Vaccines for Prevention of Bluetongue and Epizootic Hemorrhagic Disease in Livestock: A North American Perspective

Abstract

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.

Assessment of listing and categorisation of animal diseases within the framework of the Animal Health Law (Regulation (EU) No 2016/429): bluetongue

“…Vaccination is central to prevention of BT in many endemic areas, and also to the response to incursions of the disease into previously unaffected regions (Verwoerd and Erasmus, 2004;Savini et al, 2008). Zientara et al, 2010;McVey and Maclachlan, 2015). (Figures 3 and 4).…”

“…They usually contain combinations of BTV and EHDV antigens. Little published data are available for the evaluation of these products (McVey and Maclachlan, 2015).…”

Current and next-generation bluetongue vaccines: Requirements, strategies, and prospects for different field situations

“…Officially, MLVs for other serotypes were never used in Europe but have been detected, and are likely introduced via unknown introduction routes (De Clercq et al, 2009;van Rijn et al, 2012). In several parts of the world, such as the USA, Turkey, Africa, and India, MLVs are still used to protect the ruminant population against BT (Bhanuprakash et al, 2009;McVey & MacLachlan, 2015). However, uncontrolled spread of MLVs is not desired if BT eradication is the ultimate goal.…”

Epizootic haemorrhagic disease

“…The notable exception is Ibaraki disease (EHDV-2), for which both inactivated and live attenuated vaccines exist. In Japan, both types of vaccine are available, but in the United States, only locally produced autogenous inactivated vaccines for immunisation of farmed deer are available (57,98). Any efficacious vaccination strategy would involve the use of vaccines against all serotypes of EHDV endemic in a given area, as humoral immunity is serotype-specific.…”

“…Although recent studies indicate that the existing live attenuated vaccine to Ibaraki virus, unlike vaccines against BTV, does not cross the placenta after administration to pregnant cattle (G. Savini, unpublished), the potential advantages and disadvantages inherent to inactivated and live attenuated EHDV vaccines are likely the same as those for BTV. This means that there is the potential for live attenuated vaccine strains to be spread vertically in cattle and horizontally by vector midges (93,98).…”