Abstract
BackgroundEastern equine encephalitis virus (EEEV) is an expanding mosquito-borne threat to humans and domestic animal populations in the northeastern United States. Outbreaks of EEEV are challenging to predict due to spatial and temporal uncertainty in the abundance and viral infection of Cs. melanura, the principal enzootic vector. EEEV activity may be closely linked to wetlands because they provide essential habitat for mosquito vectors and avian reservoir hosts. However, wetlands are not homogeneous and can vary by vegetation, connectivity, size, and inundation patterns. Wetlands may also have different effects on EEEV transmission depending on the assessed spatial scale. We investigated associations between wetland characteristics and Cs. melanura abundance and infection with EEEV at multiple spatial scales in Connecticut, USA.ResultsOur findings indicate that wetland vegetative characteristics have strong associations with Cs. melanura abundance. Deciduous and evergreen forested wetlands were associated with higher Cs. melanura abundance, likely because these wetlands provide suitable subterranean habitat for Cs. melanura development. In contrast, Cs. melanura abundance was negatively associated with emergent and scrub/shrub wetlands, and wetland connectivity to streams. These relationships were generally strongest at broad spatial scales. Additionally, the relationships between wetland characteristics and EEEV infection in Cs. melanura were generally weak. However, Cs. melanura abundance was strongly associated with EEEV infection, suggesting that wetland-associated changes in abundance may be indirectly linked to EEEV infection in Cs. melanura. Finally, we found that wet hydrological conditions during the transmission season and during the fall/winter preceding the transmission season were associated with higher Cs. melanura abundance and EEEV infection, indicating that wet conditions are favorable for EEEV transmission.ConclusionsThese results expand the broad-scale understanding of the effects of wetlands on EEEV transmission and help to reduce the spatial and temporal uncertainty associated with EEEV outbreaks.
Highlights
Eastern equine encephalitis virus (EEEV) is an expanding mosquito-borne threat to humans and domestic animal populations in the northeastern United States
For our analyses of Cs. melanura abundance, we focus on three wetland characteristics that may have important effects wetland vegetation, wetland connectivity, and wetland inundation classification: (i) Wetland vegetation: Vegetation imposes important constraints on the suitability of wetland habitats to Cs. melanura larval development
Culiseta melanura abundance Wetland explanatory variables were most strongly associated with Cs. melanura abundance at broad spatial scales ranging from 1000 m to 3000 m from mosquito trapping sites (Fig. 2, Additional file 2: Figure S1)
Summary
Eastern equine encephalitis virus (EEEV) is an expanding mosquito-borne threat to humans and domestic animal populations in the northeastern United States. Outbreaks of EEEV are challenging to predict due to spatial and temporal uncertainty in the abundance and viral infection of Cs. melanura, the principal enzootic vector. Abundance and EEEV infection of Cs. melanura may be closely linked to local land cover characteristics, wetland cover that provides important habitat for vectors and susceptible hosts [6, 8,9,10]. Uncertainty surrounding current estimates and the relative importance of vector and hosts movement necessitates evaluating the effects of wetland cover and temporallyvarying wetland conditions at a range of potential spatial scales and temporal lags [12, 14]
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