ISSN: 2474-9214
Authors: Alvin T Reyes* and Nikko C Aliasas
The general objective of the study was to investigate the White Blood Cell (WBC) response of Nile tilapia (Oreochromis niloticus L.) of various weight groups (A1 = 45-50 g; A2 = 95-100 g and A3 = 145-150 g) to single (B2, B3 and B4), double (B5, B6 and B7) and multiple (B8) bacterial infections. The experiment utilized three different bacteria (Aeromonas hydrophila, A. sobria and Providencia rettgeri) and the experimental fish were exposed on these bacterial isolates at three different levels of infections. Morphological signs such as red spots, external nodule, fin erosion and bulging eyes were observed in infected fish after four days. Across levels of infections and weight groups, the final Total White Blood Cell (TWBC) count was higher than the initial TWBC count. Highest final TWBC counts were observed in fish that received multiple infections (1st weight group = 312.00 ± 50.27/mm3; 2nd weight group = 289.00±99.24 mm3; 3rd weight group = 293±112.12/mm3). The study also found out that P. rettgeri was more pathogenic in larger sized tilapia, and A. hydrophila or A. sobria was more pathogenic when mixed with P. rettgeri. Only three types of WBC were identified in the differential counting. Before the challenge test, the highest percentage of cell type was neutrophils, followed by monocyte and lymphocyte. The reduction of neutrophils was more distinct in double and multiple bacterial infections and largest weight group, specifically in A3B7 (A. sobria + P. rettgeri) (initial = 56.33% ± 6.81; final = 20.33% ± 13.65) and A3B8 (A. hydrophila + A. sobria + P. rettgeri) (initial = 56.33% ± 12.12; final = 23.00% ± 9.17). Percent increase rate in lymphocyte ranged from 58.45-92.68% in 45-50 g, 43.69-66.06% in 95-100 g and 43.93-85.21% in 145-150 g. By level of bacterial infections, the first five highest percent increase in lymphocyte were recorded in A1B8 (A. hydrophila + A. sobria + P. rettgeri; 92.68%), A3B1 (no infection; 85.21%), A1B3 (A. sobria; 84.73%), A1B2 (A. hydrophila; 81.62%) and A1B5 (A. hydrophila + A. sobria; 79.56%). In general, the smallest weight group and tilapia that received multiple bacterial infections had the highest increase in lymphocyte count after the challenged test. Slight reductions in percent monocyte count were observed across weight groups and level of bacterial infections after the challenge test, and statistical analysis showed no significant difference (p>0.05). Percent reduction rate in percent monocyte count was more evident in fish exposed in single infection, especially in P. rettgeri. Two-way Analysis of Variance revealed that the interaction effect of different tilapia weight groupings and level of bacterial infections showed no significant effect on TWBC and differential WBC of the experimental fishes (p>0.05).
Keywords: White Blood Cell; Bacterial Infections; Oreochromis Niloticus L
