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The ribonucleic acid (RNA) genomes of the original representatives of the four serotypes of bluetongue virus (BTV) isolated from the United States (BTV-10, BTV-11, BTV-13 and BTV-17) have been analyzed by polyacrylamide gel electrophoresis. Ten double-stranded RNA species were resolved for each virus and categorized into the size classes of large (L segments #1-3), medium (M segments #4-6) and small (S segments #7-10). Minor electrophoretic mobility differences were observed for the M5 and S10 RNA segments of BTV-10 by comparison with the other US prototype viruses. The oligonucleotide fingerprints of the individual RNA species of BTV-11 were obtained and compared to each other providing proof that each of the viral double-stranded RNA species contains unique genetic information. Alternate isolates of BTV-11 isolated in the same year (1973), but from different states (Texas, Idaho, California and Oregon), or in different years (1963, 1970, 1974 and 1975), but from the same state (Colorado), have been analyzed by both RNA gel electrophoresis and L, M and S RNA oligonucleotide fingerprinting. When compared to the individual RNA fingerprints of the US prototype BTV-11 strain, the results indicated that there has been both genetic drift (accumulation of point mutations) and recombination (RNA segment reassortment) for BTV-11 in the United States over a 12-year period since 1963.

The degree of relatedness between 4 US serotypes (10, 11, 13 and 17) of bluetongue (BT) virus (BTV) were determined by both oligonucleotide fingerprint analyses of double-stranded (ds) RNA as well as tryptic peptide analyses of viral coded polypeptides. Similar studies were undertaken using different alternate isolates of particular serotypes as well as 2 serotypes (1 and 2) of epizootic hemorrhagic disease (EHD) virus (EHDV), a closely related serogroup of orbiviruses. The results indicate that all BT viruses are genetically related to each other and although EHDV-1 and EHDV-2 originated from a common gene pool, the 2 serogroups, EHDV and BTV, are not genetically interactive.