Effect of Psidium guajava and Phyllanthus acidus Leaf Extract on Immunostimulant Response of Nile Tilapia Against Streptococcus agalactiae Infection

A study was conducted to investigate the efficacy of diets supplemented with aqueous extract of plants consisting of leaf-extracts of Psidium guajava (PGLE), Phyllanthus acidus (PALE), and the mixture of PGLE and PALE at the rates of 5 and 10 g/kg in the feed of Nile tilapia Oreochromis niloticus. Following 12 weeks of feeding, the fish were challenged with Streptococcus agalactiae for 15 days. Immuno-hematological parameters were measured before and after the challenge. Results showed significantly enhanced innate immune parameters after administration of the plant extracts. Respiratory burst activity, phagocytic assay, and serum lysozyme content were 2 to 3 times higher than that of the control treatment; PGLE-10 group showed the highest values, while fish fed PGLE-10 had the highest post-challenge WBC, RBC, Hb, and Hct values compared to the control. Survival rates were higher in the groups with dietary supplementation of plant extracts compared to the control. The positive immuno-hematological impact of plant extracts show that these can be effectively used as alternative prophylactic and antimicrobial agents in Nile tilapia culture