Invasive patterns of Biomphalaria straminea revealed by genetic mapping in the Greater Bay Area, China

Biomphalaria straminea, an intermediate host of Schistosoma mansoni, is originally native to Brazil but has invaded southern China since 1974. Nowadays, increasing human mobility raises the risk of S. mansoni dissemination. Therefore, this study aims to elucidate the genetic variation and structure of B. straminea in China and develop molecular tools for tracing its geographic origins, which could aid in schistosomiasis prevention and control.

We collected 290 B. straminea individuals from Shenzhen City (GDSZ, n = 171), Dongguan City (GDDG, n = 65), and Hong Kong (HK, n = 54). Double digest restriction associated DNA (ddRAD) sequencing was applied to genotype the samples. A subset of single nucleotide polymorphisms (SNPs) was validated by the Sequenom MassARRAY iPLEX assay. The MaxEnt model was employed to predict suitable habitats for B. straminea in China under current and future climate conditions.

Analysis of ddRAD sequencing data led to the identification of 80 high-confidence SNPs. B. straminea from GDSZ exhibited higher genetic diversity than those from other locations. The total observed heterozygosity (Ho = 0.35) was higher than the total expected heterozygosity (He = 0.26), resulting in a negative inbreeding coefficient (Fis = - 0.35), indicating that outbreeding has dominated the recent genetic history of B. straminea. Pairwise genetic distance (Fst < 0.05) and number of effective migrants (Nm > 4) indicated low genetic differentiation. The populations in GDSZ, GDDG and HK were genetically similar, with the first two being more closely related. Three high-quality SNPs displayed distinct geographical population specificity and could serve as geographically specific SNP markers. The MaxEnt model predicted an expansion of suitable habitats for B. straminea in China under future climate conditions. High invasion risk in Hainan Province, Guangxi Zhuang Autonomous Region, and Taiwan Province warrants attention.

This study provides the first genome-wide insights into the population structure and genetic diversity of B. straminea in China. The populations are genetically similar, suggesting a common invasion source. Applying the geographically specific SNPs could enable rapid prediction of the geographic origin of B. straminea in future invasion events. Future climate conditions are likely to facilitate the spread of B. straminea, increasing the risk of schistosomiasis transmission in China.