Field Studies on the Saccharomyces Yeast Strain MIIP as an Immunomodulator to Mitigate PRRSV Infection in Piglets

Porcine reproductive and respiratory syndrome virus (PRRSV) remains a significant threat to swine health worldwide, primarily due to its extensive genetic diversity and ability to evade host immune responses, which reduces the effectiveness of vaccines. This field study investigated the immunomodulatory effects of the Saccharomyces cerevisiae strain MIIP as a dietary supplement to mitigate PRRSV infection in piglets under commercial farming conditions. Four trials were conducted across PRRSV-affected herds, with variations in PRRS vaccination practices and infection status. MIIP supplementation led to a significant reduction in the PRRSV antibody-positive rate, titers, and viremia in treated piglets compared to both non-concurrent and concurrent control groups. Enhanced mucosal immunity was also observed, as evidenced by higher total IgA concentrations in serum and milk in the MIIP groups. Although not all immune parameters reached statistical significance, trends consistently favored improved antiviral responses in MIIP-treated animals. These results suggest that dietary supplementation with MIIP yeast can enhance both systemic and mucosal immunity, potentially reducing PRRSV infection and transmission. Further research into its mechanisms, particularly its interaction with innate immune pathways and the gut microbiota, is warranted to optimize PRRSV control strategies.