Diagnostics in the context of an eradication program: Results of the German bovine viral diarrhea proficiency trial.

Bovine viral diarrhea (BVD), one of the most important infectious diseases in cattle, causes major economic losses and significant impact on animal welfare worldwide. The major source for virus spread is persistently infected, immunotolerant calves and, therefore, their early identification is of utmost importance for disease prevention. Here, a ring trial was initiated to control the performance of diagnostic tests used in German regional laboratories in charge of the diagnostics within the country's BVD control program. A panel of five ear notch and five serum samples was provided for virological analysis. By an antigen ELISA, which was applied 26 times, the status of every sample was correctly identified in any case. In addition, a total of 54 real-time RT-PCR result sets was generated and also in most cases correctly classified. In addition to the virological test panel, a set of six sera and four milk samples was sent to the participating laboratories to be analyzed by serological methods. With serum neutralization tests, an excellent diagnostic sensitivity was achieved. However, one serum and both milk samples - positive for BVDV antibodies - repeatedly tested false negative by some of the used ELISA kits. All negative serum and milk samples were correctly identified by every commercial antibody ELISA. In conclusion, the BVDV proficiency test demonstrated that the used antigen/genome test systems allowed predominantly reliable diagnostics, while for four of the applied nine antibody ELISA kits adjustments are recommended.