La Crosse encephalitis virus habitat associations in Nicholas County, WestVirginia

Aedes triseriatus (Say) population density patterns and La Crosse encephali tis virus infection rates were evaluated in relation to a variety of habita t parameters over a 14-wk period. Ovitraps and landing collections were use d in a La Crosse virus-enzootic area in Nicholas County, WV. Studs sites we re divided into categories by habitat type and by proximity to the residenc es of known La Crosse encephalitis cases. Results demonstrated that Ae. tri seriatus population densities were higher in sugar maple/red maple habitats than in hemlock/mixed hardwood habitats or in a site characterized by a la rge number of small red maple trees. Sites containing artificial containers had higher population densities than those without. La Crosse virus minimu m infection rates in mosquitoes collected as eggs ranged fi om 0.4/1,000 to 7.5/1,000 in the 12 study sites, but did not differ significantly among si tes regardless of habitat type or proximity to human case residences. La Cr osse virus infection rates in landing Ae. triseriatus mosquitoes ranged fro m 0.0/1,000 to 27.0/1,000. La Crosse virus was also isolated from host-seek ing Ae. canadensis (Theobald) in two study sites, at rates similar to those found in the Ae. triseriatus populations. The Ae. triseriatus oviposition patterns and La Crosse virus infection rates suggest that this mosquito spe cies disperses readily in the large woodlands of central West Virginia. The La Crosse enzootic habitats in Nicholas County, WV, are contrasted with th ose studied in other geographic regions where La Crosse virus is found.