Canine distemper virus (CDV) is a highly contagious, systemic, viral disease that commonly causes central nervous system disease in immature dogs. CDV can produce an unusual form of encephalomyelitis known as ‘multifocal distemper encephalomyelitis in mature dogs’. This chronic progressive form is a rare manifestation of CDV.
The aim of the report is to highlight the clinicopathological findings of two spontaneous cases of multifocal distemper encephalomyelitis in mature dogs and to show the pathological differences between this form and the usual CDV form in immature dogs.
Three-year-old English setter and 10-year-old German pointer dogs were referred to clinics with a 10 day history of generalized twitching and trembling. Dogs developed the signs suddenly after they went on the same hunting trip with their owners. The dogs were euthanized and their necropsies were performed. Tissue samples were routinely processed and stained with haematoxylin & eosin (H&E) and luxol fast blue (L.F.B.) methods. Immunohistochemical analysis was carried out, using CDV antibody.
Histologically, severe nonpurulent meningoencephalomyelitis was seen (Figure 1) and few acidophilic intranuclear inclusion bodies were found located specially within astrocytic nuclei (Figure 2). Those lesions were more prevalent in the hippocampus, the brain stem, cerebellum and the spinal cord.
Despite extensive vaccination of dogs against CDV, recent reports shows re-emergence and increased activity of CDV worldwide. Our report proves that CDV should be considered in the differential diagnosis of neurologic diseases of mature dogs even if they were vaccinated.