Leishmaniasis Transmission Risk at the Forest-Peridomestic Interface in an Area of Southern Sinaloa, Mexico: Entomological, Molecular, and Climatic Evidence.

Abstract

Leishmaniasis, caused by Leishmania spp. and transmitted by phlebotomine sand flies, affects almost 1,000,000 people annually across more than 90 countries. In Mexico, growing evidence of locally acquired transmission in northwestern states makes ecoepidemiological work increasingly urgent. We aimed to conduct a 2-year ecoepidemiological study in four rural communities of Sinaloa, Mexico, to identify vectors, determine their food sources, detect Leishmania DNA, and relate it to climatic factors. CDC light traps were operated bimonthly along a peridomestic-to-forest gradient; dipterans were identified morphologically, Leishmania spp. DNA confirmed by PCR-RFLP, and habitat differences tested with Kruskal-Wallis and Spearman rank correlation (α = 0.05). We collected 9984 dipterans over 12 sampling rounds; sylvatic sites accounted for 81.5% of captures, peaking in September and November. Culicoides furens (Ceratopogonidae) was numerically dominant. Three sand fly species were recovered: B. olmeca olmeca, M. cayennensis maciasi, and P. texana. Leishmania spp. DNA was detected in 7 of 35 C. furens pools; no sand fly tested positive. C. furens fed primarily on Homo sapiens; M. cayennensis maciasi fed on Canis lupus familiaris in peridomestic settings. Rainfall was the strongest predictor of abundance (Spearman rho up to 0.824, p < 0.01); wind speed showed an inverse relationship. Repeated detection of Leishmania DNA in C. furens suggest the hypothesis that this species contacts infected reservoirs, though experimental vector competence studies remain needed. The first record of B. olmeca olmeca for Sinaloa carries clear epidemiological implications. The forest-community interface is the dominant exposure zone, and risk is likely to intensify with rising temperatures. Priority actions include: experimentally evaluating the vector competence of C. furens, and intensifying sand fly surveillance to clarify the role of local dipteran fauna in Leishmania transmission dynamics.