Studies on Tyzzer's disease: transplacental transmission of Bacillus piliformis in rats.

Clinically healthy rats with antibodies to Bacillus piliformis were given prednisolone in the last week of pregnancy. B. piliformis was demonstrated in the livers of their offspring. None of the dams or the young rats showed clinical signs of disease. Antibodies to B. piliformis were found in the young rats at birth, and presisted for several months. The importance of potential transplacental infections when attempting to establish colonies free from B. piliformis in discussed.