Minimum dose, antigen content, and immunization duration of a trivalent vaccine of inactivated Haemophilus parasuis serovars 4, 5, and 12 against Glässer's disease in pigs.

The objective of this study was to assess the minimum dose, antigen content, and immunization duration of a trivalent vaccine containing inactivated Haemophilus parasuis serovars 4, 5, and 12 and the Montanide GEL 01 PR adjuvant in piglets and pregnant sows. Our results demonstrated that the minimum vaccine dose was 2 mL per pig and the optimal antigen content 2.0 × 109, 1.0 × 109, and 1.0 × 109 colony-forming units/mL of serovars 4, 5, and 12, respectively. The vaccine provided effective protection 14 d after the 2nd vaccination, and the period of immune protection was 180 d (6 mo) after the 2nd vaccination. Maternal antibodies provided early protection for the piglets, and vaccinating the sows before farrowing helped to control disease and protected the piglets during lactation; the piglets were protected during the finishing period by being vaccinated during lactation. Our findings provide a basis for developing a commercial trivalent vaccine of inactivated H. parasuis serovars 4, 5, and 12 against Glässer's disease.