Determination of acute phase proteins aft er experimental Streptococcus iniae infection in tilapia (Oreochromis niloticus L.)

Tilapia (Oreochromis niloticus Linnaeus, 1758) were infected with Streptococcus iniae (Cat No: ATCC 29178) and the plasma changes in the acute phase protein (APP) members were examined at different time periods. A total of 72 fish with average body weights of 60 g were used. Fish in the infected group (group I) were intraperitoneally injected with S. iniae at 3.3 x 10(5) colony forming unit (CFU) in 0.1 mL level to the fish. The other group (group II) was subjected to handling stress near the infection. The control group was constituted by providing optimum conditions. On days 7, 14, and 21, blood samples were taken from the caudal veins of the fish under the appropriate anesthesia. The samples were examined on the basis of APPs, C-reactive protein (CRP), fibrinogen (FB), serum amyloid A (SAA), and transferrin (TF) and the changes in the plasma values were recorded. The internal and external symptoms seen during the examinations were detected as follows: the color concentration in 1-2 days in the infected groups, irregularity and retardation in the movements of the fish, hyperemic spots on the skin, and bloody effusion in the internal organs. In both of the infected groups, the CRP and SAA plasma values increased on days 7, 14, and 21 (P < 0.05). Remission was observed in the plasma TF levels in the first week; however, aft er the second week the levels reached normal values. Decreases in the FB levels of all of the samples were detected. Based on the data acquired in this study, it was concluded that changes in the plasma levels of the APP members can be used as a significant bioindicator in the pathogenesis of the disease in fish infections.