Schmallenberg virus challenge models in cattle: infectious serum or culture-grown virus?

Schmallenberg virus (SBV), discovered in Europe in 2011, causes mild transient disease in adult ruminants, but fetal infection can lead to severe malformation in cattle, sheep and goats. To elucidate the pathogenesis of this novel orthobunyavirus, considerable efforts are required. A reliable and standardized infection model is essential for in vivo studies. In the present study, two groups of four cattle were inoculated with either serum passaged in cattle only or cell culture-grown virus. The replication of culture-grown SBV in cattle was reduced compared to virus inoculated via infectious serum. In a second experiment, the infectious serum was titrated in calves; the tested batch contained 10(2.83) infectious doses per mL. Hence, serum-borne virus that was only passaged in the natural host is a suitable option for a standardized SBV infection model.