Vertical transmission of Neospora caninum from three generations of naturally infected dairy cattle from Brazil.

Neospora caninum is a major cause of abortion in dairy cattle, and vertical transmission is considered the most relevant route. The present study aimed to evaluate the vertical transmission of N. caninum from three generations of naturally infected dairy cows. The indirect immunofluorescence assay (IFA) for IgG anti-N. caninum was used for the serodiagnosis, considering titles ≥100 as positive for cows and calves. A total of 152 pregnant dams were selected from farms in the State of São Paulo, and 37 (24.3 %), which gave birth to heifers were selected. These animals (first generation, F1) were divided into 18 (48.7 %) seropositive (1G+), and 19 (51.3 %) seronegative (1G-) animals. In the second generation (2G), sixteen calves (89 %) that were born from 1G+ were seropositive; however, no calves (0 %) were born positive from 1G-. The risk for vertical neosporosis transmission was approximately 34.6 times higher in 1G+ than in 1G- (OD = 34.6, IC 2.2-537, p < 0.00001). Finally, only four animals from 2G were followed up, and 3G (third generation) calves were born; three calves were sera positive from three positive cows (3/3, 100 %), and one negative cow did not transmit N. caninum to offspring. Herein, a higher risk of vertical transmission was observed in N. caninum sera-positive than in sera-negative cows.