Vector competence of Florida Culicoides insignis (Diptera: Ceratopogonidae) for epizootic hemorrhagic disease virus serotype 2

Authors: McGregor, Bethany; ERRAM, DINESH - University Of Florida; ALTO, BARRY - University Of Florida; LEDNICKY, JOHN - University Of Florida; WISELY, SAMANTHA - University Of Florida; BURKETT-CADENA, NATHAN - University Of Florida

Submitted to: Viruses
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/4/2021
Publication Date: 3/4/2021
Citation: McGregor, B.L., Erram, D., Alto, B.W., Lednicky, J., Wisely, S.M., Burkett-Cadena, N.D. 2021. Vector competence of Florida Culicoides insignis (Diptera: Ceratopogonidae) for epizootic hemorrhagic disease virus serotype 2. Viruses. 13(3):410. https://doi.org/10.3390/v13030410.
DOI: https://doi.org/10.3390/v13030410

Interpretive Summary: Epizootic hemorrhagic disease virus is an arthropod-borne virus (arbovirus) that is spread by small flies in the genus Culicoides. This virus causes significant sickness and mortality in deer, primarily white-tailed deer and mule deer in North America. Currently, only one species of Culicoides midge is confirmed to spread this virus in North America; however, the virus has been found in areas where this species is rare or absent. This suggests the presence of additional vector species. This study evaluated a common Culicoides species in Florida, Culicoides insignis, to determine whether this species can become infected with and then transmit EHDV serotype 2. After experimentally infecting this species with three different amounts of virus, we found that when fed a relatively high amount of virus, C. insignis is capable of becoming infected with EHDV-2 and has the potential to spread this virus through its saliva. This study improves our understanding of the transmission cycle of EHDV-2 in North America and helps us to begin the process of implicating a new EHDV vector.

Technical 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.