Abstract
Praziquantel (PZQ) is an effective chemotherapy for schistosomiasis mansoni and a mainstay for its control and potential elimination. However, it does not prevent against reinfection, which can occur rapidly in areas with active transmission. A guide to ranking the risk factors for Schistosoma mansoni reinfection would greatly contribute to prioritizing resources and focusing prevention and control measures to prevent rapid reinfection. The objective of the current study was to explore the relationship among the socioeconomic, demographic, and epidemiological factors that can influence reinfection by S. mansoni one year after successful treatment with PZQ in school-aged children in Northeastern Minas Gerais state Brazil. Parasitological, socioeconomic, demographic, and water contact information were surveyed in 506 S. mansoni-infected individuals, aged 6 to 15 years, resident in these endemic areas. Eligible individuals were treated with PZQ until they were determined to be negative by the absence of S. mansoni eggs in the feces on two consecutive days of Kato-Katz fecal thick smear. These individuals were surveyed again 12 months from the date of successful treatment with PZQ. A classification and regression tree modeling (CART) was then used to explore the relationship between socioeconomic, demographic, and epidemiological variables and their reinfection status. The most important risk factor identified for S. mansoni reinfection was their “heavy” infection at baseline. Additional analyses, excluding heavy infection status, showed that lower socioeconomic status and a lower level of education of the household head were also most important risk factors for S. mansoni reinfection. Our results provide an important contribution toward the control and possible elimination of schistosomiasis by identifying three major risk factors that can be used for targeted treatment and monitoring of reinfection. We suggest that control measures that target heavily infected children in the most economically disadvantaged households would be most beneficial to maintain the success of mass chemotherapy campaigns.
Highlights
Despite recent progress in controlling Schistosoma mansoni infection in Latin America and the Caribbean (LAC) countries, this parasitic nematode remains a major public health problem in Brazil and in other low and middle income countries in the region [1]
The objective of the current study was to apply classification and regression tree (CART) analysis to determine the relative importance and relationships among different factors that can predict risk of reinfection with S. mansoni in schoolaged children in Northeastearn Brazil, who had been successfully treated with Praziquantel (PZQ) and followed for 12 months post-treatment to determine their level of reinfection
CART is a statistical method that allows the hierarchical analyses of such complex data sets and generates a classification tree, that uses all possible combinations to show relationships between variables and rank the potential factors related [15], enabling the application of these results to control and possibly eliminate S. mansoni in endemic areas
Summary
Despite recent progress in controlling Schistosoma mansoni infection in Latin America and the Caribbean (LAC) countries, this parasitic nematode remains a major public health problem in Brazil and in other low and middle income countries in the region [1]. Many previous epidemiological studies of schistosomiasis used multinomial models, such as logistic regression, which uses linear combinations as the primary method of expressing associations between variables and outcomes such as infection or reinfection [11,12]. These models do not estimate the interaction of the explanatory variables nor do they rank the variables according to their relative importance in light of multiple interactions among the variables. The objective of the current study was to apply CART analysis to determine the relative importance and relationships among different factors that can predict risk of reinfection with S. mansoni in schoolaged children in Northeastearn Brazil, who had been successfully treated with Praziquantel (PZQ) and followed for 12 months post-treatment to determine their level of reinfection
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