Epidemiological and molecular analysis of circulating fowl adenoviruses in Egypt and emerging of serotypes 1, 3, and 8b

Abstract Fowl adenoviruses (FAdVs) are a large group of viruses of different serotypes. They are responsible for inclusion body hepatitis (IBH), gizzard erosion disease (GED), and hepatitis/hydropericardium syndrome (HHS). This study presents a comprehensive overview of FAdVs in Egypt, with a focus on the epidemiological features of virus serotypes across the country. We conducted a molecular investigation of multiple FAdV species based on the genetic signature of hypervariable regions 1–4 in the loop1 (L1) region of the hexon gene. Epidemiologically, Delta governorates showed high positivity for FAdVs, which were more commonly found in broilers than in layers. Genetically, species D and serotype 8a/E dominated, and the findings also revealed the emergence of new FAdV serotypes 1, 3, and 8b. The comparative analysis of hypervariable regions in the L1 region of the hexon gene reveals variables specific to each virus serotype. In silico predictions of L1 region revealed variations in the molecular structure and the antigenic epitopes that could affect the cross-antigenicity between the different FAdV species and serotypes.