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Location: Arthropod-borne Animal Diseases Research

Title: European bluetongue serotype 8: Disease threat assessment for US sheep

item Drolet, Barbara
item Reister-Hendricks, Lindsey
item PODELL, BRENDAN - Colorado State University
item Breitenbach, Jonathan
item McVey, David
item VAN RIJN, PIET - Central Veterinary Institute
item BOWEN, RICHARD - Colorado State University

Submitted to: Vector-Borne and Zoonotic Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/19/2015
Publication Date: 4/25/2016
Publication URL:
Citation: Drolet, B.S., Reister-Hendricks, L.M., Podell, B.K., Breitenbach, J.E., Mcvey, D.S., Van Rijn, P.A., Bowen, R.A. 2016. European bluetongue serotype 8: Disease threat assessment for US sheep. Vector-Borne and Zoonotic Diseases. 16(6):400-407.

Interpretive Summary: Bluetongue virus (BTV) is transmitted by biting flies and causes economically significant hemorrhagic disease in livestock and wildlife. To date there are 26 different types of BTV in the world, each having different capabilities of causing disease. Although only five of these are considered ‘endemic’ to the U.S, 10 others have been isolated since 1999. The frequent and constant introduction of these new, or ‘incursive’, types pose threats of unpredictable livestock disease levels to producers. This study determined the susceptibility of a common U.S. sheep breed to a BTV type of particular concern due to the devastating outbreak it caused in Europe. Results showed that if this virus type were to come into the U.S., this white-faced sheep breed would be susceptible to disease; however, the severity of disease would likely be typical of that seen with our endemic types and not as severe as it was in Europe.

Technical Abstract: Although as many as 15 serotypes of bluetongue virus (BTV) have been detected in the United States (U.S.) in the past 15 years, only five are considered endemic. This clearly illustrates the ability of this transboundary, insect-transmitted virus to spread to new ecosystems. In the U.S., sheep are the most susceptible livestock species for bluetongue (BT) disease. The American Poll Dorset breed is the most common registered white-faced breed in the U.S. sheep industry, and therefore a breed of concern for determining disease risk of outbreaks. One outbreak serotype of particular concern is the European strain of BTV-8, which was introduced into Northern Europe in 2006 and caused unprecedented livestock disease and mortality during the 2006-2007 vector seasons. To assess disease risk of BTV-8 to American Dorset sheep, eight seronegative sheep were experimentally infected and monitored daily for clinical signs. Blood samples were analyzed for BTV RNA with quantitative real time PCR (qRT-PCR), serum for BTV antibodies by competitive ELISA, and tissues were taken at necropsy for histopathology and qRT-PCR virus load quantitation. Moderate to severe clinical disease peaked from 7 to 10 days post inoculation (dpi) with detectable virus in blood and tissues through the end of the study (28 days). As expected, American Dorset sheep were highly susceptible to BTV-8; however, clinical disease was no more severe than that typically seen with endemic BTV serotypes.