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.

Risk map for cutaneous leishmaniasis in Ethiopia based on environmental factors as revealed by geographical information systems and statistics

“…The observation of CL cases as high as 2,700 m above MSL and inclusion of areas above this altitude as high risk by the model requires further investigation. This could probably reflect a change in vector behaviour and ecology, possibly related to global warming leading to sand flies seeking higher altitudes as suggested by Aspock et al (2008) and others (Dereure et al, 2009;Fischer et al, 2010). We also found rainfall to be a predictor, a result supported by Ashford (1977), who documented that human cases of CL occur in areas with rainfall amounts above 800 mm.…”

Importance of individual analysis of environmental and climatic factors affecting the density of Leishmania vectors living in the same geographical area: the example of Phlebotomus ariasi and P. perniciosus in northeast Spain

“…Leishmaniasis is a climate-sensitive disease affected by changes in rainfall, atmospheric temperature and humidity, which can strongly impact on the ecology of vectors and reservoir hosts by altering their distribution and influencing their activity, survival and popu-lation sizes (Elnaiem et al, 1998;Killick Kendrick, 1999;Aspöck et al, 2008;Gage et al, 2008;Ready, 2010). In the Mediterranean region, most leishmaniasis foci are between 5 ºC and 10 ºC in January isotherms and between 20 ºC and 30 ºC in July (Ashford and Bettini, 1986).…”

“…Also, changes in precipitation and temperature regimes related to climate change are thought to have impacted its distribution (de La Rocque et al, 2008;Ready, 2010;WHO, 2010;Maroli et al, 2013). Long-term climate change could lead to suitable conditions for the occurrence of sand fly species in areas previously free of them (Kuhn, 1999;Aspöck et al, 2008;Ready, 2010) and for the expansion of leishmaniasis and its sand fly vectors (Rispail et al, 2002;Maroli et al, 2008;Ready, 2008;WHO, 2010).…”

The Effect of Climate Change on the Potential Distribution of the European Phlebotomus Species

“…Members of genus Phlebotomus (sandflies) are the primary vectors of the protozoan parasite genus Leishmania in the Old World. Sandflies are typical Mediterranean faunal elements (Aspöck et al, 2008) and are members of the order Diptera. The geographical distibution of leishmaniasis is…”