Infectious Bovine Rhinotracheitis
(MI) Bovine herpesvirus 1 abortion: Infectious Bovine Rhinotracheitis (IBR) was diagnosed in a 7-month-old aborted fetus from an Angus cow. Fluorescent antibody (FA) testing was positive for IBR on placenta and fetal lung, liver and kidney. The pregnant cow had been vaccinated with a modified live vaccine (MLV) in May 2019, but prior to that had not received an MLV since 2017. The manufacturer’s label states that the vaccine is safe in pregnant animals, provided they have received the same product within the past 12 months. Further efforts to sequence virus from the abortion and compare it to the vaccine virus were not performed in this case, given the failure to follow label vaccination instructions. IBR is a herpes virus that can be spread through nasal or genital secretions. Latently infected animals can recrudesce and shed virus when they are stressed, sick, or administered dexamethasone. Administration of vaccines does not eliminate infection, but it controls IBR abortions. Confirmatory antigen detection tests for IBR include FA, PCR or virus isolation on aborted fetal tissues. Acute and convalescent antibody titers performed on serum from cows can be supportive evidence of an IBR abortion when a four-fold rise in titer is seen. All of these tests are available at the AHDC.