Abstract
During an outbreak of Ibaraki disease in Kagoshima Prefecture from August through October 1997, 54 cattle demonstrated such typical symptoms as laryngopharyngeal paralysis and foamy salivation. Simultaneous with this outbreak, cows-frequently Holsteins pregnant for from 170 to 280 days-aborted or gave birth to stillborn calves. Almost all the dams that miscarried or gave stillbirths in this instance demonstrated high titers of the neutralizing (NT) antibody to the Ibaraki virus (IBAV). The NT antibody to IBAV was detected in the sera of a few aborted fetuses as well. Furthermore, 21 IBAV strains were isolated from fetal organs; and immunohistochemical staining with the and-IBAV serum revealed the viral antigen to IBAV in hindbrain cells from aborted fetuses. Reverse transcriptase-polymerase chain reaction (RT-PCR) based on the third RNA Segment gene of IBAV produced specific amplifications in all isolates as well as in the prototype IBAV strain. New isolate PCR-product restriction fragments, however, were distinguished from those of the prototypical IBAV strain. These findings suggest that a new virulent strain of IBV caused stillbirths and abortions in the outbreak.
