Identification of trans-genus biomarkers for early diagnosis of intestinal schistosomiasis and progression of gut pathology in a mouse model using metabolomics.

Schistosomiasis is one of the most devastating human diseases worldwide. The disease is caused by six species of Schistosoma blood fluke; five of which cause intestinal granulomatous inflammation and bleeding. The current diagnostic method is inaccurate and delayed, hence, biomarker identification using metabolomics has been applied. However, previous studies only investigated infection caused by one Schistosoma spp., leaving a gap in the use of biomarkers for other species. No study focused on understanding the progression of intestinal disease. Therefore, we aimed to identify early gut biomarkers of infection with three Schistosoma spp. and progression of intestinal pathology. We infected 3 groups of mice, 3 mice each, with Schistosoma mansoni, Schistosoma japonicum or Schistosoma mekongi and collected their feces before and 1, 2, 4 and 8 weeks after infection. Metabolites in feces were extracted and identified using mass spectrometer-based metabolomics. Metabolites were annotated and analyzed with XCMS bioinformatics tool and Metaboanalyst platform. From >36,000 features in all conditions, multivariate analysis found a distinct pattern at each time point for all species. Pathway analysis reported alteration of several lipid metabolism pathways as infection progressed. Disturbance of the glycosaminoglycan degradation pathway was found with the presence of parasite eggs, indicating involvement of this pathway in disease progression. Biomarkers were discovered using a combination of variable importance for projection score cut-off and receiver operating characteristic curve analysis. Five molecules met our criteria and were present in all three species: 25-hydroxyvitamin D2, 1α-hydroxy-2ß-(3-hydroxypropoxy) vitamin D3, Ganoderic acid Md, unidentified feature with m/z 455.3483, and unidentified feature with m/z 456.3516. These molecules were proposed as trans-genus biomarkers of early schistosomiasis. Our findings provide evidence for disease progression in intestinal schistosomiasis and potential biomarkers, which could be beneficial for early detection of this disease.

Comprehensive analysis of miRNA profiling in Schistosoma mekongi across life cycle stages.

Schistosoma mekongi, a significant schistosome parasite, has various life stages, including egg, cercaria, female, and male, that play crucial roles in the complex life cycle. This study aimed to explore the microRNA (miRNA) profiles across these developmental stages to understand their potential functions and evolutionary significance, which have not been studied. Pre-processed sequencing reads of small RNA (sRNA) were obtained, and annotations were performed against the S. japonicum reference miRNA database. Results indicated marked variations in miRNA profiles across different life stages, with notable similarities observed between female and male S. mekongi. Principal Coordinate Analysis (PCoA) and unsupervised clustering revealed distinct miRNA signatures for each stage. Gene ontology (GO) analysis unveiled the potential roles of these miRNAs in various biological processes. The differential expression of specific miRNAs was prominent across stages, suggesting their involvement in crucial developmental processes. Furthermore, orthologous miRNA analysis against various worm species revealed distinct presence-absence patterns, providing insights into the evolutionary relationships of these miRNAs. In conclusion, this comprehensive investigation into the miRNA profiles of S. mekongi offers valuable insights into the functional and evolutionary aspects of miRNAs in schistosome biology.

Discovery of Schistosoma mekongi circulating proteins and antigens in infected mouse sera.

Schistosomiasis is a neglected tropical disease caused by an infection of the parasitic flatworms schistosomes. Schistosoma mekongi is a restricted Schistosoma species found near the Mekong River, mainly in southern Laos and northern Cambodia. Because there is no vaccine or effective early diagnosis available for S. mekongi, additional biomarkers are required. In this study, serum biomarkers associated with S. mekongi-infected mice were identified at 14-, 28-, 42-, and 56-days post-infection. Circulating proteins and antigens of S. mekongi in mouse sera were analyzed using mass spectrometry-based proteomics. Serine protease inhibitors and macrophage erythroblast attacher were down-regulated in mouse sera at all infection timepoints. In addition, 54 circulating proteins and 55 antigens of S. mekongi were identified. Notable circulating proteins included kyphoscoliosis peptidase and putative tuberin, and antigens were detected at all four infection timepoints, particularly in the early stages (12 days). The putative tuberin sequence of S. mekongi was highly similar to homologs found in other members of the genus Schistosoma and less similar to human and murine sequences. Our study provided the identity of promising diagnostic biomarkers that could be applicable in early schistosomiasis diagnosis and vaccine development.

