Molecular Characterization of a Haemagglutinating and Non Haemagglutinating Rabbit Haemorrhagic Disease Viruses From Egypt

Rabbit viral haemorrhagic disease (RVHD) is a highly contagious, peracute and acute viral disease of both wild and domestic rabbits caused by rabbit haemorrhagic disease virus (RHDV). RHDV is considered as a haemagglutinating virus; however, there is a growing evidence for presence of non haemagglutinating RHDV strains. In this study, two RHDVs have been characterized. The two viruses were selected from ten different infected rabbit flocks. One of them had haemagglutination (HA) activity and the other one lacked HA activity. HA test was carried out on both isolates at 4°C using human red blood cells (RBC) type ‘O’. RT-PCR was performed on the liver samples of the ten infected rabbit flocks using specific primers targeting VP60 gene. The obtained partial VP60 gene sequences of the two selected strains were aligned with other haemagglutinating and non haemagglutinating strains of RHDV in the world, including ‘‘RHDVa’’ strains as France 99-05, France-Reu-00, Germany-Triptis and China TP. Phylogenetic analysis showed that the two strains were genetically different. Haemagglutinating strain was similar to Rainham strain which is low haemagglutinating virus while non haemagglutinating strain was similar to whn-1 strain which is non haeagglutinating virus. The study confirmed presence of non haemagglutinating RHDV in rabbits reared in Egypt and suggested that VP60 might be related to HA activity.