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. 2021 Jul 2;60:e31. doi: 10.6620/ZS.2021.60-31

Population Genetics Analysis of a Pomacea Snail (Gastropoda: Ampullariidae) in Thailand and its Low Infection by Angiostrongylus cantonensis

Abdulhakam Dumidae 1, Pichamon Janthu 1, Chanakan Subkrasae 1, Raxsina Polseela 1, Bandid Mangkit 2, Aunchalee Thanwisai 1,3,4, Apichat Vitta 1,3,4,*
PMCID: PMC8652421  PMID: 34963784

Abstract

Pomacea is a freshwater snail in family Ampullariidae that is native to South and Central America. This snail is among the more important intermediate hosts for Angiostrongylus cantonensis and agricultural pests. Herein, we investigated the prevalence of A. cantonensis larvae and the genetic diversity of Pomacea samples collected across Thailand based on mitochondrial cytochrome c oxidase subunit I (COI) gene sequences. The larval-infection rate was 1.7% in Pomacea canaliculata specimens collected from the Uttaradit Province of northern Thailand. We randomly selected specimens of P. canaliculata and P. maculata for genetic analysis. We analyzed 244 COI sequences, including 49 sequences from samples collected from Thailand and a publicly accessible database of snails in their native and non-native ranges. A maximum-likelihood tree of P. canaliculata and P. maculata revealed two main clades. The genetic diversity analysis identified seven P. canaliculata haplotypes and six P. maculata haplotypes, and showed genetic differences between the populations of P. canaliculata and P. maculata. The haplotype networks of P. canaliculata and P. maculata populations in Thailand are similar to those of populations in multiple countries, indicating that this species spread widely to many parts of the world.

Keywords: Angiostrongylus, Genetic diversity, Phylogeny, Haplotype, Pomacea

BACKGROUND

Pomacea spp. are freshwater snails in the family Ampullariidae (i.e., apple snails), which are native to South and Central America (Hayes et al. 2015). Pomacea spp. are distributed throughout the humid tropics and subtropics. Several species in this genus have been introduced and become widespread in many parts of the world, including Asia, Europe, North America, and the Pacific Islands (Rawlings et al. 2007; Hayes et al. 2008). Pomacea was first introduced into the Asia-Pacific region in 1980 as part of the pet trade and as a source of food for human consumption (Cowie et al. 2006; Rawlings et al. 2007; Hayes et al. 2008). It quickly spread to many countries in Southeast and East Asia via transportation or was further introduced from its native areas (Halwart 1994). Four species of Pomacea—P. canaliculata, P. maculata, P. diffusa, and P. scalaris—have been found in Southeast and East Asia (Hayes et al. 2008; Xu et al. 2012). Among them, P. canaliculata and P. maculata are highly invasive species and the most widely distributed (Hayes et al. 2012). Pomacea canaliculata was listed as one the world’s 100 most invasive species (Lowe et al. 2000). In addition, The United States Aquatic Nuisance Species Task Force has expressed concerns regarding members of Ampullariidae, including Pomacea (Burks et al. 2017).

Pomacea snails have important roles in agriculture and medicine. The snails have a voracious appetite (Qiu et al. 2011), are resistant to desiccation during dry periods (Havel et al. 2014), and reproduce rapidly (Barnes et al. 2008). They are serious agricultural pests (Mochida 1991) that were shown to have effects on the environment (Hayes et al. 2015) and human health (Lv et al. 2009a). Over the past couple of decades, Pomacea snails were designated as pests for wetland rice and other crops and shown to cause massive annual economic losses of more than US $40 million and US $18.9 billion in the Philippines and China, respectively (Cowie 2002; Xu et al. 2012). In addition, Pomacea snails are natural intermediate hosts of Angiostrongylus cantonensis (Lv et al. 2009b), which causes eosinophilic meningitis and meningoencephalitis in humans (Pipitgool et al. 1997). The genus was shown to promote the endemicity and transmission of A. cantonensis in China and the United States (Song et al. 2016; Kim et al. 2019). The invasion of these snails facilitates the establishment of the parasite’s life cycle, thus increasing the chance that native snails are exposed to A. cantonensis in endemic areas (Lv et al. 2006 2009b).

Pomacea canaliculata was illegally introduced into Thailand in 1984. It was used to clean fish aquaria because it consumes several aquatic plants and algae (Keawjam and Upatham 1990). Pomacea snails have been reported to cause serious damage to rice crops in Thailand. Three species of Pomacea snails are common in Thailand: P. canaliculata, P. maculata, and Pomacea sp. (Keawjam and Upatham 1990). Many other non-native Pomacea species are difficult to differentiate from P. canaliculata and P. maculata, and are frequently misidentified as members of one of these two species (Cowie et al. 2006; Hayes et al. 2008). Thus, morphological variation in Pomacea spp. is low, which has led to the use of alternative methods for identification.

Select nucleotide regions have been sequenced to identify several species, including gastropods. Nucleotide sequences of the mitochondrial 12S, 16S, and cytochrome c oxidase subunit I (COI) regions successfully revealed the presence of three species in the United States: P. canaliculata, P. maculata, and P. haustrum (Rawlings et al. 2007). Phylogenetic analysis of COI sequences revealed the presence of two major groups in Japan: P. maculata and P. canaliculata (Matsukura et al. 2008). In addition, COI sequences were used to study the diversity of Pomacea species in China, and confirmed the presence of P. maculata and P. canaliculata (Song et al. 2010; Yang et al. 2018a). No studies of multiple areas have been conducted on the genetic variation of Pomacea in Thailand. In the present study, a partial sequence of the COI gene was used to confirm the identification of Pomacea species. Moreover, genetic variation, phylogeny, and genetic-structure analysis were performed to evaluate the molecular diversity of Pomacea in Thailand. In addition, the infection rate of A. cantonensis larvae in Pomacea was investigated.

MATERIALS AND METHODS

Collection and identification of Pomacea snails

Pomacea specimens were randomly collected from 25 provinces across Thailand between May 2017 and July 2018 (Fig. 1, Table S1). Snails were collected by hand in several habitats—e.g., paddy fields, canals, and rivers—and placed in a plastic box with water and air ventilation. They were transported to the Department of Microbiology and Parasitology (Faculty of Medical Science, Naresuan University, Phitsanulok, Thailand). The shell morphologies of the Pomacea specimens were primarily identified according to previous studies (Hayes et al. 2012; Arfan et al. 2014; Yang and Yu 2019). Pomacea canaliculata was primarily identified based on external shell morphology with unpigmented inner pallial lip, rounded shoulder, smooth shell surface, deep suture, thin shell, and wide umbilical. Pomacea maculata was primarily identified based on external shell morphology with red or orange inner pallial lip pigmentation, angulated shoulder, rough shell surface, shallow suture, thick shell, and narrow umbilical.

