Assessment of the relationship between entomologic indicators of Aedes aegypti and the epidemic occurrence of dengue virus 3 in a susceptible population, São José do Rio Preto, Sao Paulo, Brazil

Abstract

The aims of this study were to describe the occurrence of dengue in space and time and to assess the relationships between dengue incidence and entomologic indicators. We selected the dengue autochthonous cases that occurred between September 2005 and August 2007 in Sao Jose do Rio Preto to calculate incidence rates by month, year and census tracts. The monthly incidence rates of the city were compared to the monthly Breteau indices (BI) of the Sao Jose do Rio Region. Between December 2006 and February 2007, an entomological survey was conducted to collect immature forms of Aedes aegypti in Jaguare, a Sao Jose do Rio Preto neighborhood, and to obtain entomological indices. These indices were represented using statistical interpolation. To represent the occurrence of dengue in the Jaguare neighborhood in 2006 and 2007, we used the Kernel ratio and to evaluate the relationship between dengue and the entomological indices, we used a generalized additive model in a spatial case-control design. Between September 2005 and August 2007, the occurrence of dengue in Sao Jose do Rio Preto was almost entirely caused by DENV3, and the monthly incidence rates presented high correlation coefficients with the monthly BI. In Jaguare neighborhood, the entomological indices calculated by hectare were better predictors of the spatial distribution of dengue than the indices calculated by properties, but the pupae quantification did not show better prediction qualities than the indices based on the container positivity, in relation to the risk of dengue occurrence. The fact that the municipality's population had a high susceptibility to the serotype DENV3 before the development of this research, along with the almost total predominance of the occurrence of this serotype between 2005 and 2007, facilitated the analysis of the epidemiological situation of the disease and allowed us to connect it to the entomological indicators.