“…Passive immunization of dogs (POLDING et al, 1959) or ferrets with hyperimmune RV antiserum was unsuccessful, although in vitro neutralization was found by some authors MORNET et al, 1960;IMAGAWA et al, 1960) but not by others DELAY et al, 1965) using different test systems. In agar gel diffusion tests, spur formation was seen when hyperimmune RV antiserum prepared in rabbits was diffused against CDV and RV antigens, indicating a difference in antigens (WHITE et al, 1961).…”