The response of turkeys to varying doses of live oral Pasteurella multocida vaccine.

Groups of 30 turkeys were vaccinated by the drinking water route against fowl cholera with varying doses of the low virulence, CU strain, of Pasteurella mulocida. One group (heavy dose) received 1.2 x 107, another (medium dose) 1.5 x 105, and a third (light dose) 1.0 x 103 bacteria per ml. of drinking water. Two (6.7%) vaccine induced cholera deaths occurred in the heavy dose group. No deaths resulted in the other groups. Maximum serum antibody titers per group were; light dose 1:32, medium dose 1:128, and heavy dose 1:256. Three weeks after vaccination all turkeys were challenged with a large dose of virulent P. multocida (P-1059). Mortalities resulting from the challenge were 100% in the light group, 23% in the medium group, 4% in the heavy group, and 100% in the unvaccinated controls.