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La Crosse virus (LACV) is found primarily in the Midwestern and Appalachian regions of the United States where it is a leading cause of mosquito-borne encephalitis in children. To determine whether the distribution of this virus extends further east into New England, we analyzed a bunyavirus that was isolated from a pool of eastern tree-hole mosquitoes, Ochlerotatus triseriatus (= Aedes triseriatus), collected from Fairfield, Connecticut (CT) in 2005. Nucleotide and encoded amino acid sequences from portions of the S, M, and L segments were more similar to the prototype strain of La Crosse virus than that of closely related snowshoe hare virus. Phylogenetic analysis of sequences from the M segment indicated that the CT isolate represents a distinct lineage of La Crosse virus, diverging earliest from other strains found in southeastern, central, and northeastern United States. Despite low sequence homology with other viral strains, the CT isolate was antigenically similar to the prototype strain of LACV by plaque-reduction neutralization tests with polyclonal and monoclonal antibodies. This represents the first isolation of LACV in New England to our knowledge and suggests long-term independent evolution of the CT isolate.
Received March 7, 2006. Accepted for publication May 2, 2006.
Acknowledgments: We are grateful for the technical assistance of our support staff: Shannon Finan, John Sheppard, and Michael Thomas in the collection, identification, and processing of mosquitoes for virus isolation. The authors thank Drs. Barbara Johnson, Roger Nasci, and Robert Tesh for kindly sharing their LACV isolates for sequencing and Drs. John Anderson, Andrew Main, and Brandy Russell for providing us immune reagents for PRN tests. We also thank Drs. Louis Magnarelli and Charles Vossbrinck for critically reviewing this manuscript. This work was supported in part by grants from the Centers for Disease Control (U50/CCU116806-01-1) and the US Department of Agriculture (58-6615-1-218 and CONH00768).
Financial support: This work was supported in part by grants from the Centers for Disease Control (U50/CCU116806-01-1) and the US Department of Agriculture (58-6615-1-218 and CONH00768).
* Address correspondence to: Philip M. Armstrong, The Connecticut Agricultural Experiment Station, 123 Huntington St., P.O. Box 1106, New Haven, CT 06504. E-mail: philip.armstrong{at}po.state.ct.us
Authors addresses: Dr. Philip M. Armstrong and Theodore G. Andreadis. The Connecticut Agricultural Experiment Station, 123 Huntington St., P.O. Box 1106, New Haven, CT 06504, Telephone: 203-974-8461, Fax: 203-974-8502, E-mails: philip.armstrong{at}po.state.ct.us and Theodore.Andreadis{at}po.state.ct.us.
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