Hox genes regulate asexual reproductive behavior and tissue segmentation in adult animals.

Hox genes are highly conserved transcription factors renowned for their roles in the segmental patterning of the embryonic anterior-posterior (A/P) axis. We report functions for Hox genes in A/P tissue segmentation and transverse fission behavior underlying asexual reproduction in adult planarian flatworms, Schmidtea mediterranea. Silencing of each of the Hox family members identifies 5 Hox genes required for asexual reproduction. Among these, silencing of hox3 genes results in supernumerary fission segments, while silencing of post2b eliminates segmentation altogether. The opposing roles of hox3 and post2b in segmentation are paralleled in their respective regulation of fission behavior. Silencing of hox3 increases the frequency of fission behavior initiation while silencing of post2b eliminates fission behavior entirely. Furthermore, we identify a network of downstream effector genes mediating Hox gene functions, providing insight into their respective mechanisms of action. In particular, we resolve roles for post2b and effector genes in the functions of the marginal adhesive organ in fission behavior regulation. Collectively, our study establishes adult stage roles for Hox genes in the regulation of tissue segmentation and behavior associated with asexual reproduction.

Rhesus macaques self-curing from a schistosome infection can display complete immunity to challenge.

The rhesus macaque provides a unique model of acquired immunity against schistosomes, which afflict >200 million people worldwide. By monitoring bloodstream levels of parasite-gut-derived antigen, we show that from week 10 onwards an established infection with Schistosoma mansoni is cleared in an exponential manner, eliciting resistance to reinfection. Secondary challenge at week 42 demonstrates that protection is strong in all animals and complete in some. Antibody profiles suggest that antigens mediating protection are the released products of developing schistosomula. In culture they are killed by addition of rhesus plasma, collected from week 8 post-infection onwards, and even more efficiently with post-challenge plasma. Furthermore, cultured schistosomula lose chromatin activating marks at the transcription start site of genes related to worm development and show decreased expression of genes related to lysosomes and lytic vacuoles involved with autophagy. Overall, our results indicate that enhanced antibody responses against the challenge migrating larvae mediate the naturally acquired protective immunity and will inform the route to an effective vaccine.

Immunoprotective effects of invasive Lactobacillus plantarum delivered nucleic acid vaccine coexpressing Trichinella spiralis CPF1 and murine interleukin-4.

Trichinellosis is a very important food-borne parasitic disease, that seriously endangers animal husbandry and food safety. Therefore, it is necessary to develop a safe and effective vaccine against Trichinella spiralis infection. In this experiment, invasive Lactobacillus plantarum carrying the FnBPA gene served as a live bacterial vector to deliver nucleic acids to the host to produce a novel oral nucleic acid vaccine. Coexpression of the T. spiralis cathepsin F-like protease 1 gene (TsCPF1) and murine IL-4 (mIL-4) by the nucleic acid vaccine was constructed and subsequently delivered to intestinal epithelial cells via invasive L. plantarum. Thirty-seven days after the first immunization, the experimental mice were challenged with 350 T. spiralis infective larvae by oral gavage. The results showed that mice orally immune-stimulated with invasive L. plantarum pValac-TsCPF1/pSIP409-FnBPA not only produce anti-TsCPF1-specific IgG antibodies, sIgA, Th1/Th2 cytokine distinctly increased but also intestinal damage and worm burden relieved compare to non-invasive TsCPF1 group (pValac-TsCPF1/pSIP409). Most notably, experimental mice immunized with invasive L. plantarum coexpressing TsCPF1 and mIL-4 (pValac-TsCPF1-IL-4/pSIP409-FnBPA) exhibited the highest protection efficiency against T. spiralis infection. The above results reveal that invasive L. plantarum-expressing the FnBPA protein improved mucosal and cellular immunity and enhanced resistance to T. spiralis. The nucleic acid vaccine delivered by invasive L. plantarum described in this study offers a novel idea for the prevention of T. spiralis.

Three species of Echinococcus granulosus sensu lato infect camels on the Arabian Peninsula.

We report on the genetic identity of 36 Echinococcus cysts that were collected during a recent slaughterhouse survey of 810 locally bred camels (dromedaries) in the Eastern Province of the Kingdom of Saudi Arabia. Analysis of a partial nad1 gene sequence showed that the majority (n = 29) belonged to E. granulosus sensu stricto, four to E. canadensis G6/7, and three to E. ortleppi. Eight of the 29 E. granulosus s.s. cysts contained protoscoleces; all other cysts were calcified and non-viable. This is the first report of the presence E. ortleppi from the Arabian Peninsula, a parasite that is typically transmitted via cattle. The results indicate widespread infection of camels with CE in eastern Saudi Arabia and an active role of camels in the lifecycles of at least E. granulosus s.s.. Complete cox1 haplotype analysis of 21 E. granulosus s.s. isolates shows that the majority of variants circulating in eastern Saudi Arabia is distinct from but closely related to haplotypes from neighboring countries in the Middle East, which indicates the presence of this parasite in KSA for a longer period of time. All isolates of E. granulosus s.s. in this study belonged to the G1 cluster, although the G3 genotype has previously also been reported from the Middle East.

