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In this test, four BYD strains, Tobias, NY1, VJGM and Egan, were inoculated into SPF pigs, then challenged with ALD virulent HC virus.
Close observation on clinical signs and HC neutralizing antibody response was conducted and compared among these 4 BVD strains used.
No bad post vaccination reaction was found among these 4 vaccinated groups. After ALD challenge, the pigs of NY1 with 103.8 TCID50 group showed fever for 2-3 days and slight depress, anorexia, but recovered soon. The pigs vaccinated of Tobias strain with 105.3 TCID50 did not show reaction post challenge. The pigs vaccinated with 103.0 TCID50 of VJGM strain showed fever for 2-3 days and slight decrease in spirit and appetite, after HC challenge but recovered soon. The pigs vaccinated with 103.0 TCID50 of Egan strain and101.5 TCID50 of NY1 strain showed typical HC lesions.
No HC or BYD antibody was detected in pigs vaccinated with 103.8 TCID50 of NY1 before challenge, but after challenge, HC antibody titer was reached 101.98 or above and BVD antibody titer was very low.
Trace HC neutalizing antibody and low BVD antibody with 100.91 were detected in pigs vaccinated with 105.3 TCID50 of Tobias before challenge. After challenge, HC antibody reached as high as 102.26 and BVD antibody as 102.91 or above.
Trace amount of HC antibody was also found in pigs vaccinated with with 102.5 TCID50 of VJGM before challenge and 102.41 titer was found after challenge. BVD antibody titer was 101.04 before challenge and reached 3.15 after challenge.
No HC antibody titer and 101.98 of BVD antibody titer were detected in pig vaccinated with 103.0 TCID50 of Egan befer challenge.
Though trace amount of HC antibody and 103.03 of BVD antibody were detected, the pig still died of typical HC lesions after ALD virus challenge.
No HC and BVD neturalizing antibody were dectected after 101.5 TCID50 of NY1 vaccinated and after ALD virus challeng.
From the data obtained above, the protection against HC infection by BVD vaccination depended upon virus titer contained in BVD vaccine and the development of HC antibody, but seems not depended on BVD antibody titer. Among these BVD strains, the effective protection order was Tobais, NY1 ,VJGM and Egan.
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