Association between densities of adult and immature stages of Aedes aegypti mosquitoes in space and time: implications for vector surveillance

Abstract

Background: Mosquito control is currently the main tool available to contain the spread of several arboviruses in Brazil. We have evaluated the association between entomological surveys of female adult Aedes aegypti and the Breteau index (BI) in space and time in a hyperendemic area, and compared the human resources costs required to measure each of these indicators.

Methods: Entomological surveys were conducted between 2016 and 2019 in Vila Toninho, a neighborhood in the city of São José do Rio Preto, Brazil. Monthly records of collected mosquito specimens were made and then grouped by season.

Results: Our findings showed that adult and immature mosquitoes are more related in time than in space, possibly due to differences in their habitats or in climate variables. Bayesian temporal modeling revealed that an increase in 1 standard deviation in the BI was associated with a 27% increase in the number of adult female mosquitoes when adjusted for climatic conditions. The cost of entomological surveys of adult mosquitoes was found to be 83% lower than the cost of determining the BI when covering the same geographic area.

Conclusions: For fine-scale assessments, a simple measure of adult Ae. aegypti abundance may be more realistic than aquatic indicators, but the adult indices are not necessarily the only reliable measure. Surveying adult female mosquitoes has significant potential for optimizing vector control strategies because, unlike the BI, this tool provides an effective indicator for micro-areas within an urban region. It should be noted that the results of the present study may be due to specific features of of the study area, and future studies should analyze whether the patterns found in the study neighborhood are also found in other regions.

Keywords: Bayesian analysis; Breteau index; Entomological index; Mosquito.

Fig. 1

a Geographic location of São José do Rio Preto in São Paulo State, Brazil and South America. b Study area: the Vila Toninho neighborhood and its location in São José do Rio Preto. c location of the adult mosquito traps in the study area. The maps were built using QGis software 3.16.11 (https://www.qgis.org/)

Fig. 2

Average daily precipitation (mm), average minimum temperature (°C), number of Aedes aegypti adult females and Breteau index over time. Study location was the Vila Toninho neighborhood in São José do Rio Preto, São Paulo State, Brazil, and sampling occured between December 2015 and February 2019

Fig. 3

Scatterplots with locally weighted smoothing lines showing the relationship between climate variables and adult Ae. aegypti females in the Vila Toninho neighborhood of São José do Rio Preto between October 2015 and February 2019. Abbreviations: Avg, average; BI, Breteau index. The graphs were built using R Core Team software 1.3.1093 (https://www.R-project.org)

Fig. 4

Posterior means of the spatial random effects for the spatiotemporal modeling of adult Ae. aegypti females per season and year in the Vila Toninho neighborhood. The maps were built using R Core Team software 1.3.1093 (https://www.R-project.org)