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Title: PERSISTENCE OF BLUETONGUE VIRUS SEROTYPE 2 (BTV-2) IN THE SOUTHEAST UNITED STATES

Author
item MECHAM, JAMES
item JOHNSON, DONNA - USDA APHIS NVSL AMES IA

Submitted to: Virus Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/18/2005
Publication Date: 11/1/2005
Citation: Mecham, J.O., Johnson, D.J. 2005. Persistence of bluetongue virus serotype 2 (BTV-2) in the southeast United States. Virus Research. 113:116-122

Interpretive Summary: Bluetongue virus (BTV) is an arthropod-borne orbivirus that infects both domestic and wild ruminants. Bluetongue virus serotype 2 (BTV-2) is the most recent new bluetongue serotype to be isolated in the United States (U.S.). Two strains, Ona-A and Ona-B, were initially isolated from cattle and biting midges in Florida in 1982. Subsequent virus isolations were made in Florida and Alabama. No BTV-2 isolations were reported after 1985; suggesting this serotype may have disappeared from the U.S. 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 U.S. To investigate this question, the recent isolate was compared to the original 1982 strains by RNA, protein and sequence analysis. These comparisons indicated that the Ona-B strain has persisted in the Southeast U.S. In addition, analysis of 1999 isolates of BTV-13 and BTV-17 from the same area in Florida suggests that mixed infections and reassortment have occurred between BTV-2 and other BTV serotypes in the area.

Technical Abstract: The prototype United States (U.S.)isolates of bluetongue virus serotype 2 (BTV-2 Ona-A and BTV-2 Ona-B) made in Florida in 1982 were compared to a recent BTV-2 isolate (Florida, 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 U.S. 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 the BTV-2 Ona-B strain has persisted in the Southeast U.S. since its first isolation in 1982. Sequence analysis of concurrent isolates of BTV-13 and BTV-17 from the same location in Florida in 1999 provides evidence of genetic reassortment between BTV-2 and other co-circulating serotypes of BTV.