Abstract
Bluetongue (BT) and epizootic hemorrhagic disease (EHD) cases have increased worldwide, causing significant economic loss to ruminant livestock production and detrimental effects to susceptible wildlife populations. In recent decades, hemorrhagic disease cases have been reported over expanding geographic areas in the United States. Effective BT and EHD prevention and control strategies for livestock and monitoring of these diseases in wildlife populations depend on an accurate understanding of the distribution of BT and EHD viruses in domestic and wild ruminants and their vectors, the Culicoides biting midges that transmit them. However, national maps showing the distribution of BT and EHD viruses and the presence of Culicoides vectors are incomplete or not available at all. Thus, efforts to accurately describe the potential risk of these viruses on ruminant populations are obstructed by the lack of systematic and routine surveillance of their hosts and vectors. In this review, we: (1) outline animal health impacts of BT and EHD in the USA; (2) describe current knowledge of the distribution and abundance of BT and EHD and their vectors in the USA; and (3) highlight the importance of disease (BT and EHD) and vector surveillance for ruminant populations.
Highlights
Bluetongue disease (BT) and epizootic hemorrhagic disease (EHD) are vector-borne viral diseases caused by closely related orbiviruses (Family Reoviridae) that affect domestic and wild ruminants and are transmitted by insect vectors of the genus Culicoides [1,2].Culicoides biting midges are hematophagous flies that inflict painful bites on animals and humans
In North America, C. sonorensis has been reported as the primary vector of Epizootic hemorrhagic disease virus (EHDV) and bluetongue virus (BTV), as studies have demonstrated its implication as a vector in the field and the laboratory [9]
The cattle in this study showed much higher rates of EHDV/BTV
Summary
Bluetongue disease (BT) and epizootic hemorrhagic disease (EHD) are vector-borne viral diseases caused by closely related orbiviruses (Family Reoviridae) that affect domestic and wild ruminants and are transmitted by insect vectors of the genus Culicoides [1,2]. While the first BT case reports were described from sheep and cattle in South Africa, periodic outbreaks of a hemorrhagic disease affecting wild white-tailed deer in the USA have been described in the literature since the late 1800s (Figure 1) [8]. While vector/host interactions are impacted by climate and Pathogens 2021, 10, 915 habitat suitability, our understanding of the proportion of wild ruminants affected by BTV or EHDV in the USA is limited to mostly syndromic based reporting of hemorrhagic disease rather than virus isolation in a targeted population [37]. There are remaining unknowns related to our understanding of the virus, vector, and host dynamics for BT and EHD [5,21,33,38] Both BT and EHD are listed in the USA’s National List of Reportable Animal Diseases and the OIE list of notifiable terrestrial and aquatic animal diseases [39,40]. Highlight the importance of vector and BT and EHD surveillance for ruminant populations
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