In the second half of the 20th century infectious diseases have become more and more important. According to the WHO, in 2001 there were 14.9 million fatalities due to an infectious disease; about 26 % of the annual mortalities. In the last decades, so-called emerging and reemerging infectious diseases (EID) play also an increasing role in industrialized countries. Aside from already known diseases, new ones show a rising importance. Especially when they are transmitted by vectors (e.g. blood-sucking arthropods) they can occur in the respective areas after a time delay. Global trade, biodiversity loss and climate change are the major reasons why many invasive species as well as vector-borne and zoonotic diseases increase their distribution. Furthermore higher temperatures have direct impact on the vector density in a certain area and influence therefore the likelihood for disease transmissions.
Mosquitoes are the major vectors for many different arthropod-borne diseases and many of them are extremely adaptable to changing climate conditions or the consequences of urbanization. Around 3500 different mosquito species are known to occur worldwide and around 50 are proven for Germany. Due to anthropogenic influences invasive mosquito species like the Tiger Mosquito (Aedes albopictus) or the Asian Bushmosquito (Ochlerotatus japonicus) will be brought into new areas in Europe. For both of these species the vector capacity for various arboviruses could be already proven. While in other European countries Ae. albopictus has established stable populations soon after introduction, in Germany the more successful invasive species so far is Oc. japonicus. The latter species is nowadays established, spreading into new areas of the country and continuously expanding its range, although its introduction occurred just recently a few years ago. But indigenous mosquitoes are also known to be potential carriers of diseases and pathogens such as Sindbis virus, Ockelbo virus, Usutu virus, West Nile virus or even malaria. Just recently also two different species of filarial nematodes were found in various indigenous mosquito species, indicating the still unknown vector abilities of a number of species and showing that knowledge about distribution and vector competence is scarce for many European countries.
Leishmaniasis, with its various forms is distributed worldwide and nowadays regarded by the WHO (World Health Organisation) as an neglected disease, which is transmitted by phlebotomine sandflies (Phlebotominae). Central European countries like Switzerland, Austria and Germany have previously not been associated with autochthonous leishmaniasis but must recently experience several cases of leishmaniasis. Until recently, sandflies were excluded to occur north of the Alps, indicating that sandflies have been overlooked in the past in many regions where they occur. Two species of phlebotomine sandflies have been documented in central Europe for the moment; both occurring together in Germany, Switzerland and France , and one of those occurring also in Belgium. In adjacent territories four more species of phlebotomine sandflies are known, indicating a potential risk for further transmissions and emphasizing the importance of their surveillance. Additionally, phlebotomine sandflies the vectors of leishmaniasis are also able to transmit a variety of arboviruses causing so-called sandfly fevers (Phlebovirus) like e.g. Toscana Fever, Naples Fever and Sicily Fever.