Molecular Characterization of Fowl Adenovirus D Species in Broiler Chickens with Inclusion Body Hepatitis in Egypt

In the current study, fowl adenovirus (FAdV) was detected and characterized from broiler chicken flocks with inclusion body hepatitis (IBH) in Northern Egypt during the period from March 2017 till March 2018. Grossly, the examined flocks showed hydropericardium and enlarged friable livers with ecchymotic hemorrhages. Histopathologically, liver tissues revealed intranuclear inclusion bodies in hepatocytes and hepatitis. Molecular detection by PCR assay using primer specific for the L1 loop region of hexon gene was conducted, the PCR products were sequenced for typing of FAdV. Seventeen out of 37 flocks tested were positive. Sequence analysis revealed that the 17 FAdVs were identical, suggesting a common ancestor for the FAdVs circulating in northern Egypt during the period of study. Phylogenetically, they clustered with fowl adenoviruses D species (FAdV-2 and FAdV-11). Interestingly, pathogenicity varied from non-pathogenic to more virulent with mortalities up to 20% under field condition. To our knowledge, this is the first report of FAdV-D from broiler chicken in Egypt. Further studies are needed to examine different poultry species and other geographic areas in Egypt. Moreover, studies on the pathogenicity and potential preventive measures against FAdV infection on poultry farms are necessity.