An outbreak of fowl aviadenovirus A-associated gizzard erosions and ulceration in captive bobwhite quail (Colinus virginianus)

A flock of captive bobwhite quail experienced loose droppings, depression and increased mortality starting at three weeks of age. Necropsy of the affected birds revealed intestines dilated with frothy, tan fluid. Irregular dark brown fissures within the koilin layer of the gizzard were found in 20-30% of the birds. Histologically, gizzards showed multifocal koilin degeneration/fragmentation, degeneration and necrosis of the subjacent epithelial cells, and infiltration of macrophages, lymphocytes and heterophils. Necrotic epithelial cells occasionally contained large, smudgy, basophilic intra-nuclear inclusion bodies with marginated nuclear chromatin. Adenoviral paracrystalline arrays composed of icosahedral virions (60-70 nm diameter) were seen in the nuclei of epithelial cells in the gizzard mucosa on transmission electron microscopy. Adenovirus was isolated from gizzard, liver, intestine, and trachea by inoculation of specific pathogen free embryonated chicken eggs. Homogenates of gizzard, liver and intestine were positive for adenovirus hexon gene by PCR. Sequencing of PCR amplicons confirmed the virus as fowl aviadenovirus type A. The virus showed more than 99% and 97% nt identity with quail bronchitis virus and with adenoviruses from gizzard erosion and ulceration in broilers, respectively. The viral isolates showed six substitutions (G1T, C174A, A229G, C513A, T579A, and G621C) of which two were non-synonymous (G1T and A229G) resulting in a change in the translated amino acid as A1S and S77G, respectively. These results indicate that adenovirus of the same type or species can cause different clinical presentations in quails, e.g., bronchitis or GEU (gizzard erosion and ulceration).