Bluetongue (BT) and epizootic hemorrhagic disease (EHD) are noncontagious, insect-transmitted diseases of domestic and wild ruminants caused by related but distinct viruses. There are significant gaps in our scientific knowledge and available countermeasures to control an outbreak of orbivirus-induced disease, whether BT or EHD. Both BT virus (BTV) and EHD virus (EHDV) cause hemorrhagic
fevers in susceptible ruminants; however, BT is principally a disease of domestic livestock whereas EHD is principally a disease of certain species of wild, non-African ungulates, notably white-tailed deer. The live-attenuated (modified live virus [MLV])
vaccines available in the United States for use in small ruminant livestock do provide good protection against clinical disease following
infection with the homologous virus serotype. Although there is increasing justification that the use of MLV
vaccines should be avoided if possible, these are the only
vaccines currently available in the United States. Specifically, MLVs are used in California to protect sheep against
infection with BTV serotypes 10, 11, and 17, and a MLV to BTV serotype 10 is licensed for use in sheep throughout the United States. These MLV
vaccines may need to continue to be used in the immediate future for protective immunization of sheep and goats against BT. There are currently no licensed
vaccines available for EHD in the United States other than
autogenous vaccines. If there is a need to rapidly develop a
vaccine to meet an emerging crisis associated with either BTV or EHDV
infections, development of an inactivated virus
vaccine in a conventional adjuvanted formulation will likely be required. With two doses of
vaccine (and in some instances just one dose),
inactivated vaccines can provide substantial immunity to the epizootic serotype of either BTV or EHDV. This strategy is similar to that used in the 2006-2008 BTV serotype 8 outbreaks in northern Europe that provided
vaccine to the field within 2 years of the initial incursion (by 2008). Further research and development are warranted to provide more efficacious and effective
vaccines for control of BTV and EHDV
infections.