| Riemerella anatipestifer infection also known as duck infectious serositis is an acute or chronic septic infectious disease of duckling caused by Riemerella anatipestifer. The disease is one of the infectious diseases serious against the duck industry. The morbidity rate of the disease is over 90% and the mortality rate is in general between 5%-75%. The disease also caused the death of ducks 1-8 weeks of age, salpingitis, egg production rate drop in adult duck, the resistant ducks grew retardation and most became stiff ducks. The disease led to great economic losses to farmers. Drug is used to prevent and treat the disease, but which repeatedly increased the keeping costs, easily generate resistance, and likely lead to drug residues which endanger food security. So immunization to ducklings become a preferential choice to control the disease.As RA complex serotype and lack of crossover protection between the different serotypes, so it become a key factor that choose advantage serotype in incidence areas to develop vaccine. The large and high quantity culture of RA used to develop vaccine has become another key factor to reduce vaccine production costs and improve the immune effects.The test determined the enrichment medium and liquid culture technology of RA, and identified the production process order of RAI vaccine through the study on the liquid culture and immunogenicity of GN52 strain of RA which was isolated from the incidence areas as popular and advantage serotype 10.This study identified a better enrichment medium for RA through comparison test. On the basis of early epidemiological investigation, the test compared the culture results of RA GN52 strain in three mediums of modified Martin broth, modified yeast broth and P-L broth. The results showed that the enrichment effect in modified yeast broth was better than modified Martin broth and P-L broth. The determination of bacterial growth curve proved that RA GN52 strain cultured in modified yeast broth reached to growth peak at 24h, the number of live bacteria was up to 270×108-320×108CFU/ml.This study established a liquor high density ferment technology of RA. The growth curve of RA was explored through staining and microscopy, Counting, OD450 and pH measurement after enrichment using liquid fermentation devices, to identify training methods, the best time to harvest and the best conditions to inactivate. The results showed that the pH remained unchanged basically in the process of cultured; the number of live bacteria was in the highest at 20 h, up to 320-350 million CFU / ml; the best conditions to inactivate was 0.3% formaldehyde at 37℃for 18 h; there is a certain function between OD450 and the number of live bacteria, so we can projecte the number of live bacteria by measuring its OD450.This study developed a Riemerella anatipestifer vaccine which has features of producing antibodies quickly, high protect rate, long duration of immunity and long storage time. RA GN52 strain was prepared oil emulsion vaccine after enrichment using improved liquid culture process. The immunogenicity of vaccine was studied after passing the sterile and security test. The results showed that the vaccine had a good immune response after ducklings was inoculated subentaneously at the neck with 0.3 ml per duckling at the age of 3 days. The protective ratios reached 70% and 100% in 7d and 14d post immunization with homologous strain attack, still up to 80% in 56d post inoculation. The protective efficacy reached 100% in 3 d after the second immunization at the age of 10 days. The notably enhanced cell mediate immunity in the experiment group was different (P <0.05) or very different (P <0.01) from the control and was about two weeks in duration. The vaccine could be stored one year at 4-8℃, the protective ratios was 95% and 85% after six months and one year, respectively. The field experiment identified that the vaccine was able to provide an ideal protection against RAI in ducklings.
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