Possible initiation of viral encephalomyelitis in dogs by migrating lymphocytes infected with distemper virus.

The principal pathways by which viruses spread to the central nervous system (C.N.S.) are considered to be direct invasion along peripheral nerves or the haematogenous route. The latter is thought to involve passive transfer or active replication of virus in C.N.S. endothelial cells. In this study histological evidence of mild perivascular encephalomyelitis was found 8-10 days after infection of dogs with canine distemper virus (C.D.V.). C.D.V. antigen and viral nucleocapsids were detectable in the mononuclear cells infiltrating nervous tissue and C.D.V. was isolated from lymphoid tissue and buffy-coat cells. C.N.S. infection may thus be initiated by migrating virus-infected lymphocytes and this pathway may operate in other viral disorders of the C.N.S.