Children’s Health Deficits due to Diarrhoea: Effects of Water Supply and Sanitation Systems in Slums with Different Water Logging Conditions

ABSTRACT This population-based epidemiologic study investigated the associations of individuals’ sociodemographic statuses, sanitary systems and habits, water supply and drainage conditions with diarrhoea incidences among 707 children younger than 5 years who were living in slum communities with various water logging patterns in Dhaka, Bangladesh. We conducted a homevisiting survey during the pre-monsoon period from December 2006 to April 2007. Nine slum communities were selected that had been experiencing five different water logging conditions. One non-water logging community was selected as a control. The Disability Adjusted Life Years (DALYs) were calculated using data on diarrhoea morbidity and mortality. Although DALYs lost because of diarrhoea were very small in a non-inundation type community, but were the highest in persistent drainage inundation type communities. Among the factors correlated with DALYs, control variables for mother’s illiteracy and household income strongly attenuated most of these correlations to statistical null, except for mother’s age (less than 15 years-old), using hanging latrine and not washing hands before eating, and after defecation. In conclusion, water logging conditions and socio-economic statuses may strongly contribute to diarrhoea incidence in the city’s slum communities. In such communities, interventions to address both water logging and socio-economic conditions may be critical for reducing diarrhoea incidences.

Children’s Health Deficits due to Diarrhoea: Effects of Water Supply and Sanitation Systems in Slums with Different Water Logging Conditions

Kabirul Ahsan MOLLAH*, Kei NISHIDA*, Naoki KONDO* and   Zentaro YAMAGATA*

* Interdisciplinary Graduate School of Medicine and Engineering, the University of Yamanashi

4-3-11, Takeda, Kofu, Yamanashi 400-8511, Japan

ABSTRACT

This population-based epidemiologic study investigated the associations of individuals’ socio-demographic statuses, sanitary systems and habits, water supply and drainage conditions with diarrhoea incidences among 707 children younger than 5 years who were living in slum communities with various water logging patterns in Dhaka, Bangladesh We conducted a home-visiting survey during the pre-monsoon period from December 2006 to April 2007 Nine slum communities were selected that had been experiencing five different water logging conditions One non-water logging community was selected as a control The Disability Adjusted Life Years (DALYs) were calculated using data on diarrhoea morbidity and mortality Although DALYs lost because of diarrhoea were very small in a non-inundation type community, but were the highest in persistent drainage inundation type communities Among the factors correlated with DALYs, control variables for mother’s illiteracy and household income strongly attenuated most of these correlations to statistical null, except for mother’s age (less than 15 years-old), using hanging latrine and not washing hands before eating, and after defecation In conclusion, water logging conditions and socio-economic statuses may strongly contribute to diarrhoea incidence in the city’s slum communities In such communities, interventions to address both water logging and socio-economic conditions may be critical for reducing diarrhoea incidences

Keywords: DALY, diarrhoea, poor urban community, water logging

INTRODUCTION

Poor environmental sanitation and the unsafe disposal of human and solid wastes contribute to the high incidence of water-borne diseases, including diarrhoeal diseases, malaria and dengue fever (WHO/UNICEF 2001) Many of these infections occur in developing nations that have sanitation problems (Nsubuga et al 2004) In these nations, most low-lying lands used for squatter settlements or slums have hanging latrines or open-field defecation Due to lack of access to potable water supplies, the poor rely mainly on shallow wells, rivers, streams and ponds for daily water needs (Nevondo and Cloete 1999) In most cases, water from these sources, which may be faecally contaminated, is used directly without treatment (WHO 1993) During 2002, it was estimated that 4% (60.7 million Disability Adjusted Life Years [DALYs]) of the global burden of disease and 1.6 million deaths per year were attributed to unsafe water supplies and sanitation, including lack of hygiene (WHO 2002)

Acute diarrhoeal diseases are the major causes of morbidity and mortality in developing countries, such as Bangladesh, where 1 in 10 children die before their fifth birthday (Bern et al 1992; Petri et al 2000) Bangladesh’s capital city, Dhaka, is a typical flood-prone urban habitat It is periodically devastated by floods, resulting in stagnant water and drainage problems (JICA 1990; JICA 1987; SWMC 1997) The inadequate

