Fowl Cholera: Immune Response in Turkeys

Abstract

SUMMARY Emulsified water-in-oil fowl cholera bacterins prepared from 3 strains of formalin-killed Pasteurella multocida induced a high degree of immunity in turkeys against homologous but not heterologous challenge, demonstrating at least 3 immunogenic types of P. multocida associated with fowl cholera. However, both vaccinated and unvaccinated turkeys that survived challenge exposure were immune when re-exposed to different immunogenic strains, demonstrating an immune response to live P. multocida different from that to killed. A one-ml dose of bivalent bacterin was more effective than a 0.5-ml dose in protecting turkeys against experimentally induced fowl cholera. In a comparison of exposure methods, the commonly used method of swabbing nasal clefts of turkeys with a culture of P. multocida was a more severe challenge of immunity than contact exposure challenge with infected birds. In using a challenge culture of low virulence, the intramuscular (IM) route of inoculation was better than either of the other two methods for challenging the immunity of turkeys.