Abstract:
African horsesickness is an infectious but non-contagious disease caused by an orbivirus belonging to the Reoviridae family. The disease is classified as notifiable by the OlE because of the potential severe economic consequences that can result from outbreaks. Bluetongue, an arthropod-transmitted disease of wild and domestic ruminants, is caused by the bluetongue virus, which is the prototype species of the genus Orbivirus. Bluetongue is also a notifiable disease because it can spread very rapidly in naive populations of susceptible livestock. Strict restrictions have been issued for the trade in animals and animal products from infected areas. In the present study, a duplex one-step real-time RT-PCR using the fluorogenic dye SYBR® Green I was developed for the specific detection and identification of AHSV and BTV in one reaction, using melting temperatures (Tm) to discriminate between the viruses. Two primers pairs were designed to bind to areas of homology within genome segment 7 (VP7) of AHSV and genome segment 5 (NS1) of BTV respectively. The duplex real-time RT -PCR based test utilizes single tube RT -PCR amplification in which AHSV and BTV primers were used simultaneously. The RT-PCR primers amplified 232 bp of genome segment 7 from all nine serotypes of AHSV and 79 bp of genome segment 5 from all 22 BTV serotypes that were tested. When both viruses were present, two melting peaks were simultaneously generated at 76.30°C and 80.04°C representative of BTV and AHSV amplification products respectively. Serogroup-specific products were amplified from dsRNA of field isolates of AHSV and BTV. dsRNA from EHDV and EEV failed to demonstrate either the 232 bp specific AHSV PCR product or the 79 bp specific BTV product. These results indicate that the duplex real-time RT-PCR could be a useful technique for detection of AHSV and BTV from isolated viral dsRNA.
