AN UPDATE ON THE PRESENCE AND SPREADING IN ITALY OF RABBIT HAEMORRHAGIC DISEASE VIRUS AND OF ITS ANTIGENIC VARIANT RHDVa

Rabbit haemorrhagic disease virus (RHDV) is a non-cultivable calicivirus that infects rabbits (Oryctolagus cuniculus) and causes an acute fatal hepatitis, firstly described in China in 1984. The first consistent antigenic variant originated from the classical strain, called RHDVa, was identified almost contemporaneously in Italy and Germany in 1997. We report here the results of diagnostic studies in order to compare the rate of diffusion of RHDV and RHDVa in Italy since its first detection. From 2000 to 2003 RHDVa has been identified in 53,7% of the cases and, in particular during the last two years, a total of 201 cases of RHD were diagnosed, 128 (63,7%) of which resulted RHDVa. The higher percentages (70-100%) were found in those regions where is concentrated most of intensive rabbit production (Lombardia, Emilia Romagna, Piemonte, Veneto and Campania). This survey shows that RHDVa is present in most part of Italy and that it is rapidly replacing the RHDV “classical” strain. The importance of such variant is discussed with reference to vaccine preparation and application.