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Two experiments were carried out to evaluate the effectiveness of a 12-month preservation period on the protective effect of various commercial swine Actinobacillus pleuropneumoniae (App) inactive bacterins.
total of 7 commercial A. pleuropneumoniae inactive bacterins were collected and tested. The immune defence index (!DI) against mice decreased during the 12-month preservation period in which observations were made. After 9-month period of preservation the !DI decreased to 0.98 ( which is below the accepted standard ) in one of the 7 bacterins tested. While after 12-month preservation, the ID! of the 3 bacetrins decreased to 0.98, 0.83 and 0.79 respectively ( below the accepted standard), however the !DI of the other 4 bacterins remained higher than 1.0 ( accepted standard ). The antibody response curves had a similar pattern as that measured by the ID! test by using agglutination test. The highest antibody titers were reached at 8 weeks post vaccination, its geometric mean titers were at 11.31.
A total of 3 bacterins with the !DI over 1.0 were selected for evaluation on the protection against by a virulent A. pleuroneumoniae in 6-week pigs. The results indicated that the higher the !DI ofbacterin had, the higher the immunity of pigs against App will be prospected.
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