Serologic comparison of four isolates of rabbit hemorrhagic disease virus

An acute, fatal disease of rabbits, termed Rabbit Hemorrhagic Disease (RHD), has occurred in Asia, Europe, and North America since 1984. The clinical signs, pathologic lesions, and epidemiologic features seen in the various outbreaks were very similar. Although RHD virus (RHDV) was initially characterized as a picornavirus or a parvovirus, it is now proven to be a calicivirus. This study compared the immune responses generated following the vaccination and challenge inoculation of rabbits with isolates of RHDV obtained from Italy, Korea, Mexico, and Spain. The cross-reactivity of antisera was demonstrated using the hemagglutination inhibition (HI) test. There were minimal differences between the homologous and heterologous responses. Statistical analysis of the HI results showed no difference between the isolates within the Italian, Korean, and Spanish vaccinate groups. The difference obtained between the Mexican and Korean antigens within the Mexican vaccinate group is likely due to individual animal variation. The similarity of the isolates was also demonstrated using a monoclonal antibody directed against RHDV.