Address correspondence to Kei NISHIDA, Interdisciplinary Graduate School of Medicine and

Engineering, the University of Yamanashi, Email: nishida@yamanashi.ac.jp

drainage in nearly 60% of slums assures that many slums are at risk of flooding (CUS

et al 2006), faecal contamination (Fawell 2007) and consequent cases of diarrhoea, whereas childhood diarrhoea is not prevalent in areas with higher elevations (Brussow 1993) Inavailability of sanitary facilities also contributes

Among slums in Dhaka, only over 35% of households use hygienic latrines, whereas, for garbage management, 35% just use vacant land and water bodies as waste disposal sites This neglected population in slums has become a major reservoir for a wide spectrum of adverse health conditions, including most prevalent diarrhoeal diseases, intestinal problems, fever and skin diseases (Rahman et al 1989; Hussain et al 1999;Rahman and Shahidullah 2001; Sclar et al 2005), and has a high infant mortality rate (Hoque and Selwyn 1996; Arifeen et al 2001) Consequently, urban slum dwellers have been identified as a particularly vulnerable group regarding health status by Bangladesh’s Poverty Reduction Strategy Planning (PRSP) of the Government of Bangladesh, 2005

In 2000, the United Nations Millennium Declaration pledged to tackle this challenge by setting specific goals and attempting to achieve significant improvements in the lives of

at least 100 million slum dwellers worldwide by the year 2020 (UN 2007; Riley 2007)

In light of these worldwide phenomena, the government of Bangladesh is also committed to achieving the targets embodied in the UN Millennium Declaration by

2015 (World Bank 2006a, 2007) Thus, demonstrating the impact of water logging on diarrhoeal incidence in Dhaka City, and how household and individual factors interact with this impact are of utmost necessity in finding prime locations for slum development programmes

The objectives of this study are: (1) to estimate variations in children’s diarrhoea incidence among Bangladesh’s urban slum communities based on their inundation conditions, and (2) to assess the populations’ demographic factors, socioeconomic status, sanitary facilities and attitudes as potential factors associated with diarrhoea incidence among slums with varying flood and inundation conditions

METHODS

Study population

Based on flood and inundation experience, slum communities in Dhaka were selected from different representative water logging situations categorized in terms of duration and type of inundation We proposed 4 levels based on duration of inundation (short-term, long-(short-term, persistent and non-inundation) and 5 types of inundation (rainy, stagnant-water, heavy-rainy, monsoon-flood and drainage-water inundations) Ten sub-districts were selected by integrating information regarding water logging for the past 5–10 years that was obtained from interviews with the concerned authorities and dwellers as well as on-site measurements from a preliminary survey conducted in December 2006 The slum communities selected were situated within 1 km from the Urban Development Centre project offices of the Slum Development Department of the Dhaka City Corporation (Table 1 and Figure 1) Thus, for the ‘code name’, we used the initials of inundation duration, inundation type and the respective sub-district name of

each studied community; the code name will be used for the following discussion as

corresponding to each community

Table 1 - Inundation categories and code names of studied slum communities

Duration based Type based

Long-term Stagnant-water Demra 86 LSD

Persistent Drainage-water Lalbagh 65 PDL

Heavy-rainy Sabujbagh 27 PHS

Stagnant-water Muhammadpur 47 PSM

A household was defined as people sharing the same cooking pot (Hussain et al 1999)

Using this definition, 820 households in 10 sub-districts were identified during the

preliminary survey Of the 350 households satisfying the predefined criteria (35

households from each community), presence of children less than 5 years of age, water

supply and no improvement in sanitation (WHO/UNICEF 2003; WHO/UNICEF JMP

2000) were selected for additional questionnaire surveys Informed consent was

obtained from the parents or guardians

• SHU

• LMK

• SDG

• LHT

• PHS

• NCD

• LSD

• PDL

• PSM

• SRM

N 

DHAKA CITY

Sub district  boundaries Canals RiverEmbankment

1         0       1        2 km

Fig 1 - Study site map in Dhaka, Bangladesh; adapted by authors (Source:

http://www.en.wikipedia.org)

