This study was performed to determine the levels of serum nitric oxide (NO), malondialdehyde (MDA), total sialic acid (TSA), and total oxidant capacity (TOC) and total antioxidant capacity (TAC) as well as histopathological changes in sheep naturally infected with pox virus. The study material comprised of 40 Sheep pox infected and 20 non-infected Akkaraman mixed sheep aging between 1 and 2.5 months. Diagnosis of the disease was based on the clinical and histopathological observations. Blood samples were collected from the infected and healthy animals, and serums were separated. The levels of NO (36.65±1.10 nmol/ml), MDA (5.87±0.14 μmol/L), TSA (88.51±0.82 mg/dl) as well as TOC (685.05±10.84 μmolH₂O₂Eqv/L) and TAC (1.01±0.03 mmol Trolox Eqv/L) were determined in infected animals and compared to the levels of NO (11.01±0.37 nmol/mL), MDA (2.77±0.1 μmol/L), TSA (63.07±1.36 mg/dL) as well as TOC (457.80±22.48 μmolH₂O₂Eqv/L) and TAC (1.50±0.03 mmolTrolox Eqv/L) in healthy animals, respectively. The results showed statistically significant differences between the infected and healthy animals (P<0.001). It was concluded that the increase in levels of MDA and TOC, and the decrease in TAC might indicate the development of oxidative stress in sheep naturally infected with pox virus. It can be assumed that the increase in TSA level might be an indication of the cellular damage in the infected animals.

Key words: Oxidative stress, Pox virus, Sheep, Total sialic acid