Detction Of Immune Antibody Against Newcastle Disease And Pathogen And Its Control Measures In Yan'an City

In recent years,the poultry industry in Yan'an has developed rapidly,but the new problem is that chicken disease has become one of the main factors restricting its development.There are many kinds of chicken diseases,and Newcastle disease is one of them.Newcastle disease is highly infectious and its mortality is high.At present,it is listed as notifiable disease reported to the OIE and class one animal disease ruled by Chinese government.Vaccination is the most important way to prevent Newcastle disease.The monitoring and analysis of immune antibody level is an important basis for judging the risk of chicken infection and formulating immunization procedures.In this study,we carried out detection of Newcastle disease antibody levels and pathogen in some chicken farms and chicken households in 13 counties of Yan'an city,and comprehensive prevention and control measures are also studied,so as to provide basis for chicken farms and scattered households to formulate comprehensive prevention and control measures for Newcastle disease.1.Detection of immune antibody levels and pathogen of Newcastle disease in chickensA total of 1541 blood samples,1541 laryngeal and cloacal swabs were collected from 15 large scale egg farms,13 large scale meat farms and 102 scattered households in 13 counties and districts of Yan'an.The level of antibody against Newcastle disease was detected by hemagglutination inhibition test,and pathogen of Newcastle disease was detected by PCR.The following results were obtained:(1)The qualified rate of immune antibody of Newcastle disease.The qualified rate of immune antibody of Newcastle disease in 13 counties and districts of Yanan is 73.11% ~ 93.75%,and the average in the whole city is 84.62%.The qualified rate of immune antibody in each county and whole city has reached or exceeded the national standard(?70%).Among them,the qualified rate of immune antibody in Huangling county was the highest(93.75%),and in Yanchang county was the lowest(73.11%).From the different breeding types,the qualified rate of the scale egg chicken farms was the highest(96.00%),next is the scale meat chicken farm(93.00%),and scattered households were the lowest(64.07%).The qualified rate of immune antibody in some scattered chickens is not up to the national standard.There is a risk of morbidity.(2)The immune antibody level of Newcastle disease.The distribution of immune antibody level showed that there were 237 cases in the range of 1log2 to 4log2,accounting for 15.38% of the total detection number(Unqualified immune antibody).There were 1304 cases in the range of 5log2 to 11log2,accounting for 84.62% of the total detection number(>70% qualified standard).Among them,7log2 was the most(322 samples),accounting for 20.90% of the total number of samples;1055 were between 5 log2 and 8 log2,accounting for 68.46% of the total number of samples.Judging from different breeding types,the immune antibody level of Newcastle disease in scale chicken farms is generally high,and the antibody level is mostly distributed in 7log2 ~ 8log2;the antibody level of Newcastle disease in scattered households was generally low,and the antibody levels were mostly distributed in the 3log2 ~ 6log2.(3)The positive rate of pathogen of Newcastle disease.The total number of positive pathogen was 24,the positive rate of the pathogen in the whole city was 1.56%.The positive rates of pathogen detected in counties and districts were different,the lowest in Fuxian county(0),and the highest in Huanglong county(2.9%);the positive rate of pathogen in scale farms was relatively low(0.39% in broiler farms,0.95% in layer farms),while the positive rate of pathogen was relatively high among scattered households(3.39%,P?0.05).2.Comprehensive prevention and control measures and effectsTaking some scale chicken farms and scattered households in counties and districts of Yan'an as experimental sites,comprehensive prevention and control measures were adopted,such as strengthening feeding management,reasonable immunization procedures and correct immunization methods,strengthening disinfection,strictly introducing the links of imported varieties,strengthening biosafety measures,regularly monitoring the level of antibodies against various epidemic diseases and the positive situation of pathogens.The qualified rate of immune antibody,immune antibody level,pathogen positive rate and chicken production performance were taken as the evaluation basis.After taking comprehensive preventive and control measures,the qualified rate of immune antibody of Newcastle disease in the whole city increased from 84.62% to 92.28%,and increased by 7.66%(P?0.05).Among them,the qualified rate of scattered households increased from 64.07% to 83.43%,and increased by 19.36%(P?0.01);the immune antibody level of Newcastle disease in chicken flocks increased from 6 log2 ~ 7 log2 to 8 log2 ~ 10 log2;the PCR positive rate of pathogen of Newcastle disease decreased by 0.20% ~ 2.59%(P?0.05);the incidence of chickens decreased by 0.40%(P?0.05)and the survival rate increased by 3.92%(P?0.05);the feed-meat ratio of broilers decreased by 0.07%(P>0.05);the laying rate of laying hens increased by 3.23%(P?0.05).