Rapid screening of embryonated chicken eggs for bluetongue virus infection with an antigen capture enzyme linked immunosorbent assay.

The sensitivity and specificity of an antigen capture ELISA have been compared with virus isolation in cell culture. Bluetongue virus (BLU) (serotype 23) from the blood of a sheep was titrated by inoculating embryonated chicken eggs (ECEs) and detecting viral antigen in chicken embryo livers using an antigen capture enzyme linked immunosorbent assay (ELISA) (Stanislawek et al., 1996. Detection by ELISA of bluetongue antigen directly in the blood of experimentally infected sheep. Vet. Microbiol. 52, 1-12). Five days after inoculation of ECEs with lysed red blood cells from the infected sheep the embryo livers were harvested and homogenised. The supernatant from the homogenate was used in the antigen capture ELISA to determine which livers were infected and the virus titre calculated as CEID50/ml packed red blood cells. These results were compared with a standard cell culture isolation protocol which passaged the liver homogenate supernatant through Aedes albopictus cells and up to three passages in BHK21 cells. The antigen capture ELISA showed 100% sensitivity and specificity with no false negatives or false positives when compared to cell culture isolation of the virus. The major advantage of the combination of ECE inoculation and antigen capture ELISA is the reduction in the time to less than 7 days from a maximum of 35 days for the ECE/cell culture system. The procedure is easy to undertake, cost effective and does not require expensive specialist cell culture facilities.