[Active immunoprophylaxis of Salmonella abortion in sheep]

A live vaccine was produced against the salmonellosis abortion in sheep with the use of an attenuated (chemically) strain of Salmonella abortus ovis. It was tested comparatively with a killed vaccine in sheep under experimental conditions. The dynamics of the agglutinating antibodies was followed up after immunization with the two vaccines, studying also the class of the immunoglobulins. It was found that the production of class IgG antibodies in sheep treated with the live vaccine proceeded more rapidly and at a higher level. After challenging with a virulent Salmonella abortus ovis strain te animals treated with the killed vaccine and those left as controls miscarried, while the sheep immunized with the live vaccine lambed normally. The vaccine was applied in field conditions to more than 400 000 sheep without postvaccinal accidents whatever. On farms where Salmonella abortus ovis infection was recorded in sheep the disease has no longer been a problem with the regular annual vaccinations of these animals.