Soil-transmitted helminthiasis: back to the original point
Authors: David G Addiss
Journal: The Lancet Infectious Diseases (2015)

In The Lancet Infectious Diseases,1Brooker SJ Nikolay B Balabanova D Pullan RL Global feasibility assessment of interrupting the transmission of soil-transmitted helminths: a statistical modelling study.Lancet Infect Dis. 2015; (published online April 15.)http://dx.doi.org/10.1016/S1473-3099(15)70042-3PubMed Google Scholar Simon Brooker and colleagues invite us to think more expansively about what is possible in addressing soil-transmitted helminthiasis (STH). STH is increasingly recognised as a neglected tropical disease with serious consequences for the health, nutrition, education, and economic development of affected populations.2Bundy DA Walson JL Watkins KL Worms, wisdom, and wealth: why deworming can make economic sense.Trends Parasitol. 2013; 29: 142-148Summary Full Text Full Text PDF PubMed Scopus (33) Google Scholar It has been 14 years since the World Health Assembly (WHA) approved resolution WHA54.19—a nuanced call for elimination of STH as a public health problem in areas of low transmission and for reducing morbidity in areas of high transmission.3WHOFifty-fourth World Health Assembly. WHA54.19. Schistosomiasis and soil-transmitted helminth infections.http://apps.who.int/gb/archive/pdf_files/WHA54/ea54r19.pdfDate: May, 22, 2001Google Scholar Since then, efforts have been directed primarily toward reducing STH-related morbidity in a single, although important, risk group, school-age children. We have relied overwhelmingly on one intervention—periodic mass treatment with deworming drugs (preventive chemotherapy)—and drug coverage as a single measure of success. This highly focused approach amounts to a selective reading, or at least a part implementation, of WHA54.19, which also promoted improved access to water, sanitation, and hygiene (WASH) and preventive chemotherapy for women and young children. In the words of the poet Charles Bukowski, a "fresh wild wind" has begun to energise the STH community with improved alignment with WHA's original vision. In 2012, as part of the London Declaration on Neglected Tropical Diseases, Johnson & Johnson and GlaxoSmithKline together pledged 600 million doses of deworming drugs per year, enough to treat all school-age children at risk.4Uniting to Combat Neglected Tropical DiseasesLondon Declaration on Neglected Tropical Diseases.http://www.who.int/neglected_diseases/London_Declaration_NTDs.pdfGoogle Scholar This pledge was followed by major commitments by other donors in April, 2014, and the creation of a new global STH coalition.5Uniting to Combat Neglected Tropical DiseasesDelivering on promises and driving progress: the second report on uniting to combat NTDs.http://unitingtocombatntds.org/report/delivering-promises-driving-progress-second-report-uniting-combat-ntdsGoogle Scholar The intent of the coalition is not only to facilitate scale-up of drug coverage, but also, by engaging a broad network of multisectoral partners, to achieve a lasting effect on STH-related morbidity, and, where possible, on transmission.6STH CoalitionPartners are uniting to stop the worms.http://www.childrenwithoutworms.org/sth-coalitionGoogle Scholar Reported coverage of preventive chemotherapy for at-risk school-age children was 39% in 2013,7WHOSoil-transmitted helminthiases: number of children treated in 2013.Wkly Epidemiol Rec. 2015; 90: 89-94Google Scholar still below the 2020 target of 75% set by WHO.8WHOSoil-transmitted helminthiases: eliminating soil-transmitted helminthiases as a public health problem in children: progress report 2001–2010 and strategic plan 2011–2020. World Health Organization, Geneva2012Google Scholar However, 29 countries have already achieved the WHO target.7WHOSoil-transmitted helminthiases: number of children treated in 2013.Wkly Epidemiol Rec. 2015; 90: 89-94Google Scholar Should they set their sights higher and pursue the more ambitious goal of interrupting transmission? If so, what investments will result in the greatest likelihood of success? In which of these countries is transmission interruption most readily achievable? Brooker and colleagues offer a comprehensive framework and a robust analysis to inform the debate around these important questions. They identified ten key indicators that could be expected, on theoretical and practical grounds, to contribute to the likelihood of interrupting transmission. They considered not only factors related to parasite biology, such as transmission intensity and sanitation, but also indicators of programme capacity, such as logistics, infrastructure, governance, financial resources, and strength of the health and education systems. Such a broad perspective is especially relevant for STH, since drug delivery relies on existing platforms, such as schools, vitamin A supplementation, and other neglected tropical disease programmes. Which of the ten indicators identified by Brooker and colleagues are most crucial? The investigators compared four different weighting methods and, using a composite score, ranked countries into quintiles according to feasibility of interrupting transmission. Not surprisingly, high-feasibility countries had low transmission intensity, less environmental exposure to STH (ie, improved water and sanitation), and more highly functioning systems. Some readers will undoubtedly quibble with the ranking of specific countries, but the investigators' detailed presentation of their methods and assumptions invites us all into conversation and to action. The STH community has rightly focused on scaling up preventive chemotherapy in areas of highest transmission and greatest need. However, countries vary tremendously in their capacity. For some, reaching 75% drug coverage in school-age children by 2020 will represent a monumental achievement. There are many others for which interrupting transmission is not only possible, but feasible. Brooker and colleagues identified 41 such countries. They also excluded from the analysis 57 more potentially endemic countries, small island-states, and countries undergoing rapid economic development. Many of these countries have pockets of ongoing transmission that, with improved monitoring and targeted interventions, could inform eventual end-game strategies for countries where transmission interruption is currently less feasible. Little is known about what combinations of WASH and drug coverage across different risk groups will be needed in various settings.9Anderson RM Truscott JE Pullan RL Brooker SJ Hollingsworth TD How effective is school-based deworming for the community-wide control of soil-transmitted helminths?.PLoS Negl Trop Dis. 2013; 7: e2092Crossref PubMed Scopus (112) Google Scholar, 10Truscott J Hollingsworth TD Anderson R Modeling the interruption of the transmission of soil-transmitted helminths by repeated mass chemotherapy of school-age children.PLoS Negl Trop Dis. 2014; 8: e3323Crossref PubMed Scopus (33) Google Scholar, 11Strunz EC Addiss DG Stocks M Ogden S Utzinger J Freeman MC Water, sanitation, hygiene and soil-transmitted helminth infection: a systematic review and meta-analysis.PLoS Med. 2014; 11: e1001620Crossref PubMed Scopus (453) Google Scholar, 12Anderson R Truscott J Hollingsworth TD The coverage and frequency of mass drug administration required to eliminate persistent transmission of soil-transmitted helminths.Philos Trans R Soc Lond B Biol Sci. 2014; 369: 20130435Crossref PubMed Scopus (131) Google Scholar It would be wise for the STH community to invest in learning from such situations now. By establishing appropriately ambitious STH targets in specific settings, we will mobilise resources, reveal what is possible, clarify strategies, and strengthen our resolve. To paraphrase Lao Tzu, by being far reaching, we return to the original point of the WHA vision for STH control. I have received grants from Johnson & Johnson and GlaxoSmithKline, outside of the submitted work. Global feasibility assessment of interrupting the transmission of soil-transmitted helminths: a statistical modelling studyThe interruption of STH transmission is feasible, especially in countries with low intensity of transmission, supportive household environments, strong health systems, and the availability of suitable delivery platforms and in-country funds, but to achieve local elimination of STH an intersectoral approach to STH control will be needed. Full-Text PDF Open Access