Epidemiological studies on fowl adenoviruses isolated from cases of infectious hydropericardium.

Serology, restriction enzyme analysis and polymerase chain reactions were used to classify a total of 12 fowl adenoviruses (FAV) isolated from clinical cases of infectious hydropericardium from field outbreaks in seven countries in Asia and America. All isolates belonged to FAV serotype 4. Two isolates were contaminated with avian adeno-associated virus and one of them also contained FAV1. Minor differences were observed in the BamHI restriction profiles. More variability was seen with SmaI, BglII and PstI restriction profiles. However, more than 80% of the fragments were identical in size in the five different PstI profiles, indicating the close genomic relationship between the isolates. Polymerase chain reaction assays supported the classification of the isolates as FAV4 strains. All isolates could be detected using H1/H2 or H3/H4 primer pairs. Restriction enzyme analysis of the H1/H2 polymerase chain reaction (PCR) products allowed no differentiation between the isolates, whereas the three isolates from India and Pakistan could be separated from all others after HpaII digestion of the H3/H4 PCR products. Although strain variation was demonstrated, it could be shown that all adenoviruses isolated from various field cases of infectious hydropericardium (Angara Disease) in several countries belong to fowl adenovirus serotype 4.