[Effect of routes and doses of Salmonella abortus ovis inoculation on the abortive effect and serologic response of ewes].

Three successive experiments using a restricted number of Préalpes X Lacaune ewes were designed to form a procedure allowing the reproduction of an abortive infection with Salmonella abortus ovis. Effects of inoculations at mid-gestation were estimated by the duration of gestation, bacteriological excretion at lambing and evolutions of rectal temperatures and of serological antibodies. Serological responses were revealed with four tests: O or H agglutination tests in tubes, H agglutination or complement fixation tests in microtechnics. Intravenous inoculations of 10(9) salmonella induced lethal septicaemia. Intragastric inoculations of 10(7), 10(8), 10(9) or 10(10) salmonella did not produce effects related to inoculated doses; in particular the only abortion obtained in this way occurred after inoculation of 10(7) salmonella. Subcutaneous inoculation of 10(6) to 10(10) salmonella induced serological, bacteriological and clinical responses related to the inoculated doses: ewes with at least two febrile phases during the 20 days post-inoculation aborted, including two ewes not excreting salmonella at lambing. After intragastric or subcutaneous inoculation, and with the four serological tests, the initial raising of titers was followed by an early and rapid decrease, without a new rise round about the time of abortion; no salmonella was isolated from ewes autopsied three to six months after inoculation. It appeared that the subcutaneous inoculation of 10(10) S. abortus ovis viable to ewes at mid-gestation was able to frequently induce a sublethal but abortive infection.