Submitted to: United States Japan Natural Resources Animal and Avian Health Panel
Publication Type: Abstract Only
Publication Acceptance Date: September 27, 2010
Publication Date: October 5, 2010
Citation: Brockmeier, S., Register, K.B., Loving, C.L., Nicholson, T.L. 2010. Use of an avirulent Isolate of Haemophilus parasuis as a vaccine. 45th US-Japan Cooperative Program in Natural Resources Panel of Animal and Avian Health Meeting. p 14. Technical Abstract: Pigs from an experimental herd free from known swine pathogens were used in a study to determine the virulence of several Haemophilus parasuis isolates and determine whether an avirulent isolate could provide protection against subsequent challenge with heterologous virulent isolates. Four groups of 5 pigs each were inoculated with a different isolate of H. parasuis intranasally (SW114, 12939, MN-H, and 29755), with a fifth group of 5 pigs serving as sham inoculated controls. Three of the 4 isolates caused systemic disease, with pigs showing clinical signs of disease (lameness, depression, neurologic signs) from 1 to 5 days post infection. All 5 pigs from the 12939 and 4/5 pigs from the 29755 and MN-H groups had to be euthanized or died peracutely. H. parasuis was isolated from systemic sites (pleura, peritoneum, joint, and/or meninges) from 12 of the 13 pigs showing clinical disease. One pig each from the 29755 and the MN-H group and all the SW114 pigs remained healthy with no clinical signs of disease. One control pig each was placed into the room with the lone survivor from the MN-H and the 29755 groups to determine whether transmission would occur. The contact pigs became ill 5 and 7 days later, respectively. The 5 surviving SW114 pigs and the surviving 29755 and MN-H pigs were then rechallenged with the 12939 isolate to determine if they would be protected from a heterologous virulent strain. The 3 surviving control pigs were also challenged with 12939. All three control pigs developed systemic disease, but all pigs previously challenged with SW114, 29755, or MN-H remained healthy. In a subsequent study, the SW114 strain was given as an intranasal live vaccine or as an IM bacterin to further determine the usefulness of this strain as a vaccine. Unexpectedly, 6 of 16 pigs given SW114 intranasally developed lameness with swollen hocks, and H. parasuis was isolated from the joints. Pigs that developed lameness were treated with ceftiofur and recovered uneventfully. Pigs were challenged with strain 12939 of H. parasuis 84 days after vaccination and pigs receiving both the bacterin and live intranasal vaccine were protected from challenge. Thus, the SW114 strain did protect against heterologous challenge, but demonstrated the potential to cause disease.