Untargeted serum metabolomic profiling for early detection of Schistosoma mekongi infection in mouse model.

Mekong schistosomiasis is a parasitic disease caused by blood flukes in the Lao People's Democratic Republic and in Cambodia. The standard method for diagnosis of schistosomiasis is detection of parasite eggs from patient samples. However, this method is not sufficient to detect asymptomatic patients, low egg numbers, or early infection. Therefore, diagnostic methods with higher sensitivity at the early stage of the disease are needed to fill this gap. The aim of this study was to identify potential biomarkers of early schistosomiasis using an untargeted metabolomics approach. Serum of uninfected and S. mekongi-infected mice was collected at 2, 4, and 8 weeks post-infection. Samples were extracted for metabolites and analyzed with a liquid chromatography-tandem mass spectrometer. Metabolites were annotated with the MS-DIAL platform and analyzed with Metaboanalyst bioinformatic tools. Multivariate analysis distinguished between metabolites from the different experimental conditions. Biomarker screening was performed using three methods: correlation coefficient analysis; feature important detection with a random forest algorithm; and receiver operating characteristic (ROC) curve analysis. Three compounds were identified as potential biomarkers at the early stage of the disease: heptadecanoyl ethanolamide; picrotin; and theophylline. The levels of these three compounds changed significantly during early-stage infection, and therefore these molecules may be promising schistosomiasis markers. These findings may help to improve early diagnosis of schistosomiasis, thus reducing the burden on patients and limiting spread of the disease in endemic areas.

Metabolomics reveal alterations in arachidonic acid metabolism in Schistosoma mekongi after exposure to praziquantel.

BACKGROUND: Mekong schistosomiasis is a parasitic disease caused by the blood-dwelling fluke Schistosoma mekongi. This disease contributes to human morbidity and mortality in the Mekong region, posing a public health threat to people in the area. Currently, praziquantel (PZQ) is the drug of choice for the treatment of Mekong schistosomiasis. However, the molecular mechanisms of PZQ action remain unclear, and Schistosoma PZQ resistance has been reported occasionally. Through this research, we aimed to use a metabolomic approach to identify the potentially altered metabolic pathways in S. mekongi associated with PZQ treatment. METHODOLOGY/PRINCIPAL FINDINGS: Adult stage S. mekongi were treated with 0, 20, 40, or 100 µg/mL PZQ in vitro. After an hour of exposure to PZQ, schistosome metabolites were extracted and studied with mass spectrometry. The metabolomic data for the treatment groups were analyzed with the XCMS online platform and compared with data for the no treatment group. After low, medium (IC50), and high doses of PZQ, we found changes in 1,007 metabolites, of which phosphatidylserine and anandamide were the major differential metabolites by multivariate and pairwise analysis. In the pathway analysis, arachidonic acid metabolism was found to be altered following PZQ treatment, indicating that this pathway may be affected by the drug and potentially considered as a novel target for anti-schistosomiasis drug development. CONCLUSIONS/SIGNIFICANCE: Our findings suggest that arachidonic acid metabolism is a possible target in the parasiticidal effects of PZQ against S. mekongi. Identifying potential targets of the effective drug PZQ provides an interesting viewpoint for the discovery and development of new agents that could enhance the prevention and treatment of schistosomiasis.

Identification of Low Molecular Weight Proteins and Peptides from Schistosoma mekongi Worm, Egg and Infected Mouse Sera.

Schistosoma mekongi is found in the lower Mekong river region and causes schistosomiasis. Low sensitivity of diagnosis and development of drug resistance are problems to eliminate this disease. To develop novel therapies and diagnostics for S. mekongi, the basic molecular biology of this pathogen needs to be explored. Bioactive peptides have been reported in several worms and play important roles in biological functions. Limited information is available on the S. mekongi peptidome. Therefore, this study aimed to identify S. mekongi peptides using in silico transcriptome mining and mass spectrometry approaches. Schistosoma peptide components were identified in adult worms, eggs, and infected mouse sera. Thirteen neuropeptide families were identified using in silico predictions from in-house transcriptomic databases of adult S. mekongi worms. Using mass spectrometry approaches, 118 peptides (from 54 precursor proteins) and 194 peptides (from 86 precursor proteins) were identified from adult worms and eggs, respectively. Importantly, eight unique peptides of the S. mekongi ubiquitin thioesterase, trabid, were identified in infected mouse sera 14, 28, and 56 days after infection. This protein may be a potential target for diagnosis of schistosomiasis. The S. mekongi peptide profiles determined in this study could be used for further drug and diagnostic development.

