The increasing serotypic diversity and multidrug resistance of Riemerella anatipestifer pose a serious threat to the poultry industry, necessitating novel antimicrobial agents. Although phage-derived endolysins offer rapid and specific bactericidal activity with low resistance potential, their efficacy against this Gram-negative pathogen is severely constrained by the outer membrane barrier, driving the need for strategies to enhance endolysin penetration. In this study, the native endolysin NA of phages vB_RanS_CRP2 was verified to lack antibacterial activity. To overcome this barrier, we constructed three chimeric proteins—ALC001, ALC005, and ALC007—by fusing a receptor-binding protein, a cell-penetrating peptide, or a polycationic nonapeptide, respectively. All three chimeras exhibited dose-dependent antibacterial activity, with ALC005 demonstrating the best performance. ALC005 achieved a lytic rate of 72.2% against the tested Riemerella anatipestifer strains, remained stable at 0–40 °C and pH 6–9, and was shown by transmission electron microscopy to exert its bactericidal effect by disrupting the bacterial cell envelope and inducing cell lysis. Collectively, cell-penetrating peptide fusion is a reliable and effective strategy to potentiate endolysin activity against Riemerella anatipestifer.

IntroductionNewcastle Disease Virus (NDV) is not only a significant and persistent threat to the healthy development of poultry industry, but also an important pathogen endangering food safety and harboring potential zoonotic risks.MethodsIn this study, a rapid and highly sensitive diagnostic assay was established for genotype VII NDV by integrating reverse transcription recombinase polymerase amplification (RT-RPA) with the clustered regularly interspaced short palindromic repeats (CRISPR)/Cas13a system, in combination with a lateral flow dipstick (LFD) for visual signal readout. Specific RT-RPA primers were designed based on the fusion (F) gene of genotype VII NDV, and CRISPR RNAs (crRNAs) were constructed to establish a simplified CRISPR/Cas13a-based diagnostic workflow targeting the fusion (F) gene of genotype VII NDV.ResultsThe optimized detection platform integrates RT-RPA amplification at 39 °C for 20 min and CRISPR/Cas13a-mediated cleavage at 37 °C for 20 min. The final results can be quantified by fluorescence signals or visualized via LFD band within 5 min, with the total detection procedure completed in less than 45 min. Performance evaluation demonstrated that this assay achieved a limit of detection (LOD) as low as 6 copies per microliter of input and high specificity, with no cross-reactivity against other common avian pathogens. Clinical validation of 154 samples showed 100% concordance between the RT-RPA-CRISPR/Cas13a-(LFD) assay and RT-PCR sequencing for genotype VII NDV detection.DiscussionThis method requires no sophisticated instruments and enables simple operation. It provides a field-deployable tool for rapid on-site detection of genotype VII NDV, which is suitable for preliminary screening in primary laboratories, and holds promising application potential for the early surveillance and food safety monitoring of virulent NDV strains.

Riemerella anatipestifer (RA) is the primary causative agent of infectious serositis in ducks, causing significant economic losses. In this study, a rapid and visual loop-mediated isothermal amplification (LAMP) assay targeting the conserved region of the ompA gene was developed. Specific primers and a FAM-labeled probe were designed, and amplification products were visualized using phenol red-based colorimetric detection and a lateral flow dipstick (LFD) system. Among the five candidate primer sets, primer set 2 was selected because it showed the highest amplification efficiency and specificity, with no cross-reactivity detected against 12 common waterfowl pathogens. Under optimal conditions, the phenol red-based LAMP assay yielded visible results after incubation at 65 °C for 30 min, while the LAMP-LFD assay required an additional 3~5 min probe hybridization step, with detection limits of 7.76 × 102 copies/μL for the phenol red-based method and 7.76 × 100 copies/μL for the LAMP-LFD method. Thirty clinical samples suspected of RA infection were analyzed using conventional PCR and the developed visual LAMP assays. The positive detection rates obtained with the LAMP-LFD and phenol red-based LAMP methods were 63.3% and 60%, respectively, showing high concordance with conventional PCR (56.7%). In conclusion, the LAMP assay integrating phenol red visualization and lateral flow dipstick detection is rapid, sensitive, and easy to perform, and both detection formats show potential for point-of-care or on-site applications, and can be used for the early diagnosis and detection of RA.

