Parainfluenza 3 and bovine enteroviruses as possible important causative factors in bovine abortion

In serologic studies of aborted bovine fetuses, antibodies to a number of viruses were found in a high percentage of fetuses of about 4 months of age or older. In the tests reported, parainfluenza 3 (pi 3) antibodies occurred as evidence of an apparent single virus infection in 24% of the cows (dams), but occurred in 53% of the fetuses. Enterovirus antibodies occurred in the absence of other detectable viral antibodies in 13% of the dams, but in a total of 41% of the fetuses in combination with antibodies against other viruses. Of the 8 enterovirus serogroups, 1 appeared to be most infective. This was designated BES6 of the Pennsylvania group's bovine enterovirus classification, using the presence of specific antibodies as evidence of fetal infection and possible cause of abortion. The number of possible diagnoses was increased from 27% under standard diagnostic procedures to 85% according to the results of fetal serologic tests. Evidence that the antibodies detected were of fetal origin, and not maternal origin, was shown in the difference between fetal and maternal serum antibody profiles (the dams had antibodies to at least 3 and as many as 5 viruses more than the fetus), the demonstration of antibody producing cells in aborted fetuses, the high concentration of IgM antibodies in the fetal fluids, and the low frequency of bovine viral diarrhea (BVD) virus antibodies (2%) in fetal serum in fetuses from herds in an area where BVD is known to occur in approximately 50% of the herds tested.