Friday, November 30, 2012

After a long paper on pathogens in water and on hands

Apologies for the long 'dry spell' in this blog; I will endeavor to post more regularly going forward!  JD

Hands and water as vectors of diarrheal pathogens in Bagamoyo, TanzaniaEnviron Sci Technol. 2012 Nov 26.Mattioli MC, Pickering AJ, Gilsdorf R, Davis J, Boehm AB.

Abstract: Diarrheal disease is a leading cause of under-five childhood mortality worldwide, with at least half of these deaths occurring in sub-Saharan Africa. Transmission of diarrheal pathogens occurs through several exposure routes including drinking water and hands, but the relative importance of each route is not well understood. Using molecular methods, this study examines the relative importance of different exposure routes by measuring enteric bacteria (pathogenic Escherichia coli) and viruses (rotavirus, enterovirus, adenovirus) in hand rinses, stored water, and source waters in Bagamoyo, Tanzania.

Viruses were most frequently found on hands, suggesting that hands are important vectors for viral illness. The occurrence of E. coli virulence genes (ECVG) was equivalent across all sample types, indicating that both water and hands are important for bacterial pathogen transmission. Fecal indicator bacteria and turbidity were good predictors of ECVG, whereas turbidity and human-specific Bacteroidales were good predictors of viruses.

ECVG were more likely found in unimproved water sources, but both ECVG and viral genes were detected in improved water sources. ECVG were more likely found in stored water of households with unimproved sanitation facilities. The results provide insights into the distribution of pathogens in Tanzanian households and offer evidence that hand-washing and improved water management practices could alleviate viral and bacterial diarrhea.

Tuesday, June 5, 2012

New paper from the group: Is household contamination associated with improved sanitation facilities?

Fecal Contamination and Diarrheal Pathogens on Surfaces and in Soils among Tanzanian Households with and without Improved Sanitation
Amy J. Pickering, Timothy R. Julian, Sara J. Marks, Mia C. Mattioli, Alexandria B. Boehm, Kellogg J. Schwab, and Jennifer Davis
Environmental Science & Technology. Volume 46, Issue 11, pp 5736–5743
DOI: 10.1021/es300022c

Abstract: Little is known about the extent or pattern of environmental fecal contamination among households using low-cost, on-site sanitation facilities, or what role environmental contamination plays in the transmission of diarrheal disease. A microbial survey of fecal contamination and selected diarrheal pathogens in soil (n = 200), surface (n = 120), and produce samples (n = 24) was conducted in peri-urban Bagamoyo, Tanzania, among 20 households using private pit latrines. All samples were analyzed for E. coli and enterococci. A subset was analyzed for enterovirus, rotavirus, norovirus GI, norovirus GII, diarrheagenic E. coli, and general and human-specific Bacteroidales fecal markers using molecular methods. Soil collected from the house floor had significantly higher concentrations of E. coli and enterococci than soil collected from the latrine floor. There was no significant difference in fecal indicator bacteria levels between households using pit latrines with a concrete slab (improved sanitation) versus those without a slab. These findings imply that the presence of a concrete slab does not affect the level of fecal contamination in the household environment in this setting. Human Bacteroidales, pathogenic E. coli, enterovirus, and rotavirus genes were detected in soil samples, suggesting that soil should be given more attention as a transmission pathway of diarrheal illness in low-income countries.

Tuesday, May 22, 2012

Dhaka team receives 2 awards!

Congratulations to our Dhaka / Engineers for a Sustainable World  project team (, who were awarded a first place win and a $20k prize this evening in the Social Entrepreneurship Challenge sponsored by BASES (Business Association of Stanford Entrepreneurial Students)! 

This recognition comes on the heels of the team being recommended for an EPA P3 grant for their work earlier this month.

The team has been working very hard over the past two quarters to develop an in-line chlorinator appropriate for low-income urban neighborhoods that rely on shared water points for their drinking water supply. This summer they will field test their prototype in the slums of Dhaka, Bangladesh, in collaboration with the International Center for Diarrheal Disease Research. Their technology has the potential to benefit not only the 10 million slum dwellers of Dhaka, but the half a billion urban residents worldwide whose piped networks deliver water rendered unsafe by biological contamination. 

