Local persistence of novel regional variants of La Crosse virus in the Northeast USA

Gillian Eastwood,Philip M. Armstrong,Michael J. Misencik,John J. Shepard,Theodore G. Andreadis

doi:10.1186/s13071-020-04440-4

Gillian Eastwood, Philip M. Armstrong + Show 3 more

Open Access

https://doi.org/10.1186/s13071-020-04440-4

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Abstract

BackgroundLa Crosse virus (LACV) (genus Orthobunyavirus, family Peribunyaviridae) is a mosquito-borne virus that causes pediatric encephalitis and accounts for 50–150 human cases annually in the USA. Human cases occur primarily in the Midwest and Appalachian regions whereas documented human cases occur very rarely in the northeastern USA.MethodsFollowing detection of a LACV isolate from a field-collected mosquito in Connecticut during 2005, we evaluated the prevalence of LACV infection in local mosquito populations and genetically characterized virus isolates to determine whether the virus is maintained focally in this region.ResultsDuring 2018, we detected LACV in multiple species of mosquitoes, including those not previously associated with the virus. We also evaluated the phylogenetic relationship of LACV strains isolated from 2005–2018 in Connecticut and found that they formed a genetically homogeneous clade that was most similar to strains from New York State.ConclusionOur analysis argues for local isolation and long-term persistence of a genetically distinct lineage of LACV within this region. We highlight the need to determine more about the phenotypic behavior of these isolates, and whether this virus lineage poses a threat to public health.

Highlights

La Crosse virus (LACV) is a mosquito-borne virus that causes pediatric encephalitis and accounts for 50–150 human cases annually in the USA
La Crosse virus (LACV) is a mosquito-borne virus, associated with clinical cases of pediatric encephalitis concentrated in the Midwest and Appalachian regions where it is detected in mosquitoes during surveillance activities
Entomological data A total of 14 new isolates of LACV were obtained during the mosquito surveillance activities in CT: (i) routine arbovirus monitoring detected additional isolates of LACV from the town of Redding in both 2015 and 2016, and two isolates in the towns of Weston and Fairfield during 2018, all within Fairfield county (Fig. 1, Table 1); (ii) of 14,085 mosquitoes captured at the Hamden location during the Lure evaluation study in July and August 2018, 4 novel isolates of LACV were made from three different mosquito species (Table 1); (iii) focused LACV surveillance extension in Fairfield county captured a total of 16,325 mosquitoes at three different sites, which were screened as 310 pools

Summary

Introduction

La Crosse virus (LACV) (genus Orthobunyavirus, family Peribunyaviridae) is a mosquito-borne virus that causes pediatric encephalitis and accounts for 50–150 human cases annually in the USA. La Crosse virus (LACV) (genus Orthobunyavirus, family Peribunyaviridae) is a mosquito-borne virus, associated with clinical cases of pediatric encephalitis concentrated in the Midwest and Appalachian regions where it is detected in mosquitoes during surveillance activities. Aedes triseriatus serves as the main vector of LACV which is broadly distributed throughout the eastern half of the USA [8]. This species is likely under-sampled during statewide surveillance efforts because it does not readily enter standard CDC light traps or gravid traps which are routinely used [3, 9]. Additional sampling and testing of Ae. triseriatus and other locally abundant mosquito species are needed to accurately estimate the entomological risk of LACV in enzootic sites

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