Neospora caninum,an apicomplexan parasite [1],is recognized as a major abortifacient factor in bovine [2].How does N.caninu infect host cells? The infection mechanism mosdy described includes the recognition and adhesion to the surface of host cells,entrance into the cytoplasm and parasitophorous vacuole (PV) formation,and finally replication in the PV [3,4].However,we also observed parasites without PV membrane surrounding (no-PVM) within the nucleus during this infection.How does N.caninum enter the nucleus?