Study On The Booster Immunization Of The Eimeria Acervulina Vaccine Strain And Its Cross-protection Against Different Eimeria Spp.

Chicken coccidiosis is distributed worldwide,and it is generally believed that there areseven different species of the genus Eimeria that cause chicken coccidiosis,of which Eimeria acervulina is the most prevalent,and causes huge loss in the poultry production.In this study,the immune effects of different immune doses and immune times of a precocious strain of E.acervulina were compared.An animal experiment was used to assess the cross-protection against five other Eimeria spp.,and different E.acervulina field strains isolated from different areas.The results could provide fundamental data for the popularization and application of a live coccidiosis vaccine in the future.First,this study evaluated the immune protective effect of an E.acervulina precocious vaccine strain(PAHY)and selected the optimal dose and immunization times.Seven days after receiving a primary immunization,and a booster immunization,with a dose of 12000 PAHY sporulated oocysts each bird,the immune group could resist the attackof 1 × 105 sporulated oocysts of the E.acervulina Heyuan strain.After supplementary immunization,all of theimmunization groups with doses of 4000,8000 or 12000 sporulated oocysts per bird could resist the attack of 1 ×105sporulated oocysts of the E.acervulina Heyuan strain.For actual production,it is more suitable to select 2 supplementary immunizations with the doses of 4000 PAHY sporulated oocysts for immunization.Second,the chicken groups that had established immune protection were challenged with three different regional strains of E.acervulina,and the immune protection effect was assessed.The results showed that the groups immuned with PAHY had similar protective abilities against E.acervulina Heyuan strain and virulent strains of E.acervulina isolatedfrom different regions.Finally,the chicken groups that were vaccinated with PAHY were challenged with virulent strains of E.tenella,E.necatrix,E.maxima,E.brunette and E.mitis.The results showed that the immunity of Eimeria was species-specific,and the chicken group immunized with E.acervulina only experienced aprotective effect against the virulent strain of E.acervulina,but could not resist to the virulent strains of the other five Eimeria spp.,and no interspecific cross-protection for E.acervulina immunization was found.