After decades of decline following World War II, there is now a serious recrudescence of several vector-borne diseases in the European region; in addition the densities of some vector and potential vector populations of mosquitoes and ticks are increasing in many areas. There has been an emergence of new diseases and disease syndromes such as the co–infection of leishmaniasis/HIV. It is important to understand the reasons for the recrudescence of these diseases as a basis for their control or prevention.

Ecological changes

As elsewhere, there have been massive ecological changes over the continent of Europe in the last 50 years. These include increases in human popu– lations and increased population densities as a result of urbanization. After years of urban growth there has been a trend towards movement of populations to suburban areas in more affluent countries resulting in greater exposure to vectors and to animal reservoir hosts of infections. Changed leisure habits have also increased exposure to vectors, especially ticks.

Unfortunately, there have been major displacements of human populations from some countries within the region because of conflicts; the search for economic betterment has also been the cause of population migrations. Substantial immigration has occurred from outside Europe, often from countries endemic for vector-borne diseases. This has resulted in the frequent introduction of exotic infections and occasional secondary transmission of both tick- and mosquito-borne diseases; there is a risk that these newly introduced infections may become established as has occurred with West Nile virus in North America.