Mapping the global distribution of Strongyloides stercoralis and hookworms by ecological niche modeling

Abstract

Background The WHO has established a control strategy for Strongyloides stercoralis in school-aged children as well as targets and to maintain control programs for Ascaris lumbricoides, Trichuris trichiura and hookworms. For an efficient development of control programs, it is necessary to know the target countries around the world, as well as the areas within each country where efforts should be focused. Therefore, maps that provide information on the areas at risk for soil-transmitted helminth (STH) infections on a national and sub-national scale would allow for a better allocation of resources. Methods We used the ecological niche models MaxEnt and Kuenm R library to estimate the global distribution of S. stercoralis and hookworms. We used occurrence points of both species extracted from surveys of two literature reviews and from the Global Atlas of Helminth Infection database, together with 14 raster maps of environmental variables. Results We obtained two raster maps with the presence probability of S. stercoralis and hookworm infections at a global level and then estimated the global population at risk to be 2.6 and 3.4 billion, respectively. The population at risk was also estimated at the country level using estimations for areas as small as 25 km2. A relationship was found between the probability of the presence of S. stercoralis and its prevalence, and a raster map was generated. Annual precipitation, annual temperature, soil carbon content and land cover were the main associated environmental variables. The ecological niches of Strongyloides stercoralis and hookworms had an overlap of 68%. Conclusions Here we provide information that can be used for developing more efficient and integrated control strategies for S. stercoralis and hookworm infections. This information can be annexed to the study of other risk factors or even other diseases to assess the health status of a community. Graphical Abstarct

Seroprevalence and associated risk factors of strongyloidiasis in indigenous communities and healthcare professionals from Brazil

“…stercoralis infection. It has been stated that mass deworming may be insufficient to eradicate infection in highly risk areas with optimal conditions for Strongyloides development [ 3 ], as observed in a population of schoolchildren underwent to a two-years- anthelmintic-protocol treatment, in Cambodia [ 44 ]. Herein, the second-line treatment with Albendazole has been provided to indigenous population for the last six years.…”

“…A recent ecological niche model study estimated that more than 2.6 billion persons may be at risk for infection by S . stercoralis [ 3 ]. Strongyloidiasis is asymptomatic or oligosymptomatic in most infected individuals [ 4 ].…”

“…Brazil is considered to have the highest number of people at risk for S . stercoralis infections [ 3 ]. Due to poor sanitation of living conditions, Brazilian Indigenous populations are highly predisposed to infection by intestinal parasites [ 21 , 22 ].…”

The transmission dynamics of Strongyloides stercoralis and the impact of mass drug administration

“…More generally, recent work has attempted to produce global maps of infection distribution with some based on ecological niche modelling. The work of Fleitas et al [6] and Eslahi et al [1] has provided an important guide to where the new WHO strategy for the control of S. stercoralis infection involving mass drug administration (MDA) for school-aged children should be implemented. The authors of these studies highlight the various assumptions made in producing global maps and, concomitantly, the limited epidemiological data available employing sensitive diagnostic tools for many regions and countries.…”

Strongyloidiasis-related lung involvement: too much of a bad thing

“…Strongyloidiasis is a neglected parasitic infection that affects 300–900 million individuals globally [1]. It is estimated that the population at risk for strongyloidiasis is more than 2.6 billion persons worldwide with Asia (>1.7 billion) and Africa (>510 million) representing the most affected regions [2 ▪▪ ]. Strongyloides stercoralis , the main agent of strongyloidiasis, is a nematode with a unique life cycle, which includes both free-living and parasitic stages.…”