Review of the 2017 WHO Guideline: Preventive chemotherapy to control soil-transmitted helminth infections in at-risk population groups. An opportunity lost in translation

On 29 September 2017, the World Health Organization (WHO) published a new Guideline on the implementation of preventive chemotherapy (PC) programmes for the control of soil-transmitted helminthiasis (STH) infections. The document supersedes two WHO publications that, in addition to STH, simultaneously addressed the control of schistosomiasis, onchocerciasis, and lymphatic filariasis (LF) by the coordinated implementation of regular, systematic, large-scale interventions that provide anthelminthic drug treatment to all individuals at risk of morbidity caused by these infections. Mass drug administration (MDA) is the key component in its implementation. With recent advances in understanding of the epidemiology of STH and the changing funding landscape, the neglected tropical diseases (NTDs) community has eagerly awaited new guidance from WHO on PC. This is to set and safeguard the public health stage beyond the original targets and goals defined by the WHO NTD roadmap of 2012 that inspired the London Declaration and the commitment of several partners towards the control and/or elimination of NTDs. The scientific rationale for this was summarised in an article published in the Lancet in 2012 and also sustained by the series of the Disease Control Priorities by the World Bank. Linked to this new knowledge, revised PC guidelines that incorporate novel information and address STH transmission and morbidity control were advocated in a number of publications. The scientific backbone for the suggested changes was rigorous analyses that employed epidemiological data and models of transmission to derive optimum solutions for both morbidity and transmission control based on MDA coverage of various age groupings in affected communities.

WHO describes PC as the large-scale preventive treatment against helminthiasis and trachoma with safe, often single-dose, quality-assured medicines facilitated by several large-scale donations . Without doubt, PC programmes represent a major public health intervention, delivering over 1 billion treatments every year (1.5 billion in 2016), and provide an essential standard of care for those at risk of infection or associated disease. PC policy is endorsed by a series of World Health Assembly (WHA) resolutions—including those of 2001, 2012, and 2013—and a series of informal consultations and Expert Committee reports . 

Regrettably, the opportunity to build on the previous momentum has been missed. We have identified five critical areas where the 2017 WHO guideline does not provide the necessary leadership:

1. Absence of guidance on the most urgent current issues, including school-based versus community-wide PC, drug combinations to increase anthelminthic efficacy, the use of new diagnostics, clearer protocols for monitoring anthelminthic efficacy/resistance, new prevalence thresholds for PC, morbidity control versus elimination end-game targets.
2. No mention of the need to accurately monitor drug coverage and individual compliance at successive rounds of MDA.
3. Insufficient discussion about available data on deworming and what this tells us about successes and failures, and approaches to address any data deficits.
4. Absence of any WHO recommendation for schistosomiasis, onchocerciasis, and LF, as the new guideline only considers STH and ignores opportunities for integration.
5. Inadequate pragmatic guidance for programme managers on the implementation, monitoring, and evaluation of PC STH programmes, or the integration of PC interventions needed to revise the threshold for PC when moving from control to elimination, looking beyond the 2020 deadline to reach the Sustainable Development Goals (SDGs) for NTDs by 2030.