The impact of climate on the current and future prevalence of the Aedes aegypti mosquito vector in Brownsville, Texas

Zika, chikungunya, and dengue pose a serious health threat to many areas of North and South America, and are spreading into regions that have had no prior exposure to these viruses. The most recent human health risk involves the relationship between Zika during pregnancy and microcephaly in newborns. In 2005, a large scale outbreak of dengue fever occurred in the Brownsville/Matamoros area. Serology studies conducted during the outbreak show that 38% of the Brownsville population has been exposed to dengue virus, meaning an increased risk for the more serious dengue hemorrhagic fever that sometimes comes with secondary infection. The mosquito Aedes aegypti is the primary vector for all three of these viruses in the Americas. Temperature, relative humidity, and rainfall have all been shown to affect the development and survival of this vector, which is present in a large swath of the southern United States, including Brownsville, Texas.

The goal of the current study is to assess the effect of changing climate on abundance of the Aedes aegypti vector in Brownsville, Texas. Population modeling is accomplished using the Skeeter Buster model, which uses inputs of temperature, rainfall, and relative humidity as well as neighborhood housing/artificial container data to output a dynamic and spatially explicit representation of Aedes aegypti populations. This study is the first to apply Skeeter Buster specific to Brownsville through the use of climate and housing inputs. Downscaled climate data out to year 2100 for the city of Brownsville, Texas were obtained from the Climate Science Center at Texas Tech University. The climate data includes daily temperature, relative humidity, and precipitation predictions for RCP8.5 (a scenario representative of increasing greenhouse gas emissions throughout the 21st century) and RCP4.5 (a scenario in which greenhouse gas emissions stabilize after the mid-21st century). Within each of these scenarios, six climate models were utilized in Skeeter Buster. Actual housing and container data from two neighborhoods in the city of Brownsville were also input into the model to accurately represent the city. Results demonstrate a lengthening of the vector seasonality and increasing populations of parous females, which are a strong indicator of disease risk. Additionally, high adult mosquito densities were observed equally across a high container neighborhood and low container neighborhood separation. Higher populations of parous females for a longer time period during the year imply a greater risk for disease establishment within an area. Results will provide the Brownsville Public Health Department with information that can be used to help mitigate the plausible threat that Zika, chikungunya, and dengue viruses pose into the future.