Dynamics of Vector-Host Interactions in Avian Communities in Four Eastern Equine Encephalitis Virus Foci in the Northeastern U.S.

Abstract

BackgroundEastern equine encephalitis (EEE) virus (Togaviridae, Alphavirus) is a highly pathogenic mosquito-borne zoonosis that is responsible for occasional outbreaks of severe disease in humans and equines, resulting in high mortality and neurological impairment in most survivors. In the past, human disease outbreaks in the northeastern U.S. have occurred intermittently with no apparent pattern; however, during the last decade we have witnessed recurring annual emergence where EEE virus activity had been historically rare, and expansion into northern New England where the virus had been previously unknown. In the northeastern U.S., EEE virus is maintained in an enzootic cycle involving the ornithophagic mosquito, Culiseta melanura, and wild passerine (perching) birds in freshwater hardwood swamps. However, the identity of key avian species that serve as principal virus reservoir and amplification hosts has not been established. The efficiency with which pathogen transmission occurs within an avian community is largely determined by the relative reservoir competence of each species and by ecological factors that influence contact rates between these avian hosts and mosquito vectors.Methodology and principle findingsContacts between vector mosquitoes and potential avian hosts may be directly quantified by analyzing the blood meal contents of field-collected specimens. We used PCR-based molecular methods and direct sequencing of the mitochondrial cytochrome b gene for profiling of blood meals in Cs. melanura, in an effort to quantify its feeding behavior on specific vertebrate hosts, and to infer epidemiologic implications in four historic EEE virus foci in the northeastern U.S. Avian point count surveys were conducted to determine spatiotemporal host community composition. Of 1,127 blood meals successfully identified to species level, >99% of blood meals were from 65 avian hosts in 27 families and 11 orders, and only seven were from mammalian hosts representing three species. We developed an empirically informed mathematical model for EEE virus transmission using Cs. melanura abundance and preferred and non-preferred avian hosts. To our knowledge this is the first mathematical model for EEE virus, a pathogen with many potential hosts, in the northeastern U.S. We measured strong feeding preferences for a number of avian species based on the proportion of mosquito blood meals identified from these bird species in relation to their observed frequencies. These included: American Robin, Tufted Titmouse, Common Grackle, Wood Thrush, Chipping Sparrow, Black-capped Chickadee, Northern Cardinal, and Warbling Vireo. We found that these bird species, most notably Wood Thrush, play a dominant role in supporting EEE virus amplification. It is also noteworthy that the competence of some of the aforementioned avian species for EEE virus has not been established. Our findings indicate that heterogeneity induced by mosquito host preference, is a key mediator of the epizootic transmission of vector-borne pathogens.Conclusion and s...

Seasonal Distribution, Blood-Feeding Habits, and Viruses of Mosquitoes in an Open-Faced Quarry in Connecticut, 2010 and 2011

“…Blood-feeding patterns of mosquitoes at the openfaced quarry were consistent with reports of the feeding habits of mosquitoes collected elsewhere in Connecticut (Magnarelli 1977;Molaei et al 2006aMolaei et al , 2008Molaei et al , 2016 and in other locations (Apperson et al 2002(Apperson et al , 2004Savage et al 2007). Three species of Aedes, Cq.…”

“…The feeding of 3 species of Aedes and Cq. perturbans on both birds and mammals has been documented previously, and the suggestion has been made that such species could be bridge vectors for WNV and eastern equine encephalomyelitis (Molaei et al 2008(Molaei et al , 2016.…”

Barcoding blood meals: New vertebrate-specific primer sets for assigning taxonomic identities to host DNA from mosquito blood meals

“…melanura has taken place in the northern United States, beyond the range of A . carolinensis and other abundant lizard species, or has used molecular methods specific only to avian and mammalian hosts [ 53 – 55 ]. Our small sample size for Cs .…”

Host associations of mosquitoes at eastern equine encephalitis virus foci in Connecticut, USA

“…morsitans was greatest during the month of August (28 of 34), similar to that of Cs. melanura on wood thrush in the latter study [16]. Other avian species including American robin, gray catbird and tufted titmouse, that served as hosts for Cs.…”