Abstract
Based upon the findings of aquired resistance after natural infection, effective vaccination with killed organisms and the resistance due to maternal antibodies, as repo rted previously, two attempts were made at eradicatingB. bronchisepticafrom guinea pig breeding colonies. First, it was intended to remove all animals still excreting the organisms as well as uninfected animals from the colony and to establish anew colony. After such depopulation was continued for 4 months, the detection rate of the organisms was found to lower to 11 per cent from 78 per cent at the begin fling of the experiment. Finally, in 6 months, 73 breeders carrying no organisms were selected from a stock colony consisting of 128 guinea pigs for establishing a new colony, which was proved to be free of the organisms by repeated checking for further 5 months. Another attempt was made to establish a free colony by vaccination with killed organisms. In a colony consisting of 108 breeders and their offspring and showing 71.3 per cent at the highest detection rate of the organisms, all breeders were injected with merthiolate-killed vaccine, without interruption of breeding. Beginning 4 months later, breeders shedding the organisms were destroyed, and the eradication was successfully achieved also in this colony.