Effect of Praziquantel on Schistosoma mekongi Proteome and Phosphoproteome.

Schistosoma mekongi causes schistosomiasis in southeast Asia, against which praziquantel (PZQ) is the only treatment option. PZQ resistance has been reported, thus increasing the requirement to understand mechanism of PZQ. Herein, this study aimed to assess differences in proteome and phosphoproteome of S. mekongi after PZQ treatment for elucidating its action. Furthermore, key kinases related to PZQ effects were predicted to identify alternative targets for novel drug development. Proteomes of S. mekongi were profiled after PZQ treatment at half maximal inhibitory concentration and compared with untreated worms. A total of 144 proteins were differentially expressed after treatment. In parallel, immunohistochemistry indicated a reduction of phosphorylation, with 43 phosphoproteins showing reduced phosphorylation, as identified by phosphoproteomic approach. Pathway analysis of mass spectrometric data showed that calcium homeostasis, worm antigen, and oxidative stress pathways were influenced by PZQ treatment. Interestingly, two novel mechanisms related to protein folding and proteolysis through endoplasmic reticulum-associated degradation pathways were indicated as a parasiticidal mechanism of PZQ. According to kinase-substrate predictions with bioinformatic tools, Src kinase was highlighted as the major kinase related to the alteration of phosphorylation by PZQ. Interfering with these pathways or applying Src kinase inhibitors could be alternative approaches for further antischistosomal drug development.

Proteomic analysis of adult Schistosoma mekongi somatic and excretory-secretory proteins.

Schistosoma mekongi is a causative agent of human schistosomiasis. There is limited knowledge of the molecular biology of S. mekongi and very few studies have examined drug targets, vaccine candidates and diagnostic biomarkers for S. mekongi. To explore the biology of S. mekongi, computational as well as experimental approaches were performed on S. mekongi males and females to identify excretory-secretory (ES) proteins and proteins that are differentially expressed between genders. According to bioinformatic prediction, the S. mekongi ES product was approximately 4.7% of total annotated transcriptome sequences. The classical secretory pathway was the main process to secrete proteins. Mass spectrometry-based quantification of male and female adult S. mekongi proteins was performed. We identified 174 and 156 differential expression of proteins in male and female worms, respectively. The dominant male-biased proteins were involved in actin filament-based processes, microtubule-based processes, biosynthetic processes and homeostatic processes. The major female-biased proteins were related to biosynthetic processes, organelle organization and signal transduction. An experimental approach identified 88 proteins in the S. mekongi secretome. The S. mekongi ES proteins mainly contributed to nutrient uptake, essential substance supply and host immune evasion. This research identifies proteins in the S. mekongi secretome and provides information on ES proteins that are differentially expressed between S. mekongi genders. These findings will contribute to S. mekongi drug and vaccine development. In addition, the study enhances our understanding of basic S. mekongi biology.

Phosphoproteomics analysis of male and female Schistosoma mekongi adult worms.

Schistosoma mekongi is one of the major causative agents of human schistosomiasis in Southeast Asia. Praziquantel is now the only drug available for treatment and there are serious concerns about parasite resistance to it. Therefore, a dataset of schistosome targets is necessary for drug development. Phosphorylation regulates signalling pathways to control cellular processes that are important for the parasite's growth and reproduction. Inhibition of key phosphoproteins may reduce the severity of schistosomiasis. In this research, we studied the phosphoproteomes of S. mekongi male and female adult worms by using computational and experimental approaches. Using a phosphoproteomics approach, we determined that 88 and 44 phosphoproteins were male- and female-biased, respectively. Immunohistochemistry using anti-phosphoserine antibodies demonstrated phosphorylation on the tegument and muscle of male S. mekongi worms and on the vitelline gland and gastrointestinal tract of female worms. This research revealed S. mekongi sex-dependent phosphoproteins. Our findings provide a better understanding of the role of phosphorylation in S. mekongi and could be integrated with information from other Schistosoma species to facilitate drug and vaccine development.

Proteomic and immunomic analysis of Schistosoma mekongi egg proteins.

