Schmallenberg Virus Infection Diagnosis: Results of a German Proficiency Trial.

Since Schmallenberg virus (SBV), an orthobunyavirus of the Simbu serogroup, was detected in Central Europe in 2011 for the first time, numerous diagnostic test systems for genome or antibody detection have been established. Therefore, a laboratory proficiency trial with 28 veterinary laboratories was initiated to allow performance evaluations of the different veterinary diagnostic laboratories and the performance of the used assays. A panel of selected sera and bovine semen samples for the analysis by real-time PCR and an additional set of serum samples for serological analysis were provided. All participants were asked to investigate the samples with the test systems routinely used in their laboratory. While SBV-genome was reliably detected in serum samples, the sensitivity in semen samples seems to depend on the application of the recommended optimized nucleic acid extraction method (TRIzol LS Reagent-based, Hoffmann et al., 2013, Vet. Microbiol., 167, 289). SBV-antibody-positive samples and sera negative for antibodies against Simbu serogroup viruses were in most cases correctly classified by the participants with the used commercial ELISA kits. However, a serum of the panel which contained antibodies against Akabane and Aino viruses, which are closely related to SBV, was repeatedly tested positive by two of four used ELISA kits. However, an excellent diagnostic sensitivity and specificity was achieved using a serum neutralization test. In conclusion, the here described German SBV proficiency test demonstrated that the available test systems allowed reliable SBV diagnostics in standard veterinary laboratories when recommended and approved assays are used.