Research Of Pigeon Newcastle Disease Epidemiology And Optimization Of Comprehensive Immunization Program In Pearl River Delta Region

Newcastle disease（ND）is a rapid、febricity and severe course of disease which is caused by Newcastle Disease virus（NDV）.Pigeon Newcastle disease also called pigeon plague,is caused by Avian Paramyxovirus 1（APMV-1）and acute highly contagious disease prevalent in pigeon populations.Since the first discovery of Newcastle disease in Indonesia in 1926 and the first isolation of the virus by Doyle the following year,two of the four major pandemics in the world have been closely related to pigeons.The disease spreads rapidly,its morbidity and mortality are very high,and it often causes huge economic losses to pigeon farmers.It is one of the most important diseases that harm pigeon breeding industry.At present,the vaccine against Newcastle disease virus in pigeon has not been developed,so regular antibody monitoring and reasonable immunization procedure are very important.In this paper,the Newcastle disease virus was isolated from pigeon farm,the biological characteristics and the F gene sequence were studied of the isolated virus,understand the relationship between antibody titer and protection,combining with the level of antibody in pigeon farm,a set of scientific,effective,reasonable and feasible comprehensive immunization program was established.The results of isolated virus strain some biological characteristics showed that the NDV HA titer more than 9log₂,EID₅₀0 10^-8.67/0.1 mL,MDT、ICPI and IVPI is 58 h、1.6 and2.1.The results of F gene sequencing showed that the isolated virus strains’cleavage site sequence is RRQKRF.With high similarity to dove/Italy/2736/00 strain and some amino acids in the N-terminal signal peptide region were mutated.Comprehensive results showed that there were ClassⅡandⅥgenotypic virulent NDV in breeding farm without outbreak.The results of antibody monitoring showed that the average titer of ND maternal antibody of pigeon was less than 2log₂,the titer of maternal antibody decreased gradually with the increase of pigeon age,and the high level of maternal antibody appeared 7 days after hatching.The young pigeons average antibody titer and percentage of qualified antibody of ND were low;the dispersion was large and the highest antibody qualification rate is only 50%.The breeding pigeon average antibody titer kept between3.21log₂⁶.81log₂ of ND and antibody qualified rate was 40%¹00%.The relationship between the serum antibody titer of NDV with attack protection showed that only the ND HI antibody titer of pigeon was greater than 4log₂ could protection pigeons from NDV.The comprehensive results showed that the antibody titer of pigeon immunized in pigeon farm was low,the dispersion was large and the qualified rate was small.Based on the results of the relationship between antibody titer and protection against virus attack,it was proved that the titer of antibody in pigeon field could not provide 100%protection for pigeon when the virus was coming.The results of antibody monitoring of different immunization programs showed that the antibody titer was high and the duration was longer in the strengthening immunization group,followed by the second immunization group,the inactivated vaccine immunization group lasted a long time,but the antibody titer was less than 5log₂.On the basis of the relationship between antibody titer and protection against virus attack and the establishment of immune program antibody monitoring,the best immunization procedure for pigeons was considered as one immunization with attenuated vaccine for about 14²1 days,and a second immunization with inactivated vaccine 14 days after immunization.Inactivated vaccine was used to enhance immunization 21 days after the second immunization.Breeding pigeon can be immunized again with inactivated vaccine before delivery and periodically with inactivated vaccine every 4 months thereafter.