Diarrhoea incidence and questionnaire

Among water-borne diseases, diarrhoea is a condition of morbidity that is relatively easy to monitor- as it occurs rather frequently Respondent mothers easily understand its definition, and there is little variation of symptoms from mothers’ perceptions (Killewo and Smet 1989): the occurrence of 3 or more loose, watery or mucous stools

in the previous 24 h (WHO 2009) We followed the definition of acute diarrhoea by the World Health Organization (WHO) and UNICEF: an attack of sudden onset that usually lasts 3–7 days but may last up to 10–14 days (Park 1997) We used a period of

3 intervening diarrhoea-free days to differentiate a new incidence of diarrhoea (Baqui et

al 1991) The Child Health Epidemiology Reference Group of WHO (WHO/CHERG 2004) summarized a table for the definition of diarrhoeal deaths that was used in this survey for verbal autopsy, which has a very good agreement with hospital diagnosis (Kalter et al 1990; Pacque-Margolis et al 1990)

In April 2007, investigators asked each mother to follow her child/children for 2 weeks after recruitment, and during a preliminary visit, they described how to confirm the presence of diarrhoea They also demonstrated how to mark the day that symptoms first started and the day that the illness ended or the child succumbed to the illness The information was reported to investigators at the follow-up two weeks later The 2-week interval was chosen because diseases and symptoms assessed and reported by inhabitants can be imprecise; high reliability depends on shorter recall periods (Byass et

al 1994) Final data were recorded only if the data were consistent with the mothers’ performance levels in defining the symptoms and counting the days of illness

We developed a series of household-level questionnaires based on the World Bank (World Bank 1999), WHO (WHO 1991) and United Nations guidelines (UN 2005,

2001, 1998, 1984) These questionnaires had modified wording to improve suitability for the study population after pre-testing during a preliminary visit The interview survey requested information regarding hygiene practices, water supply and sanitation situations, household income, maternal educational attainment and demographic characteristics (Mollah et al 2009)

Septic tanks and pour-flush latrines connected to a sewer line were considered as sanitary latrines for the purpose of this study Unsanitary types consisted of cesspools, pit latrines and storage tank facilities; open and homemade latrines consisted of hanging latrines Drainage pipes from latrines were usually connected to sewer lines, and human excreta were directly discharged without treatment

Calculation of Disability Adjusted Life Years (DALY)

Morbidity and mortality cases of diarrhoea for children less than 5 years old and their significance were used to estimate DALYs in each community (Murray and Acharya 1997) DALYs combine years of life lost (YLL) with years lived with disability (YLD) These are standardized using severity weights (Murray et al 1996) and durations of morbidity (Murray et al 2002) DALYs, due to premature mortality, are calculated

using standard expected YLL from model life tables and, due to disability from age a to age (a + L), consists of the following equation derived by Murray (1994) and Homedes

(2000):

(Eq 1) 

Here, β is an age-weighting parameter, C is an age-weighting correction constant, r is a time preference discount rate, D represents stages of physical disability that

consequently affected daily living activities (productive activities, for instance school or

work), a is set on an age at which the child suffered a particular disease or died and L

assumes 2 value sets, YLD and YLL

The DALY formula was established with a lost time concept of disability due to suffering from any specific disease, including fatality The value was estimated based

on life expectancy in a developed country (e.g Japanese life expectancy for male and female) as well as an age-weighted lost time discounting value for the developed world,

used for global DALY calculation Accordingly, we decided upon C (0.16243), β (0.04) and r (0.03) as the default values for a global context In contrast, applied available local data set for D = 1 in case of death, 0.3, 0.5 in case of diarrhoea, a = 1, 3 for each

age group (assumed from the interview survey, average age of infant and child,

respectively) and L, for morbidity calculation, YLD = 0.21, 0.28, 0.36, 0.43 (assumed

from the interview survey) and, for mortality calculation, YLL = 62 years for male and

