THE EMERGENCE AND SPREAD OF TICK-BORNE ENCEPHALITIS VIRUS IN SCANDINAVIA

摘要

Tick-borne encephalitis virus (TBEV) is a high-impact pathogen with approximately 12,000 diagnoses annually in Eurasia. The virus causes a variety of clinical manifestations, with neurological symptoms in up to 30percent of the patients. Lethality in Europe is <2percent but post-encephalitis syndrome is seen in over 40percent of the infected patients and results in substantial impairment in quality of life. Over the last decade a drastic increase in TBEV incidence has been reported throughout Western Europe. TBEV is a member of the Flaviviridae virus family, which are primarily spread through arthropod vectors (mainly ticks and mosquitoes). At some point during their transmission cycle, nearly all vector-borne diseases are linked in some way to a vegetated environment. This makes them suitable objects to study with remotely sensed multi-spectral data. In fact, remote sensing is becoming an important tool in active disease surveillance. Evidence of disease is monitored in endemic areas, which could help prevent outbreaks or slow tranmission in the early stage of an epidemic. Applications of remote sensing in epidemiology involve retrieving environmental variables that characterize the vector ecosystem (land cover, temperature, humidity, water pressure, precipitation). In this study we report on a discriminant analysis of remotely sensed vegetation indices applied to TBEV positive sites and to TBEV negative sites. Results indicate that there is a difference between sites, indicating a relationship between ticks with TBEV and certain environmental characteristics.