Environmental Engineering Reference
In-Depth Information
Drinking water is typically stored in 10-liter plastic buckets or open jerry cans of
5-20 l in the household. Baseline assessments of the drinking water quality in the home
indicated a median contamination of thermotolerant coliforms (TTC) of 32 TTC/100
ml (interquartile range (IQR) = 3-344; n = 223). Samples of at least one water source
per community were tested for
Giardia lamblia
and
Cryptosporidium parvum
. The
two parasites were detected in 18/24 and 11/23 water samples, respectively.
Parasites were detected by using immunomagnetic separation and polymerase
chain reaction
(PCR) techniques [11]. Piped water, when available, is not chlorinated.
Design
Twenty-seven of 78 communities in the study area fulfilled the selection criteria (geo-
graphically accessible all year round; at least 30 children <5 year; reliance on con-
taminated drinking water sources). Two communities were excluded because of other
ongoing health and hygiene campaigns, and three communities withdrew participa-
tion before baseline activities because of a change in political leadership. Community
health workers undertook a census and identified households with at least one child <5
year. All children <5 year were enrolled in the participating villages.
We pair-matched communities on the incidence of child diarrhea as measured in
an 8-week baseline survey [12]. The intervention was then assigned randomly to one
community within each of the 11 consecutive pairs. This assignment was done dur-
ing a public event because key political stakeholders were worried about possible
backlash, public outcry, or a drop-off in group participation, which would result from
providing some members with a new benefi t while others got “nothing.” It was agreed
that a public drawing event was necessary to increase perceived fairness among the
participating district and municipal authorities. Three authorities, the district head (Al-
calde), representatives of the Ministries of Health and Education, and the deputy of
the farmers union (Central Campesina), each drew one of two balls (with community
codes inscribed that were randomly assigned beforehand) representing paired com-
munities from a concealed box. It was agreed that the fi rst draw assigned the com-
munity to the intervention arm. The group allocation was immediately recorded in a
protocol by an independent witness. Subsequently, the witness disclosed the sequence,
informed the community members and the authorities present in the town hall, and all
drawers signed the protocol.
We explicitly chose community-level randomization because important compo-
nents of the intervention (i.e., community efforts to encourage adoption of the SO-
DIS-method) would occur at the community level. Randomization below the com-
munity level would not refl ect the reality of scale-up program implementation, and we
would not have captured the potential community-level reinforcement of the behavior
change. Furthermore, community-level randomization is considered ethically optimal,
because participants expect to equally benefi t from interventions within their com-
munity [13-15]. Additionally, we believed cross-contamination (of the intervention)
between the intervention and control communities was minimized by vast geographi-
cal dispersion of the communities. Control communities knew from the beginning of
the study that they would receive the intervention as part of the NGO's development
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