Fig. 1.

Fig. 1.

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Geographical locations of the 25 collection sites for P. canaliculata and P. maculata in Thailand. Details on the collection sites are in table S1.

Isolation of Angiostrongylus larvae from Pomacea

The bodies of P. canaliculata and P. maculata snails were removed from the shells. A piece of snail foot tissue was taken from each individual (approximately 8 mm3) and stored at -20°C until DNA extraction. Most remaining snail tissue was artificially digested with 0.7% pepsin solution (Acros Organics, Geel, Belgium) according to a previous study (Vitta et al. 2016a). The larva of Angiostrongylus species was identified using a light microscope. Morphological descriptions with cylindrical shape, thin and delicate body, two chitinous rods at the anterior end, genital primordium at the middle of the body, cone-shaped tail, moderately curved and pointed tail, and the anus near the rear end of the tail were used as characters for identification (Eamsobhana 2006).

DNA extraction from Pomacea snails

Genomic DNA was extracted from individual snails using the NucleoSpin® Tissue Kit (Macherey-Nagel, Duren, Germany) following the manufacturer’s instructions. Snail tissue was transferred to a 1.5-mL microcentrifuge tube containing 180 μl of tissue lysis (T1) buffer, then 25 μl of 30 mg/mL proteinase K solution was added. The tissue was ground using a sterile pipette tip for several minutes. The tube was then incubated overnight in a water bath at 56°C and vortexed occasionally during the incubation. On the next day, 200 μl of sample lysis (B3) buffer was added. The tube was vortexed vigorously and incubated in a water bath at 70°C for 10 min. The tube was vortexed again, and 210 μl of 100% ethanol was added to optimize the DNA-binding conditions. The solution was transferred to a NucleoSpin® Tissue Column in a collection tube and centrifuged for 1 min at 11,000 × g. The flow-through was discarded, and the column was placed in a new collection tube. Subsequently, two sequential washes through the silica membrane were performed by adding 500 μl of BW buffer and then 600 μl of B5 buffer. The tube was centrifuged for 1 min at 11,000 × g. The flow-through was discarded, and the column was placed back into the collection tube. The column was centrifuged again for 1 min at 11,000 × g to dry the silica membrane. The NucleoSpin® Tissue Column was placed into a 1.5-mL microcentrifuge tube, and 80 μl of Buffer BE was added. The tube was then incubated at room temperature for 1 min and centrifuged for 1 min at 11,000 × g. The genomic DNA was dissolved in Buffer BE. The DNA solution was checked by running it on a 0.8% agarose gel in 1× TBE buffer at 100 V. The gel was stained with ethidium bromide, followed by destaining with distilled water and photographing under ultraviolet light. The DNA solution was stored at -20°C until further use.

Polymerase chain reaction (PCR) amplification and sequencing

Polymerase chain reaction was performed to amplify partial regions of COI from P. canaliculata and P. maculata. A pair of primers was designed based on a deposited GenBank sequence (accession number AB433758) using the Primer-BLAST program. The primers PcCOI_forward (5'-ATGATCAGGCCTAGTTGGGG-3') and PcCOI_ reverse (5'-TTCATCCAGTTCCAGCACCA-3') were obtained and used to amplify a 308-base pair (bp) fragment. PCR was carried out in a total volume of 30 μl, containing 3 μl 10× buffer, 2.1 μl 25 mM MgCl2, 0.6 μl 200 mM dNTPs, 1.2 μl each primer (5 μM; final concentration of 0.2 μM), 0.3 μl 5 U/mL Taq DNA polymerase, 18.6 μl of distilled water, and 3 μl of DNA template (20–200 ng). The PCR temperature profile included an initial denaturation at 95°C for 1 min; followed by 35 cycles of denaturation at 95°C for 1 min, annealing at 50°C for 40 s, and extension at 72°C for 1 min; with a final extension at 72°C for 5 min. PCR was performed in a Biometra TOne Thermal Cycler (Analytik Jena AG, Jena, Germany). The PCR products were checked by 1.2% agarose gel electrophoresis. Purification of the PCR products was performed using a NucleoSpin® Gel and PCR Clean-Up Kit (Macherey-Nagel, Germany) in accordance with the manufacturer’s instructions. The purified PCR product were checked on a 1.2% agarose gel run at 100 V in 1× TBE buffer. Nucleotide sequencing was performed at Macrogen Inc., Seoul, Korea in both the forward and reverse directions.

Sequencing and phylogenetic analysis

Snails (P. canaliculata and P. maculata) were identified by running BLASTN searches to find similarities to sequences deposited in the NCBI BLAST database (http://blast.ncbi.nlm.nih.gov/Blast.cgi). The nucleotide sequences were aligned using ClustalW. The maximum-likelihood (ML) method with HKY model and neighbor-joining (NJ) method with Kimura two-parameter (K2) based on 1,000 bootstrap replicates were performed for the phylogenetic analyses with MEGA 7 (Kumar et al. 2016). Bayesian analysis was performed with MrBayes v3.2. using a four-chain run for 2,000,000 generations of Markov-chain Monte Carlo algorithm (MCMC) simulations (Ronquist et al. 2012). We added 195 COI sequences P. maculata (n = 100) and P. canaliculata (n = 95) from GenBank to the 49 COI sequences generated in this study. Genetic distances of P. canaliculata and P. maculata based on COI sequences were calculated according to the Kimura two-parameter method (Kimura 1980).

Haplotype and genetic analysis

Haplotype diversity and nucleotide diversity were calculated in ARLEQUIN, version 3.5.1.2 (Excoffier and Lischer 2010). Relationships between haplotypes were estimated using the median-joining (MJ) network (Bandelt et al. 1999). MJ-network analysis was performed in NETWORK (version 5.0.1.1) based on the COI sequences. In addition, the analysis of molecular variance (AMOVA) performed in ARLEQUIN was used to test the genetic difference among groups.

RESULTS

Infection rate of A. cantonensis in Pomacea

We collected 386 P. canaliculata and 242 P. maculata samples from 25 provinces in five regions of Thailand. We found only one P. canaliculata sample from Uttaradit Province (in northern Thailand) that was infected with A. cantonensis larva (Fig. S1). Only one A. cantonensis larva was isolated from that snail. The prevalence of A. cantonensis larvae was as low as 1.7% (1/59).

Molecular identification of Pomacea

To identify P. canaliculata and P. maculata, PCR-based analysis and sequencing of the COI gene were performed together with a BLASTN search of the sequences. Twenty-seven samples of Pomacea (GenBank accession numbers MK858525–MK858551) were identified as P. canaliculata with 99–100% identity after a BLASTN search using 282 bp of the COI gene. During the analysis of the COI sequences (283 bp) of P. maculata (GenBank accession numbers MK858552–MK858573), 22 sequences showed the highest similarity (99%) with known sequences of P. maculata (GenBank accession numbers AB728579 and GU236491).

