The Strongyloides stercoralis-hookworms association as a path to the estimation of the global burden of strongyloidiasis: A systematic review

Abstract

Soil-transmitted helminths (STH) represent a significant public health problem. However, Strongyloides stercoralis is not yet integrated into the control strategy against STH, given limitations to accurately assess its burden. Considering that S. stercoralis shares biological and epidemiological characteristics with hookworms, we describe a new approach for an improved estimation of the burden of infections by S. stercoralis based on the prevalence and burden of hookworms and the relationship between these species. A systematic review of publications reporting prevalence rates for S. stercoralis and hookworms was carried out. The data was classified into two categories: 1) “Community”, with surveys including all age groups, and 2) “SAC”, with surveys limited to school-aged children. The relationship between S. stercoralis and hookworms was characterized in order to estimate the global burden of S. stercoralis infections. The study is registered in PROSPERO (CRD42019131127). Spearman correlation coefficient between S. stercoralis and hookworms was estimated and the global burden of S. stercoralis infections was estimated using a regression model. A total of 119 articles were included, and a significant positive correlation between the burden of S. stercoralis and hookworms was identified. Spearman’s coefficient for Community surveys was 0.94 and for SAC surveys it was 0.63. Based on the linear model, the global burden of S. stercoralis infections was estimated at 386 million (95%CI 324–449 million) people, including 22 million (95%CI 20–24 million) SAC. The significant relationship between S. stercoralis and hookworms allows estimating the global burden of S. stercoralis infections in most epidemiologic settings using hookworm burden and justifies the search of integrated control activities. PROSPERO (registration code CRD42019131127). Evidence on epidemiologic similarities between Strongyloides stercoralis and hookworms was confirmed by our group. A systematic bibliographic search of surveys published between 2001 and 2018 was carried out. Results suggested that the prevalence and burden of infections by hookworms could be used as a proxy to estimate S. stercoralis infections. This approach is based on a linear relationship between the burden of these species. In addition, the models and linearity showed a better fit for surveys using diagnostic methods with high sensitivity for both species. Our estimate of 386 million people infected with S. stercoralis globally, provides an update of the burden of S. stercoralis. This implies an estimate of almost four times higher than what was estimated previously. Our approach allows evidence-based approximation to the estimations of the global burden of S. stercoralis infections, for different age groups and geographic regions. This information highlights the hidden burden of S. stercoralis while also contributing in the estimation of the potential need for ivermectin for the treatment of neglected tropical diseases.