Source Tracking of Chicken Infectious Anemia Virus in a SPF Chicken Population, the Latest Report in China

BackgroundLive attenuated vaccines have been extensively used to prevent infectious disease in poultry flocks. However, exogenous virus contamination in attenuated vaccines had been reported several times in the past, which brought enormous threat to poultry production and diseases prevention and control. Recently, an attenuated vaccine against Newcastle Disease produced in China was detected contamination with chicken infectious anemia virus (CIAV) in a routine inspection for exogenous virus. To understand the multiple routes of transmission of CIAV, and to better formulate correct prevention and control, it is necessary to find out the possible source of this contamination.Methodslood samples of SPF chickens that generated vaccines were collected to investigate CIAV antibody titers by ELISA test. Then, 14- to 18-day-old SPF chicken embryos (n=40) were randomly selected, DNA was extracted and detected by quantitative real-time PCR and nucleic acid dot hybridization assays. To further investigate the molecular features of the CIAV isolate, the complete genome of CIAV was amplified and analyzed.ResultsThe results showed both SPF chickens and embryos for vaccine preparation were CIAV-positive. In addition, the full-length genome sequences of CIAV from vaccines and SPF chicken embryos were consisted of 2,298 nucleotides (nt) with 100% homology, named as SDSPF2020 (Genbank accession number: MW660821). It demonstrated 95.7%-99.6% homology with the complete nucleotide sequences of reference strains, and shared the closest evolution relationship with the Chinese strain HLJ15125. ConclusionThis study illustrated that vertical transmission of CIAV from SPF chickens and embryos was an important way for exogenous virus contamination in vaccine production. As such, vaccine quality monitoring and health control are significant in the poultry industry from an environmental safety point of view.