African swine fever (ASF) is a contagious viral disease that causes severe economic losses in the global swine industry. Since its introduction to Vietnam in 2019, ASFV has evolved rapidly, with genotype II strains dominating initially and recombinant I/II variants emerging by 2023. Live attenuated vaccines (LAVs) have been developed and commercialized in Vietnam, including ASFV-G-ΔI177L, ASFV-G-ΔI177L/ΔLVR, and ASFV-G-ΔMGF, which confer homologous immune protection. Despite this, LAVs face challenges related to genetic stability, impossible protection against emerging recombinant strains, potential reversion to virulence, viral shedding, and safety in pregnant sows. ASFV’s ongoing evolution underscores the need for continuous genomic surveillance, evaluation of cross-protective efficacy, and implementation of biosecurity and DIVA strategies focused more on evaluating vaccine efficacy than safety. This review summarizes the current molecular epidemiology of ASFV in Vietnam after vaccines were licensed for use, the development and performance of commercial LAVs, and the practical challenges of their application in endemic settings, and provides insights for informed vaccine deployment and integrated ASF control strategies in rapidly evolving viral landscapes.

Background and Aim: Neonatal piglet diarrhea (NPD) remains a significant challenge in the swine industry, contributing to elevated pre-weaning mortality, reduced productivity, and increased economic losses. In Vietnam, despite the growing importance of commercial pig production, comprehensive studies investigating the epidemiology of NPD and associated bacterial pathogens are lacking. This study aimed to assess the prevalence of Escherichia coli, Clostridium perfringens, and Clostridioides difficile and to identify risk factors contributing to NPD on Vietnamese sow farms. Materials and Methods: A cross-sectional study was conducted on 40 commercial sow farms across North, Central, and South Vietnam between August and December 2023. Structured questionnaires captured data on farm characteristics, management practices, and health interventions. Fecal samples from symptomatic piglets aged 1–14 days were pooled and analyzed using multiplex quantitative polymerase chain reaction to detect virulence genes of E. coli (F4, F5, F6, LT), C. perfringens (alpha, beta, and epsilon toxins), and C. difficile (toxins A and B). Logistic and ordinal regression models were applied to assess associations between risk factors and pathogen prevalence. Results: All farms tested positive for at least one pathogen. C. perfringens was the most prevalent (97.37%), followed by E. coli (46.49%) and C. difficile (39.47%). Co-infections involving multiple pathogens were common (64.91%), with C. perfringens consistently present in all mixed infections. Key virulence genes detected included LT (35.96%), alpha toxin (95.61%), and toxin A (20.17%). Significant risk factors included farm type, region, weaning performance, and peripartum antibiotic administration route. Notably, farms using mixed-feed antibiotics exhibited higher E. coli prevalence. Larger farms and those practicing early piglet relocation also showed increased pathogen diversity. Conclusion: This study presents the first national-scale assessment of bacterial pathogens in NPD across Vietnamese sow farms. The findings highlight the high burden of toxin-producing bacteria, frequent co-infections, and multiple farm-level risk factors. Interventions such as targeted vaccination, optimized antibiotic use, improved weaning practices, and enhanced regional surveillance are essential for mitigating NPD impacts and improving piglet health outcomes in Vietnam. Keywords: bacterial toxins, Clostridioides difficile, Clostridium perfringens, Escherichia coli, farm management, multiplex quantitative polymerase chain reaction, neonatal piglet diarrhea, Vietnam, risk factors.

Background and Aim: The African swine fever virus (ASFV), spanning 170–193 kb, contains over 200 proteins, including p72 and p30, which play crucial roles in the virus’s entry and expression. This study investigated the capability of detecting ASFV early through the analysis of genes B646L and CP204L, encoding p72 and p30 antigen proteins, by employing ASFV, diagnosis, immunohistochemistry (IHC), quantitative polymerase chain reaction (qPCR), and IHC techniques. Materials and Methods: Samples were taken from both experimentally and field-infected pigs to evaluate the effectiveness of qPCR and IHC in detecting ASFV. Twenty-two infected pigs were necropsied at 3-, 5-, 7-, and 9-day post-infection to obtain the first set of samples, collecting anticoagulated blood and tissues each time. The thymus, spleen, and lymph nodes were processed by fixing in 10% formalin, paraffin-blocking, and undergoing IHC staining. Forty anticoagulated blood samples were collected from clinically infected sows at a pig farm for the second batch of samples. Based on the lowest Ct values, three blood samples were diluted fivefold for qPCR DNA testing, and their tissues were used for both qPCR and IHC analyses. Results: At 1-day post-infection, p30-qPCR identified more ASFV-positive pigs and measured lower Ct values compared to p72-qPCR. At later time points, both methods showed similar levels of detection. ASFV was detected earlier and with lower Ct values in lymphoid tissues using p30-qPCR compared to p72-qPCR, particularly in the spleen and lymph nodes. In a field outbreak study, p30-qPCR demonstrated superior sensitivity and lower Ct values when detecting ASFV in blood samples compared to p72-qPCR. Conclusion: The early detection of the CP204L gene encoding p30 and its corresponding antigenic protein in ASFV diagnosis compared to the gene encoding p72 suggests that CP204L and p30 are promising candidates for the development of more effective antigen and antibody testing methods. Keywords: African swine fever virus, diagnosis, immunohistochemistry, quantitative polymerase chain reaction.