Schistosomiasis remains a global health problem. In the Mekong river basin, approximately 80,000 people are at risk of infection by Schistosoma mekongi. The parasite's eggs become entrapped in the host's organs and induce massive inflammation, contributing to the pathogenesis of schistosomiasis. In addition, egg antigens are important in circumoval precipitin tests (COPTs) and other diagnostic techniques. Little is known regarding the egg proteins of S. mekongi, and so we applied immunoblotting and mass spectrometry-based proteomic approaches to study these proteins and their antigenicity. A total of 360 unique proteins were identified in S. mekongi eggs using proteomic analyses. The major protein components of S. mekongi eggs were classified into several groups by functions, including proteins of unknown function, structural proteins, and regulators of transcription and translation. The most abundant proteins in S. mekongi eggs were antioxidant proteins, potentially reflecting the need to neutralize reactive oxidative species released from host immune cells. Immunomic analyses revealed that only DNA replication factor Cdt1 and heat shock protein 70 overlap between the proteins recognized by sera of infected mice and humans, illustrating the challenges of knowledge transfer from animal models to human patients. Forty-one immunoreactive protein bands were recognized by either mouse or patient sera. Phosphoglycerate kinase, fructose-1,6-bisphosphate aldolase and elongation factor 1 appeared to be interesting immunogens of S. mekongi eggs as these proteins were recognized by polyclonal IgMs and IgGs in patient sera. Our findings provide new information on the protein composition of S. mekongi eggs as well as the beginnings of a S. mekongi immunogen dataset. These data may help us better understand the pathology of schistosomiasis as well as natural antibody responses against S. mekongi egg proteins, both of which may be useful in including S. mekongi to other schistosoma diagnostic, vaccine and immunotherapy development.

Molecular characterization of serine protease inhibitor isoform 3, SmSPI, from Schistosoma mansoni.

Serine protease inhibitors, known as serpins, are pleiotropic regulators of endogenous and exogenous proteases, and molecule transporters. They have been documented in animals, plants, fungi, bacteria, and viruses; here, we characterize a serpin from the trematode platyhelminth Schistosoma mansoni. At least eight serpins have been found in the genome of S. mansoni, but only two have characterized molecular properties and functions. Here, the function of S. mansoni serpin isoform 3 (SmSPI) was analyzed, using both computational and molecular biological approaches. Phylogenetic analysis showed that SmSPI was closely related to Schistosoma haematobium serpin and Schistosoma japonicum serpin B10. Structure determined in silico confirmed that SmSPI belonged to the serpin superfamily, containing nine α-helices, three ß-sheets, and a reactive central loop. SmSPI was highly expressed in schistosomules, predominantly in the head gland, and in adult male and female with intensive accumulation on the spines, which suggests that it may have a role in facilitating intradermal and intravenous survival. Recombinant SmSPI was overexpressed in Escherichia coli; the recombinant protein was of the same size (46 kDa) as the native protein. Immunological analysis suggested that mice infected with S. mansoni responded to rSmSPI at 8 weeks postinfection (wpi) but not earlier. The inhibitory activity of rSmSPI was specific to chymotrypsin but not trypsin, neutrophil elastase, and porcine pancreatic elastase. Elucidating the biological and physiological functions of SmSPI as well as other serpins will lead to further understanding of host-parasite interaction machinery that may provide novel strategies to prevent and control schistosomiasis in the future.

Schistosoma mekongi cathepsin B and its use in the development of an immunodiagnosis.

Schistosomiasis mekongi is one of the most important human parasitic diseases caused by Schistosoma mekongi in South-east Asia. The endemic area is the Mekong River sub-region from Laos to Cambodia. This parasite also infects dogs and pigs which are its alternative host species. Currently, the lack of reliable rapid diagnosis makes it difficult to monitor the infection and spreading of the disease. In this study, we screened the antigens of the parasite with sera of infected mice using Western blotting and identified proteins of interest with LC-MS/MS to obtain potential candidate proteins for diagnostic development. This assay yielded 2 immunoreactive bands at molecular masses of 31 and 22kDa. The 31kDa protein was the major band identified as cathepsin B, and its gene was cloned to obtain a full cDNA sequence (SmekCatB). The cDNA consisted of 1123bp and its longest reading frame encoded for 342 amino acids with some putative post translation modifications. The recombinant SmekCatB (rSmekCatB) with hexahistidine tag at the C-terminus was expressed in Escherichia coli and purified by Ni-NTA resin under denaturing conditions. The rSmekCatB reacted with sera of S. mekongi-infected mice. Indirect ELISA using rSmekCatB as the antigen to detect mouse antibodies, revealed a sensitivity of 91.67% for schistosomiasis mekongi and the specificity of 100%. Our data suggested that SmekCatB is one of the most promising parasitic antigens that could be used for the diagnosis of S. mekongi infection.