63 years for females in Bangladesh as of 2005 (WHO 2007)

Furthermore, the default values for β, C and r have no influence for the age group

younger than 15, considered as work force, which sets the priority for the time lost at

this age For D, its influence depends on each subject’s degree of end point (range 0–1) This requires quantitative and qualitative estimations to define the value of D, a technical task for this study as well The value for L also influences a greater variation for cases with very low life expectancy, whereas for a, its influences are lower and

higher at a cut-off age of 20

The team physician assessed the degree of dehydration according to the WHO criteria (WHO 1990) The severity of each diarrhoeal disease incidence was calculated using a numerical scoring system (Ruuska et al 1990), which we modified into 2 classes

Accordingly, in our study, D is decided with numerical values for adjusted morbidity

days and scored for different severities, which also substantially reduced error on the

value based only on qualitative estimation All of the above default values for β, C and

r have an influence, but only for ages over 5 years Thus, in our study, these imparted

no influences, as our subjects were children less than 5 years of age

Statistical analyses

After the DALY calculations by community types, we evaluated the factors that correlated with the DALYs lost among the 10 communities using Pearson correlation coefficient and multivariate partial correlation analyses All analyses used SPSS software version 15 (SPSS Inc., Chicago, USA, 2007)

RESULTS AND DISCUSSION

Forty percent of households had 7 or more family members, and 40% of the studied households had monthly household incomes less than 30 USD Age less than 15 years

and illiteracy of respondent mothers were also higher (greater than 40%) in this survey, except for the non-inundated community (NCD), compared to the national average (BBS 2007) (Figure 2-a)

In the NCD, tap water was used in 100% of households and 80% had sanitary latrines, whereas in other communities, only 23–54% used tap water and 0–9% had sanitary latrines (Figure 2-b and c) In particular, slums under persistent water logging conditions were likely to have worse sanitary conditions (i.e relatively higher rates of unsanitary hanging latrines or no latrine) (Figure 2-c)

Almost 67% of households among the surveyed households did not practice any

type of water treatment at home, while around 14% and 17% used only simple filtering with cloth or boiled water before drinking, respectively (Figure 2-d) We found that children’s open-field defecation occurred in 51% of all the communities, except for the NCD, where defecation in the open was not a common cultural feature For example, in the persistent and drainage-water type community (PDL), none of the children used latrines (Figure 2-e) There were remarkable differences for not washing hands among communities, both before eating and after defecation, which can be calculated from the Figure 2-f, with ranges of 17–47% and 18–85%, respectively Almost all communities showed a common tendency for washing hands before eating, but not washing hands after defecation, and PDL had a remarkably high rate of not washing hands after defecation (Figure 2-f)

On average, diarrhoea was the most common disease in the study subjects Half of them suffered from diarrhoea during the 2 week observation period, while the combined cumulative incidence of other diseases, including fever, pneumonia, jaundice, tonsillitis and skin disease, was far below that of diarrhoea However, diarrhoea incidence varied greatly across communities, and PDL had the highest rate (Table 2) There were no significant variations in days of illness on a per case basis or for frequency of incidences in each community

We calculated the average frequency of diarrhoeal incidences from cumulative incidences by dividing by the number of sick children during two weeks in the respective communities Children living in locations with stagnant and drainage water problems had comparatively higher suffering days (range 5–6 days) and frequency of

frequency as a rate of incidences per sick child and average of these rates in a corresponding community were used for comparison among communities The DALYs lost were 173–843-fold higher in the inundated locations compared to those in the non-inundated locations (Table 2) Among the inundation categories, differentials of DALYs lost were larger for the short-term compared to the long-term (1.27-fold higher,

on average), and for the long-term compared with the persistent (1.45-fold higher, on average)

10

20

30

40

50

60

70

80

SRM SHU SDG LSD LHT LMK PDL PHS PSM NCD

( a )

