Evidence of in Utero Anti-Neospora caninum Antibody Production in Paired Sow and Umbilical Cord Blood Samples

Neosporosis, caused by <i>Neospora caninum</i>, is a major protozoal disease responsible for reproductive disorders and economic losses in livestock. Swine are susceptible to <i>N. caninum</i> infection, as evidenced by serological and experimental studies, but the impact of natural infection on reproduction failure remains poorly defined. The objective of this study was to investigate <i>N. caninum</i> transplacental transmission in naturally infected sows by detecting an active fetal immune response in their stillborn piglets. Paired maternal blood and umbilical cord blood (UCB) samples were collected from 247 sows and stillborn piglets across 39 farrow-to-finish farms in mainland Greece. Sera were tested for anti-<i>N. caninum</i> IgG and IgM antibodies using an indirect fluorescence antibody test. An IgG and IgM seropositivity for <i>N. caninum</i> of 8.91% and 3.64%, respectively, was reported in sows, while lower percentages of IgG and IgM antibodies (3.24% and 0.81%, respectively) were detected in UCB samples. Overall, antibodies were detected in 4.05% of UCB samples, indicative of in utero antibody production. Positive samples were more frequently encountered on smaller farms with up to 250 sows, possibly due to lower biosecurity standards. The detection of antibodies in UCB resulting from the fetal immune response to intrauterine <i>N. caninum</i> infection is indicative of the potential involvement of <i>N. caninum</i> parasitism in reproductive system disorders. Testing of UCB for the presence of anti-<i>Neospora</i> antibodies elucidates the dynamics of parasite transmission within the farm and provides evidence for the implementation of more efficient biosecurity and preventative measures.