Serial Passage of Hog Cholera Virus in Rabbits

Abstract

Two strains of hog cholera virus were inoculated into rabbits. One strain continued in serial passage became attenuated for swine and after 15 rabbit passages produced a febrile reaction of short duration as the only sign of illness. This attenuated strain fully immunized swine to the virulent hog cholera virus. The other strain was present in rabbits for 1 but not 2 consecutive passages. With 6 continued transfers alternately between swine and rabbits, the amt. of virus in the rabbit''s spleen attained 100 times that found in the initial rabbit transfer. Serial passage in the rabbit was then successful for 2 but not 3 transfers. Evidence of attenuation of this strain was the lengthened incubation period in swine inoculated with the rabbit-passed material. Possible explanations for the difference in adaptability of these strains are discussed.