Detection of Neospora caninum in aborted bovine fetuses and dam blood samples by nested PCR and ELISA and seroprevalence in Beijing and Tianjin, China.

Neospora caninum infection is a significant cause of abortion in cattle. We investigated the tissue distribution of N. caninum in aborted bovine fetuses and dam blood samples by a nested PCR assay, and compared the nested PCR with ELISA in the diagnosis of N. caninum infection. In total, 26 aborted fetuses and 813 blood samples were collected from 8 dairy herds in Beijing (n=212) and Tianjin (n=601), China. Fifteen fetuses (57.7%) were tested N. caninum-positive by the nested PCR. N. caninum DNA was detected from the brain of 52%, kidneys of 22%, skeletal muscle of 18%, and heart of 4% of the aborted fetuses. The PCR-positive cases (55%, 11/20) were higher than seropositive cows (40%, 8/20) in a subset of 20 fetuses, but the PCR results of blood samples of the 20 cows were all negative. The seroprevalence of the 813 samples was 15.5% (43.4% of samples from Beijing, 5.7% of samples from Tianjin), compared to the PCR-positive blood samples of 0.9%. Our study showed that the nested PCR is a valuable diagnostic tool for the primary diagnosis of N. caninum in aborted fetuses, while ELISA is the preferred assay for testing blood samples collected from cows. The two assays are complementary in determining whether abortions are associated with N. caninum infection in cattle.