Building on the success of soil-transmitted helminth control - The future of deworming

There has been substantial progress over the past decade in efforts to reduce morbidity from soil-transmitted helminth infections (STH). Morbidity control through preventative chemotherapy (PC) has been embraced by endemic countries, the World Health Organization (WHO) and by partners as a clear and achievable goal. Few global health programs have achieved delivery of an intervention at a scale comparable to STH morbidity programs; over 4 billion tablets have been distributed to over 1 billion of the world’s most vulnerable populations [1]. Prior to the establishment of the albendazole and mebendazole donation program in 2012, global PC coverage had stagnated at approximately 30%. However, since 2015, treatment coverage has almost doubled (59%) and drug requests and donations continue to increase [2]. This progress has been particularly remarkable in the WHO South East Asia Region, home to the largest number of children in need of PC. In 2015 more than 75% of at-risk children in this region received STH PC. This remarkable global success is the result of significant collaborative efforts championed by endemic country governments, non-governmental organisations, philanthropic foundations and pharmaceutical companies [3]. In addition to achieving high PC treatment coverage, the global scale-up of STH programs has also had a substantial impact on morbidity in children [4]. Globally, PC has reduced the number of individuals with morbid STH infections (hookworm infections of any intensity, and ascariasis and trichuriasis of moderate and heavy intensity) by 85%. These data also suggest that after only one round of PC, the prevalence of STH-associated morbidity in children is reduced by approximately 75% and after 10 years of annual PC interventions, STH-associated morbidity can be virtually eliminated (WHO, 2015). The successful scaling-up of STH PC programs and subsequent reductions in morbidity are, in part, attributable to the establishment of ambitious NTD control program goals in the WHO Roadmap [5]. However there are a number of potential challenges that may threaten the continued success of the established STH strategy. First, less than two thirds of all individuals in need of STH treatment receive PC [2]. Nearly half of those who receive albendazole are treated through the Global Program to Eliminate Lymphatic Filariasis (GPELF), not through programs designed to directly target STH. As some countries reach elimination targets and scale down their LF PC programs, STH treatment coverage may be compromised in many areas. In addition, the emergence of drug resistance to benzimidazoles (albendazole and mebendazole) has been widely reported in the veterinary literature, and as drug coverage increases, the threat to human populations is not insignificant, particularly given the lack of alternative available drug classes for treatment [6]. Finally, despite the availability of donated drugs, the financial and operational costs of PC programs are substantial and may be a barrier to endemic countries taking over the financing of STH program delivery.