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(1) Background: Epizootic hemorrhagic disease virus (EHDV) and bluetongue virus (BTV) are orbiviruses that cause hemorrhagic disease (HD) with significant economic and population health impacts on domestic livestock and wildlife. In the United States, white-tailed deer (Odocoileus virginianus) are particularly susceptible to these viruses and are a frequent blood meal host for various species of Culicoides biting midges (Diptera: Ceratopogonidae) that transmit orbiviruses. The species of Culicoides that transmit EHDV and BTV vary between regions, and larval habitats can differ widely between vector species. Understanding how midges are distributed across landscapes can inform HD virus transmission risk on a local scale, allowing for improved animal management plans to avoid suspected high-risk areas or target these areas for insecticide control. (2) Methods: We used occupancy modeling to estimate the abundance of gravid (egg-laden) and parous (most likely to transmit the virus) females of two putative vector species, C. stellifer and C. venustus, and one species, C. haematopotus, that was not considered a putative vector. We developed a universal model to determine habitat preferences, then mapped a predicted weekly midge abundance during the HD transmission seasons in 2015 (July–October) and 2016 (May–October) in Florida. (3) Results: We found differences in habitat preferences and spatial distribution between the parous and gravid states for C. haematopotus and C. stellifer. Gravid midges preferred areas close to water on the border of well and poorly drained soil. They also preferred mixed bottomland hardwood habitats, whereas parous midges appeared less selective of habitat. (4) Conclusions: If C. stellifer is confirmed as an EHDV vector in this region, the distinct spatial and abundance patterns between species and physiological states suggest that the HD risk is non-random across the study area. [ABSTRACT FROM AUTHOR]

Hemorrhagic diseases caused by epizootic hemorrhagic disease virus or by bluetongue virus (BTV) are the most important orbivirus diseases affecting ruminants, including white-tailed deer (WTD). Bluetongue virus is of particular concern for farmed WTD in Florida, given its lethality and its wide distribution throughout the state. This study reports the clinical findings, ancillary diagnostics, and genomic characterization of two BTV serotype 1 strains isolated from two farmed WTD, from two different farms in Florida in 2019 and 2022. Phylogenetic and genetic analyses indicated that these two novel BTV-1 strains were reassortants. In addition, our analyses reveal that most genome segments of these strains were acquired from BTVs previously detected in ruminants in Florida, substantiating their endemism in the Southeastern U.S. Our findings underscore the need for additional research to determine the genetic diversity of BTV strains in Florida, their prevalence, and the potential risk of new BTV strains to WTD and other ruminants., (© 2023. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

A wild population of white-tailed deer (Odocoileus virginianus) was surveyed for evidence of past or current epizootic hemorrhagic disease virus (EHDV) and current bluetongue virus (BTV) infections. We collected 121 blood samples from hunter-harvested or live-captured deer from two state-managed properties in northwest Florida, US; live captures were in support of a movement ecology study. Blood samples were tested for antibodies against titers to three EHDV serotypes (EHDV-1, EHDV-2, and EHDV-6), and multiplex quantitative reverse transcription PCR was used to identify the presence of EHDV or BTV viral RNA. Of these samples, 81% (98/121) tested seropositive for at least one of three serotypes of EHDV. Of those testing seropositive, 33% (40/121) contained antibodies for two serotypes, and 19% (24/121) contained antibodies for all three EHDV serotypes. Furthermore, results of generalized linear models indicated that the probability of infection by EHDV serotypes 1 and 6 increased with an animal's age. Our findings indicate that seroprevalence may be high for multiple serotypes in regions where these orbiviruses are endemic. These results could prove useful for managing disease risk in naïve deer populations., (© Wildlife Disease Association 2020.)

The transmission of multiple serotypes of epizootic hemorrhagic disease virus (EHDV) between farmed and free-ranging wildlife is of interest to livestock industries and natural resource agencies. We compared the seroprevalence of EHDV-1, -2, and -6 in wild and farmed white-tailed deer ( Odocoileus virginianus ) herds in Florida, US. We compared serological prevalence, circulating serotypes, antibody titers, and viremia with the use of 171 whole-blood samples from 150 unvaccinated white-tailed deer from farm pens, a farm preserve, and wild deer on adjacent public lands between March 2016 and May 2017. Despite aggressive chemical vector control on the farm, we found higher seroprevalence and titers against the predominant EHDV serotype in farmed deer (in pens and the preserve) than in wild deer. The higher exposure to EHDV of farmed vs. wild deer may have been because of the higher densities of farmed vs. wild deer, the presence of exotic amplifying hosts such as elk ( Cervus canadensis ) in the preserve, or genetic factors that predisposed farmed deer to disease.

Background: Epizootic hemorrhagic disease virus (EHDV) is an Orbivirus of veterinary importance which is transmitted by biting midges of the genus Culicoides (Diptera: Ceratopogonidae) to ruminants. Culicoides sonorensis Wirth & Jones, the only confirmed vector of EHDV in the USA, is rare in the southeastern states where transmission persists, suggesting that other Culicoides species transmit EHDV in this region. The present study aimed to determine which Culicoides species transmitted EHDV in Florida and Alabama, two states in the southeastern USA. Viral RNA was detected in field-collected midges using molecular methods. These data are presented alongside data on Culicoides blood meal analysis, white-tailed deer (Odocoileus virginianus) aspiration, and seasonality to demonstrate an interaction between potential vector species and EHDV hosts., Results: Out of 661 pools tested, 20 pools were positive for EHDV viral RNA, including six pools from Culicoides stellifer (Coquillett) and 14 pools from Culicoides venustus Hoffman. The overall infection rate was 0.06% for C. stellifer and 2.18% for C. venustus. No positive pools were identified for a further 17 species. Serotypes identified in Culicoides included EHDV-2, EHDV-6, and coinfections of EHDV-2 and EHDV-6 and were identified in similar proportions to serotypes in deer at 3 of 4 deer farms. Viral detections conducted in Alabama also identified one positive pool of C. venustus. Blood meal analysis revealed that both Culicoides species fed on white-tailed deer (verified through aspiration), fallow deer, and elk, species for which EHDV viremia has been documented. Seasonality data indicated that both species were present throughout the period in which viral transmission occurred to EHDV hosts in 2016 in addition to the 2017 epizootic., Conclusions: Our finding of EHDV positive pools of field-collected C. stellifer and C. venustus and an interaction between these species and EHDV hosts satisfy two of the four criteria for vector incrimination as set by the World Health Organization. Determining the vectors of EHDV is an important step towards developing sound strategies for the control of vector Culicoides and management of EHDV in the southeastern USA.