Waterfowl circovirus (WFCV) is an important member of the genus Circovirus within the family Circoviridae, encompassing duck circovirus (DuCV) and goose circovirus (GoCV). As a pathogen that poses a serious threat to the global waterfowl industry, WFCV induces significant immunosuppression in its hosts, leading to growth retardation, feather abnormalities, and increased susceptibility to other pathogens. Consequently, it results in markedly elevated mortality rates among affected birds and causes substantial economic losses. In recent years, with the advancement of molecular biology techniques, notable progress has been made in research on waterfowl circoviruses. This review aims to systematically consolidate current findings on the genomic characteristics, pathogenic mechanisms, and clinical manifestations of WFCV while also summarizing the existing detection technologies and the status of vaccine development. Future research directions and prevention strategies are proposed, with the goal of providing a scientific reference for the effective control of this disease.

Fowl adenovirus (FAdV) serotype 4 (FAdV-4) is a significant pathogen causing hepatitis-hydropericardium syndrome (HHS) in poultry, which can cause severe economic losses to the global poultry industry. Molecular epidemiological investigation of FAdV-4 has not been conducted in Fujian province, southeast China. In this study, we collected 219 samples of liver exhibiting similar pathological features of hepatitis or hydropericardium syndrome (HPS)-like clinicopathology changes from Fujian province during 2023-2025, which were analyzed using PCR assays. Further isolation of the virus was performed, and complete genomic sequences of the isolates were obtained through next-generation sequencing technology. Genetic evolution analysis of the gene sequences was conducted to elucidate the prevalence, molecular characteristics, and genetic variations of FAdV-4 in Fujian province. The results indicated that among the 219 clinical samples, 65 tested positive, yielding a positive rate of 29.68% (65/219). Positive samples from broilers were predominantly detected in the 21-120 days old, while those from layers were primarily concentrated in the 200-500 days old. The positive rate of Muscovy ducks infected with FAdV-4 was 4.57%. Ultimately, seven strains of FAdV-4 were isolated and designated as FJ08, FJ09, FJ20, FJ23, FJ33, FJ35, and FJ45. The preliminary challenge assay showed that all seven isolates were highly virulent in 7 days old SPF chickens, resulting in the death of all chickens within 2-3 days, leading to a mortality rate of 100%. Comparative analysis of whole genome sequences revealed that the isolated FAdV-4 strains from Fujian province clustered within the major genetic lineage as the domestic FAdV-4 reference strains (e.g., JSJ13, HLJFAd15, and HB1510 strains) and exhibited the highest identity with the FAdV-4 BNC strain derived from black-necked cranes in Yunnan province. Notably, the Hexon genes of seven isolated strains were divided into two major lineages based on phylogenetic analysis. The FJ08, FJ09, and FJ23 strains clustered in the major lineage as representative strains of FAdV-4 from both domestic and international sources, whereas FJ20, FJ33, FJ35, and FJ45 strains formed an independent genetic lineage with the FAdV-10 AHFY19 strain. The prevalence analysis revealed that FAdV-4 has been circulating among commercial chickens, indigenous chicken breeds, and Muscovy ducks in Fujian province, southeast China, indicating that the FAdV-4 strains in Fujian province possess the potential for cross-host transmission. Moreover, the age of the infected hosts (layers) has extended to 500 days, and their genomic characteristics exhibit genetic diversity.