Phylogenetic analyses

The phylogenetic trees of P. canaliculata and P. maculata were reconstructed using the ML, NJ, and BI methods. Based on the 27 COI sequences in the present study together with 95 sequences from GenBank results for P. canaliculata, the ML tree revealed two main clades (Fig. 2). Clade 1 contained 21 sequences from this study and 39 known sequences downloaded from GenBank; bootstrap support was highest (88%) for the NJ tree. Clade 2 contained six sequences identified from this study and 45 from GenBank; bootstrap support was highest (79%) for the ML tree.

Fig. 2.

Fig. 2.

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ML phylogenetic tree generated from 122 sequences of a partial COI sequence (282 bp) of P. canaliculata (27 sequences from Thailand and 95 sequences from other geographical regions). Support values (ML bootstrap/NJ bootstrap/Bayesian posterior probabilities) are shown above the branches. Bold letters indicate the sequences obtained in this study. Pomacea maculata and P. bridgesi were used as the outgroups. Abbreviations: TH, Thailand; AR, Argentina; CL, Chile; CN, China; HK, Hong Kong; ID, Indonesia; JP, Japan; MY, Malaysia; MM, Myanmar; PG, Papua New Guinea; PH, Philippines; TW, Taiwan; US, United States; UY, Uruguay.

The maximum likelihood tree of 122 COI sequences of P. maculata (22 sequences from the present study and 100 downloaded from GenBank) revealed two main clades (Fig. 3). Clade 1 contained 16 sequences from this study and 62 from GenBank. Clade 2 contained six sequences identified in this study and 23 sequences of reference species; bootstrap support values were highest (71%) for the NJ tree.

Fig. 3.

Fig. 3.

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ML phylogenetic tree generated from 122 sequences of a partial COI sequence (283 bp) of P. maculata (22 sequences from Thailand and 100 sequences from other geographical regions). Support values (ML bootstrap/NJ bootstrap/Bayesian posterior probabilities) are shown above the branches. Bold letters indicate the sequences obtained in this study. Pomacea canaliculata and P. bridgesi were used as the outgroups. TH, Thailand; AR, Argentina; BR, Brazil; CN, China; JP, Japan; MY, Malaysia; NZ, New Zealand; ES, Spain; US, United States; UY, Uruguay; VN, Vietnam.

Genetic distances between populations of P. canaliculata and P. maculata

The genetic distances between the populations of P. canaliculata and P. maculata were calculated to compare the populations in Thailand with those of the native and non-native ranges using COI sequences. The genetic distances between the P. canaliculata population of Thailand and Argentina (native) was 0.055, while the distance between Thailand and Uruguay (native) was 0.060. The genetic distances between P. canaliculata in Thailand and its non-native range—including Chile, China, Hong Kong, Indonesia, Japan, Malaysia, Myanmar, Papua New Guinea, the Philippines, Taiwan, and the United States—was 0.033–0.047 (Table S2). Meanwhile, the genetic distance between P. canaliculata and P. maculata was 0.135.

The genetic distance between P. maculata populations in Thailand and Argentina (native) was 0.015, Thailand and Brazil (native) was 0.033, and Thailand and Uruguay (native) was 0.020. The genetic distances between P. maculata in Thailand and its non-native range—including China, Japan, Malaysia, New Zealand, Spain, the United States, and Vietnam—was 0.013–0.020 (Table S3).

Genetic variations between P. canaliculata and P. maculate

The mitochondrial COI sequences (282 bp) were obtained from 27 individuals of P. canaliculata from Thailand and 95 sequences from the native and introduced range. Twenty-five haplotypes (Pc1–Pc25) were identified with 45 nucleotide variation sites (Fig. 4, Table S4). Of these, 18 haplotypes were unique and seven (Pc1–4, Pc9, Pc13, and Pc15) were shared by at least two populations. Haplotype Pc2 was the most shared among the populations found in Argentina, the United States, Papua New Guinea, China, Hong Kong, Japan, Malaysia, the Philippines, and Thailand (Table S5).

Fig. 4.

Fig. 4.

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Mitochondrial DNA genealogy for 122 COI sequences (27 sequences from Thailand and 95 sequences from other geographical regions) of P. canaliculata constructed by median-joining network method. Each haplotype is represented by a circle. The sizes of the circles are relative to the number of individuals that share a specific haplotype. Each mutation between the haplotypes is represented with a bar. The red dot vertices represent unsampled putative or missing haplotypes.

Seven haplotypes (Pc1, Pc2, Pc21–25) were identified from 27 Thailand sequences. Among the P. canaliculata haplotypes in Thailand, Pc1 was the most widely distributed—in 11 provinces. The second most widely distributed haplotype, Pc2, was found in three provinces of Thailand. The other haplotypes, Pc21–25, were found in Buri Ram, Sukhothai, Roi Et, Khon Kaen, and Phetchaburi provinces, respectively (Fig. 1, Table S1). The haplotype diversity in each population ranged from 0 in Chile, Hong Kong, Indonesia, Myanmar, Papua New Guinea, and the United States to 1.0000 in Taiwan, with a mean of 0.8533. The nucleotide diversity in each population ranged from 0 in Chile, Hong Kong, Indonesia, Myanmar, Papua New Guinea, and the United States to 0.0401 in Taiwan, with a mean of 0.0361 (Table 1).

Table 1.

Genetic diversity of P. canaliculata populations from Thailand and other geographical regions based on mitochondrial cytochrome coxidase I gene sequences

Populations Number of samples Haplotypes Haplotype diversity (h), mean ± SD Nucleotide diversity (π), mean ± SD
Number of haplotypes Shared haplotypes Unique haplotype
Thailand 29 8 3 5 0.6281 ± 0.0894 0.0257 ± 0.0138
Argentina 9 5 2 3 0.8056 ± 0.1196 0.0263 ± 0.0154
Chile 4 1 - 1 0 0
China 32 7 4 3 0.6956 ± 0.0666 0.0268 ± 0.0142
Hong Kong 2 1 1 - 0 0
Indonesia 3 1 1 - 0 0
Japan 11 4 4 - 0.7455 ± 0.0978 0.0310 ± 0.0175
Malaysia 13 2 2 - 0.2821 ± 0.1417 0.0130 ± 0.0079
Myanmar 1 1 - 1 0 0
Papua New Guinea 1 1 1 - 0 0
Philippines 6 3 2 1 0.7333 ± 0.1552 0.0359 ± 0.0221
Taiwan 3 3 2 1 1.0000 ± 0.2722 0.0401 ± 0.0315
United States 3 1 1 - 0 0
Uruguay 5 4 1 3 0.9000 ± 0.1610 0.0312 ± 0.0203
Total 122 42 24 18 0.8533 ± 0.0218 0.0361 ± 0.0183
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Twenty-five haplotypes (Pm1–Pm25) of P. maculata from 22 sequences in Thailand and 100 sequences from the native and introduced ranges were identified based on the COI gene sequence (283 bp) with nucleotide variations at 39 sites (Fig. 5, Table S6). Of these, 22 haplotypes were unique, and three (Pm1, Pm2, and Pm5) were shared by at least two populations. Haplotype Pm1 was the most shared among the populations found in Brazil, the United States, New Zealand, Spain, China, Japan, Malaysia, and Thailand (Table S7).

