Distribution of Blastocystis subtypes isolated from various animal hosts in Thailand.

Blastocystis is a parasitic protist of a variety of hosts, including humans. Mapping the distribution of Blastocystis and its genetic variants across different host species can help us understand the epidemiology of this organism and its role in health and disease. This study aimed to identify subtypes of Blastocystis detected in different animal hosts in Thailand. A total of 825 fecal samples belonging to 18 vertebrate orders, 36 families, 68 genera, and 80 species were collected. Of these, 111 specimens were Blastocystis-positive by culture. Seventy-nine samples were subjected to small subunit (SSU) ribosomal DNA amplification by PCR, and reliable subtype data were obtained for 61 specimens. At least 14 subtypes (ST), namely ST1 to ST10, ST14/ST24/ST25 complex, ST23, ST26, and ST29 were detected. In addition, Blastocystis was found in tortoises. ST1 (3.2%) and ST5 (11.5%) were found in pigs, ST2 (1.6%) and ST3 (3.2%) in non-human primates, ST4 (14.7%) in rodents and ruminants, ST6 (4.9%), ST7 (30%), ST9 (1.6%), and ST29 (1.6%) in birds, ST8 (6.6%) in Green peafowl and East Asian Porcupine, and ST10 (4.9%), ST14/ST24/ST25 (9.8%), ST23 (1.6%) and ST26 (1.6%) in ruminants. The sequence recovered from the elongated tortoises (Indotestudo elongata) (3.2%) was phylogenetically placed within the reptilian cluster of Blastocystis, for which no subtype system is available yet. Of note, we did not obtain Blastocystis sequences from any of the many canids and felids sampled in the study, and our data are in support of host specificity of Blastocystis, according to both colonization and subtype distribution.

Genetic structure and evidence for coexistence of three taxa of Bithynia (Gastropoda: Bithyniidae), the intermediate host of Opisthorchis viverrini sensu lato (Digenea: Opisthorchiidae) in Thailand examined by mitochondrial DNA sequences analyses.

The freshwater snails, Bithynia are the first intermediate hosts of the liver fluke, Opisthorchis viverrini, the causative agent of cholangiocarcinoma (CCA) in Southeast Asia. In Thailand, there are three traditionally recognized taxa of Bithynia: Bithynia funiculata; B. siamensis siamensis; B. s. goniomphalos. This study examines the geographical distribution and genetic structure of Bithynia species from five previously reported water catchments and six new catchments in Thailand. Of these, three new catchments Kok, Wang, and Nan are from the north and the remaining three new catchments are Phetchaburi, Prachuap Khiri Khan Coast, Mae Klong from the west of Thailand. We sampled 291 Bithynia snails from 52 localities in 11 catchment systems in the northern, western and central regions of Thailand. Mitochondrial cytochrome c oxidase subunit 1 (COI) and 16S ribosomal DNA (16S rDNA) sequences were used to examine genetic diversity of Bithynia snails which revealed 200 and 27 haplotypes of COI and 16S rDNA, respectively. However, as 16S rDNA is a conserved gene, it is not suitable to distinguish Bithynia at the species and sub-species levels in our study. The phylogenetic tree and haplotype network analyses included sequences of COI from GenBank. B. funiculata was found only in the north of Thailand and the genetic structure did not differ among populations. Genetic differentiation (ΦST) analyses showed that B. s. goniomphalos contained three distinct lineages. Lineage I contained B. s. goniomphalos from the vast majority of catchment systems in Thailand and Lao PDR. Lineage II contained all B. s. goniomphalos from the Prachin Buri and Bang Pakong catchment systems in eastern and central Thailand, including samples from all catchment systems in Cambodia. While lineage III contained B. s. goniomphalos from the Songkram and Nam Kam catchment systems in Thailand and the Nam Ngum and Huai Som Pak catchment systems in Lao PDR. Furthermore, results showed that all samples of B. s. siamensis were classified into one lineage and placed phylogenetically between B. s. goniomphalos lineages I and II. Thus, the taxonomic status of B. s. goniomphalos and B. s. siamensis requires reassessment, and they should be reclassified as belonging to the species complex "Bithynia siamensis sensu lato".

Description, molecular characteristics and Wolbachia endosymbionts of Onchocerca borneensis Uni, Mat Udin & Takaoka n. sp. (Nematoda: Filarioidea) from the Bornean bearded pig Sus barbatus Müller (Cetartiodactyla: Suidae) of Sarawak, Malaysia.

