studies that is unlikely to be attributable to chance.

Summary of Effectiveness—Under 5s

Intervention Type Estimate % Δ 95% CI of Heterogeneity
(no. trials) (random) (1-RR) Estimate (Chi-square)
p=.007
Source (4) 0.85 15% 0.71 to 1.02 p<0.00001
p=0.37
Household (25) 0.56 44% 0.39 to 0.81 p=0.004
na
Filtration (5) 0.36 64% 0.24 to 0.53 p<0.00001
p=0.10
Chlorination (12) 0.76 24% 0.67 to 0.86

Solar Disinfec (0) na na na

Flocc/Disinf (7) 0.52 48% 0.20 to 1.37

Flocc/Disinf (6) (ex Doocy) 0.71 29% 0.61 to 0.84

Impr. Storage (1) 0.69 31% 0.47 to 0.81 n.a.

Compliance (n=20)

Effectiveness and Ambient Conditions

Sanitation (using Improved (n=11) Unimproved (n=8*)
0.48 (0.38 to 0.62) 0.67 (0.55 to 0.81)
WHO/UNICEF definitions) P=0.02 P<0.00001

Water Supply (using Improved (n=11) Unimproved (n=24*)
0.57 (0.46 to 0.72) 0.66 (0.55 to 0.72)
WHO/UNICEF definitions) P=0.01 P<0.00001

Water Quantity (using 15L/person/day(n=7) <15L/person/day (n=3*)
0.56 (0.44 to 0.71) 0.88 (0.72 to 1.08) P=0.01
Sphere Project minimums) P=0.005
10-99 FC/100ml (n=14) 100+ FC/100ml (n=7)
Water Quality 0.70 (0.60 to 0.80) 0.69 (0.49 to 0.96)
P<0.00001 P=0.007
Water Access (using Insufficient data

Sphere Project minimums) Insufficient data

Diarrhoea Morbidity

*Excludes Doocy, 2004

Conclusions on Effectiveness

„ The review includes 38 trials covering over 53,000 subjects from 19
countries over 20 years

„ In general, the evidence suggests that in settings with sufficient
water quantity, interventions to improve water quality are
protective against endemic diarrhoea

„ Interventions at the household level are about twice as effective as
those at the source

„ Effectiveness increased with compliance, but not combining
water quality intervention with hygiene promotion, vessel or
improved sanitation or water supply

„ Effectiveness improves with, but is not conditioned upon, the
presence of improved sanitation. Effectiveness is independent of
improved vs unimproved water supply

„ Effectiveness was higher among better quality studies, but the
only blinded trials consistently showed no statistically significant
protection from water quality interventions

Cost-Effectiveness Analysis (CEA)

„ WHO Generalized CEA allows for a comparison of
various interventions (including no intervention, or the null
scenario) on a sector-wide basis for a group of populations
with comparable health systems and epidemiological
profiles

„ Unlike cost-benefit analysis (where all benefits—improved
productivity, increased school time, etc.—are included in
the calculus), CEA is concerned with the realization of a
social objective, such as the prevention of disease

„ The output of a CEA is a ratio (the cost-effectiveness
ratio) between the cost of the intervention and healthy life
years (HLYs) gained, or deaths or disability adjusted life
years (DALYs) averted as a result of the intervention.

Estimating costs

„ Cost data for construction and maintenance of non-reticulated
source-based interventions came from WHO databases
„ useful life of the systems (20 years), plus 5% for operation
and maintenance, plus 5% (dug wells and boreholes) or 10%
(stand posts) for water resource protection

„ Cost data for household-based interventions were collected
from programme implementers responding to special cost
protocol
„ chlorination (estimates from 17 country programmes)
„ filtration (estimates from 4 programmes of locally-fabricated
and commercial ceramic filters )
„ solar disinfection (estimates from 13 country programmes)
„ flocculation / disinfection (estimates from 5 country
programmes)

„ For each intervention, a mean and range of costs were
computed

„ Estimated US$ (2002) per person covered per year

Summary of Cost Estimates

Annual cost per person in US$ of source and household interventions
(error bars represent range of costs from programmes)

$6.00

$5.00 $4.95

$4.00 $3.60
$3.00
Cost $2.00 $3.03

$2.61

$1.88

$1.00 $0.66 $0.63

$- Chlorination Ceramic Solar Flocculation-
Source-Africa Source-Asia Source-LA&C Filtration Disinfection Disinfection
System

Payment Profile--Cost Recovery Potential

„ Costs paid by public sector, NGO or other implementer, users
or some combination thereof; no uniform payment profile.

„ For its SWS products, PSI reports average cost recovery from 19
country programmes of 97% of the production cost; donor
funding used in most countries to cover indirect costs.

„ Householders in Cambodia pay 100% of the production cost for
commercially-distributed ceramic filters, but only 30.6% for
socially-marketed products which are subsidized by donor
contributions; programmatic costs are covered by donor funding
in both cases.

„ Solar disinfection programmes sometimes require beneficiaries
to purchase the required plastic bottles which represent an
average of 71% of the total intervention cost.

„ Consumer contributions toward flocculant/disinfectant products
distributed in non-emergency settings range from 35% to 100%
of the delivered cost of the sachets.

