A Mortality-Based Description of EHDV and BTV Prevalence in Farmed White-Tailed Deer (Odocoileus virginianus) in Florida, USA

Abstract

Hemorrhagic disease (HD) caused by bluetongue virus (BTV) and epizootic hemorrhagic disease virus (EHDV) is the most important viral disease of farmed and wild white-tailed deer (WTD; Odocoileus virginianus) and can cause substantial mortality in susceptible hosts. Captive cervid farming is an emerging industry in Florida, an HD-enzootic region. Morbidity and mortality due to HD are major concerns among deer farmers, but the impact of HD on Florida’s cervid farming industry is unknown. Our primary objective was to determine the prevalence of epizootic hemorrhagic disease virus (EHDV) and bluetongue virus (BTV) among WTD submitted to the University of Florida Institute of Food and Agricultural Sciences Cervidae Health Research Initiative (CHeRI) for post-mortem diagnostics. Our secondary objectives were to identify the predominant circulating EHDV serotypes during each sampling year and to determine the age class with the greatest proportion of EHDV- and BTV-positive post-mortem specimens. From 2016 to 2020, spleen samples from 539 farmed WTD with unexplained mortality were tested for the presence of EHDV and BTV by RT-qPCR. Overall, the prevalence of EHDV, BTV, or EHDV/BTV coinfection was 26%, 16%, and 10%, respectively, and 44% of deer (237/539) were diagnosed with HD by RT-qPCR. The predominant circulating EHDV serotype varied by year. Overall, EHDV-2 was the most commonly identified serotype (55% of PCR-positive cases), and EHDV-1 was the least frequently identified serotype (16% of PCR-positive cases). The greatest proportion of EHDV/BTV positives among mortality cases was observed in young WTD aged 3–6 months (50%–82% positive). There was a significant difference in the prevalence of EHDV/BTV by age when comparing specimens from WTD over 1 year old (p = 0.029, n = 527). Among these samples, the number of reported mortalities and the prevalence of EHDV/BTV were highest in yearling animals (56%). These data provide the first estimate of EHDV and BTV prevalence and virus serotypes among farmed WTD in Florida, identify the WTD age groups with the greatest proportions of EHDV- and BTV-positive specimens, and suggest that HD caused by these two viruses may be a major source of mortality challenging the captive cervid farming industry in Florida.

Spatial epidemiology of hemorrhagic disease in Illinois wild white-tailed deer

“…However, cattle may not be the only farmed ruminant that plays a crucial role as a host for BTV/EHDV. For example, a recent study identifies 44% of mortality cases in farmed WTD in Florida between 2012 and 2020 associated with BTV, EHDV, or co-infection of BTV/EHDV 67 . This study demonstrates the impact of these viral diseases in captive cervids and highlights the importance of continued surveillance and using farmed ruminants as sentinels for HD in the surrounding wild ruminant populations 67 .…”

“…Such findings may point to other variables contributing to virus transmission, dissemination, vector competence and maintenance. HD surveillance on farmed ruminants may serve as a sentinel strategy to identify risk factors for disease transmission in captive and wild populations 67 . Livestock and captive cervid facilities may be valuable sentinels for HD surveillance because it is possible to identify the recently infected (viremic) animals necessary for the infection of biological vectors 43 , 67 .…”

“…HD surveillance on farmed ruminants may serve as a sentinel strategy to identify risk factors for disease transmission in captive and wild populations 67 . Livestock and captive cervid facilities may be valuable sentinels for HD surveillance because it is possible to identify the recently infected (viremic) animals necessary for the infection of biological vectors 43 , 67 . Evaluation of native Culicoides species near captive facilities may help detect shifts in HD occurrence and the potential for maintenance of HD viruses outside the known vector home range 9 .…”

Perspectives on the Changing Landscape of Epizootic Hemorrhagic Disease Virus Control

“…A significant problem with species-specific population management is that new vector species continue to be identified each year [105][106][107], and the new tools are usually highly species-specific. Continued characterization of outbreaks, the environmental drivers, and insect vector compositions involved in new EHDV outbreaks are critical to understand the changing epidemiology [52,95,108]. Additional research hurdles still exist; field trials must be performed and deployment issues such as regulatory and end user acceptance must be overcome (reviewed in [100], but the arrival of new control tools to reduce biting midge populations which are more environmentally sustainable is expected in the near future.…”

Development of a Novel Loop Mediated Isothermal Amplification Assay (LAMP) for the Rapid Detection of Epizootic Haemorrhagic Disease Virus

“…Epizootic haemorrhagic disease (EHD), caused by the EHD virus (EHDV), is an infectious, non-contagious disease that is transmitted by Culicoides biting midges. EHD affects wild and domestic ruminants and causes a severe haemorrhagic disease in whitetailed deer with high morbidity and mortality, and is considered one of the most important diseases affecting deer [1,2]. Milder disease and higher survival rates have been reported for other species such as mule deer, black-tailed, deer and pronghorn antelope [3].…”