Brain lesions were also frequently found in the cerebrum, particularly
the gray matter in aborted Neospora-infected fetuses (18).
The cerebrum showed a significantly higher frequency of lesions
than the medulla oblongata and cerebellum (18). Our findings are
in accordance with previously published results. Most lesions
were found in superficial gray and white matter and to a lesser
extent in deeper areas. Lesions indicative of glial and inflammatory
cell activation suggest some form of immune reaction against
the parasites. It is also possible that the parasites could have already
been eradicated, thereby leading to differences in the distribution
of lesions and parasite DNA. N. caninum is believed to be
disseminated hematogenously, with perivascular cuffing a common
tissue response in neosporosis. This was actually observed in
seven of the eight experimentally infected animals. Perivascular
spaces around the artery in the brain have been shown to play an
immunological role. The structure of the perivascular space in
basal ganglia, including the amygdala, differs markedly from that
seen in the cortex (19). Although it is not clear why few lesions
were found in the deeper areas of the brain, the differences in
anatomical structure, including the vascular system of each area,
possibly affects invasion of the parasite or the host immune reaction.