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Studies on an Attenuated Swine Fever Vaccine

1966; Elsevier BV; Volume: 122; Issue: 5 Linguagem: Inglês

10.1016/s0007-1935(17)40603-8

1879-3606

S. A. Keeble, J.T. Done, J.H. Darbyshire,

Viral Infections and Immunology Research

Pigs were inoculated intramuscularly or intracerebrally with an attenuated swine fever vaccine, which had been prepared from strain I.F.F.A.22 virus and was supplied by the Institut Merieux. This virus strain was obtained by passing the S.F.A. (Hudson, 1953) strain of virus, after 504 passages in rabbits, through 22 passages in rabbit kidney tissue cultures. Blood samples were taken at intervals after vaccination and were examined for evidence of leucopenia. Some of the pigs were killed before challenge, and their brains were examined for lesions indicative of swine fever. The remainder of the pigs were challenged with a virulent strain of swine fever virus 21 days after vaccination. Immunodiffusion tests were carried out on sera at different stages of the experiment. The vaccine produced no marked changes in the white blood cell picture, such as occur with lapinized virus vaccines. Changes in the central nervous system after intramuscular injection were absent. Although after intracerebral injection lesions were found, they were not classed as swine fever-positive. All sera taken up to the 21st day gave negative reactions in immunodiffusion tests; thereafter all sera were positive except one which gave a doubtful reaction. After challenge all unvaccinated controls were killed when moribund whereas all those vaccinated survived and remained clinically normal. It is concluded that, under the conditions of the test, this vaccine is safer than standard lapinized vaccine and is capable of producing a strong immunity. It should not seriously interfere with swine fever diagnosis by histopathological methods, but could confuse the interpretation of immunodiffusion tests.