Sewerage as a protective factor for prevalence of hookworm infection in schoolchildren in Brazil: A multilevel ecological analysis of national prevalence surveys (1950–2018)

Abstract

IntroductionThe prevalence of hookworm infection in Brazil has decreased considerably in recent decades. However, there is no definitive consensus as to which changes have contributed to this reduction. A hypothesis is that improvements in environmental factors have contributed to lowering the parasite load and the level of host-parasite contact. MethodsThis is an ecological study using unbalanced panel data from two Brazilian surveys (1947–1953 and 2010–2015), with municipalities as the analysis unit. The sample comprised 1428 municipalities, in which a total of 745,983 schoolchildren aged 7 to 14 were examined. Zero-inflated Poisson regression models, with fixed and random effects were estimated to evaluate the association of potential explanatory variables with the prevalence of hookworm infection at a significance level of 5 %. ResultsWe identified a significant decrease in the prevalence between the first and last analyzed periods (RR 0.096; CI 0.086–0.107); The following variables were found to have a protective effect: access to sanitary sewage systems (RR 0.984, CI 0.982–0.986), urbanization (RR 0.995, CI 0.993–0.997), and gross domestic product (RR 0.929, CI 0.912–0.945). ConclusionThe findings of this study show a decrease in the prevalence of hookworm infections over six decades in schoolchildren in the Brazilian municipalities. Environmental, demographic, and economic factors were associated with this trend. A historical analysis indicates that interventions aimed at improving sanitation contributed to reducing the disease prevalence.