Method for constructing swine escherichia coli and haemophilus parasuis attenuated fusion strain

The invention provides a method for constructing a swine escherichia coli and haemophilus parasuis attenuated fusion strain. Strains with different immunogenicities are integrated into the same strain by a microorganism protoplast fusion technology. When a polyvalent vaccine is developed by pathogenic bacteria which have various serum types, but have no cross immune protection, the method is beneficial for improving unit antigen content of a single factor in the vaccine so as to fulfill the aim of improving the immune effect. Experimental research proves that compared with toxicity of a parent strain, toxicity of the novel fused strain is greatly reduced; and the fused strain reserves the antigen characteristics of the original parent strain. The method provides scientific basis and theoretical direction for developing a novel swine escherichia coli and haemophilus parasuis bigeminal attenuated vaccine.