Group-reactive ELISAs for detecting antibodies to African horsesickness and equine encephalosis viruses in horse, donkey, and zebra sera.

Group-reactive enzyme-linked immunosorbent assays (ELISAs) were developed to selectively detect antibodies to African horsesickness virus (AHSV) and equine encephalosis virus (EEV), 2 orbiviruses that infect equids. In indirect ELISA, guinea pig antisera to all known AHSV or EEV serotypes recognized immobilized AHSV serotype 3 or EEV Cascara, respectively. Antisera from naturally infected animals did not cross-react with their respective heterologous viruses. The ELISA was used in parallel with the complement fixation (CF) and agar gel immunodiffusion tests to detect antibodies in sera from animals in the field. The ELISA distinguished among those that contained antibodies to AHSV, EEV, or both viruses and was useful with sera that did not yield results in CF tests because of anticomplementary activity. Zebra and donkeys, both potential subclinical carrier animals in Africa, contained AHSV or EEV antibodies. Some sera reacted with 1 of the 2 orbiviruses, whereas others reacted with both. The ELISA can be used in projected epidemiological studies in which many serum samples must be assayed.