MALACOLOGICAL INVESTIGATION OF THE FULLY OPERATIONAL NAM THEUN 2 HYDROELECTRIC DAM PROJECT IN KHAMMOUANE PROVINCE, CENTRAL LAO PDR.

We conducted a malacological investigation in four districts of the Nam Theun 2 (NT2) hydroelectric dam project area, Khammouane Province, central Lao PDR (Nakai, Gnommalath, Mahaxai and Xe Bang Fai), after the first and second years of full operation in March 2010 and November 2011 to determine health risks for humans. A total 10,863 snail specimens (10 families/23 species) from 57 sampling stations and 12,902 snail specimens (eight families/21 species) from 66 sampling stations were collected in 2010 and 2011, respectively. Neotricula aperta (gamma race), the intermediate host for Schistosoma mekongi, was found in large numbers (5,853 specimens) in 2010 in Nam Gnom (downstream) at Station 25 (Mueang Gnommalath: Gnommalath District) and in fewer numbers (170 specimens) at Station 26 (Ban Thathod: Gnommalath District). In 2011, significantly fewer numbers (434 specimens) of N. aperta were found at Station 25. No snails were found to be infected with S. mekongi; however, 3.6% and 0.45% of Bithynia (D.). s. goniomphalos specimens collected were found to be infected with Opisthorchis viverrini (human liver fluke) during 2010 and 2011, respectively. Pomacea canaliculata, the rice crop pest, the intermediate host of Angiostrongylus (Parastrongylus) cantonensis, was found in the greatest numbers during 2010 and 2011; the prevalence increased significantly from 1.3% in 2010 to 53.3% in 2011. We also found seasonal variation in snail populations in terms of abundance and diversity. The snail fauna and risk for transmission of parasitic diseases need to be monitored continuously to evaluate the long-term impact of the dam project.

A new population and habitat for Neotricula aperta in the Mekong river of northeastern Thailand: a DNA sequence-based phylogenetic assessment confirms identifications and interpopulation relationships.

Neotricula aperta (Gastropoda: Pomatiopsidae), the snail intermediate host of Schistosoma mekongi, is found in Cambodia, Laos, and Thailand. We update information on the distribution of this species in the Mekong River and its tributary, the Mun River, in Thailand. DNA sequences of a portion of the mitochondrial cytochrome c oxidase subunit 1 were obtained from N. aperta collected from different locations and used to confirm species and strain identities. Specimens of the ß-strain were found in the Mun River, whereas specimens of the γ-strain were found in the Mekong River. The γ-strain (with molecular confirmation of identity) is newly reported from Nong Khai Province, where it occurred in a habitat novel for this species: under paving slabs instead of under natural bed rocks, where agal aufwuchs is extensively located on the islet in the middle of the Mekong River. The new location is approximate 400 km upstream from the nearest previously known site for this species.

Snails and trematode infection after Indian Ocean tsunami in Phang-Nga Province, southern Thailand.

The tsunami and non-tsunami affected areas of Takua Pa District, Phang-Nga Province were investigated for fresh- and brackish-water snails that transmit human parasitic diseases during 2006 and 2007. Among 46 snail species found, 17 species of 8 families were freshwater snails, 28 species of another 7 families were brackish-water snails, and 1 species was a land snail. Of these species, 11 freshwater snails, 4 brackish-water snails and 1 land snail were of medical importance. The fresh-water snails were Pomacea canaliculata, Pila angelica, P. gracilis, P. polita, Filopaludina (S.) martensi, F. (F.) s. polygramma, Melanoides tuberculata, Indoplanorbis exuxtus, Radix rubiginosa, Helicorbis umbilicalis, Gyraulus convexiusculus. Four brackish-water snails were Cerithidea cingulata, C. djadjarensis, C. alata, Sermyla riqueti and Achatina fulica was the land snail. I. exutus, M. tuberculata and F. (F.) s. polygramma harbored Xiphidio, Microcercus, Furocercus, Echinostome cercariae, and cercaria without eyespots or tail with hair. Three species of brackish-water snails, Cerithidia cingulata, C. djadjariensis, and C. alata presented with 6 types of trematode cercariae and rediae. Knowledge of medically important snails and their parasitic diseases, and prevention were given to Takua Pa people by poster, pamphlets and broadcasting through community radio.

