COUNTERMEASURES TO PREVENT THE PORCINE RESPIRATORY DISEASE COMPLEX (PRDC)
Location: Virus and Prion Research Unit
Title: Studies of pathogenesis, transmission, heterologous protection, and genomics of four isolates of Haemophilus parasuis
Submitted to: Conference Research Workers Disease Meeting
Publication Type: Abstract Only
Publication Acceptance Date: September 30, 2009
Publication Date: December 6, 2009
Citation: Brockmeier, S., Loving, C.L., Register, K.B., Nicholson, T.L., Bayles, D.O., Phillips, G.J. 2009. Studies of pathogenesis, transmission, heterologous protection, and genomics of four isolates of Haemophilus parasuis [abstract]. 2009 Conference of Research Workers in Diseases. Abstract No. 15, p. 118.
Pigs from an experimental herd free from known swine pathogens were used in a study with several Haemophilus parasuis isolates in an effort to identify isolates of varying virulence whose genome sequences could assist in elucidating virulence mechanisms. 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. Thus, pigs within susceptible groups can remain healthy and serve as reservoirs for transmission, and heterologous protection using avirulent isolates is possible. Draft genome sequences have now been obtained from H. parasuis isolates 29755, MN-H, and 12939, and preliminary comparisons suggest variation in the gene complement of distinct strains.