Sandflies and sandfly-borne infections of humans in Central Europe in the light of climate change

Abstract

In Europe, sandflies (Diptera: Psychodidae: Phlebotominae) are typical Mediterranean faunal elements of low expansivity, which are widely distributed in more than 20 species in many parts of Southern Europe. A few species have extended their distribution to the northwest invading extramediterranean regions (Western, Eastern Europe); any occurrence in Central Europe north of the Alps was excluded until recently. Since 1999 sandflies have been found in several parts in Germany and in Belgium; originally these records were ascribed to climate change and global warming. Meanwhile, the more likely assumption is that sandflies have always, probably since the Holocene climate optima (ca. 4500 and 2500 B.C.), been in Central Europe sporadically to where they have come as immigrants (or re-immigrants) from Mediterranean refugial areas. It is, however, without question that global warming will lead to an extension of the distributional areas of sandflies. A climatological analysis of the localities where sandflies have been found in Central Europe has revealed that temperature is the key factor. A comparison of climatological parameters in sandfly-localities with the climatic conditions in Austria (where sandflies have not yet been found) has shown that an increase of temperature by 1 degrees C in January (Ph. mascittii) or 1 degrees C in July (Ph. neglectus), respectively, would lead to suitable conditions for the occurrence of sandflies in certain parts of Austria. (The scenarios for an increase of temperature until the end of the century vary between 1.5 degrees C to 4.5 degrees C; 3 degrees C seem to be realistic also for critical climatologists.) Leishmaniae certainly do not occur in Central Europe primarily, but an increasing number of infections in humans, as well as in animals, acquired in Central Europe has been registered. It is highly likely that these infections are due to sandflies which have been infected by sucking blood on infected dogs. Dogs infected with Leishmania and presenting a variety of clinical symptoms are frequently brought by compassionate tourists from Mediterranean countries - often illegally - to Central Europe. Meanwhile, a flourishing market for dogs of miserable appearance suffering from leishmaniosis has been developed by profit-oriented opportunists in Mediterranean countries. With respect to the serious course of visceral leishmaniosis (particularly in infants and in immunocompromised persons) this dangerous condition merits intensive attention. Phleboviruses have not been found in Central Europe, so far. However, in the course of global warming an establishment of biological cycles after an introduction of the pathogens, particularly if vertebrates other than humans can also act as reservoir hosts, seems possible.