Morphological and molecular characterization of invasive Biomphalaria straminea in southern China.

BACKGROUND: Schistosomiasis is a common parasitic disease designated as a neglected tropical disease by the World Health Organization. Schistosomiasis mansoni is a form of the disease that is caused by the digenean trematode Schistosoma mansoni, transmitted through Biomphalaria spp. as an intermediate host. Biomphalaria was introduced to Hong Kong, China in aquatic plants shipments coming from Brazil and the snail rapidly established its habitats in southern China. Earlier studies of Biomphalaria spp. introduced to southern China identified the snails as Biomphalaria straminea, one of the susceptible species implicated in S. mansoni transmission in South America. However, recent molecular investigations also indicated the presence of another South American species, B. kuhniana, which is refractory to infection. As such, it is important to identify accurately the species currently distributed in southern China, especially with emerging reports of active S. mansoni infections in Chinese workers returning from Africa. METHODS: We combined morphological and molecular taxonomy tools to precisely identify Biomphalaria spp. distributed in Guangdong Province, southern China. In order to clearly understand the molecular profile of the species, we constructed a phylogeny using mtDNA data (COI and 16S rRNA sequences) from six populations of Biomphalaria spp. from Shenzhen City in Guangdong Province. In addition, we examined the external morphology of the shell and internal anatomy of the reproductive organs. RESULTS: Both morphological and molecular evidences indicated a close affinity between Biomphalaria spp. populations from Guangdong and B. straminea from Brazil. The shell morphology was roughly identical in all the populations collected with rounded whorls on one side and subangulated on the other, a smooth periphery, an egg-shaped aperture bowed to one side, and a deep umbilicus. The shape and number of prostate diverticula (ranged from 11.67 to 17.67) in Guangdong populations supports its close affinity to B. straminea rather than B. kuhniana. Molecular analysis did not conflict with morphological analysis. Little genetic differentiation was observed within Biomphalaria populations collected. Phylogenetic analysis of COI and 16S rRNA haplotypes from snails collected and B. straminea sequences from Brazil and China using Bayesian inference revealed that Guangdong populations were clustered in one clade with B. straminea from Hong Kong of China and B. straminea from Brazil indicating their close affinity to each other. CONCLUSIONS: Data obtained in the current study clearly show that the populations of Biomphalaria spp. investigated are B. straminea, and we assume that those snails were either introduced via passive dispersal from Hong Kong of China or as a result of multiple introduction routes from Brazil.

Predicting the spatial distribution of Biomphalaria straminea, a potential intermediate host for Schistosoma mansoni, in China.

Schistosomiasis is one of the most prevalent parasitic diseases impacting human health in the tropics and sub-tropics. The geographic distribution of Schistosoma mansoni, the most widespread species, includes areas in Africa, the Middle East, South America and the Caribbean. Snails of the genus Biomphalaria act as intermediate host for S. mansoni. Biomphalaria straminea is not indigenous in China but was accidentally introduced to Hong Kong from South America and has spread to other habitats in the southern parts of the country. This species is known for its great dispersal capacity that highlights the importance of the snail as a potential host for S. mansoni in China. In this connection, although no such infection has been recorded in the field so far, the continuous expansion of China's projects in endemic areas of Africa and import of the infection via returning workers or visitors deserve attention. The purpose of this study was to map and predict the spatial distribution of B. straminea in China. Snail occurrence data were assembled and investigated using MaxEnt software, along with climatic and environmental variables to produce a predictive risk map. Of the environmental variables tested, the precipitation of warmest quarter was the most contribution factor for snail's spatial distribution. Risk areas were found in southeastern China and it is expected that they will guide policies and control programmes to potential areas area of snail abundance and used for spatial targeting of control interventions for this invasive species.

[Species identification of freshwater snail Planorbella trivolvis and analysis of its potential distribution].

OBJECTIVE: To identify the species classification of an ornamental Planorbidae from a flower market in Shanghai and analyze its potential distribution in China. METHODS: In August 2013, six freshwater snail specimens were collected from the Wanshang flower market. The species was identified by morphology and molecular biology. An ecological niche model was constructed based on the native geographic presence occurrence data, and projected onto the whole of China to predict the potential distribution. RESULTS: Their shell external morphology suggested that the specimens belonged to Planorbella trivolvis (Say 1817) of Planorbidae, which is native in North America. The sequence data of a fragment of the mitochondrial cytochrome c oxidase subunit I (COI) confirmed its identification. A total of 2 294 georeferenced occurrence points in North America were carried out from the Global Biodiversity Information Facility databases and 614 records with coordinates were used to produce a North American native niche model by a maximum entropy method (Maxent). The projection on China results suggested high probabilities of occurrence mostly in Henan Province and its borderland with nearby provinces. CONCLUSIONS: P. trivolvis is similarly with Biomphalaria species from shell morphology. It is the first records of the species in China, and the field dispersal is not clear.

