Leukocyte Response and Phagocytic Activity in Common Carp, Cyprinus Carpio Experimentally Infected with Virulent Aeromonas Allosaccharophila

Total and differential leukocyte count, and the phagocytic activity in blood of common carp, Cyprinus carpio (Linnaeus, 1758), experimentally infected with virulent Aeromonas allosaccharophila was evaluated in this study. For experimental study, common carp fingerlings (10.0 ± 1.5 g Weight, 8.5 ± 2.3 cm Length) were divided into five groups in duplicates of un-injected fish, fish injected with sterile phosphate buffered saline (PBS), and fish injected with 4.2 x 104, 1.9 x 106 and 7.3 x 108 colony forming units per milliliter (CFU ml-1) of suspension of A. allosaccharophila. Forty eight hours after infection, the total and differential leukocyte count and phagocytic activity of blood leukocytes of common carp was determined. The leukocyte, lymphocyte and monocyte count were significantly (P< 0.05) high in experimentally infected fishes, while no significant change in neutrophils number was observed. In fishes injected with 4.2 x 104, 1.9 x 106 and 7.3 x 108 CFU ml-1 of bacterial suspension, the percentage of phagocytic activity in the blood were 55.3, 54.7 and 58.2, respectively. The result suggests that, A. allosaccharophila could influence the leukocyte number and phagocytic activity of blood of common carp, which is an integral component of innate immune system of fish.