Erysipelas rhusiopathiae Infection

Erysipelas rhusiopathiae infections were observed in an outbreak that occurred in laboratory rats in Scandinavia. Lesions included chronic fibrinopurulent polyarthritis, myocarditis, and endocarditis.

Haemophilus spp. and V-Factor-Dependent Pasteurellaceae Infection

Haemophilus spp. and V-factor-dependent Pasteurella- ceae belong to the family Pasteurellaceae. Specific path­ogen-free rats are often colonized with Haemophilus spp.

FIG. 2.39. Corynebacterium kutscheri abscess in the liver of a rat. Note the prominent colonies of bacteria (arrow) adjacent to the necrotic center of the lesion.

and V-factor-dependent Pasteurellaceae, which are gen­erally commensal in nature, but can be opportunistic pathogens under some circumstances. An undefined species of Haemophilus has been isolated from the nasal cavity, trachea, lungs, and female genital tract of rats. In rats sampled from one vendor, the organism was recov­ered from a significant percentage of animals, and anti­bodies to the Haemophilus sp. were detected in close to 50% of animals tested. On microscopic examination, mild inflammatory cell infiltrates were present in the lower respiratory tract. Coinfection with other respira­tory pathogens was not fully investigated. Experimental intranasal inoculation of athymic F344-rnu rats with V-factor-dependent Pasteurellaceae isolates resulted in colonization of the respiratory tract, but without dis­cernable clinical signs or lesions. There is a very blurred distinction between commensal and pathogen within this family, so that the Federation for European Labora­tory Animal Science Associations (FELASA) recommends screening for all members of Pasteurellaceae by serology, culture, and/or PCR.