Chicken infectious anemia (CIA), caused by chicken anemia virus (CAV), is an immunosuppressive disease characterized by growth retardation, aplastic anemia, lymphoid depletion, and immunodepression in young chickens. In this study, 33 CAV strains were isolated from broilers in Shandong Province during 2020–2021. Phylogenetic analysis of full-length genome sequences showed that most CAV strains isolated in this study were scattered across different branches, but mainly clustered in two genotypes, indicating a certain regional characteristic. Analysis of VP1 protein identified several amino acid substitutions which were relevant with the virulence and virus spread efficiency. Interestingly, four putative DNA recombination events were detected in the genomes of novel isolated CAV strains. In summary, this study demonstrated a genomic diversity of CAV in broilers isolated in Shandong Province during 2020–2021, and provided information for the further study of CAV molecular epidemiology and viral evolution.

The high incidence of Avian pathogenic Escherichia coli (APEC) in poultry has resulted in significant economic losses. It has become necessary to find alternatives to antibiotics due to the alarming rise in antibiotic resistance. Phage therapy has shown promising results in numerous studies. In the current study, a lytic phage vB_EcoM_CE1 (short for CE1) against Escherichia coli (E. coli) was isolated from broiler feces, showing a relatively wide host range and lysing 56.9% (33/58) of high pathogenic strains of APEC. According to morphological observations and phylogenetic analysis, phage CE1 belongs to the Tequatrovirus genus, Straboviridae family, containing an icosahedral capsid (80 ~ 100 nm in diameter) and a retractable tail (120 nm in length). This phage was stable below 60°C for 1 h over the pH range of 4 to 10. Whole-genome sequencing revealed that phage CE1 contained a linear double-stranded DNA genome spanning 167,955 bp with a GC content of 35.4%. A total of 271 ORFs and 8 tRNAs were identified. There was no evidence of virulence genes, drug-resistance genes, or lysogeny genes in the genome. The in vitro test showed high bactericidal activity of phage CE1 against E. coli at a wide range of MOIs, and good air and water disinfectant properties. Phage CE1 showed perfect protection against broilers challenged with APEC strain in vivo. This study provides some basic information for further research into treating colibacillosis, or killing E. coli in breeding environments.

To establish a rapid method for the simultaneous differential detection of porcine circovirus types 2 (PCV2) and 3 (PCV3), two pairs of primers and two TaqMan probes were designed according to the gene sequences of PCV2 and PCV3, and a dual TaqMan fluorescence quantitative polymerase chain reaction (PCR) method for the simultaneous detection of two virus nucleic acids was established. The results showed that the correlation coefficients (R2) of the standard curves drawn using the recombinant plasmids of PCV2 and PCV3 were greater than 0.99 and had a good linear relationship. The specific detection results of PCV type 1, Porcine parvovirus, and Porcine pseudorabies virus were negative. The detection limits of this experimental method for PCV2 and PCV3 were 10 and 1 copies/μL, respectively, which were more sensitive than those of the common PCR detection methods. The established method was used to detect 76 samples from some pig farms in Shandong Province. 11 of the 76 samples were PCV3 positive (positive rate of 14.47%), 24 were PCV2 positive (positive rate of 34.58%), and PCV3 and PCV2 were mixed in six samples (positive rate of 7.89%). The whole-genome sequence of PCV3 was amplified and sequenced to further understand the molecular biological characteristics and genetic variation of PCV3 in Shandong Province. The genomes of 11 PCV3 strains were all 2000 bp long, and the whole-genome sequence homology between them ranged from 98.4% to 99.9%. There were mutation sites in the amino acid sequences of Cap and Rep proteins, and the strains isolated in this experiment were concentrated in the PCV3a and PCV3c subgroups. This study provides technical support and molecular biological basis for nucleic acid detection, epidemiological characteristics, genetic variation, and control of PCV3 in Shandong Province.

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A cluster of vultures, artificially bred in a zoo in Shandong Province, China, displayed signs of emaciation and some even died, which raised the suspicion of an immunosuppressive pathogen. Upon conducting nucleic acid testing on the clinical samples, it was found that the CIAV was present in the tissue of dead vulture. In this study, samples of dead vulture tissue were used to isolate a chicken infectious anemia virus (CIAV) via the MDCC-MSB1 cell line, which was designated the SDTY2021-TJ strain. The full-length genomic sequence of SDTY2021-TJ was determined and analyzed in detail. The full genomic DNA of SDTY2021-TJ was found to be 2298 bp, with no omissions or additions in the coding region. The homology between the full-length genomic sequence of SDTY2021-TJ and the reference strain ranged from 95.5% (Del-Ros) to 98.7% (YN04). In comparison with the reference strain, the VP1 protein of SDTY2021-TJ contained a number of mutations. To assess the virulence of SDTY2021-TJ, one-day-old SPF chickens were inoculated with both high and low doses of the pathogen. The results demonstrated that SDTY2021-TJ had a considerable pathogenicity to SPF chickens, as the high-dose group caused a 50% mortality rate, and even the low-dose group caused a 30% mortality rate. The chickens infected with the disease exhibited paleness in the cockscomb and stunted growth, as well as a compromised response to NDV and AIV-H9 inactivated vaccine. Furthermore, histological observation revealed an atrophy and degeneration of the thymus. To the best of our knowledge, this is the first instance of CIAV being isolated from artificially bred Aegypius monachus, implying that wild birds may be involved in the transmission and spread of CIAV.