Prevalence and molecular characteristics of fowl adenovirus serotype 4 in eastern Saudi Arabia


Abstract: Fowl adenovirus serotype 4 (FAdV-4) is a new emerging viral disease of chickens worldwide. It causes inclusion body hepatitis and hepatitis-hydropericardium syndrome. Little is known about its prevalence in the Middle East. Here we report the prevalence of FAdV-4 in five chicken farms in eastern Saudi Arabia. High mortality rates were reported from birds from those five farms at 15 weeks of age. Gross examination revealed typical hydropericardium syndrome and accumulation of jelly-like materials in the pericardial cavities. We isolated FAdV-4 by using embryonated chicken egg inoculation. The inoculated embryos showed dwarfing, deformities, hemorrhage, and death after 3-5 days of inoculations. Detection of FAdV-4 in the heart and liver tissues was achieved by polymerase chain reaction (PCR) and real-time PCR using the primers targeted to the partial hexon gene. Further confirmation was done by restriction fragment length polymorphism and the digestion patterns of the isolated FAdV-4 DNAs were close to those of other known FAdV-4 strains. The average genome size of the virus was ~43 kb. Phylogenetic analysis of the partial hexon gene sequences confirmed that these strains were closely related to other Asian strains from Kuwait, India, and Pakistan reported to GenBank. To our knowledge, this is the first study that reports the isolation and molecular characterization of FAdV-4 in chickens in Saudi Arabia.

Keywords: Fowl adenovirus, hydropericardium, hexon gene, polymerase chain reaction, restriction enzyme digestion, phylogenetic analysis

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