Distribution and current infection status of Biomphalaria straminea in Hong Kong

Abstract

BackgroundSchistosomiasis, also generally known as snail fever, is a parasitic disease caused by trematode flatworms of the genus Schistosoma. In Hong Kong and mainland China, the freshwater snail Biomphalaria straminea has been introduced and has the potential to transmit intestinal schistosomiasis caused by S. mansoni, a parasite of man which has a wide distribution in Africa and parts of the New World, especially Brazil. The first identification of B. straminea in Hong Kong dates back to the 1970s, and its geographical distribution, phylogenetic relationships, and infection status have not been updated for more than 30 years. Thus, this study aims to reveal the distribution and current infection status of B. straminea in contemporary Hong Kong.MethodsSnails were collected from different parts of Hong Kong from July 2016 to January 2017. Both anatomical and molecular methods were applied to identify B. straminea. Cytochrome c oxidase subunit 1 (cox1), internal transcribed spacer 1 (ITS1), 5.8S rDNA, internal transcribed spacer 2 (ITS2), and 16S ribosomal DNA (rDNA) were sequenced from individual snails and analyzed. To detect the presence of S. mansoni, both biopsy and PCR analyses were carried out.ResultsUsing both anatomical and molecular analyses, this study demonstrated the existence of black- and red-coloured shell B. straminea in different districts in the New Territories in Hong Kong, including places close to the mainland China border. None of the B. straminea (n = 87) investigated were found to be infected with S. mansoni when tested by biopsy and PCR. The Hong Kong B. straminea are genetically indistinguishable, based on the chosen molecular markers (cox1, ITS1-5.8S-ITS2, and 16S rDNA), and are similar to those obtained in mainland China and South America.Conclusion Biomphalaria straminea is now well established in freshwater habitats in Hong Kong. No evidence of infection with S. mansoni has been found. Surveillance should be continued to monitor and better understand this schistosomiasis intermediate host in mainland China and Hong Kong.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-017-2285-3) contains supplementary material, which is available to authorized users.

Prediction of the potential global distribution for Biomphalaria straminea, an intermediate host for Schistosoma mansoni

“…The first introduction of B . straminea into Hong Kong was thought to be associated with imported tropical aquarium plants or fish from South America[ 22 , 58 ], which was reconfirmed by a recent phylogenetic analysis[ 59 ]. Subsequent colonization occurred in large outdoor concrete breeding ponds for tropical aquarium fish near the border with mainland China[ 60 ].…”

Spatial distribution and habitat suitability of Biomphalaria straminea, intermediate host of Schistosoma mansoni, in Guangdong, China

“…Besides, the infection status of S. mansoni was not detected among the specimens. To date, there has been no evidence for S. mansoni in samples collected in Hong Kong, Shenzhen and Dongguan in the mainland China [ 10 ]. Both lab-reared and field-captured B. straminea snails from a stream in Luohu District of Shenzhen seemed incompatible with the S. mansoni Puerto Rican strain [ 29 ].…”

“…We obtained additional occurrence data of B. straminea from a recent survey in Hong Kong during 2016–2017, which used similar snail sampling and identification methods to our study [ 10 ]. These presence points, together with data of our own survey, were spatially interpolated using Empirical Bayesian Kriging (EBK) in ArcGIS 10.2.2 (Environmental Systems Research Institute, Inc., Redlands, USA) to predict the spatial distribution of B. straminea in China [ 16 ].…”

“…Therefore, there was an urgent need to determine the spatial distribution of B. straminea in China. B. straminea has established in various freshwater habitats in Hong Kong but no evidence of S. mansoni was found in the snails [ 10 ]. However, there is currently a lack of large-scale, comprehensive snail survey in mainland China.…”

Genetic analysis of Cryptozona siamensis (Stylommatophora, Ariophantidae) populations in Thailand using the mitochondrial 16S rRNA and COI sequences

“…In the last few years, DNA sequencing data has been used to study and clarify the evolution of morphological characteristics of ambiguous organisms [ 15 – 18 ] while genetic studies of land snails using DNA sequence data could be valuable for their identification [ 19 – 21 ]. The most commonly used genes for genetic analysis in land snails are the mitochondrial cytochrome c oxidase subunit I (COI) and 16S rRNA genes [ 20 , 22 – 24 ].…”