A recent Cochrane review has sparked a debate among scientists concerning the effectiveness of mass deworming programs for improving childhood outcomes. To showcase these views PLOS Neglected Tropical Diseases has released 4 papers which explore responses to the Cochrane review and propose options for moving forward.
The Cochrane review examines 45 trials of mass deworming programs for schoolchildren. Included studies were all randomized control trials (RCTs - taken as the gold standard level of evidence) comparing deworming treatment with either a placebo or no treatment in children aged 16 years or under. The review concluded that treating all children in an endemic area with deworming drugs had little or no effect on average weight gain, anaemia or cognition.
Mass deworming programs are currently recommended by the World Health Organization to treat soil-transmitted helminths, so the Cochrane review could have important consequences for future discussions of public health interventions. These four PLOS Neglected Tropical Diseases articles illustrate a range of reactions from the scientific community. Authors from the World Health Organization question the suitability of the Cochrane methodology and its reliance on RCTs as the highest standard of evidence. RCTs are constructed over a relatively short time period whereas recovery from helminth infection is a long term process relying on cumulative rounds of regular treatment. They also point out that as mass deworming programs only directly affect a small proportion of infected individuals any statistical significance in outcomes will be diluted due to the large number of uninfected children who are not affected by treatment.
Researchers from the University of California Berkeley put forward the case for mass treatment, listing studies excluded from the Cochrane trail that indicate the benefits of deworming programs. Researchers from the University of Kelaniya in Sri Lanka point out that of 59 records of deworming from 2012-2015 only 10 were assessed by the Cochrane review and only 4 included in the final analysis. By excluding non-RCT methodology, the Cochrane review leaves itself biased against outcomes more likely to be recognized and observed through observational studies or case-reviews.
The Cochrane review proposes screening and treating only infected individuals. While this would improve the statistical significance of observed outcomes individual screening would be significantly more expensive to carry out as a mass public health initiative and relies on screening technology that may not be available in endemic communities. Authors from the University of Washington conclude that the Cochrane review should be seen as an opportunity to open a discussion on the best available forms of evidence and best practices for research studying soil transmitted helminths. This will allow a fully informed debate of the most useful public health initiatives, maintaining cost-effectiveness while still ensuring efficient treatment of children in endemic areas.