| Infectious serositis in duckling which was once named Pasteurella anatipestifer infection is a kind of contact, acute or chronic, hemorrhagic infectious diseases, caused by Riemerella anatipestifer. It may appear at 1-8 weeks old duckling and has a peak incidence between the weeks of 2 and 3, and mortality rate is different of ages. Now it is becoming one of the most economic importance diseases. In order to find out the biological characteristics and prevention of Riemerella anatipestifer in Weifang region, I did this research.This research consists of three parts as follows:Part one Isolation and Identification of Riemerella Anatipestifer Four Gram-positive bacillus were identificated and isolated from typical Infectious serositis in duckling cases which happened in Weifang. And finally it was identified as Riemerella anatipestifer(RA) by biochemical experiments and PCR methods and named SG1,HT2,WC3,SG4. Through further study on their pathogenicity, drug sensitivity and serological type, founding out that WC3 belong to type 1 and SG1,HT2,SG4 belong to type 3. Results all of those four cases of Riemerella anatipestifer had high pathogenicity to duckling. Most strains were highly sensitive to gentamicin, chloromycetin, ciprofloxacin, nitrofurantion, rocephin and cefotaxime.Part two Study on pathogenicity of the Riemerella Anatipestifer Against the Immune Organs of DucklingUsing WC3 RA strain bacterial suspension(bacteria amount was about 3×10~9CFU/ml) injected 10 days old ducklings through fins, and observing the symptom and pathology changes and immune organ index and histopathology changes. Results that the infected ducks showed the same clinical symptoms of natural infected ducks, and there were no specific necropsy lesions. Some ducks appeared air sac turbidity, slight pericardial effusion, cerebral blood-vessel dilates tree-likely, but there was no fibrous exudation in the internal organs for short course of disease. The infected ducks showed splenomegaly (the spleen's average weight of group 1 and group 2 was1.1g and 1.2g respectively, control group's was 1.0 g), splotchy appearance; thymic enlargement (the thymus's average weight of experimental group 1 and group 2 was 1.2g and 1.3g respectively,control group'was 0.98g), bleeding; bursa of Fabricius atrophy(average weight of experimental group 1 and group 2 was 0.8g and 0.75g respectively,control group'was 1.1g). Pathological histology injuries were serious; the lymphocytes disappeared obviously; histopathology changes of thymus gland were not observed.Part three Research and Analysis of Immunity Efficiency ofRiemerella anatipestifer Inactivated VaccineWC3(type 1) and SG4(type 3)were inoculated in fluid nutrient medium respectively. After the amount of bacteria was above 109CFU/ml, pour formalin to inactivate. And then pour in Tween-80 until the volume percentage was 2% to make it became the antigen in the form of aqueous phase. Max the aqueous phase with the oil phase which made of 94% vash oil, 6% span-80 and 2% aluminum stearate together in proportion as 1:2, and the oil-emulsion inactivated vaccines were produced. Inspection of bacteria, safety verification, stability test and passive immunization test showed that both kinds of oil-emulsion inactivated vaccines were qualified. No bacterial and mildew grow on the TAS plate or blood plate; no separate after centrifugation at 3000 r/min, 15 min; all of the ducklings were free of Clinic Symptoms, after being injected in 5 times immunity dose. 21 days after immunity, challenge test was done. And the challenge test results showed that the protective rate of the both vaccines was 90%-100% and there was no cross-protection between different serological types.
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