Protozoal encephalomyelitis of dogs involving Neospora caninum and Toxoplasma gondii in New Zealand

In a retrospective study of 15 cases of encephalomyelitis in dogs, three cases of Neospora caninum and two cases of Toxoplasma gondii infection were identified using immunohistochemical staining of central nervous system sections. All cases of neosporosis showed ataxia and progressive hind limb paralysis due to multifocal non-suppurative meningoencephalomyelitis which was most severe in the spinal cord and base of the brain stem. Neospora tissue cysts could not be distinguished morphologically from those of T. gondii using light microscopy, but electron microscopy confirmed their characteristic features. Although Neospora abortion in cattle has only recently been recognised in New Zealand, this study has shown that neosporosis has been present in dogs since at least 1972.