Streptobacillus moniliformis infection in Swiss white mice

NSW Agriculture, Regional Veterinary Laboratory, Wagga, Australia.

An epizootic of disease attributed to infection with Streptobacillus moniliformis occurred in a colony of Swiss white mice. The mortality rate among the 180 breeding females in the 6 affected pens was 100%, and most of the sucking young died from starvation. Acute septicemia, subacute septicemia, and polyarthritis were the 3 forms of disease observed. Clinically, septicemic mice either were found dead or were depressed and hunched for 1-2 days prior to death. About a half of these mice had brown skin crusts overlying the mammae. Pathologic findings in cases of acute septicemia were few; in mice with subacute septicemia, there was acute, multifocal, suppurative, embolic interstitial nephritis, and the arthritic form was characterized by many subcutaneous and periarticular abscesses. Severe, acute, diffuse neutrophilic dermatitis was responsible for the brown skin crusts. The S. moniliformis isolate conformed morphologically and physiologically to classical descriptions of the organism. The infection may have gained entry to the colony via wild rats.