Correction of the synonymy of a species of Longior/ Travassos amp; Kloss, 1958 (Nematoda: Oxyuridomorpha: Hystrignathidae) from a Cuban passalid beetle (Coleoptera: Passalidae).

García Coy (1994) described the hystrignathid nematode Longior alius García Coy, 1994 parasitizing the passalid beetle Antillanax pertyi (Kaup, 1869) from Guantánamo province, Eastern Cuba. Morffe García (2011) continued the studies on Cuban Longior and described L. longior Morffe García, 2011. Morffe et al. (2018) redescribed L. longior with the aid of SEM and molecular techniques. In their research the authors studied Longior individuals from the same host species and a locality close to the type locality of L. alius and compared their morphology, measurements and DNA markers with other material of L. longior. As a result of this analysis Morffe et al. (2018) concluded that L. alius and L. longior are conspecific and proposed L. alius as a synonym of L. longior.

The diversity of ABC transporter genes across the Phylum Nematoda.

It is estimated that one billion people globally are infected by parasitic nematodes, with children, pregnant women, and the elderly particularly susceptible to morbidity from infection. Control methods are limited to de-worming, which is hampered by rapid re-infection and the inevitable development of anthelmintic resistance. One family of proteins that has been implicated in nematode anthelmintic resistance are the ATP binding cassette (ABC) transporters. ABC transporters are characterized by a highly conserved ATP-binding domain and variable transmembrane regions. A growing number of studies have associated ABC transporters in anthelmintic resistance through a protective mechanism of drug efflux. Genetic deletion of P glycoprotein type ABC transporters in Caenorhabditis elegans demonstrated increased sensitivity to anthelmintics, while in the livestock parasite, Haemonchus contortus, anthelmintic use has been shown to increase the expression of ATP transporter genes. These studies as well as others, provide evidence for a potential role of ABC transporters in drug resistance in nematodes. In order to understand more about the family of ABC transporters, we used hidden Markov models to predict ABC transporter proteins from 108 species across the phylum Nematoda and use these data to analyze patterns of diversification and loss in diverse nematode species. We also examined temporal patterns of expression for the ABC transporter family within the filarial nematode Brugia malayi and identify cases of differential expression across diverse life-cycle stages. Taken together, our data provide a comprehensive overview of ABC transporters in diverse nematode species and identify examples of gene loss and diversification in nematodes based on lifestyle and taxonomy.

Transcriptional profiles in Strongyloides stercoralis males reveal deviations from the Caenorhabditis sex determination model.

The human and canine parasitic nematode Strongyloides stercoralis utilizes an XX/XO sex determination system, with parasitic females reproducing by mitotic parthenogenesis and free-living males and females reproducing sexually. However, the genes controlling S. stercoralis sex determination and male development are unknown. We observed precocious development of rhabditiform males in permissive hosts treated with corticosteroids, suggesting that steroid hormones can regulate male development. To examine differences in transcript abundance between free-living adult males and other developmental stages, we utilized RNA-Seq. We found two clusters of S. stercoralis-specific genes encoding predicted transmembrane proteins that are only expressed in free-living males. We additionally identified homologs of several genes important for sex determination in Caenorhabditis species, including mab-3, tra-1, fem-2, and sex-1, which may have similar functions. However, we identified three paralogs of gld-1; Ss-qki-1 transcripts were highly abundant in adult males, while Ss-qki-2 and Ss-qki-3 transcripts were highly abundant in adult females. We also identified paralogs of pumilio domain-containing proteins with sex-specific transcripts. Intriguingly, her-1 appears to have been lost in several parasite lineages, and we were unable to identify homologs of tra-2 outside of Caenorhabditis species. Together, our data suggest that different mechanisms control male development in S. stercoralis and Caenorhabditis species.

Echinostoma miyagawai Ishii, 1932 (Echinostomatidae) from Ducks in Aceh Province, Indonesia with Special Reference to Its Synonymy with Echinostoma robustum Yamaguti, 1935.

