Identifying a top cause of disease in children

Researchers working to fight the second most lethal disease for children under five may be missing the mark, according to a new Stanford study. In places like rural Bangladesh, young children often contract diarrhea at home after exposure to pathogens in feces that have entered the environment, usually from household animals. Interventions for curbing diarrheal diseases typically  promote safe drinking water and handwashing practices, but these interventions often fail to safeguard this vulnerable group. 

Stepping back and reexamining typical child behavior, postdoctoral fellow Laura Kwong, along with a collaborative group of researchers from the US. and Bangladesh, found ingestion of contaminated soil plays a central role in contracting  diarrheal disease. Kwong has worked closely with communities in Bangladesh and around the world devising simple engineered solutions to public health problems, such as improvements to latrines, chicken coops and household flooring. Below, she discusses her background in public health, her recent study bringing together long-term research of children’s exposure to fecal pathogens and the potential of the work for improving health around the world.

What does your new study reveal that might surprise people in the field?

Kwong: Stanford has been a part of the WASH Benefits trial, which tested the effect of different interventions, including an improved pit latrine, a child potty, a scooper for animal feces, handwashing stations and water treatment with a water storage container, to see if they could reduce children’s diarrhea. All of these interventions are at the household-level. I wondered about how much they would affect children –  many don’t use latrines and potty training is not common. 

I really wanted to better understand exposure from a child's perspective, so our staff used video cameras to record everything children did. I looked at their activities all day and what they put in their mouths that could expose them to fecal contamination and the pathogens that are sometimes in feces. What we see is children put dirt, dirty hands and dirty objects in their mouths. Every parent knows this, but it’s not anything that’s traditionally been looked at in water, sanitation and hygiene research when thinking about how to reduce children’s exposure to fecal contamination. It turns out that for children in rural Bangladesh who are 6 to 24 months old, 40 percent of the E. coli ingestion comes from soil they put in their mouth. That tells us the pathway we should be looking at and trying to intervene upon, and that's far more important in this setting than drinking water. 

What led you to this area of study?

Kwong: Diarrheal deaths have been quite steadily decreasing over time, but it's still the number two killer of children over one month old and under five years old, so we're trying to figure out ways to reduce that. There’s a diagram that shows the ways feces from the environment are transmitted into a child's mouth. I remember in the first year of my PhD at Stanford asking which of those pathways is the most important, and nobody had an answer. And I thought, “Wait a second, really? Why are we putting all of our effort into treating drinking water when the primary problem could be a different pathway?” In order to create the most benefit for young children, we need to use our limited resources to focus on the most impactful interventions. 

How did this change your perspective on WASH work?

Kwong: In settings where animals are unconfined and can defecate wherever they choose, soil can be highly contaminated with animal feces. In Bangladesh, 89 percent of households have chickens that are roaming around, so it’s no surprise that soil is contaminated. Soil can also be contaminated by human feces from latrines that are overflowing or emptied improperly, open defecation by children or adults, or improper disposal of child feces. Direct and indirect ingestion of this soil transfers those animal or human feces to the child. This is a previously underappreciated pathway by which children may be ingesting fecal matter and may result in diarrhea. It’s important to continue efforts to improve water quality and feces management. In many settings both rural and urban, it may also be very important to think about animal husbandry practices to avoid animal feces from contaminating the soil where children play.

How do you envision these findings being implemented to help combat diarrheal disease?

Kwong: Now that we’ve identified ingestion of contaminated soil and children putting dirty hands in their mouths as a problem, we’re thinking about what we can do about it. It is nearly impossible to keep children’s hands clean after washing them, so instead we are focusing on preventing and reducing fecal contamination of soil in and around the household. The primary solutions we’re exploring are animal husbandry strategies and improved, washable flooring.

I’m working on a project in Bangladesh to figure out how households can transition chickens from sleeping under a child’s bed to sleeping outside. If chickens live outside, then chicken feces won’t be swept into the air when cleaned from under the bed. Developing the habit of cleaning up animal feces quickly can also be helpful. In addition to working on chicken coops, I also work on improved flooring with an NGO called EarthEnable. It grew out of the Design for Extreme Affordability program at the Stanford d.school and operates in Rwanda and Uganda. EarthEnable floors can be made from local materials that are varnished to make a water-resistant seal. The result is a floor that is 10 times cheaper than concrete and is still smooth and able to be mopped so it’s easier to clean than a dirt floor. I think these types of household infrastructure changes can be very effective because you can create a one-time change in the physical environment and motivate formation of new habits, like sweeping. 

Where is this work going next? 

Kwong: I’ve expanded this idea of looking at children’s exposure to fecal contamination to other countries. I’m currently doing studies in Uganda, Indonesia and Fiji, and we’re about to add Mali. It’s really useful to be able to compare children in different locations and ask if the frequency that children put their hands in their mouth is universal, which helps us estimate children’s exposure even in places we haven’t been, or if those frequencies are culturally specific.

Coauthors on the study include: Ayse Ercumen, North Carolina State University; Amy J. Pickering, Tufts University; Joanne E. Arsenault, UC Davis; Mahfuza Islam, Sarker M Parvez,  Leanne Unicomb and Mahbubur Rahman, International Centre for Diarrhoeal Disease Research; Jennifer Davis and Stephen P. Luby, Stanford University.