Aedes aegypti oviposition in urban communities in the Northern Chihuahuan Desert.

BACKGROUND OBJECTIVES: Aedes aegypti (Linnaeus) is the vector of multiple arboviruses, the most important being dengue viruses (DENV) that causes more than 90 million cases per year. The expanded range of Ae. aegypti into temperate climates has contributed to the increasing risk of DENV to new human populations. As an effort to better understand the ecology of Ae. aegypti in a temperate climate, larval surveillance was conducted to identify oviposition locations of this species from 2016-2018 in two nonincorporated communities located in El Paso, Texas and Ciudad Juárez, Chihuahua, Mexico. METHODS: This survey was conducted inside and outside private residences examining any possible water holding containers to collect with a dipper, turkey baster, or Pasteur pipette. Larvae and pupae were transported to the laboratory and reared to adults for morphological identification. A total of 601 Ae. aegypti larvae were collected and reared to adults from 24 containers in the Sparks community. In contrast, a total of 68 Ae. aegypti were collected and reared to adults from seven containers in the Anapra community. RESULTS: In both locations, the predominant container type that yielded immature mosquitoes were plastic buckets. Although the results were based on a small sample size, the finding provided a preliminary understanding of the oviposition sites of Ae. aegypti in two urban communities in a temperate climate region. INTERPRETATION CONCLUSION: The identification of oviposition sites can be used to develop and implement vector control strategies.

Genomic Analysis of Aedes aegypti in the Northern Chihuahuan Desert of Texas and Mexico.

Background: Aedes aegypti, is the primary vector of dengue, Chikungunya, Zika, and yellow fever viruses. Both natural and human-impacted landscapes have selective pressures on Ae. aegypti, resulting in strong genomic structure even within close geographical distances. Materials and Methods: We assess the genetic structure of this medically important mosquito species at the northern leading edge of their distribution in Southwestern USA. Ae. aegypti were collected during 2017 in the urban communities of El Paso and Sparks, Texas (USA) and in the city of Ciudad Juárez, Mexico. Results: Thousands of nuclear loci were sequenced across 260 captured Ae. aegypti. First, we recovered the genetic structure of Ae. aegypti following geography, with all four major collection communities being genetically distinct. Importantly, we found population structure and genetic diversity that suggest rapid expansion through active-short distance dispersals, with Anapra being the likely source for the others. Next, tests of selection recovered eight functional genes across six outliers: calmodulin with olfactory receptor function; the protein superfamily C-type lectin with function in mosquito immune system and development; and TATA box binding protein with function in gene regulation. Conclusion: Despite these populations being documented in the early 2000s, we find that selective pressures on specific genes have already occurred and likely facilitate Ae. aegypti range expansion.