Health Cost Offsets

Costs Averted Variable Data Source Data value (and range)
Unit cost per treatment WHO regional
Health sector $4.30-$9.70 per visit
expenses averted Number of cases unit cost $16.10-$39.70 per day
due to prevention Visits or days per case data
of diarrhoeal WHO BoD data Variable by region
disease Expert opinion
1 outpatient visit per case (0.5-1.5);
Patient Hospitalisation rate WHO Data 5 days for hospitalized cases
(householder) Assumptions Probably much less than 0.5.
costs averted due Transport cost per visit Assumptions 91.8% ambulatory
to prevention of
diarrhoeal disease % patients using $0.50 per visit
transport
Number of cases 50% of patients

Visits or days per case WHO BoD data Variable by region
Expert opinion
Hospitalization rate 1 outpatient visit per case (0.5-1.5);
WHO data 5 days for hospitalized cases
91.8% ambulatory

Adapted from Hutton & Haller (2004). Evaluation of the Costs and Benefits of Water and Sanitation
Improvements at the Global Level. Geneva: World Health Organization

Gross and Net Costs (50% Coverage)

Epidemiological Sub- Intervention Gross Annual Cost Annual Net
Region (and countries) (and range*) in Health Annual
US$ millions Cost Cost in
Offsets US$
in US$ millions
millions
7.3
Afr-E (Botswana, Source 128.4 (50.6-336.8) 121.0
Burundi, Central African 104.7 (104.7-599.4) -125.2
Republic, Congo, Cote Household 480.5 (320.3-610.5) 229.9
d’Ivoire, Democratic chlorination 101.5 (76.1-139.5) 391.4 89.1
Republic of the Congo, Household 192.6 -91.1
Eritrea, Ethiopia, Kenya, filtration 785.0 (157.0-785.0)
Lesotho, Malawi, Household solar 192.6 592.4
Mozambique, Namibia, disinfection
Rwanda, South Africa,
Swaziland, Uganda, Household
United Republic of flocculation
Tanzania, Zambia, disinfection
Zimbabwe)

*Based on range of cost estimates per person per year for each intervention

Calculating DALYs Averted

„ Uses WHO’s PopMod to simulate the effect of a 10-year
intervention on a population over 100 years

„ Population figures by sex and age were entered using WHO
estimates from the Global Burden of Disease (GBoD) 2000

„ As the risk of diarrhoea varies with water and sanitation coverage
levels, the population was then distributed among the various
exposure scenarios for water and sanitation (Prüss 2002)*
prevailing in each country based on the Global Water Supply and
Sanitation Assessment (WHO/UNICEF 2000).

„ The relative risk of diarrhoea was then entered for each sub-
population based on WHO estimates for risks associated with
unsafe water (Prüss-Űstün 2004). These, in turn, are based on
published reviews, large surveys and multi-country studies.

*VI (no improved water supply and no basic sanitation in a country which is not extensively covered by those services, and where water
supply is not routinely controlled; Vb (improved water supply and no basic sanitation in a country which is not extensively covered by
those services, and where water supply is not routinely controlled); Va (improved sanitation but no improved water supply in a country
which is not extensively covered by those services and where water supply is not routinely controlled); IV (improved water supply and
improved sanitation in a country which is not extensively covered by those services, and where water supply is not routinely controlled)

Yearly DALYs Averted (millions) DALYs Averted

Yearly DALYs averted from implementation of water quality interventions to
prevent diarrhoea at 50% coverage level

6

Chlorination
5

Ceramic Filtration
Solar Disinfection
Flocculation Disinfection
Source
4

3

2

1

0 Afr-E Amr-B Amr-D Emr-B Emr-D Eur-B Eur- C Sear-B Sear-D Wpr-B
Afr-D

WHO Epidemiological Sub Region

Annual DALYs Averted

Epidemiologic Intervention Annual DALYs
al Sub-Region averted (and range*)
in millions
Afr-E Source
1.05 (0 to 3.65)

Household chlorination 1.99 (1.34-2.58)

Household filtration 3.4 (2.74-3.87)

Household solar disinfection 1.67 (1.34-1.99)

Household 1.67 (0.97-2.26)
flocculation/disinfection

*Based on 95% confidence interval around pooled estimate of effectiveness

Interpreting CE data

Following the recommendation of the
CMH, WHO uses the following categories
to determine cost effectiveness:

„ $ per DALY averted < GNI per capita =
“highly CE”

„ $ per DALY averted 1-3 * GNI per capita =
“CE”

„ $ per DALY averted > 3* GNI per capita =
“not CE”

„ Afr-E GNI per capita: $369

Cost-Effectiveness Ratios

(US$ per DALY Averted)

Cost Effectiveness Ratio (CER) $9,000 Chlorination
(US Dollars per DALY Averted) $8,000 Ceramic Filtration
$7,000 Solar Disinfection
$6,000 Flocculation Disinfection
$5,000 Source
Cost-Effective
Highly Cost-Effective

$4,000

$3,000

$2,000

$1,000

$0 Afr-E Amr-B Amr-D Emr-B Emr-D Eur-B Sear-B Sear-D Wpr-B
Afr-D

WHO Epidemiological Sub-Regions

Cost-effectiveness ratios*

Sub- Intervention Cost per DALY Cost effectiveness
Region averted (and (CMH Benchmark)
range**) in
US$s

Afr-E Source 123 (14-322) Highly cost effective

Household chlorination 53 (41-447) Highly cost effective

Household filtration 142 (83-223) Highly cost effective

Household solar 61 (38-104) Highly cost effective
disinfection 472 (70-813)
Cost effective (Highly
Household flocculation CE at net cost of
disinfection US$354)

*Gross cost, excluding health cost offsets **Minimum/maximum costs; 95%CI of effectiveness