Studies On Oil Emulsion Inactivated Vaccine Against Duck-origin Newcastle Disease

Duck-origin Newcastle disease (i.e. Duck Paramyxovirus Disease) is an acute, highly contagious and lethal infectious disease caused by duck-origin Newcastle virus (i.e. duck paramyxovirus). Duck-origin Newcastle virus was isolated from different sick ducks in Anhui, Fujian, Zhejiang and other places by Zhang Xunhai, Zhang cun, Chen Shao Ying and He yongqiang and other scholars in 2001-2005. This disease has high morbidity and mortality and has serious harm to the duck industry.Vaccination is one of the effective measures to control the disease. But at present, China has not yet had the commercialization supply of duck paramyxovirus vaccine. So the development of duck paramyxovirus inactivated vaccine is important for the promotion and protection of the industry of the healthy development of duck. Because of this we use isolates of duck paramyxovirus to develope duck paramyxovirus inactivated oil emulsion vaccine. And the safety, stability, efficiency, and other research of vaccine were certificated. The study is on biological characterization such as virulence, propagation andimmunology characterization, specificity of duck paramyxovirus strain and Newcastle disease (ND) virus LaSota strain. For duck paramyxovirus strain in this study, the intravenous pathogenecity index is 2.59, the Mean Death Time in embrocated eggs with minimal lethal dose (MDT/MLD) is 56.6 hours the lethality rate to10-day old embryo is 10/10, the positive isolation rate after inoculation of 4-5weeks old SPF chickens is 10/10, the erythrocyte HA titer is 1:128, the virus titer is 107.67EID50/0.1ml, the virus with good immunogenicity could be neutralized differentially by the positive antiserum of duck paramyxovirus.For NDV LaSota in this study,the intracerebral pathogencity index (ICPI) is 0.41, the lethality rate to 10-day old embryo is 8/10,the erythrocyte HA titer is 1:1024,the virus titer is 108.0EID50/0.1mL,2-7old SPF chickens are safe post inoculation with the LaSota strain of NDV,and the virus could be neutralized differentially by the antiserum of NDV. 10-day-old embryos derived from non-immunized chickens are inoculated separately with NDV LaSota strain,duck paramyxovirus strain allantoic fluid are harvested,the final virus titers are 108.0EID50/0.1mL and 107.67EID50/0.1mL). All the viruses are inactivated by formaldehyde with 0.2% final concentration, and the HA titers of the three kinds of virus reached l: 1024.Two bathes of vaceines are manufactured with the above gained virus fluid. The vaccine proved to be ivory w/o emulsion by physical test; A centrifuging tube with 10 mL vaccine sample are centrifuged for 15 minutes , 3000r/min no batehes of vaccine appears delamination: l mL vaccine sample at 25℃are assimilated in to an 1mL straw (the upper diameter is 2.7mm,the lower diameter is l.2mm) , then discharged naturally,the time15 recorded when 0.4ml sample finish discharging, the time all the samples needed should be within 8 seconds.Ten 4-5 weeks old SPF chickens and ducks are vaccinated with the trial-manufaetured vaccine via neck subcutaneous injection or intramuscular injection,1.0 mL vaccine is used per chick, the chickens are examined daily for 14 days,all of them are live post vaccination,and no systemic or local side responses related to the vaccine are found. 26-90 day-old SPF chicks and 26-51 day-old non-immune ducklings were challenged with duck paramyxovirus SDFCH strain and Newcastle disease virus F48E10 strain which virus content are between 101.0EID50/mL and 108.5EID50/mL. For 14 days, the results showed that minimum lethal dose of SDFCH strain and F48E10 strain to SPF chickens was 103.0EID50/mL. The minimum lethal dose of SDFCH strain to duckling is 108.5EID50/mL.4-5 weeks old SPF chickens and non-immune ducklings were inoculated with duck paramyxovirus (SDFCH strain) inactivated vaccine and Newcastle disease (LaSota strain) inactivated vaccine by neck subcutaneously injection. Each group included 15 chicks or ducklings. Blood sera were separated 21days after immunization. HI antibody titers of Newcastle disease and duck paramyxovirus SDFCH strain of challenged group were higher than 1:16. HI antibody titers of Newcastle disease and duck paramyxovirus SDFCH strain the chickens and ducklings of control groups were negative. When the HI titer is higher than 2~4 , the chickens and ducks of immune group can get 100% protection after challenging with SDFCH strain virus. When the HI titer is lower than 24, ducks of the groups immunized with duck paramyxovirus inactivated vaccine can get 80% protection after challenging with SDFCH strain virus and NDV (F48E10 strain). Ducks of the groups immunized with ND inactivated vaccine only can get 67.7% protection SDFCH strain virus, and 83.3% protection after challenging with NDV (F48E10 strain). Chicks and ducks of the control group were all dead after challenging with SDFCH strain and F48E10 strain.The related trials on duration and storage are carried out,it proved that the immunity duration of the manufactured vaccine is more than 18 weeks and the guarantee period is more than 6 months.Test results showed that the vaccine is safe and reliable, the spirit of the duck was in good condition, and injection site was not seen obvious changes. The result indicated that the antibodies against the virus were generated 21 days after inoculation and the highest antibodies were generated after 60 days. The HI titer is 91og2 at 60days after immunization. 25 days after vaccination, the protection rate could be up to 90%.