Neuronal spread of swine hemagglutinating encephalomyelitis virus (HEV) 67N strain in 4-week-old rats.

Abstract

The HEV 67N strain causes encephalomyelitis or vomiting and wasting syndrome in piglets 1,2. In experimental infection of piglets, the virus spreads along the nerve pathways to the central nervous system (CNS), and is restricted to the neurons. In our experimental studies of HEV 67N strain, the virus produced encephalitis in mice when inoculated by several routes, and propagated mainly in the neurons in the CNS 4. However, 20-day-old or older mice were resistant to the virus inoculated by intravenous (i.v.), intraperitoneal (i.p.) or subcutaneous (s.c.) route. In contrast, 4-week-old rats died of encephalitis after i.v., i.p. and s.c. as well as intracerebral (i.c.) and intranasal (i.n.) inoculation. However, when rats were inoculated by s.c. route, they died a few days earlier than those by i.p. and i.v. routes, suggesting that the virus might be spread to the CNS by neural routes rather than blood stream. To see the virus spread from the peripheral nerve to the brain, the virus was directly inoculated in to the sciatic nerve of rats. These studies demonstrated that HEV spread from the sciatic nerve to the brain by the neural route, and that persistent infection of HEV was established in rats6.