VI, 1. Epidemiology of toroviruses.

The discovery of the toroviruses, which comprise a genus of the family Coronaviridae, began with the serendipitous isolation of the morphologically unique Berne virus (ETV) in feces of a horse. This chapter discusses the epidemiology of toroviruses. ETV was first detected by the isolation of the virus in cell culture. Growth of ETV in cell culture allowed for the characterization of the virus, in terms of its morphology, morphogenesis, protein and nucleic acid composition, and facilitated investigations into its replication strategy. The successful propagation of ETV in cell cultures facilitated the development of a virus-neutralization assay that made it possible to gain an insight into the sero-epidemiology of this virus in various animal populations. Although ETV has been isolated, only once from a horse, there is evidence that antigenically related viruses are widespread in the equine population. The sero-prevalence of ETV-specific antibody as measured by virus neutralization test is very high in the horse population with 35% of randomly collected sera in Germany and 81% in Switzerland being positive.