Pathogenicity and Genotyping of Fowl Adenoviruses Associated with Gizzard Erosion in Commerciallayer Grower Chicken in India

Abstract

During the year 2013–2014, commercial layer birds showed heavy economic losses due to gizzard erosion (GE) and mortality (10 to 30%). The affected birds revealed dullness, uneven growth, decreased feed and water intake. GE with detachment of the koilin layer and blackish discoloration of gizzard contents were observed during necropsy examination. Fowl adenoviruses (FAdVs) were isolated using passage in chicken embryo liver cells and genotyped by DNA sequencing. Phylogenetic analysis of the hexon loop L1 gene FAdVs isolates was grouped into FAdV-A (serotype 1), FAdV-C (serotype 4), D (serotypes 2, 3 and 11) and E (serotype 8) species. The pathogenicity of FAdVs was investigated in 4-week-old specific pathogen-free chickens; FAdV serotypes 4, 8 and 11 were found pathogenic and cause GE. Histologically, basophilic intranuclear inclusion bodies were seen in the gizzard mucosal layer from day 7 to 11-day post infection. This is the first report of the GE associated with FAdV serotypes 4, 8 and 11 in layer birds. These findings suggest that GE outbreaks associated with FAdVs lead to economic losses in commercial layer grower birds in India.