Theresearch On Cattle Bivalent Vaccine To Both Type A And B Pasteurella Multocida

In recent years, with the rapid development of China’s cattle industry, the increase in cattle transport between the various regions leads to occurrence of transport stress-related infectious diseases. The most severe disease is called bovine respiratory disease complex which always arises after transportation, shows mainly lung disease, and its morbidity and mortality is high, causing significant losses to the cattle industry in China. The pathogenic study revealed that Mycoplasma bovis is the etiological pathogen, but often co-infected with type A Pasteurella multocida (Pm). The co-infection makes the disease more difficult to be treated and prevented.Currently, the clinical Pasteurella multocida vaccine used for the prevention of bovine hemorrhagic septicemia which is caused by type B Pm, is made by type B Pm. Since Pasteurella multocida induces poor cross-protection between serotypes, the vaccine to type B Pm can not effectively protect the cattle against the attacks of the type A Pm. Therefore, this study aimed to screen a vaccine candidate of type A Pm strain, which has a strong virulence and good immunogenicity and further make a bivalent vaccine to both type A and B Pm. Therefore we can prevent two types of pasteurellosis with one vaccine.Four clinical isolates of capsular serotype A Pasteurella mutocida, designated as Pm-HG, Pm-HH, and Pm-ZX, and Pm-ZMD respectively, were previously isolated from lesioned lung tissues of cattle at Huanggang, Honghu, and Zhongxiang in Hubei, and Zhumadian in Henan. The bacterial culture and staining, biochemistry test and PCR detection of specific genes were performed to characterize the isolates. As a result, the growth curves of these four isolates were found to be similar to the reference strain which was bought from China Veterinary Culture Collection. The pathogenicity test in mice showed that Pm-HG, Pm-HH and Pm-ZX have a stronger virulence. The isolates were killed by formalin as the immunogen and emulsified with mineral oil to make the inactivated vaccines and inoculated into mice. At week2after2inoculations, the titers of serum antibody reached1:20000for all groups with Pm-ZMD and Pm-HG the highest. The cross-challenge of the immunized mice was conducted with the4virulent strains and results showed that Pm-HG had the highest rate of cross-protection. It provided a complete protection against the self challenge, and meanwhile, the cross protection rates for the attack of other three strains were above90%. Therefore the strain Pm-HG could be taken as an ideal stain for development of potential inactivated vaccine against P. mutocida.Got a type B Pm virulent strain CVCC44701from China Veterinary Culture Collection. The culture characteristics and PCR detection were performed to characterize the isolates. The virulence test shows that CVCC44701have a stronger virulence. It provided a60%protection against the self challenge, and meanwhile the mice immuned the type A Pm can’t resist the challenge of CVCC44701. At week2after2inoculations, the titers of serum antibody reached1:15000.Made a bivalent vaccine to both type A and B Pm, included the Pm-HG and CVCC44701. Mice immunized with the bivalent inactivated vaccine can resist the challenge of Pm-HG, but can’t resist the challenge of CVCC44701.