Abstract
Eastern equine encephalitis virus (EEEV) is maintained in an enzootic cycle involving Culiseta melanura mosquitoes and avian hosts. Other mosquito species that feed opportunistically on mammals have been incriminated as bridge vectors to humans and horses. To evaluate the capacity of these mosquitoes to acquire, replicate, and potentially transmit EEEV, we estimated the infection prevalence and virus titers in mosquitoes collected in Connecticut, USA, by cell culture, plaque titration, and quantitative reverse transcription-PCR. Cs. melanura mosquitoes were the predominant source of EEEV (83 [68%] of 122 virus isolations) and the only species to support consistently high virus titers required for efficient transmission. Our findings suggest that Cs. melanura mosquitoes are primary enzootic and epidemic vectors of EEEV in this region, which may explain the relative paucity of human cases. This study emphasizes the need for evaluating virus titers from field-collected mosquitoes to help assess their role as vectors.
Highlights
Eastern equine encephalitis virus (EEEV) is maintained in an enzootic cycle involving Culiseta melanura mosquitoes and avian hosts
EEEV infection rates were higher in Cs. melanura mosquitoes (MLE 3.44, 95% confidence intervals (CIs) 2.76–4.24) than in all other mosquito species tested except An. quadrimaculatus (MLE 3.27, 95% CI 0.59–10.55) and Ur. sapphirina (MLE 1.35, 95% CI 0.44–3.23) mosquitoes
Our analysis of EEEV-positive mosquito pools showed major differences in virus titer among different mosquito species obtained in Connecticut
Summary
Eastern equine encephalitis virus (EEEV) is maintained in an enzootic cycle involving Culiseta melanura mosquitoes and avian hosts. Human and equine cases occur infrequently despite relatively high rates of EEEV infection in Cs. melanura during virus amplification (ArboNET) Other mosquito species such as Aedes vexans, Coquillettidia perturbans, Ochlerotatus canadensis, and Oc. sollicitans have been implicated as epidemic/epizootic bridge vectors from viremic birds to horses and humans [4,5,6]. These species are competent vectors of EEEV [7,8,9] and may acquire virus infection during disease outbreaks by feeding occasionally on birds but prefer mammalian hosts [10,11,12,13,14]. To evaluate the capacity of these mosquitoes to replicate and potentially transmit virus, we estimated EEEV titers from virus-positive mosquito pools with the expectation that the most efficient vectors will support consistently high virus titers
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