Antigenic and morphologic comparisons of Ibaraki and bluetongue viruses

Bluetongue disease virus, type 10, and Ibaraki disease virus, which causes a bluetongue-like disease of cattle, were compared to determine whether they are the same or different viruses. They were similar in morphology, but neutralization tests, complement-fixation tests, and ferritin tagging indicated that they have antigenic differences. Therefore, they should be considered as different viruses. Two other viruses of this group, African horsesickness and equine encephalosis, were included to show that Ibaraki and bluetongue had developmental morphological features that could be used to differentiate them from the two equine viruses.