IntroductionGoose adenovirus type 4 (GoAdV-4) is an emerging pathogen that causes inclusion body hepatitis and hepatic necrosis in goslings, with mortality rates reaching up to 80% in severe outbreaks. Since its first identification in China in 2022, GoAdV-4 has spread rapidly across major goose-producing provinces, posing a serious threat to the domestic goose industry. However, no sensitive and specific quantitative assay has been available for the rapid diagnosis and viral load monitoring of GoAdV-4.MethodsWe developed a TaqMan-based real-time quantitative PCR (qPCR) assay targeting the hexon gene of GoAdV-4 and systematically validated its analytical sensitivity, specificity, and repeatability. The assay was then applied to 582 clinical samples of five specimen types (tissues, blood, goose embryos, and cloacal swabs), and its diagnostic performance was compared with conventional PCR.ResultsThe assay demonstrated a linear detection range of 6.4 × 101 to 6.4 × 107 copies/μL (R2 = 0.9968) with an amplification efficiency of 97.5%, and a limit of detection (LOD) as low as 6.4 × 101 copies/μL. No cross-reactivity was observed with fowl adenovirus serotype 4, duck adenovirus type 3, egg drop syndrome virus, goose circovirus, goose astrovirus, goose parvovirus, or nuclease-free water. Intra-assay and inter-assay coefficients of variation ranged from 0.87% to 1.17% and 1.06% to 1.48%, respectively, indicating high reproducibility. The assay identified 55 GoAdV-4-positive samples (9.45%), compared with 48 positives (8.25%) detected by conventional PCR, with an overall concordance rate of 98.80% (positive concordance 87.27%, negative concordance 100%).DiscussionThe TaqMan qPCR assay detected seven additional positive samples missed by conventional PCR, all confirmed as true positives by Sanger sequencing, demonstrating superior sensitivity. These results show that the established TaqMan qPCR assay is a rapid, sensitive, specific, and reproducible tool for GoAdV-4 detection, providing a valuable diagnostic instrument for the surveillance and control of this emerging waterfowl pathogen.

Introduction:Duck hepatitis A virus type 3 (DHAV-3) causes acute fatal hepatitis in ducklings. Methods:This study compared host transcriptomic responses in duck livers following infection with virulent (HB) or attenuated (HB80) strains. Results:RNA sequencing (RNA-Seq) revealed that the virulent HB strain induced 2,355 differentially expressed genes (DEGs) at 2 days post-infection (dpi), compared to only 322 DEGs triggered by the attenuated HB80 strain. Functional analysis showed that the HB strain robustly activated immune pathways, particularly Toll-like receptor (TLR) and RIG-I-like receptor (RLR) signaling, leading to a potent type I interferon (IFN-I) response and marked chemokine upregulation. In contrast, the HB80 strain elicited a markedly milder immune reaction. Among the DEGs, 77 immune-related genes were identified, with significant enrichment in the IFN-I signaling pathway, suggesting their critical role in initiating an interferon storm and subsequent chemokine upregulation. Selected key genes (IFN-α2, RSAD2, RIG-I, MDA5, TBK1, TLR7) were validated by RT-qPCR and ELISA for targeted protein confirmation. Discussion:These findings delineate divergent host transcriptomic responses to virulent vs. attenuated DHAV-3 and highlight IFN-I signaling as a central axis in antiviral immunity.

Duck adenovirus 3 (DAdV-3) causes liver damage and bleeding, with morbidity rates ranging from 40 to 55% and mortality rates between 35 and 43%. Co-infection with other pathogens complicates disease control, significantly impacting the duck breeding industry. Currently, there have been no effective vaccines or treatments for DAdV-3. Therefore, rapid, specific, and sensitive detection methods are crucial for preventing and controlling this virus. Our study developed a lateral flow strip (LFS) detection method using recombinase polymerase amplification (RPA) and CRISPR/Cas12a. The RPA-CRISPR/Cas12a-LFS method, performed at 37°C, allowed for result visualization without sophisticated equipment. It targeted the DAdV-3 Fiber-2 gene and achieved a detection limit of 3.0 gene copies. Additionally, this method demonstrated high specificity, with no cross-reactivity to eight other avian viruses. The reaction time of RPA-CRISPR/Cas12a-LFS is only 45 min. Analysis of 95 waterfowl samples showed 98.95% consistency and agreement with quantitative polymerase chain reaction using the Fiber-2 RPA-CRISPR/Cas12a-LFS method. These findings highlighted the potential of this user-friendly, rapid, sensitive, and accurate detection method for on-site DAdV-3 detection.