Fig. 5.

Fig. 5.

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Mitochondrial DNA genealogy for 32 COI sequences (22 sequences from Thailand and 100 sequences from other geographical regions) of P. maculata constructed by the median-joining network method. Each haplotype is represented by a circle. The sizes of the circles are relative to the number of individuals sharing a specific haplotype. Each mutation between haplotypes is represented with a bar.

Six haplotypes from 27 COI sequences of P. maculata were identified (Pm20–25). Among the P. maculata haplotypes in Thailand, Pm20 was the most widely distributed in six provinces. The second most widely distributed haplotype was Pm23, which occurred in four provinces of Thailand. The remaining haplotypes—Pm21 and Pm24—were less widely distributed, and found in three provinces (Samut Sakhon, Nakhon Phanom, and Phetchaburi) and two provinces (Nakhon Phanom and Chai Nat), respectively. Two haplotypes (Pm22 and Pm25) were found in Phichit and Phetchabun, respectively (Fig. 1, Table S1). The haplotype diversity in each population ranged from 0 in Spain, New Zealand, Malaysia, and Vietnam to 0.9000 in Uruguay, with a mean of 0.7878. Nucleotide diversity in each population ranged from 0 in Spain, New Zealand, Malaysia, and Vietnam to 0.0260 in Brazil, with a mean of 0.0181 (Table 2).

Table 2.

Genetic diversity of P. maculata populations from Thailand and other geographical regions based on mitochondrial cytochrome coxidase I gene sequences

Populations Number of samples Haplotypes Haplotype diversity (h), mean ± SD Nucleotide diversity (π), mean ± SD
Number of haplotypes Shared haplotypes Unique haplotype
Thailand 23 7 1 6 0.7826 ± 0.0605 0.0108 ± 0.0065
Argentina 10 3 1 2 0.6444 ± 0.1012 0.0040 ± 0.0032
Brazil 15 7 1 6 0.8952 ± 0.0433 0.0260 ± 0.0144
China 31 4 1 3 0.3419 ± 0.1016 0.0146 ± 0.0083
Japan 6 2 2 - 0.6000 ± 0.1291 0.0127 ± 0.0086
Malaysia 9 1 1 - 0 0
New Zealand 1 1 1 - 0 0
Spain 9 1 1 - 0 0
United States 12 3 2 1 0.6212 ± 0.0867 0.0113 ± 0.0070
Uruguay 5 4 1 3 0.9000 ± 0.1610 0.0098 ± 0.0073
Vietnam 1 1 - 1 0 0
Total 122 34 12 22 0.7878 ± 0.0365 0.0181 ± 0.0098
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DISCUSSION

The data generated in this study showed that Pomacea canaliculata samples collected from the Uttaradit Province in northern Thailand were positive for A. cantonensis larva. A previous study reported the prevalences of A. cantonensis in snails from several provinces in northeastern Thailand: 20% for Hemiplecta distincta, 7.6% for Achatina fulica, 5% for Pila polita, and 2.4% for P. pesmei (Tesana et al. 2009). A recent survey showed that the prevalences of A. cantonensis larvae in A. fulica, Cryptozona siamensis, and Megaustenia siamensis snails from several provinces in Thailand were 1.08, 0.07, and 0.01%, respectively (Vitta et al. 2016b). We now report that A. cantonensis larva naturally infected P. canaliculata snails in Thailand. An experimental study previously noted a low infection adaptability (Chaichana and Sumpan 2015). Therefore, Pomacea snails were found to be of increasing importance as the intermediate host for A. cantonensis transmission in this region. Previous data showed that, in other countries, the prevalence of A. cantonensis larvae in P. canaliculata was 20.4, 6.1, and 2% in Taiwan, China, and the Philippines, respectively (Wang et al. 2011; Tujan et al. 2016; Hu et al. 2018). Expansive epidemiological data indicate that P. canaliculata is becoming the most important intermediate host for A. cantonensis in China, Laos, Cambodia, and Vietnam because of its wide environmental tolerance and its high susceptibility to the parasite (Yang et al. 2013; Lv et al. 2018).

The patterns of epidemiological of eosinophilic meningitis caused by A. cantonensis in Southeast Asia, Japan, and China are changing. For instance, slugs were widely used in Traditional Chinese Medicine in China (Li et al. 2006), but this usage is declining. In addition, snails were important for animal rearing in Taiwan in the 1970s (Yii 1976), but this practice, too, is diminishing. In contrast, the spread of invasive snails, growth of tourism, and consumption of foods that use snails, which have become popular among tourists, are all important factors driving the spread of A. cantonensis (Lv et al. 2009b). Between 1997 and 2006, 116 cases of human angiostrongyliasis in China were traced back to infection via P. canaliculata (Zheng et al. 2001; Lin et al. 2003; Yang et al. 2004; Han et al. 2005; Wei et al. 2005). In addition, eating raw P. canaliculata or A. fulica was confirmed to be the route of A. cantonensis infection in the outbreak of angiostrongyliasis in Beijing in 2006 (Lv et al. 2008). Even though A. cantonensis infection was low in P. canaliculata, the host might be a vector that transmits the parasite to humans who eat “koi hoi,” a traditional snail dish in Thailand (Eamsobhana et al. 2010).

In this study, identification of the Pomacea snail was confirmed based on 99–100% sequence identity after BLASTN searching. Previously, investigators have used the shell morphology, soft tissue morphology, and egg mass to identify Pomacea (Thiengo et al. 1993; Cowie et al. 2006). Using these criteria, it is difficult to distinguish all species of Pomacea due to intraspecific variation and ecological environments, especially with P. canaliculata and P. maculata (Matsukura et al. 2008; Hayes et al. 2012). Differentiating between P. canaliculata and P. maculata is difficult due to the low variation in shell morphologies (Hayes et al. 2012). To assist in the identification, the COI sequence can be used to differentiate between P. canaliculata and P. maculata (Matsukura et al. 2008; Yang et al. 2018a). These findings agreed with our COI sequencing results. Therefore, sequencing a partial region of the COI gene may be used to differentiate between P. canaliculata and P. maculata, due to nucleotide variations in the mitochondrial gene.

