Understanding the factors that determine the emergence of anthroponotic cutaneous leishmaniasis due to Leishmania tropica: Comparison of the density and mitochondrial lineage of Phlebotomus sergenti between endemic and free areas in Morocco

Anthroponotic cutaneous leishmaniasis (ACL) due to Leishmania tropica is spreading to new areas. Exposure to the vector, Phlebotomus sergenti, is the only proven risk factor. Our objective was to compare the densities and genetic characteristics of P. sergenti populations in two nearby localities in Morocco, one within an ACL endemic area (El Borouj) and another undamaged (Sidi Hajjaj). Statistically significant differences were detected between P. sergenti densities with a higher density of P. sergenti in the endemic town (p≤ 0.032). A different main P. sergenti mitochondrial lineage was evidenced in each one of the 2 localities, and for the first time, the lineage of P. sergenti specimens that are acting as a vector of L. tropica has been identified. Bioclimatic differences were detected between both localities. In conclusion, between an ACL endemic locality and another ACL free there are differences in both the density of P. sergenti and the mitochondrial lineage that may explain the different epidemiological situation. Given that the density of P. sergenti in the locality without ACL cases seems sufficient to allow transmission, the main factor that would justify its ACL undamaged character could be the absence of P. sergenti Lineage IV, which seems to prefer warmer and drier climates.