Rare detection of Neospora caninum in placentas from seropositive dams giving birth to full-term calves

Neospora caninum is thought to be transmitted to cattle by dogs, the only known definitive host. Although aborted fetuses seem the most likely source of infective material for dogs, placentas from seropositive darns appear also as a potential source of infective material. The objective of the study was to evaluate the presence of N. caninum organisms in placentas of full-term calves born to seropositive cows. Sixteen placentas, 11 from Neosporct-sewpositive cows, were examined histologically and by immunohistochemistry and polymerase chain reaction (FCR) assay for the presence of N. canimim. Mild placentitis was observed in all placentas. Neospom caninum was not identified by immunohistochemistry, but placentas from 2 seropositive dams were positive for N. caninum by PCR. These results suggest that placentas of full-term calves from seropositive cows may be a potential source of N. caninum for dogs, but the incidence of this mode of uansnussion is likely to be low.