A Comparative Study on Histopathologic Effects of Iranian Newcastle Disease Virus Isolates

The histopathologic effects of Iranian Newcastle disease viruses isolated From different outbreaks across the country wcre studied on difTerent organs of specifie pathogen free chickens. Clinically, time and sequence of the signs' occurrence were varied among the groups receiving different isolates. Depression was the first c1inical sign observed by 48h postinfection (PI) in ail groups except two groups, which showed depression by 97h PI. Grossly, among the three systems, gastro-intestinal, respiratory and central nervous system that were examined in infected groups, the latter two showed less remarked lesions. Macroscopically, From 72h PI toward the end of experiment the spleen showed atrophy in ail infected groups. At 96h PI and later on, the brain was slightly hyperaemic in limited infected groups. The early findings were observed in proventriculus, Iiver, small intestine and spleen. Generally ail nine Iranian Newcastle disease viruses can affect visceral organs [aster than other organs and could be placed in viscerotrop velogenic group.