Probiotics as a Strategy for Mitigating Viral Infections in Poultry: Immunomodulatory Mechanisms and Therapeutic Potential

Poultry viral infections remain a persistent challenge for the poultry industry, causing significant economic losses and posing potential threats to human health. The escalating frequency of outbreaks involving pathogens, such as infectious bronchitis virus (IBV), Newcastle disease virus (NDV) and avian influenza virus (AIV), underscores the urgent need for effective interventions. Probiotics have gained attention as a promising strategy to combat these viral infections due to their potential in enhancing immune responses and establishing a healthy gut microbiome. A literature search was carried out on Google Scholar, Scopus and PubMed using key search terms, such as 'probiotics', 'Lactobacillus', 'acidophilus', 'poultry', 'viral infections', 'Newcastle Disease Virus (NDV)' and other relevant terms. Inclusion criteria for manuscripts used were based on the relevance to probiotic-based interventions in poultry, the focus on immunological mechanisms and the examination of viral pathogens commonly found in West African poultry farming systems. This review explores the role of probiotics in mitigating the effects of NDV, AIV and IBV in poultry, focusing on their immunomodulatory effects and antiviral mechanisms. Lactobacillus acidophilus, L. casei and L. plantarum have shown an interesting promise in countering NDV infections by modulating immunological parameters and enhancing antibody responses. Similarly, these probiotics have exhibited antiviral activity against AIV, promoting immune activation and reducing viral loads. Additionally, L. acidophilus and L. plantarum have emerged as potential adjuvants for IBV vaccines, improving antibody responses and humoural immunity.