Recent US Bluetongue virus serotype 3 isolates found outside of Florida indicate evidence of reassortment with endemic co-circulating endemic serotypes

Authors: Schirtzinger, Erin; Jasperson, Dane; OSTLUND, EILEEN - Animal And Plant Health Inspection Service (APHIS); JOHNSON, DONNA - Animal And Plant Health Inspection Service (APHIS); Wilson, William

Submitted to: Journal of General Virology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/19/2017
Publication Date: 2/5/2018
Citation: Schirtzinger, E.E., Jasperson, D.C., Ostlund, E.N., Johnson, D.J., Wilson, W.C. 2018. Some recent US Bluetongue virus serotype 3 isolates found outside of Florida indicate evidence of reassortment with endemic co-circulating serotypes. Virus Genes. 99:157-168.
DOI: https://doi.org/10.1099/jgv.0.000965

Interpretive Summary: Eleven serotypes of bluetongue virus (BTV) similar to Central American or Caribbean strains have been isolated in the southeastern United States since 1999, eleven serotypes of bluetongue virus (BTV) similar to Central American or Caribbean strains have been isolated in the southeastern United States, predominantly in Florida. The majority of the incursive serotypes have remained restricted to the southeastern US. In recent years, a particular exotic type, BTV serotype 3 (BTV3), has been isolated in areas increasingly distant from Florida. The current study uses whole genome sequencing of recent and historical BTV3 isolates from the US, Central American and the Caribbean with additional sequences from GenBank to conduct genetic analyses of the individual segments of the BTV genome to determine if the recent BTV3 isolates have exchanged genome segments with local endemic strains or if they retain a Central American/Caribbean genome segments. The analyses show that BTV3 isolates from Mississippi 2006, Arkansas 2008 and Mississippi 2009 have very similar evolutionary histories with Mississippi 2006 and Arkansas 2008 being nearly identical. In contrast, the BTV3 South Dakota 2012 isolate has a majority of segments that are more similar to other BTV3 isolates from Florida. The different genetic histories of the BTV3 isolates suggest that there are at least two different lineages of BTV3 that are currently circulating in the US.

Technical Abstract: Since 1999, eleven serotypes of bluetongue virus (BTV) similar to Central American or Caribbean strains have been isolated in the southeastern United States, predominantly in Florida. The majority of the incursive serotypes have remained restricted to the southeastern US. In recent years BTV serotype 3 (BTV3) has been isolated in areas increasingly distant from Florida. The current study uses whole genome sequencing of recent and historical BTV3 isolates from the US, Central American and the Caribbean with additional sequences from GenBank to conduct phylogenetic analyses of the individual segments of the BTV genome to determine if the recent BTV3 isolates are reassortants with local endemic strains or if they retain a Central American/Caribbean signature. The analyses show that BTV3 isolates from Mississippi 2006, Arkansas 2008 and Mississippi 2009 have very similar evolutionary histories with Mississippi 2006 and Arkansas 2008 being nearly identical. These three isolates contain 7 segments that cluster with those of US endemic BTV serotypes. In contrast, the BTV3 South Dakota 2012 isolate has a majority of segments that are more similar to other BTV3 isolates from Florida. The different genetic histories of the BTV3 isolates suggest that there are at least two different lineages of BTV3 that are currently circulating in the US.