Bluetongue and Epizootic Hemorrhagic Disease in the United States of America at the Wildlife–Livestock Interface

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.

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

“…3 a). These findings of northern expansion are consistent with previous reports 5 and with the high morbidity and mortality usually reported when naïve populations are exposed to HD viruses 9 .…”

“…There are seven EHDV and 27 BTV serotypes around the world. Three EHDV serotypes and 15 BTV serotypes have been documented in the USA 9 . The viruses are transmitted through the bite of infected midges of the genus Culicoides 10 .…”

“…The former is considered the primary vector in North America due to its broad distribution while the latter is limited to the extreme southeastern USA but appears to be expanding 13 . However, it is suspected that additional species could be acting as vectors, contributing to augment transmission during outbreaks 9 . Culicoides develop in aquatic and semi-aquatic habitats, including streams, ponds, moist soils, and mud, depending on the species 14 , 15 .…”

“…This outbreak coincided with the EHD outbreak affecting wild WTD in that region 41 and followed the major outbreaks in domestic ruminants in the USA in 2012 28 . Cattle and deer have been considered important vertebrate hosts in the EHDV/BTV transmission cycle 9 , 42 . Furthermore, recent studies in the USA have demonstrated animal host density 43 and biting midges preference patterns for different Cervidae and Bovidae hosts 44 as important factors for maintaining HD viruses in captive ruminant herds.…”

“…Furthermore, recent studies in the USA have demonstrated animal host density 43 and biting midges preference patterns for different Cervidae and Bovidae hosts 44 as important factors for maintaining HD viruses in captive ruminant herds. The occurrence of HD in captive herds may have consequences for subsequent infection in wild WTD populations 9 . In Illinois, cattle and deer often inhabit the same large-scale geographic areas and are often close to habitats where HD competent vectors occur.…”