BACKGROUND: The genus Onchocerca Diesing, 1841 includes species of medical importance, such as O. volvulus (Leuckart, 1893), which causes river blindness in the tropics. Recently, zoonotic onchocercosis has been reported in humans worldwide. In Japan, O. dewittei japonica Uni, Bain & Takaoka, 2001 from wild boars is a causative agent for this zoonosis. Many filarioid nematodes are infected with Wolbachia endosymbionts which exhibit various evolutionary relationships with their hosts. While investigating the filarial fauna of Borneo, we discovered an undescribed Onchocerca species in the bearded pig Sus barbatus Müller (Cetartiodactyla: Suidae). METHODS: We isolated Onchocerca specimens from bearded pigs and examined their morphology. For comparative material, we collected fresh specimens of O. d. dewittei Bain, Ramachandran, Petter & Mak, 1977 from banded pigs (S. scrofa vittatus Boie) in Peninsular Malaysia. Partial sequences of three different genes (two mitochondrial genes, cox1 and 12S rRNA, and one nuclear ITS region) of these filarioids were analysed. By multi-locus sequence analyses based on six genes (16S rDNA, ftsZ, dnaA, coxA, fbpA and gatB) of Wolbachia, we determined the supergroups in the specimens from bearded pigs and those of O. d. dewittei. RESULTS: Onchocerca borneensis Uni, Mat Udin & Takaoka n. sp. is described on the basis of morphological characteristics and its genetic divergence from congeners. Molecular characteristics of the new species revealed its close evolutionary relationship with O. d. dewittei. Calculated p-distance for the cox1 gene sequences between O. borneensis n. sp. and O. d. dewittei was 5.9%, while that between O. d. dewittei and O. d. japonica was 7.6%. No intraspecific genetic variation was found for the new species. Wolbachia strains identified in the new species and O. d. dewittei belonged to supergroup C and are closely related. CONCLUSIONS: Our molecular analyses of filarioids from Asian suids indicate that the new species is sister to O. d. dewittei. On the basis of its morphological and molecular characteristics, we propose to elevate O. d. japonica to species level as O. japonica Uni, Bain & Takaoka, 2001. Coevolutionary relationships exist between the Wolbachia strains and their filarial hosts in Borneo and Peninsular Malaysia.

Genetic structure and geographical variation of Bithynia siamensis goniomphalos sensu lato (Gastropoda: Bithyniidae), the snail intermediate host of Opisthorchis viverrini sensu lato (Digenea: Opisthorchiidae) in the Lower Mekong Basin revealed by mitochondrial DNA sequences.

The freshwater snail Bithynia siamensis goniomphalos sensu lato is widely distributed in the Lower Mekong Basin where it acts as the first intermediate host of the liver fluke Opisthorchis viverrini, a group 1 carcinogen causing cholangiocarcinoma. This study explores the genetic structure and geographical variation of B. s. goniomphalos from eight previously studied catchments and eight new catchments. These catchments belong to five previously studied catchment systems and one new catchment system (Tonlesap) in the Lower Mekong Basin. Two new catchment systems, Prachin Buri and Bang Pakong from eastern and central Thailand, respectively, were also examined. We collected 289 specimens of B. s. goniomphalos from 15 previously studied localities and 18 new localities in Thailand, Lao PDR (People's Democratic Republic), and Cambodia. The mitochondrial cytochrome c oxidase subunit 1 and 16S ribosomal DNA sequences were used to determine genetic variation. Classification of haplotypes specified 100 at the cox1 locus and 15 at the rrnL locus. Comparison between 16 catchment populations found significant genetic differences (ФST) between all populations. The phylogenetic tree and haplotype network analyses classified B. s. goniomphalos into three evolutionary lineages (lineage I-III). Lineage I contained B. s. goniomphalos from the Mekong, Chi, Mun, Prachin Buri and Bang Pakong catchments in Thailand, including the Nam Ngum catchment in Lao PDR. Lineage II contained all specimens from the Tonlesap catchment, whereas lineage III contained specimens from the Mekong and Sea Bang Heang catchments in Thailand and Lao PDR, respectively. Interestingly, Bithynia siamensis siamensis was placed between lineages I and II of B. s. goniomphalos. This study supports the hypothesis that B. s. goniomphalos is a species complex containing at least three distinct evolutionary lineages in the Lower Mekong Basin, and that comprehensive molecular genetic analyses need to be conducted to further our understanding of the evolutionary and systematic relationships of these Bithynia snail taxa.

Zoonotic infection with Onchocerca dewittei japonica in an 11-year-old boy in Kansai Region, Western Honshu, Japan.

An 11-year-old boy living in Otsu City, Shiga Prefecture, Kansai Region, Western Honshu, Japan had zoonotic onchocercosis. The patient developed a painful swelling on the little finger of his left hand. The worm detected in the excised mass had external transverse ridges but did not have inner striae in the cuticle. On the basis of the parasite's histopathological characteristics, the causative agent was identified as a female Onchocerca dewittei japonica (Spirurida: Onchocercidae). The species of the filarial parasite was confirmed by sequencing the cox1 gene of the parasite. The Japanese wild boar Sus scrofa leucomystax is a definitive host for O. dewittei japonica, which is then transmitted by blackflies as the vector to humans. The current case described occurred in the Kansai Region, Western Honshu, where such infections were previously not reported.