Bovine Rotavirus G and P Types and Sequence Analysis of the VP7 Gene of Two G8 Bovine Rotaviruses from Japan

A total of 1481 fecal specimens were collected from diarrheic calves under 1 month of age on 29 dairy and beef farms in 11 prefectures in Japan during the period from 1987 to 2000. Those calves and their dams were not vaccinated against rotavirus. One hundred and forty-two bovine rotaviruses were isolated on MA-104 cell cultures and detected by latex agglutination test. They were classified into 18 G6P[1] (11.2%), 53 G6P[5] (37.3%), 15 G6P[11] (10.6%), 12 G10P[5] (8.5%), 42 G10P[11] (29.6%) and 1 G8P[11] (0.7%) by reverse transcription-polymerase chain reaction. One serotype G8 virus was untypable for the P genotype suggesting a new type of bovine origin. The least common G8 serotype viruses were isolated from the samples of farms from Niigata and Tokushima prefectures. The VP7 gene sequences of the two isolates exhibited a high degree of homology as well as previously reported G8 viruses with 93.3-98.8% identity of deduced amino acids. A phylogenetic analysis of the VP7 gene of the two G8 viruses and 13 previously reported G8 viruses by the neighbor-joining method indicated that the two newly isolated G8 rotaviruses had a common origin and they were assigned to a new disparate cluster.