A competitive ELISA for the detection of group-specific antibodies to African horse sickness virus.

A competition enzyme-linked immunosorbent assay (ELISA) has been developed for the rapid identification and quantification of antibodies against African horse sickness (AHS) in sera from solipeds. The data showed the ELISA to be sensitive, specific and reliable. More than 1600 sera from 37 different countries were examined and results compared with those obtained by agar gel immuno-diffusion (AGID) tests. In no case did any of 775 sera from countries where AHS has never been reported and where AHS vaccines are not used, record an ELISA titre greater than 4. A titre equal to or greater than 8 was considered positive. Using this criterion, 96.3% of sera tested in both assays were in agreement. Doubtful results by AGID (1.7%) were clearly defined in terms of positivity and negativity by ELISA. This ELISA is suited for the rapid laboratory confirmation of AHS and should be considered as a replacement for the traditional AGID test.