Adult echinostomes having 37 collar spines collected from the intestine of Pitalah ducks in Aceh Province, Indonesia in 2018 were morphologically and molecularly determined to be Echinostoma miyagawai Ishii, 1932 (Digenea: Echinostomatidae). Among 20 ducks examined, 7 (35.0%) were found to be infected with this echinostome, and the number of flukes collected was 48 in total with average 6.9 (1-17) worms per duck. The adult flukes were 7.2 (6.1-8.5) mm in length and 1.2 (1.0-1.4) mm in width (pre-ovarian or testicular level) and characterized by having a head collar armed with 37 collar spines (dorsal spines arranged in 2 alternating rows), including 5 end group spines, and variable morphology of the testes, irregularly or deeply lobed (3-5 lobes) at times with horizontal extension. The eggs within the worm uterus were 93 (79-105) µm long and 62 (56-70) µm wide. These morphological features were consistent with both E. miyagawai and Echinostoma robustum, for which synonymy to each other has been raised. Sequencing of 2 mitochondrial genes, cox1 and nad1, revealed high homology with E. miyagawai (98.6-100% for cox1 and 99.0-99.8% for nad1) and also with E. robustum (99.3-99.8% for nad1) deposited in GenBank. We accepted the synonymy between the 2 species and diagnosed our flukes as E. miyagawai (syn. E. robustum) with redescription of its morphology. Further studies are required to determine the biological characteristics of E. miyagawai in Aceh Province, Indonesia, including the intermediate host and larval stage information.

Echinostoma mekongi: Discovery of Its Metacercarial Stage in Snails, Filopaludina martensi cambodjensis, in Pursat Province, Cambodia.

Echinostoma mekongi was reported as a new species in 2020 based on specimens collected from humans in Kratie and Takeo Province, Cambodia. In the present study, its metacercarial stage has been discovered in Filopaludina martensi cambodjensis snails purchased from a local market nearby the Tonle Sap Lake, Pursat Province, Cambodia. The metacercariae were fed orally to an experimental hamster, and adult flukes were recovered at day 20 post-infection. They were morphologically examined using light and scanning electron microscopes and molecularly analyzed by sequencing of their mitochondrial cox1 and nad1 genes. A total of 115 metacercariae (1-8 per snail) were detected in 60 (60.0%) out of 100 Filopaludina snails examined. The metacercariae were round, 174 µm in average diameter (163-190 µm in range), having a thin cyst wall, a head collar armed with 37 collar spines, and characteristic excretory granules. The adult flukes were elongated, ventrally curved, 7.3 (6.4-8.2)×1.4 (1.1-1.7) mm in size, and equipped with 37 collar spines on the head collar (dorsal spines in 2 alternating rows), being consistent with E. mekongi. In phylogenetic analyses, the adult flukes showed 99.0-100% homology based on cox1 sequences and 98.9-99.7% homology based on nad1 sequences with E. mekongi. The results evidenced that F. martensi cambodjensis snails act as the second intermediate host of E. mekongi, and hamsters can be used as a suitable experimental definitive host. As local people favor to eat undercooked snails, these snails seem to be an important source of human infection with E. mekongi in Cambodia.

Genetic identification of Anisakis spp. (Nematoda: Anisakidae) from cetaceans of the Southwestern Atlantic Ocean: ecological and zoogeographical implications.

Adult Anisakis Dujardin, 1845 were found in two specimens of killer whale Orcinus orca and one specimen of franciscana Pontoporia blainvillei stranded from off the coast of Buenos Aires Province, Argentina. Genetic identification of the nematodes (N = 144) was performed by sequence analysis of the mitochondrial (mtDNA cox2) and the nuclear (nas 10 nDNA) gene loci. Anisakis pegreffii and Anisakis berlandi were detected in the two individuals of O. orca, while Anisakis typica and A. pegreffii were identified in P. blainvillei. Morphological and morphometric analysis also carried out on adult specimens of A. pegreffii and A. berlandi has allowed to underlining the usefulness of genetic/molecular markers in their recognition. This represents the first record of A. pegreffii in O. orca and P. blainvillei and of A. berlandi in O. orca. This is also the first sympatric and syntopic occurrence, as adults, of A. pegreffii and A. berlandi from the Austral Region of the Atlantic Ocean waters. These results provide insights into the knowledge of the host ranges and geographical distribution of these parasites in the basin waters of the region. Pontoporia blainvillei showed low abundance values of infection with Anisakis spp., which is the general pattern for coastal dolphins in the area, whereas O. orca harboured higher abundance of Anisakis spp. than those previously recorded among cetacean species in the Argentine Sea. Differences in the Anisakis spp. distribution and their parasitic loads, observed among the three host specimens, are discussed in relation to the oceanographic parameters, as well as to the host ecology. The usefulness of genetic/molecular markers in the recognition of adults of the sibling species A. pegreffii and A. berlandi with considerable overlapping in morphometric and morphological characters was underlined. The distribution of Anisakis species from Southwestern Atlantic waters is discussed in relation to their value as indicators for studies on the zoogeography of their hosts at a regional-scale level.

