Environ Sci Technol. 2012 Apr 9.

Linking quantitative microbial risk assessment and epidemiological data: Informing safe drinking water trials in developing countries.

Enger K, Nelson KL, Clasen T, Rose JB, Eisenberg JN.

Intervention trials are used extensively to assess household water treatment (HWT) device efficacy against diarrheal disease in developing countries. Using these data in policy, however, requires addressing issues of generalizability (relevance of one trial in other contexts) and systematic bias associated with design and conduct of a study. To illustrate how quantitative microbial risk assessment (QMRA) can address water safety and health issues, we analyzed a published randomized controlled trial (RCT) of the LifeStraw® Family Filter in the Congo.

The model accounted for bias due to 1) incomplete compliance with filtration, 2) unexpected antimicrobial activity by the placebo device, and 3) incomplete recall of diarrheal disease. Effectiveness was measured using the longitudinal prevalence ratio (LPR) of reported diarrhea. The Congo RCT observed an LPR of 0.84 (95% CI: 0.61, 1.14). Our model predicted LPRs, assuming a perfect placebo, ranging from 0.50 (2.5-97.5 percentile: 0.33, 0.77) to 0.86 (2.5-97.5 percentile: 0.68, 1.09) for high (but not perfect) and low (but not zero) compliance, respectively.

The calibration step provided estimates of the concentrations of three pathogen types (modeled as pathogenic E. coli, Giardia, and rotavirus) in drinking water consistent with the longitudinal prevalence of reported diarrhea measured in the trial constrained by epidemiological data from the trial. Use of a QMRA model demonstrated the importance of compliance in HWT efficacy, the need for pathogen data from source waters, the effect of quantifying biases associated with epidemiological data, and the usefulness of generalizing the effectiveness of HWT trial to other contexts.

IRC has published a literature review focusing on 14 technologies used in Africa in the water, sanitation and hygiene (WASH) sector.

• Parker, A. et al., 2011. Africa wide water, sanitation and hygiene technology review. (WASHTech Deliverable 2.1). The Hague: WASHTech c/o IRC International Water and Sanitation Centre and Cranfield: Cranfield University. 93 p. : 1 box, 9 fig., 1 tab. Includes references.
• Available at: http://wp.me/a1szDW-1o

For each technology there is a description of the range of literature available on it, a concise description of the technology itself, a description of its application, a selection of interesting case studies, and an explanation as to whether the technology meets technical, financial, social and institutional success criteria.

• Included in the Household Water Treatment & Safe Storage technologies are:  Household bio-sand filters,  Constructed rain water harvesting jars,  Life straw and Tippy tap.

For each technology there is a description of the range of literature available on it, a concise description of the technology itself, a description of its application, a selection of interesting case studies, and an explanation as to whether the technology meets technical, financial, social and institutional success criteria.  Only two technologies met all four success criteria: hand dug wells and the India Mark II pump, and the latter only with the caveat that there was a functional maintenance system.

The least successful technology was the Playpump, which was only institutionally successful, and even that was only after significant pressure was put on governments by non-conventional donors. Jerry cans and the gulper only met one success criteria (technical success); they may meet other success criteria but further research is required. Most technologies were technically successful – the only failures were bio-additives and Playpumps. The other success criteria were met by roughly half of the technologies.

Core issues that WASHTech plans to take up further include the appeal of inappropriate technologies like Playpumps and Lifestraws to naive donors, and ways to get government approval for low-cost, locally managed technologies.