Detection and molecular characterisation of fowl adenovirus associated with inclusion body hepatitis and hydropericardium syndrome in Uganda

Fowl Adenovirus (FAdV) infections and associated clinical conditions are of major economic significance in broiler chickens but have never been reported in Uganda and East Africa. Between July 2020 and June 2021, 120 farms submitted chicken diagnostic samples to Central Diagnostic Laboratory (CDL), Makerere University, Uganda, of which FAdV infections were suspected in 19 flocks during necropsy. Following bacteriology, histopathology and Polymerase Chain Reaction (PCR), FAdV infections were confirmed in ten flocks. The 10 flocks were aged between 9 and 24 days. They had a history of sudden onset of depression, anorexia and huddling together and high mortality rates (range = 12%-89%). Necropsy revealed hepatomegaly with pale yellow discolourations, multiple petechial haemorrhages, icterus and necrosis. Hydropericardium was evident in nine of the 10 flocks but was more frequent in a flock which had 89% mortality rate. Histopathology revealed multifocal hepatocytic necrosis and diffuse hepatocytic spherical vacuolations with large basophilic inclusion bodies. Confirmation of the FAdV infections was undertaken using two diagnostic PCRs on liver samples which targeted 590 bp and 900 bp conserved segments of the hexon gene, respectively. PCR-restriction enzyme analysis of the 900 bp amplicons categorized the viruses into serotypes 5 and 8. Sanger sequencing of the 900 bp amplicons and phylogenetic analysis clustered the FAdVs among the D and E species. This study presents the first report of FAdV in Uganda and in East Africa. FAdV infections should be included among differential diagnoses in broiler flocks. Further surveillance to determine the spread of the disease in poultry is recommended.