Impacts of Climate, Land Use, and Biological Invasion on the Ecology of Immature Aedes Mosquitoes: Implications for La Crosse Emergence

Abstract

Arthropod-borne viruses (arboviruses) cause many diseases worldwide and their transmission is likely to change with land use and climate changes. La Crosse virus is historically transmitted by the native mosquito Aedes triseriatus (Say) in the upper Midwestern U.S., but the invasive congeners Aedes albopictus (Skuse) and Aedes japonicus (Theobald), which co-occur with A. triseriatus in water-holding containers, may be important accessory vectors in the Appalachian region where La Crosse encephalitis is an emerging disease. This review focuses on evidence for how climate, land use, and biological invasions may have direct abiotic and indirect community-level impacts on immature developmental stages (eggs and larvae) of Aedes mosquitoes. Because vector-borne diseases usually vary in space and time and are related to the ecology of the vector species, we propose that the ecology of its mosquito vectors, particularly at their immature stages, has played an important role in the emergence of La Crosse encephalitis in the Appalachian region and represents a model for investigating the effects of environmental changes on other vector-borne diseases. We summarize the health effects of La Crosse virus and associated socioeconomic costs that make it the most important native mosquito-borne disease in the U.S. We review of the transmission of La Crosse virus, and present evidence for the impacts of climate, land use, and biological invasions on Aedes mosquito communities. Last, we discuss important questions about the ecology of La Crosse virus mosquito vectors that may improve our understanding of the impacts of environmental changes on La Crosse virus and other arboviruses.

Invasion Biology ofAedes japonicus japonicus(Diptera: Culicidae)

“…Leisnham & Juliano (59) have reviewed this within the context of LAC emergence in Appalachia but repeatedly note that relatively little is known about the Ae. j. japonicus side of the interaction.…”

“…Its role as a primary disease vector in North America or Europe is unclear; however, the impact of Ae. j. japonicus on local disease dynamics may result indirectly from its interactions with other established and critical vector mosquito species (e.g., 59). In this review, we discuss the characteristics of the subspecies in its expanded range that are likely involved in its invasion success and what appears to be permanent establishment among mosquito species that utilize container habitats in much of North America and Central Europe.…”

Epidemiology of La Crosse Virus Emergence, Appalachia Region, United States

“…We predict that the invasive tiger mosquito should actually reduce disease transmission in wildlife reservoirs and human populations (even accounting for the fact that tiger mosquitoes are aggressive human biters). Thus, the presence of the invasive tiger mosquito does not sufficiently explain the dramatic increase in LACV disease cases in Appalachia ( 8 , 12 – 14 , 30 ) (http://trace.tennessee.edu/utk_gradthes/1788/), suggesting that correlations between tiger mosquito invasion and the epidemiologic risk for LACV disease are driven by other, concomitant, changes. In support of this conclusion is the absence of any increase in LACV disease prevalence in the Midwest, despite the presence of a tiger mosquito infestation.…”

“…However, since the mid-1990s, Appalachia has emerged as a new focus for the disease ( 8 , 12 – 14 ). One potential explanation is the introduction of the invasive Asian tiger mosquito ( Aedes albopictus ), hereafter called the tiger mosquito ( 15 ).…”

“…One potential explanation is the introduction of the invasive Asian tiger mosquito ( Aedes albopictus ), hereafter called the tiger mosquito ( 15 ). This suggestion is based on the laboratory-demonstrated competence of the tiger mosquito ( 16 , 17 ), isolation of LACV from field-collected tiger mosquito pools ( 18 ), observation of LACV-positive tiger mosquitoes at sites of LACV infections of humans ( 19 ), and the coincidental link between tiger mosquito invasion and the emergence of LACV in the Appalachian region ( 12 ). Unfortunately, although these observations demonstrate the potential for the tiger mosquito to influence LACV dynamics, the contribution of this mosquito to observed increases in LACV transmission remains unclear.…”