Structural and biological characteristics of reoviruses isolated from Muscovy ducks (Cairina moschata).

Two Muscovy duck reoviruses, strains y1/79 and 1625/87, were investigated with regard to their genome organization, polypeptide pattern, serotype specificity, and pathogenicity. Electrophoretic analysis of the genome revealed the migration pattern of avian reoviruses. In spite of general conformity, great polymorphism was detected in the electrophoretic mobility of individual genome segments of the two strains sharing only three segments of identical size (L1, M2, M3). Only one segment (M3) migrated into the same position as the corresponding segment of prototype chicken reovirus S1133. The basic electrophoretic mobility pattern of the immunoprecipitated polypeptides, eight structural and two non-structural, closely resembled that of the chicken reovirus. However, considerable strain-specific variation was also seen at the protein level, with the sigma(c) polypeptides exhibiting the most obvious migration differences. Based on the results of cross-neutralization assays the two Muscovy duck reovirus strains were grouped into one serotype, with no cross-reactivity to the chicken serotype S1133. In experimental infections, despite virus replication proved by faecal virus excretion and antibody response, only strain y1/79 was pathogenic for 16-day-old Muscovy ducklings, thus making strain 1625/87 a possible candidate as vaccine strain.