0 10 20 30 40 50 60 70 80 90 100

Family members ≥7

Girls aged <5yrs

Mothers aged <15yrs

Respondent mother’s illiteracy

Family’s monthly income < USD30

Filtering water by cloths at home Boiling/warming water at home Alum treatment of water at home

No treatment of water at home

0

10

20

30

40

50

60

70

80

90

( c )

0 10 20 30 40 50 60 70 80 90

Households using overhead hanging latrine

Households using sanitary latrine

Households using unsanitary latrine

Households using no latrine at all

Hand washing with soap before eating Hand washing without soap before eating

No hand washing before eating Hand washing after defecation with soap Hand washing after defecation without soap

No hand washing after defecation

0

10

20

30

40

50

60

70

80

90

100

( b )

0 10 20 30 40 50 60 70

( e )

Households using tap water supply

Households using ground water

Households using surface water

Households using mixed sources of water

Households with children defecating in open field Households with children defecating in room Households with children defecating in verandah Households with children defecating in latrine

Family members ≥7  

Households with children defecating in latrine  

Fig 2 - Household survey findings for (a) family status, utilities for (b) water supply and (c) sanitation systems and attitudes for (d) water treatment at home, (e) children’s defecation habits and (f) hygiene practices

Note: Communities code name, SRM: Short-term and Rainy, SHU: Short-term and Heavy rainy, SDG: Short-term and Drainage, LSD: Long-term and Stagnant, LHT: Long-term and Heavy rainy, LMK: Long-term and Monsoon flood, PDL: Persistent and Drainage, PHS: Persistent and Heavy rainy, PSM: Persistent and Stagnant, NCD: Non inundation and Control

Table 2 - Disease burden due to diarrhoea among 707 children by community characteristics (rate/1000 population) during a 2-week pre monsoon period

Morbidity Mortality DALYs lost Ratio of

DALYs lost (vs NCD) Non-inundation community (NCD) 133 0.00 0.70 1.00

Short-term inundation communities (average) 466 19.8 222 336

Long-term inundation communities (average) 373 30.0 281 426

Persistent inundation communities (average) 543 36.4 410 622

Pearson correlation analysis showed that DALYs lost were positively associated with the following factors: girls less than 5 years old, having mothers less than 15 years old, mothers’ illiteracy, lower household income, not using a tap water supply, using an overhead latrine or not having a latrine, not filtering or boiling water, no water treatment procedures, defecating in open field rather than a latrine and without hand washing (with and without soap) before eating and after defecation However, control variables for mother’s illiteracy and household income strongly attenuated most of these correlations to statistical insignificance, except for mother’s age (less than 15 years old), using a hanging latrine and without hand washing before eating and after defecation (Table 3)

0 0.2 0.4 0.6 0.81 1.2 1.4 1.6 1.82

0 1 2 3 4 5 6

SRM SHU SDG LSD LHT LMK PDL PHS PSM NCD

Average Suffering days per incidence Average frequency of incidences

Fig 3 - Diarrhoea morbidity severity by communities

Note: Average frequency of incidence was calculated from the accumulated incidences divided by the total

rate of incidences per sick child

Table 3 – Health losses due to diarrhoea associated with some selected determinants

DALYs lost Partial correlation with DALYs lost

Pearson Correlation a, b Correlation b

Family status

Girls aged <5yrs 0.71* -0.48

Mothers aged <15yrs 0.95** 0.85**

Respondent mother’s illiteracy 0.80** Control variable

Family’s monthly income < USD30 0.86** Control variable

Utilities:

Water supply

Households using tap water supply -0.83** -0.32

Households using ground water 0.71* 0.20

Households using surface water 0.56 -0.21 Households using mixed sources of water 0.09 0.23

Sanitation system

Households using overhead hanging latrine 0.76* 0.75*

Households using sanitary latrine -0.65* 0.03 Households using unsanitary latrine -0.30 -0.72 Households using no latrine at all 0.85** 0.57

Attitudes:

