| Avian nephritis virus(ANV)and chicken astrovirus(CAstV)are two avian Astroviruses that infect chickens,causing symptoms such as "white chicken" syndrome,diarrhea and growth and development disorders.In this study,the serological investigation and analysis of chicken astrovirus infection in Chinese chickens were carried out by ELISA.The pathogenic investigation of avian astrovirus was carried out by PCR.The representative positive samples were selected for avian astroviruses virus genome.The production performance of an infected avian astrovirus intensive broiler farm was analyzed,in order to lay a foundation for rational evaluation of the infection pressure of Chinese flock avian astrovirus.The Netherlands BioChek CAstV antibody ELISA kit was systematically evaluated,and serological tests for CAstV infection were performed on 1760 samples from 85 different breeds of chickens from 21 provinces in China from 2016 to 2017.The results showed that there were positive samples in 77 of the 85 surveyed flocks,the average positive rate was 90.6%,and the average positive rate of individual chickens was 60.68%.The positive rate of chickens of different ages varied greatly,and with the increase of age,the seroprevalence rate increased from 34.17%to 74.44%.The positive rates among different varieties were also significantly different.The positive rates of commercial broilers,commercial laying hens,parental laying hens,parental broiler breeders,and local breed chickens were 70.17%,89.00%,31.67%,59.05%,and 45.79%,respectively.The results indicate that CAstV infection is very common in Chinese flocks.The pathogenicity of avian Astrovirus was detected by PCR method in 76 tissue samples from 52 serologically positive farms.The results showed that 42 of the 76 tissue samples showed positive avian stellate virus with a positive rate of 55.3%.Among the 42 positive samples,9 were positive for CAstV,accounting for 21.4%;24 were positive for ANV,accounting for 57.1%;9 were positive for TAstV,accounting for 21.4%.The results showed that avian astrovirus infection was common in chickens in China,and there were many avian Astrovirus infections,mainly avian nephritis virus.Genomic sequencing analysis was performed on ANV and CAstV representative samples.The genomic sequences of four strains including ANV/CHN/GXJL815/2017,ANV/CHN/BJCP510-2/2018,CAstV/CHN/HBLP717-1/2018,CAstV/CHN/GDYHTJ718-6/2018 were successfully amplified.The results of sequence analysis showed that the four avian Astroviruses were 7588nt,7586nt,6914nt and 6899nt,respectively.They all have the typical genomic structure of avian astrovirus:it includes three ORFs,namely ORF1a,ORF1b and ORF2;The region between ORF1a and ORF1b overlaps between 28nt and 33nt,including the seven-base sliding sequence of ribosomal frameshift signal(AAAAAAC);its non-structural protein contains characteristic domains and motifs.According to the genetic evolution analysis of ORF2 amino acid sequence,ANV/CHN/GXJL815/2017 and ANV/CHN/BJCP510-2/2018 are classified as ANV2,CAstV/CHN/HBLP717-1/2018 and CAstV/CHN/GDYHTJ718-6/2018 classified as CAstV-B.The CAstV-negative Datun broiler farm and the positive Dongsanshijia broiler farm were selected to analyze the effect of CAstV infection on the performance of broilers.The two chicken farms have the same variety,the same feeding mode,similar geographical location,and simultaneous feeding and other factors,tracking and monitoring the antibody level of chicken astrovirus,and conducting pathogen detection on the eliminated chickens.The mortality rate,water consumption,daily gain,consumption,feed-to-meat ratio and feces were tracked during the breeding process.The results showed that the Datun chicken farm detected 15 chickens at different time points,no avian astro virus was detected,CAstV antibody continued to be negative throughout the production process,FCR was 1.48;Dongsanshijia chicken farm detected 16 chickens,7 detected Positive,the CAstV detection rate of chicken was 43.8%,CAstV antibody turned positive in the third week,and the VI value was as high as 858,suggesting that CAstV infection has occurred.The death rate of Dongsanshijia chicken farm was 4.45%,which was 1.36%higher than the 3.09%of Datun chicken farm;the abnormal production day of manure reached 59%of the total production cycle,and the FCR was 1.54,which was 0.06 more than that of Datun chicken farm.It is suggested that the infection of CAstV has impact on production performance.This study aims to clarify the prevalence of avian Astrovirus in China,the molecular characteristics of pathogens,and the effects of chicken astrovirus infection on broiler performance through systematic investigation,which will help to further understand its potential for poultry production.Hazard provides a valuable reference for the development of reasonable countermeasures in the future. |
PDF Full Text Request