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item Mecham, James

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 10/27/2003
Publication Date: 10/27/2003
Citation: Mecham, J.O. 2003. Evidence that bluetongue virus serotype 2 (btv-2) has persisted in the southeastern united states for the past 20 years. OIE Symposium on Bluetongue virus. Taormina, Italy. Paper No. C9, p. 96.

Interpretive Summary: Bluetongue virus (BTV) is an arthropod-borne orbivirus that infects both domestic and wild ruminants. Bluetongue virus serotype 2 (BTV-2) was first isolated in the United States in Florida in 1982 from cattle and biting insects (midges). No BTV-2 isolations were reported after 1985; suggesting this serotype may have disappeared from the United States. However, in 1999, BTV-2 was again isolated in Florida from sheep, suggesting that either the virus had persisted or had been re-introduced into the southeastern United States. To investigate this question, the recent BTV-2 isolate, as well as other recent BTV serotypes isolated in the area, were compared to 1982 BTV-2 isolates by sequence analysis of selected RNA genome segments. These comparisons indicated that BTV-2 has persisted in the southeastern United States since 1982, and that it has evolved by reassortment with other endogenous strains of BTV in the region.

Technical Abstract: Bluetongue virus serotype 2 (BTV-2) is the most recent bluetongue serotype to be introduced into the U.S. It was first isolated from sentinel cattle and Culicoides insignis at Ona, Florida in 1982. The initial isolates demonstrated two RNA electropherotypes and were designated Ona-A and Ona-B. The electropherotype of the Ona-A variant was identical to that of the South African BTV-2 prototype. It was isolated in September and October of 1982 and then disappeared. The Ona-B variant was isolated in late October and November of 1982 at the same site and at additional sites in Florida the following year. Isolations of Ona-B were subsequently made in 1984 and 1985 from cattle in Alabama. No isolations of either variant were reported after 1987, and it was widely assumed that BTV-2 had disappeared from the southeastern United States. However, BTV-2 was recently isolated from sheep in Florida, suggesting that this serotype had been reintroduced or had persisted since its first appearance in 1982. To investigate this question, selected genome segments of this recent isolate were sequenced and the sequences compared to those of the prototype isolates and recent Florida isolates of other BTV serotypes. Phylogenetic analysis suggests that reassortment may have generated the Ona-B variant; and that this virus has persisted in the southeastern United States for the past 20 years.