[Species composition and distribution of medical mollusca in Shanghai City].

OBJECTIVE: To investigate the species diversity and distribution of medical mollusca in Shanghai City. METHODS: From August 2012 to October 2013, all kinds of habitats in 8 districts and counties in Shanghai City, namely Jiading, Qingpu, Baoshan, Minhang, Songjiang, Jinshan, Chongming, Pudong, were selected for the field survey according to the distribution characteristics of the river system, and all the specimens of medical mollusca in the investigation sites were collected and classified by morphological identification. Meanwhile, the species composition, habitats as well as the fauna of the medical mollusca collected were analyzed. RESULTS: A total of 5,211 specimens were collected, which belonged to 2 classes, 14 families, 18 genera and 25 species, including Oncomelania hupensis hupensis, Pomacea canaliculata, Parafossarulus striatulus, Alocinma longicornis, Physa acuta, Galba pervia, Hippeutis cantori, etc. The species numbers of medical mollusca in Chongming, Jinshan, Pudong new area and Qingpu districts (counties) were 22, 22, 21 and 20, respectively, which were more than those of other areas. The habitat analysis suggested that the species numbers in the river and wetland were the most, both of which were 14 species. The main faunas of the medical mollusca in Shanghai were the cosmopolitan and oriental species. CONCLUSIONS: The freshwater gastropod species are paucity in Shanghai City, but almost of them can be served as the intermediate hosts of certain parasites to transmit snail-related parasitic diseases, so the surveillance of medical mollusca should be strengthened.

[Comparative analysis of mitochondrial genomes of Angiostrongylus cantonensis].

OBJECTIVE: To compare the diversity of mitochondrial genomes of Angiostrongylus cantonensis in the mainland of China. METHODS: According to the population genetic of A. cantonensis, seven female worms were selected to characterize the mitochondrial (MT) genomes. Twelve primer pairs based on known MT genome (GQ398121) were used for PCR. The target fragments were sequenced and aligned. The gene localization, genome structure, composition of nucleotide, distribution of variable sites, and phylogeny were analyzed by employing multiple softwares. RESULTS: Five distinct types were identified from seven complete MT genomes. They were similar in size and structure, i.e., ranging 13,491-13,502 bp, including 12 protein-coding genes, 2 ribosomal genes, 22 tRNA genes, and 2 major non-coding regions. All the genes were localized at the same strand and had the same transcription direction. A total of 745 variable sites were identified, accounting for 5.5%. Among the variable sites, 59 were deletion/insert mutations, 105 transversions, and 581 transitions. The variable sites distributed evenly at the complete genome. CONCLUSION: The study reveals the mutation profile in the whole MT genome of A. cantonensis and thus will facilitate the development of intraspecific differential diagnosis.

[Investigation on the species distribution and infection status of host snails of Angiostrongylus cantonensis in Shanghai].

OBJECTIVE: To investigate the species distribution and infection status of host snails of Angiostongylus cantonensis in Shanghai. METHODS: From August 2012 to October 2014, 10 districts or counties were selected for this investigation in Shanghai, including Jiading, Qingpu, Putuo, Baoshan, Yangpu, Minhang, Songjiang, Jinshan, Chongming, and Pudong. All of the snails were examined by lung-microscopy and tissue homogenate methods. RESULTS: Totally 1074 snail samples were identified, belonging to 8 families, 10 species, including Pomacea canaliculata (133), Achatina fulica (25), Cipangopaludina chinensis (183), Bellamya aeruginosa (78), Physa acuta (349), Radix swinhoei (224), Bradybaena similaris (45), B. ravida sieboldiana (32), Limax flavus (2), and Philomycus bilineatus (3). A. fulica was sold in market, and was not found in the field. The natural population of P. canaliculata was found in the field in Jinze Town of Qingpu District. A. cantonensis larvae were not detected. CONCLUSION: No snails were found to be infected with A. cantonensis in Shanghai. Attention needs to be paid to the monitoring of P. canaliculata.