Wetland characteristics linked to broad-scale patterns in Culiseta melanura abundance and eastern equine encephalitis virus infection

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.Electronic supplementary materialThe online version of this article (10.1186/s13071-017-2482-0) contains supplementary material, which is available to authorized users.

The Role of Temperature in Transmission of Zoonotic Arboviruses

“…Modeling studies on temperature for remaining viruses include: EEEV [3,171], LACV [13], MVEV [3], Sindbis virus (SINV) [3,172,173], St. Louis encephalitis virus (SLEV) [3,174], and Western equine encephalitis virus (WEEV) ([174,175,176] and citations therein, [3]). Note that modeling studies that did not include temperature were omitted here (e.g., EEEV: [177,178]). The treatment of temperature in environmental models varies substantially, from simple statistical correlations to complex mechanistic models.…”

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“…Risk factors that were associated with exposure to EEEV or acquiring EEEV in mosquito populations were reported in 5 of 209 articles (Crans et al 1994, Takeda et al 2003, Hachiya et al 2007, Skaff et al 2017. In vectors, the method of identifying EEEV was described in 92 of 155 articles, the most common diagnostic method used was virus isolation (60/92) followed by molecular tests (37/92), or immunoassays (37/92).…”

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“…The enzootic cycle is largely limited to freshwater hardwood swamps or other such wooded wetlands, primarily due to the habitat requirements required for development of Cs. melanura larva [64,91,95,96]. Cs.…”