Infectious bronchitis (IB), Newcastle disease (ND) and Avian influenza (AI) are
highly contagious and the most economically important diseases of the poultry
affecting the respiratory tract and causing economic losses in the poultry industry
throughout the world. In the present study, 180 broiler flocks were sampled from
6 different Egyptian provinces (Giza, Qaluobia, Sharqia, Menofia, Al Behira and
Fayoum) during 2014 to 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, rRT-PCR results for each governorate separately go
more or less parallel to that of all governorates collectively, 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.