Recombinant genotype I–II African swine fever virus (ASFV) strains with high virulence have been increasingly reported in China and Vietnam since 2023, raising significant concerns for disease control. In this study, we characterized the hematological, virological, pathological, and immunological dynamics in ASFV-inoculated pigs, with particular emphasis on temporal changes associated with mortality following the onset of viremia. Specific-pathogen-free pigs were intramuscularly inoculated with 1 × 10³ or 1 × 10⁵ HAD₅₀/mL of ASFV LS100 virus strain and developed acute disease characterized by high fever and severe hemorrhagic manifestations. The incubation period ranged from 3 to 5 days, with mortality occurring between 6 and 10 days post-inoculation (dpi). Viral genomic DNA was detected in blood, oral swabs, and rectal swabs as early as 2–4 dpi. Pathological examination revealed prominent necrotic skin lesions and joint swelling. Although hematological parameters and serum biochemical profiles were comparable between high- and low-dose groups, differences in viral load distribution were observed. Notably, cytokine profiling in whole blood revealed a strong and persistent upregulation of pro-inflammatory mediators, including IL-1β, IL-6, IL-12p40, TNF-α, IFN-γ, CCL2, CCL3, CCL14, CXCL9, and CXCL10, which correlated with persistent fever from 2 to 7 dpi. Collectively, these findings confirm that naturally occurring recombinant genotype I–II ASFV strains are highly virulent and capable of inducing severe systemic inflammation. Their continued circulation poses substantial challenges for ASF control and prevention in Vietnam and threatens the global swine industry.

Porcine reproductive and respiratory syndrome virus (PRRSV) is a major pathogen that poses a serious threat to the global pig industry. North Central Vietnam, comprising six provinces, is one of the country’s largest pig-breeding regions; however, the information of molecular characterization of this virus circulating in this area have been limited. To address this gap, 130 samples were collected from these provinces between 2023 and 2024. The results showed a PRRSV-positive rate of 23.07% (30/130). Molecular characterizations of PRRSV were further analyzed based on sequences of the ORF5 and NSP2 hypervariable regions (HVRs), in comparison with reference strains from Vietnam and other countries downloaded from GenBank (NCBI). Phylogenetic analysis revealed that the sequenced strains belonged to PRRSV-2 (lineages 1, 5, and 8). Specifically, 28 PRRSV-2 strains were selected for ORF5 analysis and classified into sublineage 8.7 (HP-PRRSV), sub-lineage 5.1 (classical PRRSV), and the newly identified sub-lineage 1.8 (NADC30-like). The NSP2 HVRs of the identified strains showed amino acid identities ranging from 38.63% to 100%, while ORF5 identities ranged from 80.3% to 100%. Sequence analysis of ORF5 indicated that GP5 mutations were mainly concentrated in HVR1, HVR2, and virulence-associated sites. In summary, the detection of NADC30-like PRRSV for the first time in Vietnam is important, indicating that this HP-PRRSV and classical PRRSV strains reported previously are currently co-circulating among the pig population in North Central Vietnam. Additionally, these findings suggest that PRRSV strains in Vietnam are undergoing substantial genomic divergence.

This study aimed to evaluate the pathogenic potential of the 2024 Vietnam PRRSV genotype 2 (NA01/2024, isolate). Fifteen 6-week-old piglets were intramuscularly inoculated with 1 × 10^5.5 TCID₅₀/mL of PRRSV, while fifteen control piglets remained uninfected. Blood and nasal swabs were collected every 3 days until 21 days post-infection (dpi). Necropsies were performed on piglets at 6, 15, and 21 dpi. Infected piglets exhibited fever, blue ear, weight loss, respiratory distress, diarrhea, and leucopenia between 3 and 12 dpi. PRRSV was detected in serum and nasal secretions up to 21 dpi, peaking between 6 and 9 dpi. Seroconversion began at 6 dpi, with the highest antibody titers at 21 dpi. Virus load was highest in lung tissues at all intervals, while the spleen and lymph nodes showed higher viral load at later stages. Routine blood tests indicated a slight decrease in red blood cells, hemoglobin, and reticulocytes, along with a notable increase in monocytes in infected piglets. Cytokine levels (IFN-γ, IL-6, and IL-10) in serum and lung tissues were significantly higher in infected piglets compared to controls. Additionally, the PRRSV infection triggered innate immune responses, including cytokines, growth factors, and chemokines in whole blood and tissues such as IFN-α, IFN-β, TNF-α, IL-1β, etc. These findings highlight the pathogenicity of the Vietnam PRRSV NA01/2024 isolate and its impact on the immune response, providing insights into PRRSV infection mechanisms and strategies for prevention and control.