Isolation And Identification Of Pathogenic Bacteria Of Duck Serositis And Evaluation Of Vaccine Effect

Epidemic disease prevention and control is a very important link in animal production,serosa inflammation,as a major disease in duck breeding,needs to be solved urgently.In this study,bacterial isolation,serotyping and analysis of serotypes of serous inflammatory diseases collected clinically are important for the selection of targeted vaccines in the breeding process,to collect and analyze the feedback of vaccine effect from farmers,in order to guide the prevention and control of infectious serositis and colibacillosis in Xuzhou area of Jiangsu Province,and to improve the economic benefit of duck breeding.In 2019,32 suspected serositis cases were collected from Xuzhou area.After isolation and identification of the bacteria,it was confirmed that Riemerella anatipestifer and Escherichia coli were the main causes of serositis,the main epidemic strains of Riemerella anatipestifer in Xuzhou are Serotypes Ⅱ and Ⅰ,and 19 different serotypes of Escherichia coli were isolated.The results showed that the virulent strains of Riemerella anatipestifer type ⅡL-9 and Escherichia coli type O1 D-17 were stronger than other strains,the minimal total lethal dose of the two strains was determined by experiments.In addition,it was found that the low concentration of Escherichia coli and Riemerella anatipestifer could not directly cause the death of experimental ducks,but the weight of infected ducks decreased obviously(P<0.05),the ratio of feed to meat is increased.In the experiment,two kinds of Riemerella anatipestifer and Escherichia coli bivalent vaccine were selected as A and B,and one kind of mucosal vaccine C,and the routine quality test,potency test,immunity times and immunity duration test were carried out to determine the best immunity procedure,to study the effect of immune procedure on duck production performance,and finally to carry out clinical trials.The results showed that A,B and C were all qualified in routine quality test,a had the best immune effect on Riemerella anatipestifer type Ⅱ L-9 strain and reached complete protection,C had the best immune effect on Escherichia coli type O1 D-17 strain,but only reached 40%protection.The protection rate of single immunization decreased after two weeks;The protective rate of double immunization A and B against L-9 was complete,and the protection rate of double immunization C against D-17 was 50%.There was no significant difference in the average body weight between the two groups before and after challenge(P>0.05),indicating that the immune vaccine did not affect the weight gain of ducks.The method of vaccine use was recommended to the farmers for their free choice,and the feedback data of the farmers were collected.The results showed that all the emergency immunization B were ineffective,and the effect of the emergency immunization A 27.27%was not obvious.After immunization with A alone,only One family did not develop the disease,and Only B and C were immunized once.One family was immunized twice with Vaccine B and used with Vaccine C daily.The ducks grew normally without disease and loss.Therefore,the following conclusions were drawn from this study:For urgent immunization,A vaccine corresponding to the serotype should be selected to ensure a good effect;Routine immunization suggests that farmers in the Xuzhou region should be immunized separately against Escherichia coli and Riemerella anatipestifer,Riemerella anatipestifer vaccine contains type Ⅰ and type Ⅱ Riemerella anatipestifer vaccine,while Escherichia coli serotype is numerous,no targeted vaccine,it is suggested to use mucosal vaccine C.