Genetic Evidence of Contemporary Dispersal of the Intermediate Snail Host of Schistosoma japonicum: Movement of an NTD Host Is Facilitated by Land Use and Landscape Connectivity

Abstract

BackgroundWhile the dispersal of hosts and vectors—through active or passive movement—is known to facilitate the spread and re-emergence of certain infectious diseases, little is known about the movement ecology of Oncomelania spp., intermediate snail host of the parasite Schistosoma japonicum, and its consequences for the spread of schistosomiasis in East and Southeast Asia. In China, despite intense control programs aimed at preventing schistosomiasis transmission, there is evidence in recent years of re-emergence and persistence of infection in some areas, as well as an increase in the spatial extent of the snail host. A quantitative understanding of the dispersal characteristics of the intermediate host can provide new insights into the spatial dynamics of transmission, and can assist public health officials in limiting the geographic spread of infection.Methodology/Principal findingsOncomelania hupensis robertsoni snails (n = 833) were sampled from 29 sites in Sichuan, China, genotyped, and analyzed using Bayesian assignment to estimate the rate of recent snail migration across sites. Landscape connectivity between each site pair was estimated using the geographic distance distributions derived from nine environmental models: Euclidean, topography, incline, wetness, land use, watershed, stream use, streams and channels, and stream velocity. Among sites, 14.4% to 32.8% of sampled snails were identified as recent migrants, with 20 sites comprising >20% migrants. Migration rates were generally low between sites, but at 8 sites, over 10% of the overall host population originated from one proximal site. Greater landscape connectivity was significantly associated with increased odds of migration, with the minimum path distance (as opposed to median or first quartile) emerging as the strongest predictor across all environmental models. Models accounting for land use explained the largest proportion of the variance in migration rates between sites. A greater number of irrigation channels leading into a site was associated with an increase in the site’s propensity to both attract and retain snails.Conclusions/SignificanceOur findings have important implications for controlling the geographic spread of schistosomiasis in China, through improved understanding of the dispersal capacity of the parasite’s intermediate host.

Population Genetics of Oncomelania hupensis Snails from New-Emerging Snail Habitats in a Currently Schistosoma japonicum Non-Endemic Area

“…As control strategies for the parasite infection in wild animals (e.g., rodents) may not prove logistically feasible or practical, control and removal of the intermediate host snails may be an alternative with the ongoing focus on molluscides and/or environment management. Therefore, our understanding of the genetic characteristics and dispersal potential of O. hupensis in new emerging snail habitats in Taicang of Jiangsu, China may provide a basis for formulating targeted prevention measures, which would exert epidemiological implications for final schistosomiasis elimination across the country [ 45 , 46 ].…”

Oncomelania lorelindoensis: the intermediate host of Sulawesi’s Schistosoma japonicum

“…According to nucleotide sequences, people with S. japonicum from China, Japan, and Taiwan brought this parasite to Sulawesi, Indonesia (Nelwan, 2022) Human and birds can transmit Sulawesi schistosomiasis japonica distance from an endemic areas. For example, in rare cases, birds may transport ingested snails long distances and secreted alive in a new area (Head et al, 2016). Carney et al reported that a few cases of the disease occur in the Kulawi Valley and the Palu Valley, with individuals in these cases spending considerable time visiting or working in the Lindu Valley (Sudomo and Carney, 1974).…”

Influences of Land-Use Dynamics and Surface Water Systems Interactions on Water-Related Infectious Diseases—A Systematic Review

“…Temperature, turbidity, pH Dengue [75] Temperature Malaria [59,75,87] E. coli, fecal coliform Cholera [45,61,62,81,88] E. coli, fecal coliform, turbidity, pH Dysentery [61,62,89] E. coli, fecal coliform Typhoid fever [61,62] E. coli, fecal coliform, BOD, temperature, DO Cryptosporidiosis [70,81] Fecal coliform Schistosomiasis [76,77,83,85,[90][91][92] E. coli, fecal coliform, temperature, turbidity Buruli ulcer [85] E. coli, fecal coliform, temperature, DO, BOD, TSS, turbidity Hookworm [92] pH = Potential of Hydrogen; DO = Dissolved Oxygen; BOD = Biochemical Oxygen Demand; TSS = Total Dissolved Solid.…”