Hypervirulent fowl adenovirus serotype 4 (FAdV-4) has emerged as a significant poultry pathogen since 2015, exhibiting clinical multi-organ and multi-tissue tropism post-infection, resulting in substantial economic losses in the poultry industry. However, the molecular mechanism underlying kidney injury caused by FAdV-4 infection remains unclear. Our results indicated that FAdV-4 infection in chickens induces damage to kidney tissues, characterized by the degeneration and necrosis of kidney epithelial cells, glomerular injury, endoplasmic reticulum stress, and the activation of a robust inflammatory response in the kidney cells. Notably, autophagosome-like vesicles enclosed clusters of viral particles that were transmitted between kidney cells post-infection. There might be a novel mechanism of vesicle-mediated cell-to-cell transmission of hypervirulent FAdV-4 that hijacks autophagosome-like vesicles. We also investigated cellular autophagy in kidney cells in vivo and in vitro during early FAdV-4 infection. The autophagy-related marker proteins LC3B, ATG5, and BECN1 were upregulated post-infection, whereas SQSTM1 was downregulated, indicating that FAdV-4 infection enhances autophagic flux and induces complete autophagy. The viral structural protein Fiber 2 was also observed to colocalize with the autophagy-related marker protein LC3B and the exosome-specific marker protein CD63 in the kidney cells at 24 hpi, suggesting that FAdV-4-induced cellular autophagy promotes viral replication in kidney cells and that autophagosome-like vesicles are involved in early FAdV-4 replication in vivo in chickens. Our results offer novel insights into the pathogenesis of hypervirulent FAdV-4 from the perspective of kidney injury post-infection. IMPORTANCE:Hypervirulent fowl adenovirus serotype 4 (FAdV-4) has become globally prevalent since 2015 as a predominant pathogen on poultry farms, leading to substantial economic losses for the poultry industry. However, the molecular mechanisms underlying kidney injury induced by FAdV-4 infection remain unclear. In this study, we primarily elucidated the mechanisms of kidney injury induced by FAdV-4 infection in chickens, utilizing both in vitro and in vivo models. Our results demonstrate that FAdV-4 infection in chickens causes degeneration and necrosis of kidney epithelial cells, glomerular injury, and expansion of the endoplasmic reticulum, while also triggering a robust inflammatory response in kidney cells. Notably, we observed the cell-to-cell transmission of virus particles delivered by autophagosome-like vesicles, and the viral infection-induced cellular autophagy facilitated viral replication in the kidney cells. These findings offer a novel perspective to understand the molecular mechanisms of FAdV-4-induced kidney injury and establish a basis for further investigation into the molecular pathogenesis of hypervirulent FAdV-4.

Pasteurella multocida is a zoonotic pathogen responsible for severe diseases in domestic and wild animals, posing threats to public health and causing substantial economic losses. Here, we describe a naturally attenuated P. multocida strain, FCF147, isolated from a mortality event involving black-necked swans (Cygnus melancoryphus) in a wildlife habitat in Fujian, China. Genomic and phylogenetic analyses revealed that FCF147 is evolutionarily distant from other P. multocida lineages and lacks the entire capsule gene cluster. Morphological observations revealed that the loss of the capsule exposed proteins on the bacterial surface. Phenotypic characterization demonstrated reduced capsule production, enhanced biofilm formation, and increased tolerance to heat stress. In vivo infection models confirmed that FCF147 exhibits markedly attenuated virulence in both mice and poultry. However, immunization with FCF147 did not provide effective protection against the challenge of a virulent capsular type A strain. These findings suggest that while FCF147 is poorly virulent, its ability to form robust biofilms and survive thermal stress may facilitate persistence in wild bird reservoirs and potential transmission routes. These findings offer novel insights into the ecological adaptation and pathogenic potential of naturally capsule-deficient P. multocida in wildlife, highlighting their relevance to wildlife surveillance and disease ecology.

