Comparison of the pathogenicity for chickens of Erysipelothrix rhusiopathiae and Erysipelothrix tonsillarum.

Twenty-two strains of Erysipelothrix rhusiopathiae, 14 strains of Erysipelothrix tonsillarum, and four other strains representing two serovars were examined for virulence in 30- to 40-day-old specific pathogen-free chickens. Some of the chickens that were given strains of serovars la, 2, 5, 6, 8, 9, 15 or 21 of E. rhusiopathiae showed signs of disease, lesions, bacteraemia or recovery of the bacterium. In contrast, there were no clinical signs, pathological lesions or bacterial isolations in chickens inoculated with the E. tonsillarum or other strains. The study thus confirmed that strains of some serovars of E. rhusiopathiae are pathogenic for chickens, but that E. tonsillarum strains are not pathogenic and should be omitted from potential causes of erysipelas in chickens.