Vector-Host Interactions and Epizootiology of Eastern Equine Encephalitis Virus in Massachusetts

Abstract

Eastern equine encephalitis (EEE) virus is a highly pathogenic mosquito-borne zoonosis that is responsible for outbreaks of severe disease in humans and equines, resulting in high mortality or severe neurological impairment in most survivors. In the northeastern United States, EEE virus is maintained in an enzootic cycle involving the ornithophilic mosquito, Culiseta melanura (Coquillett) and passerine birds in freshwater swamp habitats. To evaluate the role of Cs. melanura and Culiseta morsitans (Theobald) in recent episodes of EEE virus activity in Massachusetts, we collected blood-fed mosquitoes between June, 2007, and October, 2008, from virus foci in 6 counties, and identified the source of blood meals by PCR amplification of mitochondrial cytochrome b gene and sequencing. Analysis of 529 Cs. melanura and 25 Cs. morsitans revealed that nearly 99% and 96% of mosquitoes, respectively, acquired blood meals solely from avian hosts. American Robin, Turdus migratorius Linnaeus was identified as the most common vertebrate host for Cs. melanura (21.7%, n=115), followed by Tufted Titmouse, Baeolophus bicolor (L.) (8.7%, n=46), Black-capped Chickadee, Poecile atricapillus (L.) (8.5%, n=45), Scarlet Tanager, Piranga olivacea (Gmelin) (6.8%, n=36), Field Sparrow, Spizella pusilla (Wilson) (6.2%, n=33), Northern Cardinal, Cardinalis cardinalis (L.) (5.7%, n=30), and other mostly Passeriformes birds. Mammalian-derived blood meals were identified as white-tailed deer, Odocoileus virginianus Zimmermann, domestic cow, Bos taurus L., and human, Homo sapiens L. There were 4 isolations of EEE virus, West Nile virus, and Highland J virus from Cs. melanura. Our results in conjunction with other lines of evidence, including reservoir competency, prevalence of antibody, and infection in nature, suggest that the American Robin, Tufted Titmouse, Black-capped Chickadee, and a few other passerine birds may play key roles in supporting EEE virus transmission in Massachusetts. Infrequent blood feeding of Cs. melanura on mammalian hosts, including humans, also indicates that this mosquito may occasionally contribute to epidemic/epizootic transmission of EEE virus in this region.

Ecology ofCuliseta Melanuraand Other Mosquitoes (Diptera: Culicidae) from Walton County, FL, During Winter Period 2013–2014

“…Five of these species (grasshopper sparrow, house wren, Tennessee warbler and yellow-rumped warbler, hermit thrush, and blackand-white warbler) are reported as hosts of Cs. melanura from New York (Molaei et al 2006), Massachusetts, or both (Molaei et al 2013). Hermit thrush and black-and-white warbler are of broader potential interest in the ecology of EEEV, based on the current findings and those from previous investigations at other sites.…”

“…Hermit thrush was also a minor host of Cs. melanura at an EEEV focus in New York (Molaei et al 2006), but not Massachusetts (Molaei et al 2013). Hatch-year black-and-white warbler was found EEEV viremic in New Jersey in late September and antibody positive (14.7%) at the same location (Crans et al 1994).…”

“…Black-and-white warbler was also fed upon by Cs. melanura in New York (Molaei et al 2006) and Massachusetts (Molaei et al 2013). An ecological assessment of bird characteristics that contribute to higher antibody prevalence among bird species in New Jersey found that summer resident species and species with lower nesting heights had significantly higher antibody prevalence than other species (Crans et al 1994).…”

Mapping eastern equine encephalitis virus risk for white-tailed deer in Michigan

“…These habitats support primary and bridge vector species (Snow, 1955; Rey, et al, 2012), as well as avian hosts (Estep et al, 2011; Molaei et al, 2013). White-tailed deer in Michigan also heavily utilize lowland forests during spring and summer (Hiller et al, 2009), which coincides with peaks in EEEV transmission.…”

Widespread Detection of Antibodies to Eastern Equine Encephalitis, West Nile, St. Louis Encephalitis, and Turlock Viruses in Various Species of Wild Birds from Across the United States

“…4,5 WNV (family Flaviviridae, genus Flavivirus) is considered the most widely distributed arbovirus in the world and can be associated with flu-like symptoms or viral encephalitis and neurological disease as well as mortality in humans 6 and high mortality in corvids 3,7 and other bird species native to North America. 8 SLEV (family Flaviviridae, genus Flavivirus) is another important flavivirus that is distributed throughout most of the western hemisphere and although rare, can cause fever, meningitis, encephalitis, or mortality in humans.…”