Abstract
The recorded clinical cases of S. mansoni at primary health facility level contain an excessive number of zero records. This could mean that no S. mansoni infection occurred (a true zero) in the health facility service area but it could also that at least one infection occurred but none were reported or diagnosed (a false zero). Standard statistical analysis, using exploratory or confirmatory spatial regression, fail to account for this type of data insufficiency. This study developed a zero-inflated Poisson model to explore the spatiotemporal variation in schistosomiasis risk at a fine spatial scale. We used environmental data generated at primary health facility service area level as explanatory variables affecting transmission risk. Identified risk factors were subsequently used to project the spatial variability of S. mansoni infection risk for 2050. The zero-inflated Poisson model shows a considerable increase of relative risk of the schistosomiasis over one decade. Furthermore, the changes between the risk in 2009 and forecasted risk by 2050 indicated both persistent and emerging areas with high relative risk of schistosomiasis infection. The risk of schistosomiasis transmission is 69%, 29%, and 50% higher in areas with rice cultivation, proximity to rice farms, and proximity to a water body respectively. The prediction and forecasting maps provide a valuable tool for monitoring schistosomiasis risk in Rwanda and planning future disease control initiatives in wetland ecosystem development context.
Highlights
The recorded clinical cases of S. mansoni at primary health facility level contain an excessive number of zero records
We investigated S. mansoni transmission in Rwanda using routinely collected data of confirmed cases recorded at primary health facility level[13]
The annual risk rit (RR) of S. mansoni depicts the changes in the period 2001 to 2009
Summary
The recorded clinical cases of S. mansoni at primary health facility level contain an excessive number of zero records. We used environmental data generated at primary health facility service area level as explanatory variables affecting transmission risk. In Rwanda, Schistosomiasis mansoni (S. mansoni) infection constitutes a significant public health problem It has an overall country prevalence of 2.7%, which is an average from minimum value of 0.0% for most of mapping units to as much as 69.5% among school c hildren[3]. We investigated S. mansoni transmission in Rwanda using routinely collected data of confirmed cases recorded at primary health facility level[13]. In our study socio-economic risk factors were excluded from the explanatory risk factors (including access to improved water for domestic uses, proper sanitation, wearing shoes, bush defecation behavior, etc.)[14] Those factors are represented by qualitative (%ge) and not spatially explicit figures—result of integrated living conditions surveys extrapolated at district level (10 times + bigger than a HFSA). It is assumed that the missing information on human ecology related to rice cropping landscape, such as putting-off shoes while cultivating, increased behavior of defecating in the bush and use of river/wetland water (while far from their home toilet and other facilities) is captured in significant relation of infection (new hotspots) and distribution and trend of wetland and rice cropping (as proxy)
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