Congratulations to team Dhaka on a terrific job!!
Keegan Cooke
Kara Bennett
Valerie Bauza
Yoshika Crider
Nabil Mansouri
Isaac Madan
Olivia Vagelos
Camil Diaz
Dr. Amy Pickering (mentor)
Eng. Suprio Das (collaborator)

Sunday, May 13, 2012

Delhi has its own "Great Stink"

Roughly 150 years ago, the House of Commons in London's Parliament had to be evacuated because of the foul odors emanating from the River Thames on whose banks the houses of Parliament were built. Subsequent fallout from this "Great Stink," as it came to be known, as well as from recurrent cholera epidemics, eventually resulted in the construction of the London sewer system.

Today the BBC is reporting that India's upper house of parliament was similarly evacuated, also because of poor management of human wastes. Although not nearly as dramatic as the London case, perhaps this experience will spur lawmakers in India to take a hard look at the fact that half of the country's population lacks access to even the most basic form of sanitation!


Saturday, April 28, 2012

New paper from the group:

Does User Participation Lead to Sense of Ownership for Rural Water Systems? Evidence from Kenya

Sara J. Marks, Jennifer Davis

World Development

Abstract: Despite broad acceptance of the idea that “sense of ownership” among users is critical to infrastructure sustainability in developing countries, little is known about what sense of ownership is, or its drivers. We present a novel measure of sense of ownership for piped water systems using empirical data collected from 1140 households in 50 rural Kenyan villages. This study establishes an empirical referent for households’ sense of ownership. We find that some, but not all, types of participation enhance community members’ sense of ownership for rural water projects.

Wednesday, March 28, 2012

Water MDG met at the global level

We had good news this World Water Day--at the global level, the Millennium Development Goal for access to improved water supply has been met, some 2.5 years ahead of schedule. During the period 1990-2012 more than 2 billion people gained access to improved water supply services (as per the Joint Monitoring Program definitions). Quite a feat. More information here:

Water sector specialists were quick to point out that 780 million people (roughly a tenth of the world's population) are still lacking access to this basic service, relying for their water supplies on rivers, ponds, unprotected springs and wells. What hasn't been pointed out is that more than three times this number--2.5 billion, or ~36% of the global population--are now considered to have access, although they have pretty low levels of service, e.g., a congested handpump sited a few hundred yards from their home. Such non-networked water sources have, in many cases, not been shown to reduce infectious disease or confer time savings as compared to unimproved sources. Will ticking the 'has access' box for these households reduce the pressure on governments to continue working for higher levels of service?

Fortunately there is a vigorous debate underway about the definitions used to monitor progress in the sector post-2015. It is tough to identify valid and reliable indicators of access to improved water supply that can be feasibly monitored on a regular basis. It is even tougher to figure out who should pay for collecting those data, from which so many institutions and organizations benefit.

Monday, February 13, 2012

New paper from the group: Walk times to water source and health

Freshwater Availability and Water Fetching Distance Affect Child Health in Sub-Saharan Africa

Amy J. Pickering and Jennifer Davis
Environ. Sci. Technol., Article ASAP
DOI: 10.1021/es203177v
Publication Date (Web): January 12, 2012

Currently, more than two-thirds of the population in Africa must leave their home to fetch water for drinking and domestic use. The time burden of water fetching has been suggested to influence the volume of water collected by households as well as time spent on income generating activities and child care. However, little is known about the potential health benefits of reducing water fetching distances. Data from almost 200 000 Demographic and Health Surveys carried out in 26 countries were used to assess the relationship between household walk time to water source and child health outcomes. To estimate the causal effect of decreased water fetching time on health, geographic variation in freshwater availability was employed as an instrumental variable for one-way walk time to water source in a two-stage regression model. Time spent walking to a household’s main water source was found to be a significant determinant of under-five child health. A 15-min decrease in one-way walk time to water source is associated with a 41% average relative reduction in diarrhea prevalence, improved anthropometric indicators of child nutritional status, and a 11% relative reduction in under-five child mortality. These results suggest that reducing the time cost of fetching water should be a priority for water infrastructure investments in Africa.