Research On The Immune Efficacy Of Precocious Strain Of E.Necatrix In Chickens

In order to provide the basis for clinical trials on Coccodiosis vaccine(E.necatrix precocious strain) in chickens,the basic study on the minimum immunization dosage and immunization program test,the effect test of the target animal inoculated,the period of generation、stability and security of immunity were done by means of the relative weight gaining rate、the average lesion score、the oocysts reduction rate、 the reduction of lesion score (RLS)and the anticoccidial index (ACI) according to the require made by Ministy of Agriculture 《The technical guidelines on experimental study for veterinary biologies》.The results showed that:(1)Immunization once at4d, twice at4d and14d with E.necatrix precocious strain respecitvely in different dosage to chickens were investigated. The results showed that:①The larger the immunization dosage was, the smaller the weight gain was.②When immunization once, the immune protection effect generated at the dosage of100per chicken, the average lesion score and feces score was0.83and1at the dosage of200per chicken, so the dosage of200per chicken was taken as minimal immunizing dose when adopting once-immunization.③The average lesion score and feces score were0.60and0, the relative weight gaining rate were80.44%, the protection rate was100%when adopting twice-immunization with a good protective effect at the dosage of200and400per chicken, so200oocysts per chicken in first immunization and400oocysts per chicken in second times were taken when adopting twice-immunization.④Complete immune protection was generated at the9th day of once-immunization and the3rd day of twice-immunization at the minimal immunizing dose, both could defeat the attack of E.necatrix parental strain.(2)1,4,6-day-old chicks were immunized respectively first,then were immunized again after10days at the minimal immunizing dose, with immune-day-old increasing after challenged, the average lesion score decreased, the relative weight gain rate and ACI increased, no chickens died in the immunity classes, the average lesion score and bloody score were1or less than1, all of them achieved the assessment standard of the immunity effectiveness; chicks were immunized first at4day, then were immunized again interval3,5,7,10d,with interval days increasing after challenged, the relative weight gaining rate, the oocyst reduction rate, RLS, ACI increased, the average lesion score decreased, the state of mind of the interval7,1Od twice immunization groups is good, the average lesion score and bloody score were were1 or less than1, ACI were above175, all of the two achieved the assessment standard of the immunity effectiveness, indicating that all of them could play a good immune protection when the chicks were immunized with the vaccine in the period of1to6days first,then were immunized again interval7-10days.(3) When the chicks were cage-reared and floor-reared, under the two rearing methods the bloody score and the average lesion score were1or less than1, the protection rate was100%, the relative weight gaining rate were more than90%, indicating that the safety and immune efficacy of the vaccine weren’t related to the feeding methods.(4) The immune efficacy trials on different immune methods (gavage, dripping mouth, drinking,mixing into feed) showed that the average lesion score and bloody score of gavage group, dripping group and drinking group (duplication) were less than1, ACI were above170, all of them achieved the assessment standard of the immunity effectiveness.(5) The immune efficacy trials of vaccine stored to2～8℃in the dark for17months showed that the relative weight gaining rate, the oocysts reduction rate,RLS and ACI decreased, the average lesion score rised;The vaccine stored for10months achieved the assessment standard of the immunity effectiveness, the average lesion scores were less than1,the bloody score are0, no chickens died, ACI were above175; but saved more than10months, the protection of the vaccine declined markedly and could not achieve standards,the average lesion score is more than1, ACI is less than160.(6) The safety test on only infecting with a single dose, twice infecting with a single dose and infecting with overdose confirmed that the coccidiosis vaccine achieved the safety requirements.