Disease caused by infection of piglets with Streptococcus suis is responsible for some of the most significant and disturbing losses in swine production. The disease is recognized by many producers and veterinary swine specialists as the most important infectious disease currently affecting swine production in North America.
The three main objectives of this vaccine trial were to control disease in piglets by vaccinating sows in an infected herd, to determine whether vaccination alters anti-Streptococcus suis antibody titre in sow colostrums, and to compare the disease in two groups that were vaccinated with subunit bacterins to a control group. Two strains of S. suis (serotypes 3 and 9) were isolated from untreated pigs showing signs of meningitis in this herd. Two subunit vaccines (A and B) were prepared from a combination of both of these strains and were combined with adjuvant. The control group was given placebo vaccine (C ) prepared from sterile saline and adjuvant. Sows and gilts were randomly assigned to one of the three groups and were vaccinated intramuscularly at four weeks before farrowing and one week before farrowing. Barn staff recorded the identification of pigs that died and whether they showed signs of S. suis disease prior to death. The antibody titre in the colostrums of the sows that were vaccinated with vaccine A (titre of 3581) or vaccine B (titre of 1807) was significantly (P < 0.01) greater than the titre in the colostrums of the control sows (titre of 109). Likewise, piglets nursing sows vaccinated with A or B vaccines had greater antibody titres than piglets nursing control sows. The number of piglets born alive was not different among groups A, B or C, but more pigs in control group C died of S. suis disease than in vaccine groups A or B. In conclusion, both vaccine A and vaccine B reduced death from S. suis disease in litters from sows or gilts vaccinated with either of them. Both the vaccinated sows and their piglets had more antibody than controls.