Submitted to: Research Workers in Animal Diseases Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: September 23, 2013
Publication Date: N/A
Technical Abstract: Haemophilus parasuis is the cause of Glasser's disease in swine, which is characterized by systemic infection resulting in polyserositis, meningitis, and arthritis. An enormous difference exists in the severity of disease caused by H. parasuis strains, ranging from lethal systemic disease to asymptomatic carriage. To identify differences in genotype that could account for virulence phenotypes, whole genome sequence analysis was performed on 10 H. parasuis strains. Genomic DNA from strains Nagasaki, 12939, SW140, 29755, MN-H, 84-15995, SW114, H465, D74, and 174 was used to generate Illumina paired-end libraries for genomic sequencing and de novo assembly. Virulence was evaluated using an intranasal challenge in caesarian-derived, colostrum-deprived (CDCD) pigs. H. parasuis strains Nagasaki, 12939, SH0165, SW140, 29755, and MN-H exhibited a high level of virulence as all pigs challenged with these strains developed clinical signs consistent with Glasser's disease between 1-7 days post challenge, although there were some distinctions among these groups. H. parasuis strains 84-15995 and SW114 were moderately virulent, in that approximately half of the pigs in each group developed Glasser's disease. H. parasuis strains H465, D74, and 174 were minimally virulent or avirulent in the CDCD pig model. Subsequently, pigs originally challenged with the avirulent strain 174 were rechallenged with the highly virulent strain Nagasaki and prior exposure to strain 174 induced partial protection from disease with Nagasaki. Initial comparative genomic analysis of the different strains has identified several significant differences in coding regions. These coding regions include predicted outer membrane, metabolism, and pilin or adhesin related genes, some of which likely contributed to the differences in virulence and systemic disease observed following challenge. These studies will be useful for identifying H. parasuis virulence factors and vaccine targets.