Evaluation of sialic acid and acute-phase proteins (haptoglobin and serum amyloids A) in healthy and avian infection bronchitis virus-infected chicks

Forty-five 24-day-old Cobb chicks infected with infectious bronchitis virus (IBV) and ten healthy 24-day-old Cobb chicks without any clinical signs of IBV as control group were selected for the study. All of the diseased chicks showed some or all of the clinical signs of infectious bronchitis including gasping, coughing and nasal discharge, wet eyes, swollen sinuses, reduction of food consumption and weight gain. Diagnosis of IBV was based on clinical signs and ELISA test. Blood samples were taken from the wing vein into two tubes: one containing ethylenediaminetetraacetic acid (EDTA) and one without EDTA. Haptoglobin (Hp), serum amyloid A (SAA), total sialic acid (TSA), lipid-bound sialic acid (LBSA) and protein-bound sialic acid (PBSA) concentrations were measured. All of the study variables were significantly higher in diseased birds compared with control group. Results showed that there were significant positive correlations between TSA, LBSA and PBSA in both groups. No correlation was observed between Hp and SAA with any other parameters; however, there was significant negative correlation between Hp and SAA in the control group. Results for receiver operating characteristic analysis showed that area under the curve (AUC) for TSA, LBSA, PBSA, Hp and SAA were 0.93, 0.98, 0.90, 0.90 and 0.80, respectively. According to AUC, LBSA was the most sensitive factor to change in the diseased birds. It can be concluded that in naturally occurring IBV infection, significant increases in TSA, LBSA, PBSA, Hp and SAA concentrations are expected and among study variables, LBSA had the most obvious change so it may be considered as the most sensitive parameter.