Effectiveness of Guava Leaf Fraction on Phagocytosis Activity and Leukocyte Differentiation in Tilapia (Oreochromis niloticus) Infected with Aeromonas hydrophila

One obstacle to the sustainability of fisheries is the bacterial infection caused by Aeromonas hydrophila (A. hydrophila). To overcome the sustainability issues posed by antibiotic use against A. hydrophila in fisheries, guava leaf (Psidium guajava L.) immunostimulants offer a promising natural alternative. The present study aimed to examine the impact of dynamic compounds derived from guava leaves on leukocyte differentiation and phagocytosis in tilapia infected with A. hydrophila. A completely randomized design was established, consisting of three treatment groups and two controls, with three replications. The groups included 150 ppm of guava leaf fraction (Group A), 125 ppm of guava leaf fraction (Group B), and 100 ppm of guava leaf fraction (Group C), which were injected into tilapia. The negative control group was infected with A. hydrophila bacteria without receiving the guava leaf fraction, and the positive control group was not infected with A. hydrophila bacteria and did not receive the guava leaf fraction. The dosage determination of the guava leaf fraction was conducted using the lethal concentration 50% test. The results demonstrated that Fraction 5 of guava leaf extract significantly enhanced the non-specific immune response of tilapia. The optimal dose of 150 ppm led to a substantial increase in lymphocyte counts and phagocytic activity following infection with A. hydrophila. Consequently, all treatment groups (100, 125, and 150 ppm) exhibited survival rates statistically equivalent to those of the positive control group, which was significantly higher than the 39% survival rate in the negative control group. Thus, guava leaf Fraction 5, particularly at 150 ppm, serves as an effective immunostimulant and natural antibiotic alternative for controlling A. hydrophila in tilapia.