Thesis (M.Sc.) - Cairo University - Faculty of Veterinary Medicine - Department of Animal Diseases

In the present study, 180 broiler flocks were sampled from 6 different Egyptian provinces (Giza, Qaluobia, Sharqia, Menofia, Al Behira and Fayoum) during January 2014 to December 2015. The birds showed respiratory illness and they were examined for 4 respiratory viral diseases; avian influenza (AI subtype H5 and H9), vNDV and IBV. All farms were vaccinated against IBV, ND and AI and were investigated using RT-PCR. The results showed that 41 out of 180 broiler farms were positive for either IBV or vND or AI-H5 and AI-H9 as a single infection as follows: 24, 10, 5 and 2 farms respectively. There were 62 farms detected as mixed infection, the highest incidence was shown in 40 farms co-infected with IBV and AI (H9) and 11 with IBV and vNDV, There was no clear geographical preferences in positive viruses among governorates. Mortality rate and clinical signs incidence showed the highest percentage for birds reared in winter and Autumn compared with the other seasons. The results revealed that IBV as a single or a mixed infection had a major role in the respiratory problem in the field, so, we characterized 10 field isolate of IBV from a broiler flock as single infection and as coinfection with Avian influenza H9. In addition to characterization for one field isolates from each respiratory examined viruses vNDV, AI-H5 and AI-H9.The S1, HA and F gene was partially amplified and directly sequenced. The obtained sequence for S1 gene of IBV for 8 isolates were related to Egyptian variant that was commonly circulating at the same year and 2 isolates were related to the classical strain (Mass-like strain)

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