Novel Serotype of Bluetongue Virus, Western North America

Bluetongue Virus, Western North AmericaTo the Editor: Bluetongue is an arboviral disease of domestic and wild ruminants characterized by vascular injury that produces widespread edema and tissue necrosis (1).Bluetongue virus (BTV), the causative agent of bluetongue, is the prototype virus of the genus Orbivirus in the family Reoviridae (2).BTV occurs throughout temperate and tropical areas of the world coincident with the distribution of vector Culicoides spp.midges (3-5).Different midge species transmit different constellations of BTV serotypes in distinct global episystems (3,5).For example, C. sonorensis is the principal, if not exclusive, vector of BTV serotypes 10, 11, 13, and 17 in much of North America, whereas C. insignis is the major vector of multiple BTV serotypes (including BTV 1-4, 6, 8, 12, 17, 19, 20, and probably others) in the Caribbean basin, Central America, and South America.C. insignis is also found in the southeastern United States, and although this species might have recently expanded its range in the region, its distribution in North America remains poorly defined.Serotypes of BTV other than 10, 11, 13, and 17 are found in areas of the United States: BTV-2 was first reported in Florida in 1982.Since 1998, ten additional serotypes 3,5,6,9, 12, 14, 19, 22, and 24) have been identified in the southeastern United States (6).Approximately 26 BTV serotypes have been described and the global distribution of BTV has recently been altered (2,4).Coincident with the invasion of novel BTV serotypes into the southeastern United States (6), likely by extension from the adjacent Caribbean basin, multiple BTV