Pasteurella multocida (Pm) is a zoonotic pathogen that poses a significant threat to animal health and causes substantial economic losses, further aggravated by rising tetracycline resistance. To restore the efficacy of tetracyclines to Pm, we evaluated the synergistic antibacterial activity of doxycycline combined with metformin, an FDA-approved antidiabetic agent. Among several non-antibiotic adjuvant candidates, metformin exhibited the most potent in vitro synergy with doxycycline, especially against capsular serogroup A strain (PmA). The combination demonstrated minimal cytotoxicity and hemolysis in both mammalian and avian cells and effectively inhibited resistance development under doxycycline pressure. At 50 mg/kg each, the combination of metformin and doxycycline significantly reduced mortality in mice and ducks acutely infected with PmA (from 100% to 60%), decreased pulmonary bacterial burdens, and alleviated tissue inflammation and damage. Mechanistic validation confirmed that metformin enhances membrane permeability in Pm without compromising membrane integrity, dissipates membrane potential, increases intracellular doxycycline accumulation, and downregulates the transcription of the tetracycline efflux gene tet(B). Morphological analyses further revealed pronounced membrane deformation and possible leakage of intracellular contents. These findings highlight metformin as a potent, low-toxicity tetracycline adjuvant with cross-species efficacy, offering a promising therapeutic approach for managing tetracycline-resistant Pm infections.

Since 2021, an epidemic disease characterized with hydrosalpinx fluid syndrome (HFS) has been circulating in the laying Sheldrake ducks in China, which seriously endangers the healthy development of the duck industry. The causative agent of this disease has been traced to avian metapneumovirus subtype C (aMPV/C), known to cause acute upper respiratory tract infections and egg-drop in poultry. To date, no reports have been made to isolate and characterize aMPV/C infection in Sheldrake ducks in China. Here, a strain of virus, designated aMPV-FJ21, was successfully isolated from the diseased ducks exhibiting HFS. Transmission electron microscopy revealed that the virus is an enveloped particle exhibiting a spherical or pleomorphic morphology. Indirect immunofluorescence assays demonstrated that the aMPV-FJ21 strain had an obvious reactive activity with the ploy-antibody against aMPV/C F protein. The complete genome of aMPV-FJ21 was determined to be 14,149 nucleotides in length. Notably, the amino acid sequence of the G protein was only 55.6%-78.7% identical to those of other aMPV/C reference strains. Phylogenetic analysis indicated that aMPV-FJ21 forms a distinct lineage within the aMPV/C group and is genetically distant from the North American and Eurasian lineages, suggesting that it may represent a novel genetic lineage. In challenge experiments, laying Sheldrake ducks with aMPV-FJ21 reproduced the typical clinical symptoms and pathological lesions observed in the field cases. Altogether, we had isolated a novel aMPV/C variant from Sheldrake ducks exhibiting HFS, distinct from previously reported strains, and provided the first evidence confirming its role as the causative agent of HFS in ducks.

Infectious Bursal Disease (IBD) is an immunosuppressive viral disease caused by the Infectious Bursal Disease Virus (IBDV). It primarily affects young chickens, targeting the bursa of Fabricius, and poses significant economic threats to the poultry industry. To date, in addition to strict biosecurity measures, large-scale immunization is the optimal strategy and effective method to prevent and control IBDV infection. The emergence of new variant strains has made it more urgent to develop new vaccination strategies against IBD. Over the past few decades, many high-quality vaccines have been available on the market for the control of IBD, which can provide solid protection against the infections and diseases caused by classic IBDV to very virulent IBDV that had been continuously evolving and were endemic worldwide. However, viruses are not static. As they continue to circulate and evolve in the fields, novel antigenic variant viruses have been emerged in the last few years, and vaccines need to keep up with their pace. Collectively, this review summarizes the strategic evolution of IBDV vaccines from traditional methods to cutting-edge molecular platforms, providing promising strategies for developing the next-generation vaccines with higher safety, efficacy, and the ability to keep pace with the antigenic drift in IBDV.

Nationwide surveillance of avian influenza viruses (AIVs) in live poultry markets across China has occurred since 2014, providing a resource for AIV prevalence and genetic diversity studies. Here we report that 3,237 of 18,425 samples from poultry were AIV positive (17.57%) between 2019 and 2023, with H9N2 being the dominant subtype. We developed an automated phylogeny-based nomenclature system to classify genetic clades of the dominant H9N2 lineage, the BJ94 lineage. Using this model, we found that ten haemagglutinin (HA) sub-subclades cocirculated in poultry and showed antigenic variation. In addition, 99.46% and 96.17% of H9N2 AIVs in 2021-2023 possessed human-receptor binding-related HA-L226 and human MxA-resistance-related NP-N52 mutations, respectively. H9N2 strains with these two mutations preferred human-type receptors and increased replication in human cells in vitro, regardless of the presence of PB2-V/K/E627. Moreover, H9N2 AIVs containing HA-L226, PB2-V/K627 and NP-N52 were transmitted from infected to naive guinea pigs and ferrets through direct contact and respiratory droplet. This highlights the potential zoonotic risks of H9N2 AIVs.

