Cross-reactions between bluetongue (BT) and epizootic haemorrhagic disease (EHD) virus serogroups have been reported. Ibaraki (IB), a member of EHD the serogroup, is endemic in Japan. The agar gel immunodiffusion test (AGID) is performed to survey for BT antibody in Japan. BT AGID-positive results are sometimes observed in areas of Japan in which IB is endemic, and this makes the interpretation of BT surveillance results difficult. However, the frequency of cross-reactions between BT virus (BTV) or IB virus (IBV)-positive field samples against the IB and BT AGID tests is not clear. The frequency of serological cross-reactions between Ibaraki and bluetongue viruses using the agar gel immunodiffusion test was investigated. Also, we evaluated the cross-reaction between IB and BT in the competitive enzyme-linked immunosorbent assay (c-ELISA). The percentage of IB neutralisation-positive bovine serum samples that showed a positive result in the BT AGID test was 42.5%; 12.2% of the BT AGID-positive serum samples and 2.5% of the BT AGID-negative serum samples showed a positive result in the IB AGID test. When the BT c-ELISA was used, these cross-reactions disappeared. These results indicate that serum samples from areas in which IB is epidemic often have positive results in the BT AGID test, but negative results in the BT virus neutralisation test (VNT). To obtain specific BT surveillance results in these IB endemic areas, the AGID-positive results should be confirmed using the c-ELISA or VNT.
(Immunopathology Section, Department of Immunology TEL +81-29-838-7833)
Reference:
Shimizu et al. (2004) Vet. ltal. 40: 583-586.
