Vector Competence of Florida Culicoides insignis (Diptera: Ceratopogonidae) for Epizootic Hemorrhagic Disease Virus Serotype-2.

Bethany L. McGregor,Barry W. Alto,John A. Lednicky,Dinesh Erram,Samantha M. Wisely,Nathan D. Burkett-Cadena

doi:10.3390/v13030410

Abstract

Epizootic hemorrhagic disease virus (EHDV; family Reoviridae, genus Orbivirus) is an arthropod-borne virus of ungulates, primarily white-tailed deer in North America. Culicoides sonorensis, the only confirmed North American vector of EHDV, is rarely collected from Florida despite annual virus outbreaks. Culicoides insignis is an abundant species in Florida and is also a confirmed vector of the closely related Bluetongue virus. In this study, oral challenge of C. insignis was performed to determine vector competence for EHDV serotype-2. Field-collected female midges were provided bovine blood spiked with three different titers of EHDV-2 (5.05, 4.00, or 2.94 log10PFUe/mL). After an incubation period of 10 days or after death, bodies and legs were collected. Saliva was collected daily from all females from 3 days post feeding until their death using honey card assays. All samples were tested for EHDV RNA using RT-qPCR. Our results suggest that C. insignis is a weakly competent vector of EHDV-2 that can support a transmissible infection when it ingests a high virus titer (29% of midges had virus positive saliva when infected at 5.05 log10PFUe/mL), but not lower virus titers. Nevertheless, due to the high density of this species, particularly in peninsular Florida, it is likely that C. insignis plays a role in the transmission of EHDV-2.

Highlights

Epizootic hemorrhagic disease virus (EHDV) is an arthropod-borne virus, transmitted by biting midges of the genus Culicoides (Diptera: Ceratopogonidae), that causes disease in ungulates of the families Cervidae and Bovidae [1]
The range of C. sonorensis in the United States is primarily west of the Mississippi River [10], sporadic populations do occur in the eastern half of the country [10,11], and increasing northeastern range expansion has been documented [12]
Based on the results of the current study, C. insignis is a weakly competent vector for EHDV-2 capable of developing infection, dissemination, and transmission potential when feeding on blood containing a viral titer of 5.05 log10PFUe/mL

Summary

Introduction

Epizootic hemorrhagic disease virus (EHDV) is an arthropod-borne virus, transmitted by biting midges of the genus Culicoides (Diptera: Ceratopogonidae), that causes disease in ungulates of the families Cervidae and Bovidae [1]. Infection with EHDV can result in extreme morbidity and mortality of infected animals, primarily white-tailed deer (Odocoileus virginianus) in North America, resulting in significant impacts to wild populations and devastating losses for North American deer farmers [2,3]. These pathogens can impact other economically important animal industries, such as cattle operations, resulting in significant losses to milk production in dairy cattle [4]. Despite periodic EHDV outbreaks in the southeastern US, multiple large-scale collection efforts have recorded few to no C. sonorensis [13,14,15,16], suggesting the role of other species in the transmission of EHDV in this region

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