[Prediction of sites with an increased risk of infestation with Ixodes ricinus and tick-borne encephalitis infection in the Central Bohemia Region based satellite data].

Based on elaboration of a prediction map of sites of increased incidence of Ixodes ricinus associated with an increased risk of attack on humans and activation of the virus of tick-borne encephalitis it was assumed that different types of vegetation can serve this purpose as suitable indicators. For assessment of these sites and their location on the territory of the Central Bohemian region (on an area of 11,508 sq.km) data from spectral analysis of reflected light recorded by a scanner, Thematic Mapper, working on satellite LANDSAT 5 with a spatial resolution of 30 m, obtained in six bands of the visible and near infrared spectrum resp. was used. Digital satellite data were processed in station IBM RISC 6000 using the professional software EASI/PACE of PCI Co. Inc. Canada. First by supervised classification seven main classes describing the position of the whole area were differentiated and then by a combination of unsupervised and subsequently supervised classification the forest areas were divided into nine classes of forests (with a different structure and different composition as to species), which have a different incidence of ticks. These classes were then compared by statistical methods with the epidemiological map of risk of acquisition of the tick-borne encephalitis virus. This resulted in the finding that coniferous tree forests ("1" and "2") are practically devoid of risk, while mixed and deciduous forests ("3" to "9") involve a varying degree of risk. The maximum risk was found in class 6 which comprises very heterogeneous young deciduous growth and ecotones. The results are presented graphically on the specimen of the prediction map (part of the classified picture supplemented by topographic signs at scale 1:25,000) and on classified satellite picture of the whole area (scale of the original computer printout 1:300,000). In the legend the grade of risk of different classes is expressed verbally, corresponding to values of the Spearman coefficient of rank correlation (Table 1). The laboratory tests were verified and characterized from the botanical aspect during the field investigation.