The spatial relationship between leishmaniases and sand flies in Europe and neighboring countries.

Background: Leishmania infantum is endemic in Europe (and elsewhere) while L. donovani s.s., L. tropica and L. major are not but are present in neighboring countries in North Africa, the Middle East, (the Asian part of) Turkey and the Southern Caucasus. Lists of sand fly vector species in the scientific literature vary with the criteria for vector incrimination, and criteria vary because, for some, evidence is difficult to generate. With minimal criteria, about 20 sand fly species are proven or suspected vectors of L. infantum in Europe and neighboring countries, while for L. tropica and L. major, there are seven and four proven or suspected vector species, respectively, in this area. For L. donovani s.s., present in Cyprus, the Middle East and (the Asian part of) Turkey, no local vectors have been incriminated so far. The aim was to assess the degree of spatial agreement between Leishmania spp. and various vectors species and their relative contribution to the explained variation.

Methods: We used multivariate regression modeling to analyze the spatial relationship between autochthonous Leishmania spp. and clinical forms in humans and animals and 14 Phlebotomus spp. in Europe and neighboring countries.

Results: There was only fair agreement between parasite and vector distributions. The most parsimonious models describing the distribution of Leishmania spp. and clinical forms included three to six sand fly species and explained between 12% (L. infantum) and 37% (L. donovani) of the observed variation. Selected models included confirmed and suspected vector species as well as unexpected species.

Conclusions: The relatively low agreement between Leishmania and vector distributions highlights the need to improve leishmaniasis reporting and vector surveillance in areas where no information is available, both for a better understanding of the epidemiology of infection in endemic areas and to monitor possible spread of infection into non-endemic areas. While some of the unexpected sand fly-Leishmania spp. statistical associations might be spurious, for others, the existence of sporadic or recent reports of infections warrants further vector competence studies that consider strain variation.