Habitat comparisons and geographic distribution of La Crosse encephalitis in eastern Tennessee utilizing geographic information systems

by 1978- Morton, Howard Joe

In eastern Tennessee there was a total of 17 cases of a La Crosse (LAC) encephalitis viral infection reported to the East Tennessee Department of Health in 2000. During that same time, 25 cases of other Central Nervous System Infection (CNSI) that were not La Crosse were also reported. Out of those 42 cases 11 were chosen to be revisited (6 Control and 5 LAC) and the nearby wooded habitats were surveyed. Geographic Information Systems (GIS) was utilized to plot each case location on various maps. The sites were all in eastern Tennessee, in the Appalachian Valley and Ridge geographical area, across four counties. There was no difference in amount of precipitation that the LAC and Control Sites received. Control Sites had 8 species of exotic trees but the same soil categories as the LAC Sites. LAC Sites were mixed hardwood habitats and more mosquitoes were collected from them than the Control Sites which were not mixed hardwood. There was a total of 24 cases of a LAC encephalitis viral infection reported to the East Tennessee Department of Health from 1999-2001. During that same time, 78 cases of other CNSI that were not LAC were also reported. Geographic Information Systems was utilized to plot each case location on various maps. Case site locations were divided into LAC Sites for La Crosse cases and Control Sites for CNSI cases that were not due to LAC. ii The sites fell into one of the four physical regions of eastern Tennessee: Blue Ridge, Appalachian Valley and Ridge, Cumberland Plateau, and Eastern Highland Rim. There was no difference in amount of precipitation that the LAC and Control Sites received. A High LAC Area and a Low LAC Area were noted and included parts of four counties. The High Lac Area had a similar incidence as the Low LAC Area for CNSI but the High LAC Area had 12 cases of La Crosse while the Low LAC Area had none. The difference between the two areas was the LAC case site proximity to larges wooded areas. In all counties except Hamblen County, LAC Sites were found to be in close proximity to large wooded areas unlike the Control Sites that occurred whether or not they were in close proximity to large wooded areas. iii