Host interactions of Aedes albopictus, an invasive vector of arboviruses, in Virginia, USA

Abstract

Background: As an invasive mosquito species in the United States, Aedes albopictus is a potential vector of arboviruses including dengue, chikungunya, and Zika, and may also be involved in occasional transmission of other arboviruses such as West Nile, Saint Louis encephalitis, eastern equine encephalitis, and La Crosse viruses. Aedes albopictus feeds on a wide variety of vertebrate hosts, wild and domestic, as well as humans.

Methodology/principal findings: In order to investigate blood feeding patterns of Ae. albopictus, engorged specimens were collected from a variety of habitat types using the Centers for Disease Control and Prevention light traps, Biogents Sentinel 2 traps, and modified Reiter gravid traps in southeast Virginia. Sources of blood meals were determined by the analysis of mitochondrial cytochrome b gene sequences amplified in PCR assays. Our aims were to quantify degrees of Ae. albopictus interactions with vertebrate hosts as sources of blood meals, investigate arboviral infection status, assess the influence of key socioecological conditions on spatial variability in blood feeding, and investigate temporal differences in blood feeding by season. Analysis of 961 engorged specimens of Ae. albopictus sampled between 2017-2019 indicated that 96%, 4%, and less than 1% obtained blood meals from mammalian, reptilian, and avian hosts, respectively. Domestic cats were the most frequently identified (50.5%) hosts followed by Virginia opossums (17.1%), white-tailed deer (12.2%), and humans (7.3%), together representing 87.1% of all identified blood hosts. We found spatial patterns in blood feeding linked to socioecological conditions and seasonal shifts in Ae. albopictus blood feeding with implications for understanding human biting and disease risk. In Suffolk Virginia in areas of lower human development, the likelihood of human blood feeding increased as median household income increased and human blood feeding was more likely early in the season (May-June) compared to later (July-October). Screening of the head and thorax of engorged Ae. albopictus mosquitoes by cell culture and RT-PCR resulted in a single isolate of Potosi virus.

Conclusion and significance: Understanding mosquito-host interactions in nature is vital for evaluating vectorial capacity of mosquitoes. These interactions with competent reservoir hosts support transmission, maintenance, and amplification of zoonotic agents of human diseases. Results of our study in conjunction with abundance in urban/suburban settings, virus isolation from field-collected mosquitoes, and vector competence of Ae. albopictus, highlight the potential involvement of this species in the transmission of a number of arboviruses such as dengue, chikungunya, and Zika to humans. Limited interaction with avian hosts suggests that Ae. albopictus is unlikely to serve as a bridge vector of arboviruses such as West Nile and eastern equine encephalitis in the study region, but that possibility cannot be entirely ruled out.

Fig 1. Map of the study area.

The city of Suffolk is located in the southeastern corner of the State of Virginia.

Fig 2. Human Development in Suffolk.

(A) National Land Cover Database classification for open water, developed, undeveloped, and agricultural land in Suffolk. (B) The proportion of blood meals from domestic cats (Felis catus), Virginia opossums (Didelphis virginiana), white-tailed deer (Odocoileus virginianus), and humans (Homo sapiens) across quartiles of human development.

Fig 3. Median Household Income in Suffolk.

(A) Median household income classified by quartile in Suffolk. (B) The proportion of blood meals from domestic cat (Felis catus), Virginia opossum (Didelphis virginiana), white-tailed deer (Odocoileus virginianus), and human (Homo sapiens) across quartiles of median household income.

Fig 4. Spatial distribution of Ae. albopictus blood meals.

The proportion of blood meals from domestic cats (Felis catus), Virginia opossums (Didelphis virginiana), white-tailed deer (Odocoileus virginianus), and humans (Homo sapiens) across Suffolk. Pie charts only illustrated for trap sites with more than 10 identified Ae. albopictus blood meals.

Fig 5. Mediating effects.

Mediating effects of human development on the influence of median household income on Ae. albopictus host interactions with domestic cats (Felis catus), Virginia opossums (Didelphis virginiana), white-tailed deer (Odocoileus virginianus), and humans (Homo sapiens).