Evaluation of Total Oxidant/Antioxidant Capacity and Ceruloplasmin Levels in Horses with Inflammatory Airway Disease

Abstract

Background: Respiratory disease negatively affects the physiological performance of racehorses. Inflammatory Airway Disease (IAD) is a typical respiratory disease that affects young horses. The pathogenesis of IAD remains incompletely defined but it is thought to be associated with the inhalation of irritants such as barn dust and air pollution. Although noninfectious agents are likely to be central to the development of IAD, infectious agents can be associated with the disease. The main objective of the present study was to determine the relationships between IAD and antioxidant capacity, ceruloplasmin levels and bacterial and fungal infection status, in racehorses. Materials, Methods & Results: In this study, 25 thoroughbred race horses with exercise intolerance and respiratory system symptoms were evaluated as the study group and 10 healthy horses were included in the control group. Clinical examinations, endoscopic evaluation and tracheal lavage were administered to all horses. Mucus accumulation in the trachea was scored and the horses having a mucus score of >= 3 were included the study group. Tracheal lavage fluids were investigated to determine the microbiological status of all animals. In addition, blood samples were collected and total oxidant capacity (TOC), total antioxidant capacity (TAC) and ceruloplasmin (Cp) levels were determined with a spectroscopic method. Exercise intolerance and various respiratory system symptoms such as coughing, nasal discharge and noisy breathing, were the common findings from horses in the study group. Fungal culture was negative and only Streptococcus equi subsp. zooepidemicus strain was isolated from 6 samples. No statistical difference was determined between the TOC, TAC and Cp levels of the groups (P > .05). Discussion: Racehorses with IAD typically exhibit poor performance, chronic coughing and/or nasal discharge. This study showed little association between coughing and the isolation of bacterial species from tracheal aspirates, with only S. zooepidemicus strains isolated from 6 samples. Endoscopic examination of the airways after exercise and detection of excess mucus accumulation is an important diagnostic tool. In the present study, all animals of the study group had a mucus score of >= 3 (= excessive) mucus accumulation in the trachea. Excessive oxidant generation or antioxidant insufficiency can lead to oxidative stress (OS). A regular training regime helps horses to adapt to the higher levels of oxidative substances during exercise. Similarly, although there were IAD symptoms in the horses in the present study, no differences were detected in TAC and TOC levels between the study and control groups. Serum Cp is defined as an acute-phase protein (APP) and antioxidant. The APP concentration was not detectably different between exercise intolerant racehorses, with and without IAD in an earlier study of racehorses. Similarly, in our study, no differences were detected for Cp levels between the control and study group. These results may be pointing to non-systemic infection in the horses with respiratory symptoms. In conclusion, based on the clinical, endoscopic and microbiological findings in the present study, IAD was diagnosed in 25 racehorses. Probably, due to high adaptation ability of racehorses a systemic response was not observed in IAD which causes only mild to moderate pulmonary disorders. However, further studies involving a microscopic evaluation of tracheal aspirates for inflammatory cells should be performed for a detailed evaluation of acute phase proteins and oxidative stress parameters in racehorses with respiratory diseases and poor performance.