Molecular characterization of fowl adenoviruses isolated from chickens with gizzard erosions

摘要

Broiler chickens with clinical signs of uneven growth, depression, and dull feathers were submitted to our laboratory and, at necropsy, lesions in proventriculus, gizzard, and intestines were detected. Fowl adenovirus serotype 1 (FAdV-1) was isolated from digestive tissues. The virus, assigned as FAdV-PL/G068/08, showed 99.5% nucleotide homology and 99.2% amino acid homology in hexon gene with chicken embryo lethal orphan (CELO) strain classified as the European reference of FAdV-1. One-day-old and 21-d-old SPF chickens were inoculated with FAdV-PL/068/08 by both nasal and ocular routes and then observed daily and examined by necropsy at 6, 10, and 14 d postinoculation. Experimental infection with isolated virus was fatal for younger chickens and major lesions occurred in the gizzards. No clinical or pathological changes were observed in chickens infected at 21 d of age, but the presence of intranuclear inclusion bodies in gizzard epithelial cells was detected. Molecular characterization was based on the long and short fibers genes sequencing and comparison of obtained sequences with other FAdV-1 strains. The homology between FAdV-PL/G068/08 and other sequences available in GenBank was between 98.9 and 99.8% (short fiber region) and 99.0 and 99.7% (long fiber region) at nucleotide level and between 98.4 and 100% (short fiber region) and 99.3 and 99.9% (long fiber region) at amino acid level. No correlation between identified amino acid changes in short and long fiber proteins and pathogenicity of studied FAdV-1 strains was observed. Although short and long proteins were indicated as factors influencing virus pathogenicity, the role of identified sequence differences in infectivity determination remain unclear.