Genetic diversity and population structure of visceral leishmaniasis vector sandflies in China

Visceral leishmaniasis (VL) has re-emerged in several regions of China, particularly in mountain-type zoonotic foci. Its major vectors, Phlebotomus chinensis, Phlebotomus longiductus, and Phlebotomus wui, may shape regional transmission risk through differences in population structure and dispersal. However, their large-scale genetic connectivity remains poorly understood. This study aimed to assess their mitochondrial genetic diversity, population structure, and gene flow across VL-endemic regions of China.

We analyzed mitochondrial genetic diversity and population structure of sandflies collected from eight VL-endemic sites across six provinces and the Xinjiang Uygur Autonomous Region. Partial sequences of the mitochondrial cytochrome c oxidase subunit I (COI) and cytochrome b (cytb) genes were obtained, yielding 226 COI and 222 cytb high-quality sequences. Haplotype diversity, phylogenetic relationships, population differentiation, gene flow, and isolation-by-distance were assessed using haplotype networks, FST/Nm estimation, AMOVA, and Mantel tests.

Both markers showed high genetic polymorphism and pronounced population structuring. Haplotype networks revealed two distinct mitochondrial lineage clusters that were not strictly associated with geographic distance, suggesting historical lineage differentiation. Populations from Shanxi, Henan, and Shaanxi showed high gene flow, whereas those from the Chuanbei-Longnan and northwestern regions exhibited strong genetic differentiation and limited connectivity. AMOVA showed that most genetic variation occurred within populations, and Mantel tests indicated significant isolation-by-distance.

These findings reveal marked spatial heterogeneity in sandfly genetic structure across VL-endemic regions in China, suggesting region-specific dispersal potential and transmission risk. This study provides a genetic basis for targeted vector surveillance and control strategies.