New genotype Muscovy Duck Parvovirus (N-MDPV), a member of the Parvoviridae family, exhibits broad host tropism affecting Muscovy ducks, semi-Muscovy ducks, and white Kaiva duck. This pathogen causes severe morbidity and mortality in ducklings under 3 weeks of age, characterized by classic parvoviral lesions, beak atrophy, and growth retardation, posing substantial economic threats to China’s duck industry. To address diagnostic challenges, we developed an equipment-free detection platform targeting the conserved VP3 gene of N-MDPV. By integrating recombinase polymerase amplification (RPA) with CRISPR/Cas12a-mediated lateral flow strip (LFS) visualization, this method achieved isothermal amplification at 37°C within 35 min, eliminating dependency on thermocyclers. Validation experiments demonstrated exceptional sensitivity with a detection limit of 1.3 gene copies. Specificity testing revealed no cross-reactivity with eight common avian pathogens, confirming target exclusivity. Clinical validation using 98 field-collected duck tissue samples showed 98.98% concordance between our RPA-CRISPR/Cas12a-LFS and quantitative PCR. This study establishes the first CRISPR/Cas12a-based on-site diagnostic tool for N-MDPV, combining rapidity, sensitivity, accuracy and field-deployability.

Duck hepatitis A virus type 3 (DHAV-3) is an infectious virus that is highly fatal to ducklings and causes significant economic losses in the duck industry worldwide. Biosecurity and vaccination are required to control the pathogen. In the present study, we attenuated a lowly pathogenic DHAV-3 clinical isolate, named as HB, by serial passaging in duck embryos, and followed by several adaptive proliferations in specific-pathogen-free (SPF) chicken embryos. The virulence of DHAV-3 at different passages was assessed by infecting 3-day-old ducklings. We found that the HB strain lost pathogenicity to ducklings from the 55th passage onwards. The 80th passage strain (HB80), which achieved good growth capacity in duck embryos with a viral titer of 108.17 50% egg lethal dose per milliliter (ELD50/mL), was selected as a live attenuated vaccine candidate. The HB80 strain did not induce clinical symptoms or pathological lesions in 3-day-old ducklings and showed no virulence reversion after 5 rounds of in vivo back-passage. The minimum effective dose of HB80 was determined to be 104.5 ELD50 by hypodermic inoculation of the neck. Importantly, a single dose of HB80 elicited good immune responses and provided complete protection against challenge with the lethal DHAV-3 strain. Compared with the genomic sequence of the parental HB strain, HB80 had 7 amino acid substitutions, two of them are in the hypervariable region of the VP1 and polymerase-encoding 3D regions, which may play a role in virulence attenuation. Our data suggest that the attenuated HB80 strain is a promising vaccine candidate for the prevention of DHAV-3 infections in China. HB80 has been registered as a New Veterinary Drug Registration Certificate by the Chinese Ministry of Agriculture and Rural Affairs (MARA), and is the first live attenuated DHAV-3 vaccine strain to be officially licensed in China.

The recent emergence of hepatitis-hydropericardium syndrome caused by highly pathogenic fowl adenovirus serotype 4 (FAdV-4) has resulted in significant economic losses to the poultry industry. However, the early innate immune response of immune organs within 24 hpi and the induction of autophagy in vivo after FAdV-4 infection have not been fully elucidated. In this study, 35-day-old specific pathogen-free (SPF) chickens were artificially infected with hypervirulent FAdV-4, which resulted in a mortality rate of up to 90%. The results showed that FAdV-4 infection rapidly triggered the innate immune response in vivo of chickens, with the spleen eliciting a stronger innate immune response than the thymus and bursa. During the early stage of viral infection within 24 hpi, the main receptors TLR3/7/21, MDA5, and cGAS were activated via the NF-κB and TBK1/IRF7-dependent signaling pathways, which up-regulated production of inflammatory cytokines and type I interferons. Additionally, the expression levels of the autophagy-related molecules LC3B, Beclin1, and ATG5 were significantly up-regulated at 24 hpi, while degradation of SQSTM1/p62 was observed, suggesting that FAdV-4 infection elicits a complete autophagy response in the spleen. Besides, the colocalization of Fiber2 and LC3B suggested that FAdV-4 infection induced autophagy which benefits FAdV-4 replication in vivo. This study provides new insights into the immunoregulation signal pathways of the early innate immunity in response to hypervirulent FAdV-4 infection in vivo within 24 hpi and the close relationship between viral replication and autophagy.

