DETECTION OF AFRICAN HORSESICKNESS VIRUS AND DISCRIMINATION BETWEEN 2EQUINE ORBIVIRUS SEROGROUPS BY REVERSE TRANSCRIPTION-POLYMERASE CHAIN-REACTION

A reverse transcription polymerase chain reaction (RT-PCR), based on t he gene encoding the NS2 protein of African horsesickness virus (AHSV) , was developed for rapid serogroup-specific detection of AHSV. The sp ecificity of RT-PCR products was confirmed by Southern blot hybridizat ion using a radioactively labelled cDNA probe specific for the NS2 gen e. This RT-PCR could discriminate between all known members of the AHS V and equine encephalosis virus serogroups. AHSV RNA was detected in a sample representing 0,005 plaque forming units in a dilution series m ade of infected cell culture material. In an immune horse which had be en vaccinated with a baculovirus expressed AHSV (serotype 4) VP2 subun it vaccine, viral RNA could be detected for up to 22 weeks post challe nge. AHSV RNA was detected in various organs of an infected horse. Vir al RNA was also detected by RT-PCR in nine suspected field cases of Af rican horsesickness while virus isolation was successfully performed o n eight of these cases.