Viral quantity and pathological changes in broilers experimentally infected by IRFIBV32 isolate of infectious bronchitis virus

An Iranian isolate of avian infectious bronchitis virus IRFIBV32 was quantified in experimentally infected broilers using real-time reverse transcriptase polymerase chain reaction and histopathological changes was investigated. Thirty-six 3-week-old commercial broilers were inoculated by 10(5) ELD50/0.1 ml of the virus. On the various days post inoculation (dpi) different tissues were collected. The virus strongly started the replication in trachea at 1 dpi and reached to the maximum titer at 3 dpi. The highest IBV RNA level was shown in this organ. In lung, the virus was replicated with the titer lower than that of the trachea, but it rose up more at 5 dpi. The kidneys were the tissues with the least viral genome copy number, although the duration of the virus presence was considerable. The virus replicated in testes sooner than ovaries also disappeared sooner but the maximum viral yield in the ovaries was more. The virus titer in the studied tissues had an interesting fluctuation especially in caecal tonsils. Testes and ovaries were the organs that the virus could reactivate without using any chemical. The most severe lesions were observed in tracheae but they appeared in the lungs later. Lymphocyte infiltration in the kidneys was noted from 5 dpi even sooner than the lungs. There were no lesions in the caecal tonsils, testes and ovaries in spite of the virus replication in a high titer.