Assessing the adherence to HWT use- A tricky business Ghislaine Rosa Environmental Health Group Department of Disease Control London School of Hygiene and Tropical Medicine University of London Improving health worldwide

HWT is a complex process

High adherence is necessary for achieving health benefits Several Quantitative Microbial Risk Assessment (QMRA) studies have shown that high levels of adherence to HWT use are necessary to ensure a protective effect against waterborne infections (Brown & Clasen 2012, Enger et al. 2013, Hunter et al. 2009). Figure : DALYs averted per 100,000 population, per year, based on assumptions about technology effectiveness (2 log10 reductions in each pathogen class), and varying levels of adherence to HWT and background water quality (Brown and Clasen 2012)

A key measure of interest is thus Adherence to HWT use No standard definition of adherence in the HWT literature. No standardized measure or indicator in the HWT research context Paucity of data on adherence to HWT use in the POU evidence base Consistent and correct use of HWT method over a period of time (Clasen et al. 2009). Total proportion of treated water out of (Brown & Clasen, 2012, Enger et al. 2013).

HWT use is measured in a variety of ways Self- reported use Ask Observational spot-checks Look for clues Availability of treated water Test

HWT use is measures in a variety of ways Self- reported use Ask Observational spot-checks Look for clues Availability of treated water Test Do you usually do anything to your water to make it safer to drink?

HWT use is measures in a variety of ways Self- reported use Ask Availability of treated water Test Is there are filter in the households? Is there water in the lower container? Are there SODIS bottle on the roof? Are their bottles ready to drink? Does the household have chlorine tablets? Observational spot-checks Look for clues

HWT use is measures in a variety of ways Self- reported use Ask Observational spot-checks Look for clues Availability of treated water Test Is there FCR in the reportedly chlorinated drinking water? Are there indicator bacteria in the reportedly treated water?

A key measure of interest is thus Adherence to HWT use No standard definition of adherence in the HWT literature. No standardised measure or indicator in the HWT research context Paucity of data on adherence to HWT use in the POU evidence base Self-reported user Confirmed-user Exclusive-user

A key measure of interest is thus Adherence to HWT use No standard definition of adherence in the HWT literature. No standardised measure or indicator in the HWT research context Paucity of data on adherence to HWT use in the POU evidence base Self-reported user Confirmed-user Exclusive-user However, these do not properly capture adherence to HWT use.

Longitudinal assessment of HWT use Few studies have assess compliance (deveined in a variety of ways) longitudinally. Assessing % of times a household had treated water in 100%, 50%... of all visits. Extra layer of understanding. Figure: Percentage of total households having boiled water in preparation or available for drinking at the follow up visits. Cambodia, (Brown and Sobsey 2012).

Exclusive drinking of treated water at home Even if HWT uptake is high in intervention studies, participants may still consume untreated water, leaving them exposed. Water filter intervention in West Bengal, India: On average 40.1% reported drinking untreated water in previous 24hr, 25% reporting so at 3 or more of all follow-up visits (n=4). Crossover flocculant-disinfectant study in Pakistan and Zambia: 26% and 62% of participant in Pakistan and Zambia reported drinking untreated water (Shaheed A., unpublished). Water filter intervention in the Rep. of Congo: 73% of adults and 95% of children reported drinking untreated water the previous day to the interview (Boisson, Kiyombo et al. 2010). SODIS intervention in India: 85% of participants reported that their children drank untreated water (Rose, Roy et al. 2006).

The household is not the participant’s sole environment Little is known about what water participants consume outside of their home. Though POU intervention target the household, little attention has been directed at recommendations outside the home. School Social Agricultural fields Work

Recommendations Promote the inclusion and reporting of a set of standard indicators of adherence to HWT in all POU intervention/programs. Indicators should be based on combination of self-reported and observed indicators (ideally collected longitudinally). Fine balance should be achieve between repeated assessments and potential participant reactivity/bias. Concomitant consumption of untreated water should be monitored and reported. Guidelines or recommendations should be developed around water consumption outside the home.

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