Co-circulation of bluetongue and epizootic haemorrhagic disease virusesin cattle in Reunion Island

Bluetongue virus (BTV) and epizootic haemorrhagic disease virus (EHDV) in deer havealready been isolated in Reunion Island and have caused more or less severe clinical signsin cattle (EHDV) or in sheep (BTV), as observed in 2003. In January 2009, cattle in ReunionIsland showed clinical signs suggesting infection by one or the other of these arboviraldiseases. A study was set up to determine the etiology of the disease. Analysis by reversetranscriptase-polymerase chain reaction (RT-PCR) performed on blood samples from 116cattle from different districts of the island detected the presence of the EHDV genome in106 samples and, in 5 of them, the simultaneous occurrence of BTV and EHDV. One strainof EHDV (7 isolates) and one of BTV were isolated in embryonated eggs and a BHK-21 cellculture. Group and subgroup primer-pairs were designed on the segment 2 sequencesavailable in GenBank to identify and type the EHDV strains.Phylogenetic analysis of the genomic segment 2 (encoding the VP2 serotype-specificprotein) of the isolates confirmed the serotypes of these two orbiviruses as BTV-2 andEHDV-6 and allowed them to be compared with previously isolated strains.