PEER REVIEWED Review of epizootic hemorrhagic disease in cattle and a study defining seroprevalence of epizootic hemorrhagic disease virus serotype 2 in Texas cattle Thomas B. Hairgrove,1 DVM, PhD, DABVP; Sandy Rodgers,2 BS, MS; W alter Cook,3 DVM, PhD, DACVPM; Christine Budke,4 DVM, PhD; W illiam B. Smith,5 PhD, PAS d epartm ent of Animal Science, Texas A&M AgriLife Extension Service, College Station, TX 77843 2Texas A&M Veterinary Medical Diagnostic Laboratory, College Station, TX 77843 departm ent of Veterinary Pathobiology, College of Veterinary Medicine, Texas A&M University, College Station, TX 77843 d epartm ent of Integrative Biosciences, College of Veterinary Medicine, Texas A&M University, College Station, TX 77843 d ep artm ent of Soil and Crop Sciences, College of Agriculture and Life Sciences, Texas A&M University, College Station, TX 77843. Current address: Department of Animal Science and Veterinary Technology, Tarleton State University, Stephenville, TX 76402. Corresponding author: Dr. Thomas B. Hairgrove; tbhairgrove@tamu.edu; phone: 979-458-3216 A bstract Epizootic hemorrhagic disease virus is an orbivirus transmitted by Culicoides spp. In North America, it is recog nized as a m ajor cause of disease affecting w hite-tailed deer, but it can impact other wildlife species as well as domestic cattle. Although minimal clinical disease had been noted in Texas, periodic outbreaks in other states caused Texas cattle producers to question the risks to their cattle. The objective of this study was to estimate the proportion of Texas cattle exposed to epizootic hemorrhagic disease virus serotype 2 by observing seroprevalence in auction markets. Serum samples collected from cattle >18 mo of age sold through 11 Texas auc tion markets were collected during June of 2014. Antibody levels were measured using the virus neutralization test as the diagnostic protocol. Market sampling indicated 97.08% of adult cattle had been exposed to epizootic hemorrhagic disease virus serotype 2. There were no significant differ ences in mean titers between individual markets. However, when markets were grouped there was a significant mean titer difference between groups, increasing in the southern and w estern regions. The lack of clinical disease is likely related to enzootic stability as a result of high viral infec tions in cattle and white-tailed deer and the abundance of Culicoides vectors. Key words: seroprevalence, cattle, EHD, epizootic hemor rhagic disease virus, Culicoides Resume Le virus de la maladie hemorragique epizootique ap- partient au genre Orbivirus et est transmis par Culicoides spp. En Amerique du Nord, ce virus constitue une cause majeure de maladie chez le cerf de Virginie mais il peut aussi affecter d'autres animaux de la faune de meme que des bovins domestiques. Bien que peu de cas cliniques de maladie ont ete observes au Texas, des foyers de maladie dans d'autres etats ont amene les producteurs du Texas a se questionner sur les risques pour leur betail. L'objectif de cette etude etait d’estim er la proportion de bovins du Texas exposes au virus de la maladie hemorragique epizootique de type 2 en mesurant la seroprevalence dans des encans. Des echantillons de serum ont ete recueillis chez des bovins ages de 18 mois ou plus vendus dans 11 encans en Juin 2014. Comme protocole diagnostic dans cette etude, on a utilise l'essai de neutralisation virale pour mesurer les niveaux d’anticorps. L’echantillonnage des encans a montre que 97.08% des bovins adultes avaient ete exposes prealable- ment au virus de la maladie hemorragique epizootique de type 2. II n'y avait pas de difference significative au niveau des titres moyens entre les differents encans. Toutefois, lorsque les encans ont ete combines, les titres moyens dans les regions du sud et de l’ouest etaient significativement plus eleves. L'absence de maladie clinique est probable- ment reliee a l’enzootie stable decoulant du niveau tres eleve d’infection chez les bovins et les cerfs de Virginie et a l’abondance des vecteurs Culicoides. Introduction Epizootic hemorrhagic disease (EHD) is a non-conta gious infectious viral disease of wild and domestic ruminants transmitted by biting midges of the genus C u lic o ides.19'23'37 The causative agent, epizootic hemorrhagic disease virus (EHDV), is a double-stranded RNA virus belonging to the 10 THE BOVINE PRACTITIONER-VOL. 52, NO. 1 © Copyright American Association of Bovine Practitioners; open access distribution.