Long Term Surveys on Tyzzer's Disease in Three Rat Breeder Colonies

Abstract

Retired rats of SD strain from three breeder colonies (A, B and C) were monthly monitored for CF antibody to Tyzzer's organism for 2 to 6 years. In colony A, antibody-positive rats were found at frequencies ranging from 5 to 100% with a single peak during about one year without any detectable signs of apparent disease. However, in colony B, in spite of the outbreak of the disease, antibodypositive animals were only sporadically detected during about 4 years after the outbreak. Thereafter, in this colony, the antibody was not demonstrated in all animals examined for 2 years, and susceptibility to the disease of 3-week-old rats was the same as that of ones from non-infected colony. Cortisone test did not suggest the infection. In colny C, no antibody-positive rats were detected for 3 years.