Epidemiological Distribution of respiratory viral pathogens in marketable vaccinated broiler chickens in six governorates in the Nile Delta, Egypt, January to October 2022

Abstract Background and Aim: Respiratory viral infections have a considerable detrimental impact on animal welfare as well as significant financial ramifications in the poultry industry. Avian influenza virus (AIV) subtypes H5 and H9, Newcastle disease (ND), and infectious bronchitis (IB) are the most economically significant illnesses impacting the poultry sector worldwide, including Egypt. From January to October 2022, this study examined the presence of respiratory viral infections (AI-H5, AI-H9, ND, and IB) in 359 flocks of broiler chickens (33–38 days) in six Egyptian governorates (Beheira, Gharbia, Giza, Monufiya and Qalyoubia). Results Out of 359 flocks examined, 293 tested positive, whereas 66 tested fully negative for the four viruses tested with the highest positive results in Beheira. Out of 293 positive flocks, 211 were positive to a single virus with Beheira having the highest rate, followed by Qalyoubia, Giza, and Monufiya. NDV was found to be the highest across all governorates, followed by IBV, AI-H9, and AI-H5. Double infection was detected in 73 flocks with either H9 or ND or both H9 and IB would co-infect one another. The most common viral co-infection was H9 + IB, ND + IB, and ND + H9. Giza had the greatest prevalence of co-infection with ND + H9, H9 + IB, and ND + IB in the governorates, followed by Monufiya and El Buhyera. Only 6 out of 359 flocks were tribally infected with ND + H9 + IB in three governorates: Giza, Monufiya, and Beheira. According to the number of flocks and the month of the year, July had the fewest tested flocks (23) and both September and October had the most (48 flocks). The positive flocks were highest in October and lowest in January. Conclusion The results revealed that IBV and H9 as a single or a mixed infection had a great role in the respiratory infection in broiler. The used vaccine (regardless their origin and type) is not able to protect broiler chickens from developing infection and shedding of virus to the poultry environment. Therefore, poultry vaccines need regular evaluation, renovation in face infective field virus mutants and also, poultry farms must be adopting more biosecurity measures.