Glial fibrillary acidic protein (GFAP) is an intermediate filament protein that is expressed by numerous cells in the central nervous system. For determine the distribution of GFAP in brain tissues of normal and infected chicken and duck we conduct this study. A twenty-three 32-day-old male white Leghorn SPF chickens and twenty-three 32-day-old male commercial ducks were divided into control group (n= 5) and infected group (n= 18) from each bird type. 9a5b Newcastle disease virus (NDV) was used for bird infection and brain tissues from all groups were fixed in neutral buffered formalin and prepared for immunohistochemical investigation of GFAP expression. The expression of GFAP in control chickens brain tissues is different than those of duck. While Bergmann-glia is GFAP-negative in control chickens; it appears positive in control ducks. GFAP expression in chickens is centered in the granular layer of cerebellum but in ducks it concentrated around the Purkinje cell layer. In the infected birds, numerous reactive astrocytes were observed in brain sections stained for GFAP in both chickens and ducks after 9a5b NDV infection. In chickens, GFAP-positive astrocytes were observed in the cerebellum, cerebrum, and midbrain as well as in the medulla oblongata. These changes were more prominent in areas of inflammatory response and neuronal loss. In turn, the brain tissues of infected duck express GFAP less than infected chickens. Duck brain tissues did not show any signs of inflammatory response, therefore, the expression of GFAP in ducks brain tissues still needs farther studies to explain the real causes underlying this expression.
Key words: GFAP; Astrocyte; Newcasle Disease Virus, Chickens; Ducks