A new study today said the number of childhood diarrhoea cases has been “substantially underestimated” and it may be nearly twice as high as the previous analysis in seven countries of Asia and Africa, including India, where it kills 13 children under the age of 5 every hour.
“The number of cases of childhood diarrhoea attributable to pathogens like bacteria, parasites, viruses or other infections have been substantially underestimated and may be nearly twice as high as previous analysis suggests.
“The analysis of over 10,000 samples from Bangladesh, India, Pakistan, The Gambia, Kenya, Mali and Mozambique finds that Shigella and rotavirus were the most common infections among children aged under five, followed by adenovirus, enterotoxin-producing E coli (ETEC), Cryptosporidium, and Campylobacter,” a new research published in The Lancet said.
The findings come from a re-analysis of samples from the Global Enteric Multicenter Study (GEMS).
Previous estimates of the infectious causes of diarrhoea were based on a variety of different detection methods, but this study, for the first time, uses a molecular diagnostic testing method called quantitative real-time PCR (qPCR) to test for 32 pathogens.
Researchers re-analysed stool samples from 10,608 children with and without diarrhoea obtained from regions in seven countries in Asia (Bangladesh, India and Pakistan) and Africa (The Gambia, Kenya, Mali, and Mozambique).
“The original GEMS study published in 2013 estimated that 51.5 per cent of childhood diarrhoea cases could be attributed to pathogens but the new re-analysis finds the proportion is much higher at 89.3 per cent.
“The original study identified four major pathogens – rotavirus, shigella spp, cryptosporidium spp and heat-stable enterotoxin-producing E coli (ST-ETEC). This re-analysis reaffirmed these four and added two others – adenovirus 40/41 and campylobacter jejuni/coli.
“Together, these six pathogens accounted for 77.8 per cent of all diarrhoea. Among the children who had a diarrhoea- causing pathogen, about half had more than one infection, highlighting the challenges of treating multiple infections,” the study said.
According to Health Ministry figures, in India, 1.2 lakh children under the age of five succumb to diarrhoea every year. This translates to 328 diarrhoeal deaths every day and 13 every hour.
While an oral vaccine for rotavirus exists, the findings highlight the need for prioritisation of Shigella and ETEC vaccines.
Lead author Eric R Houpt of University of Virginia in Charlottesville in the US said childhood diarrhoea remains an enormous problem made more confusing by the long list of possible infections, the difficulties in diagnosis and the large number of undiagnosed cases.
“We developed sensitive quantitative methods that levelled the diagnostic playing field and closed the diagnostic gap. Sadly, the ‘healthy’ control children carried on average four infections, so determining the cause of diarrhoea is tricky.
“We found that when an infection replicates and reaches a certain threshold, then diarrhoea happens. Our study was able to identify what that threshold is, pathogen by pathogen. In so doing, we concluded that six infections constitute the vast majority of disease, and these should be heavily prioritised.
“An oral vaccine for rotavirus exists, and development of vaccines for Shigella and ETEC are underway. Cryptosporidium, Campylobacter, and adenovirus now need a lot more attention,” Houpt said.
The authors point to some limitations, including that the analysis may underestimate pathogens that are shed with high frequency, so longitudinal studies will be needed to further understand these pathogens.
Additionally, although the findings should provide evidence to prioritise vaccines for certain pathogens, vaccine development relies on subtyping of infections which was not provided in this study.
Finally, the authors warn that qPCR does not assess antimicrobial resistance, and therefore the technology should be used in conjunction with conventional culture methods to detect antibiotic resistant pathogens.
“These results imply that prioritising vaccine development for these six pathogens could lead to a substantial decrease in diarrhoea burden among children younger than five years over the next few decades, as has been seen for rotavirus,” said Karen Keddy of Centre for Enteric Diseases, National Institute for Communicable Diseases, Johannesburg in South Africa and a co-author.