The rise of antibiotic-resistant bacterial infections necessitates alternative therapeutic strategies, such as phage therapy. This study investigates the potential of phage vB_PmuM_CFP3 (CFP3) as a therapeutic agent against avian cholera caused by Pasteurella multocida (P. multocida). Phage CFP3 was isolated from the feces and wastewater of a laying hen farm and underwent comprehensive biological characterization, including host range, lytic activity, and environmental stability. Transmission electron microscopy revealed CFP3′s typical myovirus morphology, with a head diameter of approximately 60 nm and a tail length of about 120 nm. CFP3 demonstrated high stability across a pH range of 4–10 and temperatures of 30–40 °C, making it suitable for oral administration in poultry. The phage exhibited a latent period of about 90 min and an optimal multiplicity of infection (MOI) of 1. Despite its narrow host range, with a lysis rate of 28.2% against avian-derived type A P. multocida, CFP3′s specificity minimizes impact on non-target bacteria. Whole-genome sequencing revealed a 32,696 bp linear double-stranded DNA genome with 46 predicted open reading frames (ORFs) and no tRNA or antibiotic resistance genes, enhancing its safety profile. Phylogenetic analysis indicated a close evolutionary relationship with Haemophilus phages HP1, HP2, and Pasteurella phage F108. While CFP3 shows promise as a precision therapeutic tool, further in vivo studies are required to evaluate its efficacy and safety. Future research should focus on expanding the phage library, optimizing phage mixtures, and exploring synergistic effects with other antimicrobial strategies. This study provides foundational data supporting the development of CFP3 as a viable alternative to antibiotics for controlling avian cholera.

In April 2022, a novel Goose adenovirus (GoAdV) isolated from diseased Lion head gooses exhibiting swelling and hemorrhage of liver and kidney, accumulation of fluid in pericardial, in Fujian province of China. The GoAdV was propagated in goose embryo fibroblasts (GEFs), the morphological properties of the virions were studied by electron microscopy, and the full genome sequence was determined and analyzed. The results revealed that the infected cells became round and clustered like grapes, virions accumulated and were arranged in crystal lattice formations in the nucleus of GEFs with a diameter of ∼80 nm. The new isolate (named CH-FJZZ-202201) has a viral genome size of 43,480 bp and shared 96.69% sequence identity with GoAdV-4 (P29), representing the species Goose aviadenovirus A. Phylogenetic analysis showed that CH-FJZZ-202201 was in the same genetic evolutionary branch with the viruses of Aviadenovirus and was the closest relative to GoAdV-4 P29/Hungary. This is the first report of the GoAdV-4 outside of Hungary, indicating the reemergence of new AdV strains in China.

Duck circovirus (DuCV) infections commonly induce immunosuppression and secondary infections in ducks, resulting in significant economic losses in the duck breeding industry. Currently, effective vaccines and treatments for DuCV have been lacking. Therefore, rapid, specific, and sensitive detection methods are crucial for preventing and controlling DuCV. A lateral flow strip (LFS) detection method was developed using recombinase polymerase amplification (RPA) and clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 12a (Cas12a). The RPA-CRISPR/Cas12a-LFS targeted the DuCV replication protein (Rep) and was operated at 37 ℃ and allowed for visual interpretation without requiring sophisticated equipment. The results revealed that the reaction time of RPA-CRISPR/Cas12a-LFS is only 45 min. This method achieved a low detection limit of 2.6 gene copies. Importantly, this method demonstrated high specificity and no cross-reactivity with six other avian viruses. In a study involving 97 waterfowl samples, the Rep RPA-CRISPR/Cas12a-LFS showed 100