La Crosse Virus Field Detection and Vector Competence of Culex Mosquitoes

Abstract

Abstract. La Crosse virus (LACV), a leading cause of arboviral pediatric encephalitis in the United States, is emerging in Appalachia. Here, we report field and laboratory evidence that suggest LACV may be using Culex mosquitoes as additional vectors in this region. This bunyavirus was detected by reverse-transcriptase polymerase chain reaction in two pools of Culex mosquitoes in southwestern Virginia and in six pools in West Virginia. To assess vector competence, we offered LACV blood meals to field-collected Culex restuans Theobald, Cx. pipiens L., and Aedes triseriatus (Say). Both Culex species were susceptible to infection. LACV-positive salivary expectorate, indicative of the ability to transmit, was detected in a small proportion of Cx. restuans (9%) and Cx. pipiens (4%) compared with Ae. triseriatus (40%). In a companion study of Cx. restuans only, we found that adults derived from nutritionally stressed larvae were significantly more likely to disseminate and transmit LACV. Our results indicate a potential role of Culex spp. in LACV dynamics that should be explored further in endemic areas.

Influence of Forest Disturbance on La Crosse Virus Risk in Southwestern Virginia

“…pipiens/restuans and found no detectable effects of disturbance on the abundance of this group [27]. Although known to be ornithophilic, there is evidence that Culex mosquitoes will feed on mammals [74] and may play a role in LACV dynamics [25,26]. Although both detections of LACV from Cx.…”

“…japonicus, and Cx. pipiens/restuans) shown to be competent for La Crosse virus in past work [26,55]. Further, although both positive Cx.…”

“…pipiens/restuans were detected in nearby West Virginia using more stringent protocols [26]. Similarly, we previously performed vector competence experiments to demonstrate that both Culex species are competent vectors of LACV [26], albeit to a lesser degree than other species. Quantitative RT-PCR revealed no positive pools in 2010, but two positive Ae.…”

“…Two positive samples from Cx. pipiens/restuans (Table 2) collected in 2008 were previously published [26] as part of a study evaluating the vector competence of both Culex species for LACV. Similarly, one positive Ae.…”

“…canadensis (Theobald) [23], Ae. vexans (Meigen) [24] and Culex mosquitoes [25,26], may play a role in LACV dynamics. Thus, several Culicidae vectors have been implicated in LACV dynamics.…”