Abstract: Thirty specific pathogen free (SPF) 20-day-old chicks were inoculated by the intra-tracheal (n=15) or oral (n=15) routes with serotype 793/B of IBV, isolated of Iran. Two groups of 15 SPF chicks which as controls received PBS, either by the intra-tracheal or oral route. All the chicks were observed and examined daily for clinical signs. Each day for 5 days three chicks from each infected and control group were post-mortemed and examined pathological changes in the trachea, lungs, kidneys and intestines. Sections of these tissues were prepared, stained and examined microscopically for histopathological and immunohistochemical changes. Grossly, a small amount of clear mucus and slight congestion were found only in the lumen of the trachea and the lungs of the group chicks which were infected with IBV. The kidneys were pale and slightly enlarge. Immunohistochemical examination revealed similar changes in the kidneys of both groups of chicks infected by the intra-tracheal and oral routes. Viral antigens were detected in the infected cells. The viral antigens were apparent prior to the development of lesions and were detected in the cytoplasm of epithelial cells by 3 days post infection with IBV. The results of this study clearly indicate that IBV (serotype 793/B), isolated in Iran by Momayes et al. (2001), is capable of causing lesions in different tissues most severely in the kidneys of experimentally infected chicks. On the other hand, the serotype has a greater affinity and positive tropism for the kidney than to other tissues.
Key words: infectious bronchitis, serotype 793/B, immunohistochemistry, avian diseases.
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