Serological diagnosis of bovine fetal neosporosis

To evaluate the efficacy of fetal serology in the diagnosis of bovine neosporosis abortion, sera from 48 fetuses with immunohistochemically confirmed neosporosis and 42 fetuses without demonstrable Neospora caninum were examined in the indirect fluorescent antibody test (IFAT). Fetal sera were diluted 2-fold starting at a 1:25 dilution. Antibodies to N. caninum were detected in 31 of 48 (65%) fetuses with confirmed neosporosis; the IFAT antibody titers were 1:25 (5 fetuses), 1:50 (17 fetuses), 1:200 (6 fetuses), and > or = 1:800 (3 fetuses). Neospora caninum antibodies were found in 3 of 42 fetuses without demonstrable protozoa; in all 3 cases, a high titer was found suggesting undiagnosed congenital neosporosis. A recombinant antigen enzyme-linked immunosorbent assay was not useful for the detection of fetal antibodies to N. caninum.