Phylogenetic analysis of Pomacea revealed two main clades for each species (P. canaliculata and P. maculata), which was closely related to Pomacea from several countries. These data indicate that the P. canaliculata and P. maculata Thai strains are most closely related to multiple countries. Pomacea species— including P. canaliculata, P. maculata, P. diffusa, and P. scalaris—have been detected in several countries in Asia (Hayes et al. 2008). Pomacea canaliculata and P. maculata may have been introduced into Asian countries from multiple origins (Argentina, Brazil, and Central America) (Mochida 1991; Hayes et al. 2008). Haplotype network analyses of P. canaliculata and P. maculata from Thailand included sequences from the native and introduced range. Haplotype Pc2 and Pm1 were the most widely distributed in the country, and were shared among snail populations in native and non-native countries. The presence of shared haplotypes among different populations from different countries indicates that the species were widely distributed to many countries from their native range. Although this particular snail has a low dispersal ability, man-made ecological transformation and climate change have driven the spread of exotic species like these and their establishment in new areas (Stachowicz et al. 2002; Bardsley and Edwards-Jones 2007). In addition, the frequent agriculture contacts among neighboring countries or regions further facilitates the introduction of Pomacea snails and speeds up their spread into new areas (Cowie 2002; Yusa et al. 2006).

In Thailand, seven haplotypes of P. canaliculata were identified, of which Pc1 was the most widely distributed (11 provinces). For P. maculata, six haplotypes were identified, and Pm20 was the most widely distributed in six provinces. Our findings are similar to those of Yang et al. (2018b), who identified several haplotypes of P. canaliculata from several countries (Yang et al. 2018b). This genetic variation indicates that haplotype diversity is found globally. The genetic variation in P. canaliculata and P. maculata may result from founder effects or bottlenecks (Matsukura et al. 2013). Founder effects may occur when invading propagules contain only a small number of individuals from a successful invasive population. Both effects may result in a low population diversity in invasive populations (Lombaert et al. 2010). In addition, climate change (Byers et al. 2013) and environment factors such as calcium carbonate (White et al. 2007; Perlman 2016), pH (Byers et al. 2013), salinity (Martin and Valentine 2014), and dissolved oxygen (Seuffert and Martín 2009) may affect Pomacea populations in Thailand.

CONCLUSIONS

In conclusion, Angiostrongylus cantonensis had a low infection rate in Pomacea canaliculata in Thailand. The populations of P. canaliculata and P. maculata in this country may have undergone recent expansions. Seven and six haplotypes based on the COI gene were identified from populations of P. canaliculata and P. maculata, respectively. Genetic differentiation in some populations of P. canaliculata may result from genetic drift. The Pomacea population in Thailand may help maintain the A. cantonensis life cycle and may be a potential source of transmission among humans. Our finding answers basic ecological questions about A. cantonensis and its Pomacea host and maps out the genetic diversity of Pomacea in Thailand.

Supplementary materials

Fig. S1.

Third stage larvae of A. cantonensis isolated from Pomacea canaliculata collected from Uttaradit Province of Thailand. It is characterized by two chitinous rods at the anterior end (arrow) being triangular-shaped and half-opened, tail tip slightly curved (arrow-head) (40x magnification under light microscope).

zoolstud-60-031-s001.pdf (193.7KB, pdf)
Table S1.

Pomacea canaliculata and P. maculata sampling locations used in this study.

Table S2.

Genetic distance between populations of P. canaliculata from Thailand with the native and non-native populations based on mitochondrial cytochrome c oxidase I gene sequences.

zoolstud-60-031-s003.pdf (291.2KB, pdf)
Table S3.

Genetic distance between populations of P. maculata from Thailand with the native and non-native populations based on mitochondrial cytochrome c oxidase I gene sequences.

zoolstud-60-031-s004.pdf (192.3KB, pdf)
Table S4.

Forty-five variable sites across the 25 haplotypes of P. canaliculata based on the 282-bp COI sequences.

Table S5.

The P. canaliculata COI sequences from GenBank used in this study.

zoolstud-60-031-s006.pdf (231.9KB, pdf)
Table S6.

Thirty-nine variable sites across the 25 haplotypes of P. maculata based on the 283-bp COI sequences.

zoolstud-60-031-s007.pdf (327.7KB, pdf)
Table S7.

Available COI sequences of P. maculata in GenBank used in this study.

zoolstud-60-031-s008.pdf (229.1KB, pdf)

Acknowledgments

This work was supported by Naresuan University (grant numbers R2562B078 and R2562B079). We thank Professor Dr. Pairot Pramual (Faculty of Science, Maha Sarakham University) for his guidance in analyzing the population genetics of P. canaliculata and P. maculata. We also thank Professor Jorge Aigla, Department of Anatomy, Faculty of Medical Science, Naresuan University for the helpful comments and assistance with the English in the manuscript.

Footnotes

Authors’ contributions: Conceptualization: AD, AT, AV; Data curation: AD, AV; Formal analysis: AD, AT, AV; Funding acquisition: AV; Methodology: AD, PJ, CS, RP, BM, AT, AV; Resources: AT, AV; Supervision: AV; Visualization: AV; Writing –original draft: AD, PJ, CS, BM, RP, AT, AV; Writing –review and editing: AD, PJ, CS, BM, RP, AT, AV.

Competing interests: The authors declare that they have no conflicts of interests.

Availability of data and materials: All relevant data are included in the manuscripts and the supplementary data.

Consent for publication: Not Applicable.

Ethics approval consent to participate: Experi-ments involving the use of animals were approved by the Center for Animal Research of Naresuan University (Project Ethic No: NU-AQ610711), and the biosafety protocols were approved by the Naresuan University Institutional Biosafety Committee (Project No: NUIBC MI 61-08-50).

