Persistence of bluetongue virus serotype 2 (BTV-2) in the southeast United States.

The prototype United States (US) strains of bluetongue virus serotype 2 [BTV-2 (OnaA) and BTV-2 (OnaB)] made in Florida in 1982 were compared to a recent BTV-2 (FL99) isolate made in Florida in 1999 to determine if the original strain(s) had persisted or if a new strain of BTV-2 had been re-introduced into the southeast US. Viral RNA and protein electropherotypes, and sequence analysis of five RNA genome segments for these early and later BTV-2 isolates were compared. These comparisons indicated that BTV-2 (OnaB) has persisted in the southeast US since its first isolation in 1982. Sequence analysis of concurrent isolates of BTV-13 (FL99) and BTV-17 (FL99) from the same location in Florida in 1999 provides evidence of genetic reassortment between BTV-2 and other co-circulating serotypes of BTV.