Characterization of fowl adenoviruses isolated in Ontario and Quebec, Canada.

Fowl adenoviruses (FAdV) are generally considered ubiquitous, but certain serotypes and strains are known to be associated with primary diseases, such as inclusion body hepatitis (IBH). Fifty-two FAdV isolates were collected from the provinces of Ontario and Quebec over a 4-year period. These 2 provinces have the largest poultry industries in Canada. Except for one virus, which originated from a guinea fowl, all other viruses were isolated from chicken samples. Most of these were from broilers, although some were from broiler breeders, and one was from layer pullets. Thirty-four isolates were from clinical IBH cases with the final laboratory diagnosis of IBH; however, for 18 isolates, the varied case diagnosis was seemingly unrelated to FAdV. All IBH-associated viruses had deoxyribonucleic acid (DNA) profiles compatible with FAdV species E (28 cases) or species D (6 cases), and the DNA fragment profiles of 26 species E viruses were indicative of serotype 8. Two viruses were serotype 6, as confirmed by virus neutralization. All species D viruses had a DNA profile similar to that of FAdV-2. The number of serotype 8 virus isolations has increased over the years, and by 2001 serotype 8 had become the dominant serotype in Ontario, and continues to be so. Moreover, this virus (FAdV-8) has shown a strong association with IBH.