References

  1. Arfan A, Muhamad R, Omar D, Azwady AN, Manjeri G. 2014. Distribution of two Pomacea spp. in rice fields of Peninsular Malaysia. Annu Res Rev Biol 4:4123–4136. doi:10.9734/ARRB/2014/11398.
  2. Bandelt HJ, Forster P, Rohl A. 1999. Median-joining networks for inferring intraspecific phylogenies. Mol Biol Evol 16:37–48. doi:10.1093/oxfordjournals.molbev.a026036. [DOI] [PubMed]
  3. Bardsley DK, Edwards-Jones G. 2007. Invasive species policy and climate change: social perceptions of environmental change in the Mediterranean. Environ Sci Policy 10:230–242. doi:10.1016/j.envsci.2006.12.002.
  4. Barnes MA, Fordham RK, Burks RL, Hand JJ. 2008. Fecundity of the exotic apple snail, Pomacea insularum. J N Am Benthol Soc 27:738–745. doi:10.1899/08-013.1.
  5. Brandt RAM. 1974. The non-marine aquatic mollusca of Thailand. Archiv fur Molluskenkunde 105:1–423.
  6. Burks RL, Bernatis J, Byers JE, Carter J, Martin CW, McDowell WG, Van Dyke J. 2017. Identity, reproductive potential, distribution, ecology and management of invasive Pomacea maculata in the southern United States. In: Joshi RC, Cowie RH, Sebastian LS (eds) Biology and management of invasive apple snails. Philippine Rice Research Institute (PhilRice), Maligaya, Science City of Munoz, Nueva Ecija, pp. 293–334.
  7. Byers JE, Mcdowell WG, Dodd SR, Haynie RS, Pintor LM, Wilde SB. 2013. Climate and pH predict the potential range of the invasive apple snail (Pomacea insularum) in the Southeastern United States. PLoS ONE 8:e56812. doi:10.1371/journal. pone.0056812. [DOI] [PMC free article] [PubMed]
  8. Chaichana R, Sumpan T. 2015. Environmental tolerance of invasive golden apple snails (Pomacea canaliculata (Lamarck, 1822) and Thai native apple snails (Pila scutata, (Mousson, 1848). Trop Ecol 56:347–355.
  9. Cowie RH. 2002. Apple snails (Ampullariidae) as agricultural pests: their biology, impacts and management. In: Barker GM (ed) Molluscs as crop pests, Wallingford (UK), pp. 145–192.
  10. Cowie RH, Hayes KA, Thiengo SC. 2006. What are apple snails? Confused taxonomy and some preliminary resolution. In: Joshi RC, Sebastian LS (eds) Global Advances in Ecology and Management of Golden Apple Snail, Philippine Rice Research Institute (Nueva Ecija), pp. 3–23.
  11. Eamsohana P. 2006. The rat lungworm Parastrongylus (= Angiostrongylus) cantonensis: parasitology, immunology, eosinophilic meningitis, epidemiology and laboratory diagnosis. Wankaew (IQ) Book Center, Bangkok, Thailand.
  12. Eamsobhana P. 2014. Eosinophilic meningitis caused by Angiostrongylus cantonensis -a neglected disease with escalating importance. Trop Biomed 31:569–578. [PubMed]
  13. Eamsobhana P, Yoolek A, Yong HS. 2010. Effect of Thai ‘koi–hoi’ food flavoring on the viability and infectivity of the third-stage larvae of Angiostrongylus cantonensis (Nematoda: An-giostrongylidae). Acta Trop 113:245–247. doi:10.1016/j.actatropica.2009.11.004. [DOI] [PubMed]
  14. Excoffier L, Lischer HE. 2010. Arlequin suite ver 3.5: a new series of programs to perform population genetics analyses under Linux and Windows. Mol Ecol Resour 10:564–567. doi:10.1111/j.1755-0998.2010.02847.x. [DOI] [PubMed]
  15. Halwart M. 1994. The golden apple snail Pomacea canaliculata in Asian rice farming systems: present impact and future threat. Int J Pest Manage 40:199–206. doi:10.1080/09670879409371882.
  16. Han JF, Zhu YH, Ji WZ, Li Y, Yan Y, Yin M. 2005. Clinical analysis of 25 cases with eosinophilic meningitis. Chin J Epidemiol 26:679.
  17. Havel JE, Bruckerhoff LA, Funkhouser MA, Gemberling A. 2014. Resistance to desiccation in aquatic invasive snails and implications for their overland dispersal. Hydrobiologia 741:89–100. doi:10.1007/s10750-014-1839-z.
  18. Hayes KA, Burks RL, Castro-Vazquez A, Darby PC, Heras H, Martín PR, Qiu JW, Thiengo SC, Vega IA, Wada T, Yusa Y, Burela S, Cadierno MP, Cueto JA, Dellagnola FA, Dreon MS, Frassa MV, Giraud-Billoud M, Godoy MS, Ituarte S, Koch E, Matsukura K, Pasquevich MY, Rodriguez C, Saveanu L, Seuffert ME, Strong EE, Sun J, Tamburi NE, Tiecher MJ, Turner RL, Valentine-Darby PL, Cowie RH. 2015. Insight from an integrated view of the biology of apple snails (Caenogastropoda: Ampullariidae). Malacologia 58:245–302. doi:10.4002/040.058.0209.
  19. Hayes KA, Cowie RH, Thiengo SC, Strong E. 2012. Comparing apples with apples: clarifying the identities of two highly invasive Neotropical Ampullariidae (Caenogastropoda). Zool J Linn Soc 166:723–753. doi:10.1111/j.1096-3642.2012.00867.x.
  20. Hayes KA, Joshi RC, Thiengo SC, Cowie RH. 2008. Out of South America: multiple origins of non-native apple snails in Asia. Divers Distrib 14:701–712. doi:10.1111/j.1472-4642.2008.00483.x.
  21. Hu QA,Zhang Y,Guo YH,Lv S,Xia S,Liu HX,Fang Y,Liu Q, Zhu D, Zhang QM, Yang CL, Lin GY. 2018. Small-scale spatial analysis of intermediate and definitive hosts of Angiostrongylus cantonensis. Infect Dis Poverty 7:100. doi:10.1186/s40249-018-0482-8. [DOI] [PMC free article] [PubMed]
  22. Keawjam RS, Upatham ES. 1990. Shell morphology, reproductive anatomy and genetic patterns of three species of apple snails of the genus Pomacea in Thailand. J Med Appl Malacol 2:45–57.
  23. Kim JR, Wong TM, Curry PA, Yeung NW, Hayes KA, Cowie RH. 2019. Modelling the distribution in Hawaii of Angiostrongylus cantonensis (rat lungworm) in its gastropod hosts. Parasitology 146:42–49. doi:10.1017/S0031182018001026. [DOI] [PubMed]
  24. Kimura M. 1980. A simple method for estimating evolutionary rate of base substitutions through comparative studies of nucleotide sequences. J Mol Evol 16:111–120. doi:10.1007/BF01731581. [DOI] [PubMed]
  25. Kumar S, Stecher G, Tamura K. 2016. MEGA7: Molecular Evolutionary Genetics Analysis Version 7.0 for Bigger Datasets. Mol Biol Evol 33:1870–1874. doi:10.1093/molbev/msw054. [DOI] [PMC free article] [PubMed]
  26. Li LS, Lin JX, Zhang RY, Fang YY, Lin, KX. 2006. A severe infection with Angiostrongylus cantonensis after eating raw slugs. Chin J Parasitol Parasit Dis 24:460–461. [PubMed]
  27. Lin JX, Li YS, Zhu K, Chen BJ, Cheng YZ, Lin JC, Cao Y, Chen RZ. 2003. Epidemiological study on group infection of Angiostrongylus cantonensis in Changle city. Chin J Parasitol Parasit Dis 21:110–112. [PubMed]
  28. Lombaert E, Guillemaud T, Cornuet JM, Malausa T, Facon B, Estoup A. 2010. Bridgehead effect in the worldwide invasion of the biocontrol harlequin ladybird. PLoS ONE 5:e9743. doi:10.1371/journal.pone.0009743. [DOI] [PMC free article] [PubMed]
  29. Lowe S, Browne M, Boudjelas S, De Poorter M. 2000. 100 of the world’s worst invasive alien species a selection from the global invasive species database. In: Invasive Species Specialist Group (ISSG) a specialist group of the species survival commission (SSC) of the world conservation union (IUCN). Auckland, p. 12.
  30. Lv S, Guo YH, Nguyen HM, Sinuon M, Sayasone S, Lo NC, Zhou XN, Andrews JR. 2018. Invasive Pomacea snails as important intermediate hosts of Angiostrongylus cantonensis in Laos, Cambodia and Vietnam: Implications for outbreaks of eosinophilic meningitis. Acta Trop 183:32–35. doi:10.1016/j.actatropica.2018.03.021. [DOI] [PubMed]
  31. Lv S, Zhang Y, Chen SR, Wang LB, Fang W, Chen F, Jiang JY, Li YL, Du ZW, Zhou XN. 2009a. Human angiostrongyliasis outbreak in Dali, China. PLoS Negl Trop Dis 3:e520. doi:10.1371/journal. pntd.0000520. [DOI] [PMC free article] [PubMed]
  32. Lv S, Zhang Y, Liu HX, Hu L, Yang K, Steinmann P, Chen Z, Wang LY, Utzinger J, Zhou XN. 2009b. Invasive snails and an emerging infectious disease: results from the first national survey on Angiostrongylus cantonensis in China. PLoS Negl Trop Dis 3:e368. doi:10.1371/journal.pntd.0000368. [DOI] [PMC free article] [PubMed]
