Genetic characterization of Novel fowl aviadenovirus-4 (FADV-4) from the outbreak of hepatitis-hydropericardium syndrome in commercial broiler chickens in Egypt

Summary Hepatitis-hydropericardium syndrome (HHS) is an acute infectious disease caused by fowl adenovirus serotype-4 (FAdV-4), which mainly infects broilers aged 4-5 weeks. During winter, definitely in January 2021, a 32-day-old broiler flock (Cobb-500), in Alexandria Gevernorate, suffered from unusually high mortality. The infected chickens showed up a depression, ruffled feathers, and greenish diarrhea with a 15% mortality rate. Typical pathologic features of HHS were clear as a flabby heart with an accumulation of straw-coloured fluid in the pericardic sac, pale enlarged hemorrhagic, and friable liver with necrotic foci.Additionally, swelling liver and kidneys which exhibite edema with uric acid deposition.The molecular characterization has been accomplished by RT-PCR and sequence analysis for HVRs on Loop1 of the Hexon gene, which demonstrated a pathogenic fowl aviadenovius-4 (FAdV-4) genotype that was closely similar to Israeli strain IS/1905/2019 with an identity percent 98%. Accordingly, a further study are needed to elucidate the epidemiological situation of Fad-4 in all poulry sectors and exact role of Fad-4 associated with severe economic losses, thereby, providing insights into control and prevention of FAdV-4.