[Genetic polymorphisms of common sandflies in selected areas of Henan Province based on DNA barcoding]

To characterize the species of common sandflies in Henan Province using DNA barcoding with cytochrome c oxidase subunit I (COI) gene as the molecular marker, and to analyze the genetic polymorphisms of sandflies, so as to provide insights into visceral leishmaniasis prevention and control in Henan Province.

Sandfly specimens were sampled from 13 sandflies surveillance sites from 2021 to 2023 in Anyang City, Zhengzhou, Luoyang and Xuchang cities (Zhengzhou-Luoyang-Xuchang areas) where visceral leishmaniasis cases were reported and in Jiaozuo and Xinxiang cities (Jiaozuo-Xinxiang areas) without visceral leishmaniasis cases reported. Genomic DNA was extracted from a single sandfly, and COI gene was amplified. The amplification product was subjected to bidirectional sequencing. Following sequence assembly, the species of sandflies was characterized through sequence alignment using the BLAST tool. The intra-specific and inter-specific genetic distances of sandflies were estimated among different areas using the software Mega 11, and phylogenetic trees were created. The polymorphisms of nucleotide sequences in the sandflies COI gene were estimated using the software DnaSP. The fixation index (F) of different geographical isolates of sandflies was calculated using the Arlequin software, and the gene flow value (Nm) was used to measure the gene flow in the sandflies populations. In addition, the population genetic structure of different geographical populations of Phlebotomus chinensis was analyzed using the STRUCTURE software.

A total of 978 sandflies were collected from 13 sandflies surveillance sites in Zhengzhou-Luoyang-Xuchang areas, Jiaozuo-Xinxiang areas and Anyang City of Henan Province from 2021 to 2023, and 475 sandflies were randomly sampled for subsequent detections. A total of 304 Ph. chinensis, 162 Se. squamirostris and 9 Se. bailyi were identified based on molecular biological detection of the COI gene, and Se. bailyi was reported for the first time in Henan Province. The intraspecific genetic distances of sandflies were 0.000 to 0.040, and the inter-specific genetic distances ranged from 0.133 to 0.161. Phylogenetic analysis revealed that each of the three sandfly species was clustered into a clade. The genetic polymorphisms of Ph. chinensis populations varied among different areas, with the highest haplotype diversity (0.966 ± 0.007) and the greatest nucleotide diversity (0.011) in Zhengzhou-Luoyang-Xuchang areas, and the lowest haplotype diversity (0.720 ± 0.091) and nucleotide diversity (0.004) in Anyang City. The dominant haplotype of Ph. chinensis populations was Pch_Hap_2 in Anyang City and Jiaozuo-Xinxiang areas, with moderate genetic differentiation (0.05 < F < 0.15) and frequent gene exchange (Nm value > 1) between Ph. chinensis populations sampled from Anyang City, and Jiaozuo-Xinxiang areas. Population genetic structure analysis showed that the dominant component of Ph. chinensis populations was K5 in Anyang City and Jiaozuo-Xinxiang areas. No obvious dominant haplotype was observed in Ph. chinensis populations sampled from Zhengzhou-Luoyang-Xuchang areas, which had very high genetic differentiation (F > 0.25) and little gene exchange (Nm value < 1) with Ph. chinensis populations from Anyang City, and Jiaozuo-Xinxiang areas, with K3 as the dominant component. In addition, there was no significant difference in the genetic polymorphism level among Se. squamirostris populations from the three areas.

There are Ph. chinensis, Se. squamirostris and Se. bailyi in Henan Province, and S. bailyi is recorded for the first time in Henan Province by molecular biological assays. There are different levels of genetic differentiation and gene exchange among P. chinensis populations in different areas of Henan Province.