WHO guideline on preventive chemotherapy for public health control of strongyloidiasis 

Übersicht

Human strongyloidiasis is a chronic parasitic disease caused by infection with Strongyloides stercoralis, a soil-transmitted helminth that is estimated to infect 300–600 million people worldwide. This neglected tropical disease (NTD) is endemic globally, predominately in the South-East Asia, African and Western Pacific regions, and in South and Central America. Strongyloidiasis has a wide range of clinical presentations, including subclinical disease, symptomatic disease (often with diarrhoea, abdominal pain and urticaria) and a rare but deadly complication of hyperinfection with disseminated disease. The feared complication of disseminated strongyloidiasis can occur in the setting of immunocompromising conditions (e.g. human T-cell lymphotropic virus type 1 infection and malignancies) or immunosuppressive medications (e.g. steroids) and has an estimated case-fatality rate exceeding 60%. The standard treatment for chronic S. stercoralis infection is oral medication with ivermectin.

In recent years, the World Health Organization (WHO) has been contacted by the health ministries of several countries in which strongyloidiasis is endemic for advice on how to address the disease as a public health problem, as no current WHO guidance exists. While there are no public health programmes specifically for control of strongyloidiasis, in some settings, large-scale mass drug administration (MDA) programmes with ivermectin are being conducted to control lymphatic filariasis and onchocerciasis. These programmes have demonstrated a reduction in prevalence of S. stercoralis infection, suggesting that preventive chemotherapy may be a potential public health strategy in areas endemic for strongyloidiasis. Furthermore, secondary patents for ivermectin have now expired, leading to two generic formulations of ivermectin being prequalified by WHO in 2020 and 2021 with preferential pricing for public health use.

In 2021, WHO published a road map to guide the global strategy and targets for NTDs from 2021 to 2030. This global strategy outlined a need for formal guidance on whether to recommend preventive chemotherapy against strongyloidiasis and provided an opportunity to integrate strongyloidiasis control programmes into existing public health programmes for NTDs. These programmes could be targeted at school-aged children alone (i.e. targeted preventive chemotherapy) or to the entire community (i.e. MDA) in endemic settings. Consequently, a guideline development group (GDG) was convened to address the need to control strongyloidiasis and develop guidance.

The objective of this WHO guideline is aligned with that of Sustainable Development Goal 3: to “ensure healthy lives and promote well-being for all at all ages” and the World Health Assembly resolution to expand access to prevention, diagnosis, treatment and care interventions for NTDs as a contribution towards the achievement of universal health coverage by 2030.

Its goal is to provide an evidence-informed recommendation on whether preventive chemotherapy with ivermectin as a public health intervention to reduce the disease burden caused by strongyloidiasis should:

• be implemented as a programme targeting both adults and school-aged children (i.e. MDA) in endemic settings that are above a defined prevalence threshold of strongyloidiasis;
• be implemented as a school-based programme alone (i.e. targeted preventive chemotherapy) in endemic settings that are above a defined prevalence threshold of strongyloidiasis; or
• not be implemented through preventive chemotherapy and instead be given following standard clinical care of individual cases.

This public health guideline recommendation is not intended to replace any standard of care for treatment of clinical strongyloidiasis. No public health approach replaces the need for timely diagnosis and treatment for strongyloidiasis through accessible health care.