Investigation on Fowl Adenovirus Outbreaks in some Broiler and Broiler Breeders’ Flocks in Egypt

Egypt's poultry industry has been adversely impacted by multiple outbreaks of inclusion body hepatitis (IBH) and hepatitis hydropericardium syndrome (HPS) in recent years, resulting in significant economic losses. So, this research aimed to identify and characterize IBH and HPS in broiler and broiler breeders’ flocks across the country for three years (2020-2022). Clinical cases of fowl adenovirus (FAdVs) infection in 835 flocks (10,000–20,000 birds in each flock) were investigated from 11 Egyptian provinces for identifying and genotyping FAdVs. The examined flocks showed variant symptoms of diarrhea, anemia, and general weakness. An enlarged, yellowish, and friable liver with necrotic foci was observed at necropsy, along with hydropericardium effusions, an enlarged, mottled spleen, enteritis, severe pancreatitis, and an inflamed bursa. DNA extracted from suspected isolates was analyzed by conventional polymerase chain reaction (PCR) and sequencing targeting the loop L1 of the hexon gene. The sequences were analyzed using BLAST and compared to adenovirus available in the GenBank database NCBI.  FAdVs were detected in 22.4% (146/650) of broiler flock samples and 32.9% (61/185) of broiler breeders’ flocks. Additionally, the hexon gene was subjected to phylogenetic analysis, which revealed that FAdVs can be classified into four genotypes. (FAdVs B-E) were detected from 34 represented samples (n= 34), 1 out of 34 FAdV-B, 3 out of 34 FAdV-C, 22 out of 34 FAdV-D, and 8 out of 34 FAdV-E (4 with 8a and 4 with 8b), FAdV-D was the most predominant. This investigation revealed the existence of infectious FADVs of various genotypes, and it is critical to design an effective vaccination program and comprehensive epidemic prevention in both broiler and broiler breeders’ flocks in Egypt.