Suggesting the possible role of Turkey Herpesvirus or HVT-like as a predisposing factor or causative agent in multiple sclerosis.

Wild birds are referred to as 'vectors' of an exogenous causative agent of MS, in particular the Marek's disease virus, but this has yet to be confirmed. The epidemiology of MS shows that it occurs worldwide but that there is a high incidence of MS clusters within specific geographical distributions such as in cooler, temperate, zones in a North/South gradient from the equator. Furthermore, these regions are well known as preferred zones for wintering/breeding/feeding purposes and for having a high density of wild birds. A significant observation is that these MS clusters are located on the main global flyways of migratory birds. In 1973, herpesvirus of turkeys (HVT) was isolated for the first time in Florida in asymptomatic wild turkeys and serological studies indicated that it was widespread throughout this region. Experimental data for HVT showed that in chickens it causes prolonged latent infection and no clinical disease, and as showed in latent infected chickens viral RNA was detected in lymphocytes, feather follicles and peripheral nerves. Also in ovo infection or in young infected chickens the HVT can cause demyelination in peripheral nerves. Possible latency and demyelination have both been referred in MS. This study attempts to draw a link between HVT or HVT-like, probably spread with the global migration wild bird flyways, and its possible involvement in multiple sclerosis (MS) aetiology, as an initiate or causative agent. A map with the world's main migratory bird flyways and key MS related regions are included.