Water treatment at home

Filtering water by cloths at home -0.83** -0.59

Boiling/warming water at home -0.80** -0.02

Alum treatment of water at home -0.63* -0.34

No treatment of water at home 0.88** 0.44

Habit of defecation

Households with children defecating in open field 0.71* -0.10

Households with children defecating in room -0.29 0.38

Households with children defecating in verandah 0.19 -0.32

Households with children defecating in latrine -0.76* 0.07

Hygiene practices

Hand washing with soap before eating -0.79** -0.13

Hand washing without soap before eating 0.31 -0.32

No hand washing before eating 0.85** 0.76*

Hand washing after defecation with soap -0.93** -0.73* Hand washing after defecation without soap -0.14 0.39

No hand washing after defecation 0.72* 0.00

* Correlation is significant at the 0.05 level (2-tailed) a. List wise N=10

** Correlation is significant at the 0.01 level (2-tailed) b. df=6

This population-based epidemiological study provides a framework for quantifying

health implications associated with water supply, sanitation facilities and hygiene

practices for typical urban slum communities that experience various types of

inundation in Dhaka, Bangladesh We found that a slum situated in a non-inundated

community had the lowest DALYs lost due to diarrhoea as well as the best water supply

utilities, socioeconomic status and sanitary attitudes According to the types of

inundation, stagnant and poorly drained situations, such as PDL, were in a severely

vulnerable position in terms of disease burden, family characteristics, community

utilities and hygiene practices Our multivariate analysis demonstrated that household

socioeconomic status could explain most of the correlations of DALYs lost with water supply utilities and sanitary attitudes

The findings of this study suggest that socioeconomic status is an important, indirect cause of diarrhoea, which was also found by other investigators (Kunii et al 2002; Emch 1999) As a consequence of social selection, even among slum communities, people in lower socioeconomic positions may live in slums with worse water logging conditions and is a strong environmental hazard for diarrhoea These populations might also be less educated in terms of sanitation, which can also critically increase the risk for diarrhoea incidence However, it should be noted that the correlation between DALYs lost due to diarrhoea and some factors relevant to hygiene practices, including using overhead hanging latrines, not washing hands before eating and after defecation,

as well as young maternal age, remain statistically significant even after controlling children’s socioeconomic status Therefore, poor habits of hand washing and toilet use may be important factors for inducing diarrhoea that are independent of socioeconomic status In addition, extremely young mothers (less than 15 years old) may also be a crucial risk factor, as these mothers might be less likely to have opportunities to acquire skills to protect their children from water-borne diseases

Importantly, the study findings suggest that poor drainage may be more problematic when inundation is persistent, and that the duration of the inundation condition does not matter if the inundation type is heavy rainy This may be because persistently non-drained water can be severely contaminated by dwellers’ unfavourable sanitary attitudes such as open-field defecation, while even if it is persistent, if inundation occurs due to heavy rain, the rain water can flush away contaminated water in a short time Regardless of the types of inundation, except for non-inundated areas, our study population used contaminated water without sufficient treatment It has been reported that the use of surface or ground water, rather than tap water, is a risk for diarrhoea (Chongsuvivatwong 1994)

However, there was a possibility that community water sources might have been contaminated due to imperfect distribution systems (Clark et al 1993; Geldreich 1996)

or secondary contamination during collection (The Sphere Project 2004), and that some households’ water might have been contaminated during handling (Sutherland et al 2002; Molbak et al 1989)

Our multivariate analysis showed that water treatments such as boiling and filtering through cloth were ineffective This might have been due to improper procedures and dirty cloths used for treatments at home, as reported earlier (Molla et al 2008) Recent studies have supported the protective health effects arising from well-managed water treatment (Sobsey 2002; Sobsey et al 2003) In addition, water used for washing hands might have been contaminated, probably by secondary contamination due to storage, as some of the storage tanks had been used for a long time without cleaning However, hand washing practices appeared to contribute to DALYs lost and constituted a significant association similar to that described by Shahid et al 1996 In fact, household drinking water treatment would be a paramount necessity in the slum communities in our studied area to reduce the incidence of diarrhoea