Food behavior and folate status of hill-tribe schoolchildren and women of childbearing age on the northern border of Thailand.

An insight into the folate nutritional status of the population is important from a public health perspective. The protective effect of folate against neural tube defects (NTDs) is widely recognized. To assess the health and nutritional status, especially folate status, of vulnerable hill-tribe groups, a cross-sectional study was conducted on 197 schoolchildren and 136 women of childbearing age in Chaloem Phra Kiat District, Nan Province, Thailand. The nutritional status of the study group was investigated by dietary survey, and blood samples were taken to determine hematocrit, protein, and serum and red blood cell folate. Anthropometric measurements were taken to assess body size, composition and nutritional indexes. The health and nutritional status of the hill-tribe schoolchildren and women of childbearing age were found to be unacceptable, particularly inregard to folate status, which was indicated by low folate levels found in the blood samples, and in the intake of this micronutrient.

Intertidal snail-trematode communities on the southern Thailand before and after the South Asia tsunami.

Intertidal snail-trematode communities in southern Thailand were examined before and after the South Asia tsunami. Infection rates and species diversity of cercaria in the host snail Cerithidea in tidal zones did not change significantly from one year before to one month after the tsunami. However, the host snails C. quadrata, C. alata and C. obtusa disappeared from greatly damaged sites. It is important to follow up on the intertidal snail-trematode community recovery process after destruction of the intertidal ecosystem.

Freshwater mollusks at designated areas in eleven provinces of Thailand according to the water resource development projects.

The study was conducted at 75 collecting loci in 15 districts of 11 provinces in Thailand during 1999-2004. A total of 12,079 live mollusks were collected, 11,874 were snails and 205 were clams. The snails were comprised of 39 species and classified into 9 families: Ampullariidae, Bithyniidae, Buccinidae, Potamiopsidae, Stenothyridae, Thiaridae, Viviparidae, Planorbidae and Lymnaeidae. The clams were comprised of 14 species classified into 2 families: Amblemidae and Corbiculidae. Fifteen species were medically important snails: Pomacea canaliculata, Pila ampullacea, P. pesmei, P. polita, Bithynia (Digoniostoma) funiculata, B. (D.) siamensis goniomphalos, B. (D.) s. siamensis, Filopaludina (Siamopaludina) martensi martensi, F. (Filopaludina) sumatrensis polygramma, Melanoides tuberculata, Tarebia granifera, Helicorbis umbilicalis, Gyraulus convexiusculus, Indoplanorbis exustus and Radix rubiginosa. Of these 3 snail species harbored trematode cercariae. I. exustus harbored Echinostoma malayanum, Xiphidio and Schistosoma spindale, and R. rubiginosa and B. (D.) siamensis goniomphalos harbored Xiphidio and intestinal flukes, respectively.

Health and nutrition survey of tsunami victims in Phang-Nga Province, Thailand.

The post-tsunami health and nutritional statuses of survivors were surveyed three months after the disaster struck. Non-participant observations and questionnaires were used to study the effects of the disaster on their lifestyles and health while residing in temporary shelters provided by the government and private donors. Anthropometrics were measured and dietary surveys conducted to elicit nutritional status. Our findings indicated good management of drinking water in the temporary shelters. Toilet construction and water supply were adequate, but wastewater and sewage systems were poorly managed. The study group still suffered from injuries after the disaster, and complained of back pain, stress, and sleep disorders. Most in the study group had unsatisfactory health behaviors, and obesity was an increasing problem among female participants.

Malacological survey in Phang-Nga Province, southern Thailand, pre- and post-Indian Ocean tsunami.

Three malacological surveys were conducted in the Takua Pa District of Phang-Nga Province, southern Thailand, before and after the Indian Ocean Tsunami disaster. Twenty-nine species of fresh- and brackish-water snails were found, in which 10 species of freshwater snails were present, including live Pila polita; 8 species were of medical importance. Two brackish-water snails, Nerita articulata and Littorinopsis scabra, were absent after the tsunami disaster, while brackish-water Cerithidea cingulata and C. djadjariensis harbored 9 types of trematode cercariae.