Designation of 15 serovars of Haemophilus parasuis on the basis of immunodiffusion using heat-stable antigen extracts

Abstract

Previous independent investigations of the serotyping of Haemophilus parasuis strains have led to the designation of serovars A to D, 1 to 7, Jena 6 to Jena 12, and ND1 to ND5. Heat-stable antigen preparations from the reference strains for these serovars were tested by immunodiffusion with rabbit hyperimmune antisera. The existence of 15 distinct serologic groups was apparent, for which we propose the designations serovars 1 to 15. Examination of 290 field isolates from swine in the former German Democratic Republic indicated a prevalence of serovars 4 and 5, which together accounted for 41% of the isolates examined. However, 26.2%O of the isolates were nontypeable with this test procedure and available antisera. Intraperitoneal inoculation of specific-pathogen-free pigs with cells representing the 15 serovars indicated differences in virulence which may be serovar related. Cells of strains representing serovars 1, 5, 10, 12, 13, and 14 were the most virulent, causing death or moribundity in inoculated pigs. Cells of serovars 2, 4, 8, and 15 caused polyserositis, but not death, in inoculated pigs. However, inoculation of cells of strains representing serovars 3, 6, 7, 9, and 11 resulted in no clinical symptoms or lesions indicative of H. parasuis infection. Haemophilus parasuis is the etiologic agent of porcine polyserositis and arthritis (Glasser's disease), which has historically been considered a sporadic, stress-associated disease of young pigs (17). In recent years, however, trends in swine production have resulted in large populations of swine maintained as isolated high health status or specificpathogen-free (SPF) herds. Introduction of H. parasuis into such herds, if they represent a nonimmune population, may have a devastating effect: infection may spread as a contagious disease of high morbidity, affecting pigs of all ages without obvious associated stress factors (1, 20, 22). Recent outbreaks in Europe (5, 10) and North America (11, 12, 29) attest to the increasing importance of H. parasuis as a pathogen of economic significance in swine. Considerable antigenic heterogeneity among H. parasuis isolates has been demonstrated by serotyping. In 1955, Bakos (2) described serovars A to D on the basis of examination of 120 isolates using a precipitation test. Schimmel et al. (27) serotyped 115 isolates from the former German Democratic Republic by using an agglutination test and defined three additional serovars. By using immunodiffusion with heat-stable antigen extracts, Morozumi and Nicolet (16) and Nicolet et al. (19) examined isolates from Japan and Switzerland and defined seven serovars, designated 1 to 7. Recently, Kielstein (4) and Kielstein et al. (8) examined 158 isolates from the former German Democratic Republic and reported the existence of seven new serovars provisionally designated Jena 6 to Jena 12. On the basis of examination of 243 isolates, primarily from North America, Rapp-Gabrielson and Gabrielson (24) reported the existence of five new serovars, which were designated ND1 to ND5. The pur...

Virulence, Transmission, and Heterologous Protection of Four Isolates of Haemophilus parasuis

“…One of the goals of this study was to directly compare the virulences of a set of H. parasuis isolates so as to identify strains with divergent virulences for future genome sequence comparisons. Based on previous experimental work and/or diagnostic information, it was expected that isolates 29755, 12939, and MN-H would be pathogenic with various virulences and strain SW114 would be nonpathogenic (7)(8)(9). Results from experiment 1 indicate that 3 of the 4 isolates are capable of causing systemic disease.…”

“…These pigs recovered quickly and without complications after treatment with ceftiofur, but it is unknown whether disease would have progressed had treatment not been initiated. This strain was believed to be nonpathogenic based on previous reports where it was given either intranasally or intraperitoneally to specific-pathogen-free pigs with no resulting clinical signs of disease and no gross lesions seen at necropsy (9,26,27). It is a strain that was originally isolated from the nasal cavity of a healthy pig (28).…”

“…Fifteen serovars of H. parasuis have been identified, but many isolates are nontypeable (9). Serovars 4 and 5 are isolated most frequently in conjunction with clinical disease in the United States (10).…”

Application of ERIC PCR for the comparison of isolates of Haemophilus parasuis

“…Many of the strains of the Moruzumi and Nicolet 18 and the Bakos 19 schemes are also used in the KRG scheme. 3 Hence, both REA and ERIC-PCR appear to show a similar ability to differentiate strains of H parasuis that are clearly unrelated.…”

“…2 The principal lesions associated with the disease are fibrinous or serofibrinous meningitis, serositis, pleuritis, peritonitis and arthritis that can occur in various combination or occasionally singly. 1 Considerable heterogeneity among H parasuis isolates has been demonstrated by methods such as serotyping, 3 colony morphology, 4 whole cell and outer membrane protein profiles 5,6 and REA of chromosomal DNA. 7,8 Despite this widespread recognition of intra-species heterogeneity, there have been few studies examining the strains associated with outbreaks of Glässer's disease.…”