Only 6 pathogens guilty for most childhood diarrhea, new study reveals

Sierra Leone, May 2011. Aged just two years old, Abdul Kamara’s life was threatened by severe diarrhea, but he's just received rehydration treatment and is beginning to recover. (Credit: Doune Porter / GAVI / DFID / Flickr)

Scientists are delighted with a new study that suggests vaccines and antibiotics just need to target six pathogens to tackle 78 percent of cases of childhood diarrhea, the second leading cause of death in children under 5.

“It’s not a hopelessly long list of infections that we can’t do anything about,” Eric Houpt, professor of infectious diseases and international health at the University of Virginia and co-author of the study, told the Guardian.

The study, published in the Lancet and funded by the Bill & Melinda Gates Foundation, also revealed that pathogens – bacteria, viruses, parasites and other disease-causing microorganisms – are responsible for nearly 90 percent of childhood diarrhea cases, almost double what researchers thought just three years ago.

The World Health Organization estimates that diarrhea, which causes malnutrition and dehydration, kills about 760,000 children under the age of 5 every year, second only to pneumonia. “Infection is spread through contaminated food or drinking-water, or from person-to-person as a result of poor hygiene,” the WHO reported.

Most of cases of childhood diarrhea, Houpt said, are in Africa and south Asia. The researchers accordingly analyzed over 10,000 samples from seven countries across those regions: Bangladesh, India, Pakistan, Gambia, Kenya, Mali and Mozambique.

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The study is actually a re-examination of the Global Enteric Multicenter Study (GEMS) from 2013, which estimated only 51.5 percent of childhood diarrhea cases were attributable to pathogens and pinpointed four major pathogens among more than 40 using conventional diagnostic methods.

Revisiting the GEMS study with new molecular diagnostic techniques confirmed the four previously identified pathogens and added two others, which together accounted for 77.8 percent of diarrhea cases. Shigella and rotavirus led the pack, with adenovirus, ETEC (a type of E. coli), cryptosporidium and campylobacter following.

Additionally, about 40 percent of the samples examined showed more than one infection present, while some children carried pathogens without exhibiting symptoms.

“These results imply that prioritizing vaccine development for these six pathogens could lead to a substantial decrease in diarrhea burden among children younger than 5 years over the next few decades, as has been seen for rotavirus,” wrote Karen Keddy, Anthony Smith and Nicola Page of the National Institute for Communicable Diseases in South Africa in an accompanying comment.

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Rotavirus is currently the only identified pathogen with a vaccine, though vaccines are in the works for shigella and ETEC, according to the Guardian.

But previous studies also found variances according to environmental factors. “…The poorest of the poor might succumb to different pathogens at different rates in different parts of the world, which potentially affects prioritization of interventions,” wrote Keddy, Smith and Page.

The authors acknowledge that many questions remain to be answered and a lot of work lies ahead.

“For the moment, though,” wrote Keddy, Smith and Page, “we must be satisfied with knowing that the excessive burden of diarrhea in children younger than 5 years in developing countries can now be reduced by targeting specific responsible pathogens on the basis of the invaluable data gleaned by [this study].” And that’s worth celebrating.

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Joanne Lu

Joanne Lu is a South Carolina-based writer and editor dedicated to global development, poverty alleviation and social justice. After a year in Rwanda, she now covers Asia and the Pacific. Find her on Twitter @joannelu or email joanne@humanosphere.com.