Differential ecological traits of two Phlebotomus sergenti mitochondrial lineages in southwestern Europe and their epidemiological implications

Abstract

Abstractobjectives The introduction of leishmaniasis in a new area requires a well-established population of the sandfly vector species of the parasite. No autochthonous cases of anthroponotic cutaneous leishmaniasis have been detected in southwestern Europe, and Leishmania infantum is the only causative agent of leishmaniasis in this area. Phlebotomus sergenti, the main vector of Leishmania tropica, is commonly found in the Iberian Peninsula at sufficient densities to be able to act as a vector. It is characterised by high genetic diversity and classified in four mitochondrial lineages. Our aim was to analyse the composition and distribution of P. sergenti mitochondrial lineages in southwestern Europe given the possibility of phenotypic differences of biomedical importance between them.methods Sandflies were captured in the Iberian Peninsula and on the Canary and Balearic Islands. Mitochondrial lineage identification of 137 P. sergenti was performed using a novel PCR-RFLP that avoids the necessity of gene sequencing.results Two lineages were evidenced, the typical Iberian one (lineage I) and another, held in common with North Africa (lineage III), that show a distinctive distribution. P. sergenti lineage I shows a better correlation to the bioclimatic diversity in southwestern Europe. Conversely, P. sergenti lineage III prefers warmer temperatures and less precipitation, which are typical of the Mediterranean.conclusion Lineage I seems to have adaptive advantages given its wider tolerance to temperature and altitude than lineage III, and it would seem more suitable to lead a potential geographical expansion towards the rest of Europe.

Modeling the climatic suitability of leishmaniasis vector species in Europe

“…These variables are typical characteristics of the sandflies’ microhabitats 38 , 49 , 55 , 56 and are assumed to influence the species’ distribution on a smaller spatial scale 57 . Here, we only used climatic variables that are considered important drivers for large-scale distributional patterns in Europe 23 , 32 , 57 .…”

“…Hence, these rodents could presumably also play an important role in the transmission of leishmaniasis in Europe 29 , 65 . Moreover, pathogens require certain temperatures for a sufficient replication rate as well as for the infectious life stage 23 , 28 . The risk for humans to acquire leishmaniasis might currently be low, however, our models show that the climatic development could promote the expansion of sandfly vector species to non-endemic areas and therefore increase the risk of leishmaniasis outbreaks in Europe.…”

“…This subset comprises annual extrema (minimum and maximum) as well as a variable describing the annual variability for both, temperature and precipitation. Temperature and precipitation are relevant drivers for the distribution of sandflies 23 , 30 – 33 (see also Introduction). More specifically, low temperature in winter 32 and insufficient moisture 30 , 31 are known to inhibit sandflies.…”

“…However, recent studies have shown a higher virus diversity than initially suspected in the Mediterranean area, including continental Europe, yielding a higher infection risk for people living south and east of the Mediterranean Sea 4 , 15 – 22 . The genus Phlebotomus is native to Europe 23 , where dogs are considered main reservoir hosts for the Leishmania parasites 24 – 28 . Other possible reservoir hosts are wild rodents 29 .…”

“…perniciosus , the main vector species in the Mediterranean area, immobilize and die when exposed to cold temperatures between 2 °C and 10 °C 9 , 31 . Temperature is therefore considered an essential factor for the development and survival of different life stages, and thus, it influences the geographical distribution of sandflies 23 , 32 . Precipitation and moisture also play an important role in the sandflies’ life cycle.…”