  33. Lv S, Zhang Y, Steinmann P, Zhou XN. 2008. Emerging angiostrongyliasis in mainland China. Emerg Infect Dis 14:161–164. doi:10.3201/eid1401.061529. [DOI] [PMC free article] [PubMed]
  34. Lv S, Zhang Y, Wang XH, Liu HX, Zhu D, Yin WG, Zhou XN. 2006. Experimental study on compatibility of three species of freshwater snails with Angiostrongylus cantonensis. Chin J Parasitol Parasit Dis 24:277–280. [PubMed]
  35. Martin CW, Valentine JF. 2014. Tolerance of embryos and hatchlings of the invasive apple snail Pomacea maculata to estuarine conditions. Aquat Ecol 48:321–326. doi:10.1007/s10452-014-9486-z.
  36. Matsukura K, Okuda M, Cazzaniga NJ, Wada T. 2013. Genetic exchange between two freshwater apple snails, Pomacea canaliculata and Pomacea maculate invading East and Southeast Asia. Biol Invasions 15:2039–2048. doi:10.1007/s10530-013-0431-1.
  37. Matsukura K, Okuda M, Kubota K, Wada T. 2008. Genetic divergence of the genus Pomacea (Gastropoda: Ampullariidae) distributed in Japan, and a simple molecular method to distinguish P. canaliculata and P. insularum. Appl Entomol Zool 43:535–540. doi:10.1303/aez.2008.535.
  38. Mochida O. 1991. Spread of freshwater Pomacea snails (Pilidae, Mollusca) from Argentina to Asia. Micronesica 3:51–62.
  39. Perlman H. 2016. Water hardness. USGS (United States Geological Survey) Water Science School. http://water.usgs.gov/edu/hardness.html. Accessed 20 Jul. 2019.
  40. Pipitgool V, Sithithaworn P, Pongmuttasaya P, Hinz E. 1997. Angiostrongylus infections in rats and snails in northeast Thailand. Southeast Asian J Trop Med Public Health 28:190–193. [PubMed]
  41. Qiu JW, Chan MT, Kwong KL, Sun J. 2011. Consumption, survival and growth in the invasive freshwater snail Pomacea canaliculata: does food freshness matter. J Molluscan Stud 77:189–195. doi:10.1093/mollus/eyr005.
  42. Rawlings TA, Hayes KA, Cowie RH, Collins TM. 2007. The identity, distribution, and impacts of non-native apple snails in the continental United States. BMC Evol Biol 7:97. doi:10.1186/1471-2148-7-97. [DOI] [PMC free article] [PubMed]
  43. Ronquist F, Teslenko M, van der Mark P, Ayres DL, Darling A, Höhna S, Larget B, Liu L, Suchard MA, Huelsenbeck JP. 2012. MrBayes 3.2: efficient Bayesian phylogenetic inference and model choice across a large model space. Syst Biol 61:539–542. doi:10.1093/sysbio/sys029. [DOI] [PMC free article] [PubMed]
  44. Seuffert ME, Martín PR. 2009. Dependence on aerial respiration and its influence on microdistribution in the invasive freshwater snail Pomacea canaliculata (Caenogastropoda, Ampullariidae). Biol Invasions 12:1695–1708. doi:10.1007/s10530-009-9582-5.
  45. Song HM, Hu YC, Wang PX, Mou XD, Li XH, Wang XJ, Luo JR. 2010. Sequencing cytochrome oxidase subunit I of mitochondrial DNA and the taxonomic status of apple snails. Chinese J Zool 45:1–7.
  46. Song L, Wang X, Yang Z, Lv Z, Wu Z. 2016. Angiostrongylus cantonensis in the vector snails Pomacea canaliculata and Achatina fulica in China: a meta-analysis. Parasitol Res 115:913–923. doi:10.1007/s00436-015-4849-5. [DOI] [PubMed]
  47. Stachowicz JJ, Terwin JR, Whitlatch RB, Osman RW. 2002. Linking climate change and biological invasions: ocean warming facilitates nonindigenous species invasions. Proc Natl Acad Sci U S A 99:15497–15500. doi:10.1073/pnas.242437499. [DOI] [PMC free article] [PubMed]
  48. Tesana S, Srisawangwong T, Sithithaworn P, Laha T. 2008. Angiostrongylus cantonensis: experimental study on the susceptibility of apple snails, Pomacea canaliculata compared to Pila polita. Exp Parasitol 118:531–535. doi:10.1016/j.exppara.2007.11.007. [DOI] [PubMed]
  49. Tesana S, Srisawangwong T, Sithithaworn P, Laha T, Andrews R. 2009. Prevalence and intensity of infection with third stage larvae of Angiostrongylus cantonensis in mollusks from northeast Thailand. Am J Trop Med Hyg 80:983–987. [PubMed]
  50. Thiengo SC, Borda CE, Barros Araujo JL. 1993. On Pomacea canaliculata (Lamarck, 1882) (Mollusca; Pilidae: Ampullariidae). Mem Inst Oswaldo Cruz Rio de Janeiro 88:67–71.
  51. Tujan MA, Fontanilla IK, Paller VG. 2016. Vectors and spatial patterns of Angiostrongylus cantonensis in selected rice-farming villages of Muñoz, Nueva Ecija, Philippines. J Parasitol Res 2016:3085639. doi:10.1155/2016/3085639. [DOI] [PMC free article] [PubMed]
  52. A, Polsut W, Fukruksa C, Yimthin T, Thanwisai A, Dekumyoy P. 2016a. Levels of infection with the lungworm Angiostrongylus cantonensis in terrestrial snails from Thailand, with Cryptozona siamensis as a new intermediate host. J Helminthol 90:737–741. doi:10.1017/S0022149X15001042. [DOI] [PubMed]
  53. Vitta A, Srisongcram N, Thiproaj J, Wongma A, Polsut W, Fukruksa C, Yimthin T, Mangkit B, Thanwisai A, Dekumyoy P. 2016b. Phylogeny of Angiostrongylus cantonensis in Thailand based on cytochrome c oxidase subunit I gene sequence. Southeast Asian J Trop Med Public Health 47:377–386.
  54. Wang JJ, Chung LY, Lin RJ, Lee JD, Lin CW, Yen CM. 2011. Eosinophilic meningitis risk associated with raw Ampullarium canaliculatus snails consumption. Kaohsiung J Med Sci 27:184–189. doi:10.1016/j.kjms.2010.12.013. [DOI] [PMC free article] [PubMed]
  55. Wei LP, Zheng KW, Wei Y. 2005 Clinical nursing of 9 cases with angiostrongyliasis. J Clin Nurs 4:21–22.
  56. White M, Chejlava M, Fried B, Sherma J. 2007. The concentration of calcium carbonate in shells of freshwater snails. Am Malacol Bull 22:139–142. doi:10.4003/0740-2783-22.1.139.
  57. Xu HG, Qiang S, Genovesi P, Ding H, Wu J, Meng L, Han ZM, Miao JL, Hu BS, Guo JY, Sun HY, Huang C, Lei JC, Le ZF, Zhang XP, He SP, Wu Y, Zheng Z, Chen L, Jarosik V, Pysek P. 2012. An inventory of invasive alien species in China. NeoBiota 15:1–26. doi:10.3897/neobiota.15.3575.
  58. Yang FZ, Zhang YZ, Tu ZP, Xu LS. 2004. Investigation of an outbreak of angiostrongyliasis presumably caused by consumption of snail meal. Strait J Prev Med 10:44–45.
  59. Yang Q, Liu S, He C, Cowie RH, Yu X, Hayes KA. 2018a. Invisible apple snail invasions: importance of continued vigilance and rigorous taxonomic assessments. Pest Manag Sci 75:1277–1286. doi:10.1002/ps.5241. [DOI] [PubMed]
  60. Yang QQ, Liu SW, He C, Yu XP. 2018b. Distribution and the origin of invasive apple snails, Pomacea canaliculata and P. maculata (Gastropoda: Ampullariidae) in China. Sci Rep 8:1185. doi:10.1038/s41598-017-19000-7. [DOI] [PMC free article] [PubMed]
  61. Yang QQ, Yu XP. 2019. A new species of apple snail in the genus Pomacea (Gastropoda: Caenogastropoda: Ampullariidae). Zool Stud 58:e13. doi:10.6620/ZS.2019.58-13. [DOI] [PMC free article] [PubMed]
  62. Yang TB, Wu ZD, Lun ZR. 2013. The apple snail Pomacea canaliculata, a novel vector of the rat lungworm, Angiostrongylus cantonensis: its introduction, spread, and control in China. Hawaii J Med Public Health 72(6, Suppl. 2):23–25. [PMC free article] [PubMed]
  63. Yii CY. 1976. Clinical observations on eosinophilic meningitis and meningoencephalitis caused by Angiostrongylus cantonensis on Taiwan. Am J Trop Med Hyg 25:233–249. doi:10.4269/ajtmh.1976.25.233. [DOI] [PubMed]
  64. Yusa Y, Sugiura N, Wada T. 2006. Predatory potential of freshwater animals on an invasive agricultural pest, the apple snail Pomacea canaliculata (Gastropoda: Ampullariidae), in southern Japan. Biol Invasions 8:137–147. doi:10.1007/s10530-004-1790-4.
  65. Zheng RY, Jin R, Lin BC, Pan CW, Xue DY. 2001. Probing and demonstrating etiological factors for the outbreak of angiostrongyliasis cantonensis in Wenzhou. Sh J Prev Mede 13:105–107.

Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Supplementary Materials

Fig. S1.

Third stage larvae of A. cantonensis isolated from Pomacea canaliculata collected from Uttaradit Province of Thailand. It is characterized by two chitinous rods at the anterior end (arrow) being triangular-shaped and half-opened, tail tip slightly curved (arrow-head) (40x magnification under light microscope).

zoolstud-60-031-s001.pdf (193.7KB, pdf)
Table S1.

Pomacea canaliculata and P. maculata sampling locations used in this study.

zoolstud-60-031-s002.pdf (238KB, pdf)
Table S2.

Genetic distance between populations of P. canaliculata from Thailand with the native and non-native populations based on mitochondrial cytochrome c oxidase I gene sequences.

zoolstud-60-031-s003.pdf (291.2KB, pdf)
Table S3.

Genetic distance between populations of P. maculata from Thailand with the native and non-native populations based on mitochondrial cytochrome c oxidase I gene sequences.

zoolstud-60-031-s004.pdf (192.3KB, pdf)
Table S4.

Forty-five variable sites across the 25 haplotypes of P. canaliculata based on the 282-bp COI sequences.

zoolstud-60-031-s005.pdf (345KB, pdf)
Table S5.

The P. canaliculata COI sequences from GenBank used in this study.

zoolstud-60-031-s006.pdf (231.9KB, pdf)
Table S6.

Thirty-nine variable sites across the 25 haplotypes of P. maculata based on the 283-bp COI sequences.

zoolstud-60-031-s007.pdf (327.7KB, pdf)
Table S7.

Available COI sequences of P. maculata in GenBank used in this study.

zoolstud-60-031-s008.pdf (229.1KB, pdf)

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