Observations on mouse-infective stocks of Cowdria ruminantium: attempts to demonstrate persistence of the organism in mice immune to the Kwanyanga stock.

Mice immunised against the Kwanyanga stock of Cowdria ruminantium by infection and treated with oxytetracycline proved immune to challenge on day 40 and also to a second challenge on day 125 after infection. Treatment with the experimental dithiosemicarbazone gloxazone on days 59 and 73 did not abolish immunity to challenge on day 125. No persistence of the organism in immune mice that had been challenged on day 40 could be demonstrated by subinoculating blood and liver homogenate on day 126. These results are different from findings reported elsewhere with the mouse-infective Kumm stock.