Abstract
BackgroundSchistosomiasis is a water-borne disease caused by trematode worms belonging to genus Schistosoma, which is prevalent most of the developing world. Transmission of the disease is usually associated with multiple biological characteristics and social factors but also factors can play a role. Few studies have assessed the exact and interactive influence of each factor promoting schistosomiasis transmission.MethodsWe used a series of different detectors (i.e., specific detector, risk detector, ecological detector and interaction detector) to evaluate separate and interactive effects of the environmental factors on schistosomiasis prevalence. Specifically, (i) specific detector quantifies the impact of a risk factor on an observed spatial disease pattern, which were ranked statistically by a value of Power of Determinate (PD) calculation; (ii) risk detector detects high risk areas of a disease on the condition that the study area is stratified by a potential risk factor; (iii) ecological detector explores whether a risk factor is more significant than another in controlling the spatial pattern of a disease; (iv) interaction detector probes whether two risk factors when taken together weaken or enhance one another, or whether they are independent in developing a disease. Infection data of schistosomiasis based on conventional surveys were obtained at the county level from the health authorities in Anhui Province, China and used in combination with information from Chinese weather stations and internationally available environmental data.ResultsThe specific detector identified various factors of potential importance as follows: Proximity to Yangtze River (0.322) > Land cover (0.285) > sunshine hours (0.256) > population density (0.109) > altitude (0.090) > the normalized different vegetation index (NDVI) (0.077) > land surface temperature at daytime (LSTday) (0.007). The risk detector indicated that areas of schistosomiasis high risk were located within a buffer distance of 50 km from Yangtze River. The ecological detector disclosed that the factors investigated have significantly different effects. The interaction detector revealed that interaction between the factors enhanced their main effects in most cases.ConclusionProximity to Yangtze River had the strongest effect on schistosomiasis prevalence followed by land cover and sunshine hours, while the remaining factors had only weak influence. Interaction between factors played an even more important role in influencing schistosomiasis prevalence than each factor on its own. High risk regions influenced by strong interactions need to be targeted for disease control intervention.
Highlights
Schistosomiasis is a water-borne disease caused by trematode worms belonging to genus Schistosoma, which is prevalent most of the developing world
In this study focused on schistosomiasis, we used a method of a series of detectors based on variables commonly used in geographical information systems (GIS) as proposed by Wang et al [15] to assess risk factors associated with health outcomes by means of spatial variance analysis (SVA)
The specific detector identified the significant risk factors and their relative influence on schistosomiasis prevalence ranked by Power of Determinate (PD) value as follows (Table 1): proximity to Yangtze River (0.322) > Land cover (0.285) > sunshine hours (0.256) > population density (0.109) > digital elevation model (DEM) (0.090) > normalized different vegetation index (NDVI) (0.077) > land surface temperature at daytime (LSTday) (0.007)
Summary
Schistosomiasis is a water-borne disease caused by trematode worms belonging to genus Schistosoma, which is prevalent most of the developing world. Transmission of the disease is usually associated with multiple biological characteristics and social factors and factors can play a role. Few studies have assessed the exact and interactive influence of each factor promoting schistosomiasis transmission. Schistosomiasis, caused by a trematode worms belonging to the genus Schistosoma [1], is a chronic, debilitating disease that occurs in tropical and subtropical environments, where it remains a burden of major public health and economic significance [2]. Transmission of schistosomiasis is usually associated with multiple biological characteristics and social factors, which influence vector biology, ecology, economic and policy factors [6]. Understanding the relationship between risk factors and schistosomiasis is of great importance as it supports the implementation of effective control programs
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