Morphology and Molecular Identification of Echinostoma revolutum and Echinostoma macrorchis in Freshwater Snails and Experimental Hamsters in Upper Northern Thailand.

Echinostome metacercariae were investigated in freshwater snails from 26 districts in 7 provinces of upper northern Thailand. The species identification was carried out based on the morphologies of the metacercariae and adult flukes harvested from experimental hamsters, and on nucleotide sequences of internal transcribed spacer 2 (ITS2) and nicotinamide adenine dinucleotide dehydrogenase subunit 1 (nad1) genes. Twenty-four out of 26 districts were found to be infected with echinostome metacercariae in freshwater snails with the prevalence of 40.4%. The metacercariae were found in all 6 species of snails, including Filopaludina martensi martensi (21.9%), Filopaludina doliaris (50.8%), F. sumatrensis polygramma (61.3%), Bithynia siamensis siamensis (14.5%), Bithynia pulchella (38.0%), and Anenthome helena (4.9%). The echinostome metacercariae found in these snails were identified as Echinostoma revolutum (37-collar-spined) and Echinostoma macrorchis (45-collar-spined) morphologically and molecularly. The 2-week-old adult flukes of E. revolutum revealed unique features of the cirrus sac extending to middle of the ventral sucker and smooth testes. E. macrorchis adults revealed the cirrus sac close to the right lateral margin of the ventral sucker and 2 large and elliptical testes with slight indentations and pointed posterior end of the posterior testis. The ITS2 and nad1 sequences confirmed the species identification of E. revolutum, and the sequences of E. macrorchis have been deposited for the first time in Gen-Bank. The presence of the life cycle of E. macrorchis is a new record in Thailand and the snail F. doliaris as their second intermediate host seems to be new among the literature.

Ocular Sparganosis: The First Report of Spirometra ranarum in Thailand.

A 22-year-old Thai man from the Northeast region presented with acute eye swelling, itching, and discharge on his left eye. He was suspected of having gnathostomiasis and treated with albendazole and prednisolone for 3 weeks. Nine months later, he was treated with high-dose oral prednisolone for the preliminary and differential diagnoses with thyroid-associated orbitopathy and lymphoma. He had been administered prednisolone intermittently over a few years. Then he developed a painless movable mass at the left upper eyelid and recurrent pseudotumor oculi was suspected. The surgical removal of the mass was performed. A white pseudosegmented worm revealed a definite diagnosis of ocular sparganosis by a plerocercoid larva. Molecular diagnosis of the causative species was made based on the mitochondrial cytochrome c oxidase subunit 1 (cox1) gene. Proper technique of extraction and amplification of short fragments DNA from formalin-fixed paraffin-embedded tissue successfully identified parasite species. The result from the sequencing of the PCR-amplified cox1 fragments in this study showed 99.0% sequence homology to Spirometra ranarum. This is the first report of S. ranarum in Thailand.

[Establishment of the gene detection method of Schistosoma mansoni based on the recombinase-aided isothermal amplification assay].

OBJECTIVE: To establish a recombinase-aided isothermal amplification (RAA) assay for nucleic acid detection of Schistosoma mansoni. METHODS: The 121 bp highly-repeated sequence of S. mansoni was selected as the target gene fragment to be detected. The primers and fluorescent probes were designed using the Amplfix software, and a fluorescent RAA assay was established and optimized. The fluorescent RAA assay was performed to detect gradient diluent recombinant plasmids containing target gene fragment and different concentrations of S. mansoni genomic DNA to determine the sensitivity, and this assay was applied to detect the genomic DNA of S. japonicum, S. haematobium, Ancylostoma duodenale and Clonorchis sinensis to evaluate the specificity. RESULTS: A fluorescent RAA assay was successfully established, which was effective to amplify the specific gene fragments of S. mansoni within 20 min at 39 ℃. The minimum detectable limit of the fluorescent RAA assay was 10 copies/µL using recombinant plasmids as templates and 0.1 fg/µL using S. mansoni genomic DNA samples as templates. The fluorescent RAA assays were all negative for detecting the genomic DNA from S. japonicum, S. haematobium, A. duodenale and C. sinensis. CONCLUSIONS: A novel fluorescent RAA assay is successfully established, which is simple, rapid, sensitive and specific to detect genomic DNA of S. mansoni.

Application of DNA barcoding and morphometric analysis in differentiating cystacanths of Polymorphus species (Acanthocephala: Polymorphidae) from central Alberta, Canada.

Acanthocephalans are multi-host endoparasites, many of which use freshwater amphipods as intermediate hosts for their larval stages (e.g., cystacanths) while adults live in the intestines of vertebrates, including waterfowl. In central Alberta, Canada, several co-occurring species of the acanthocephalan genus Polymorphus use the amphipod Gammarus lacustris Sars, 1863 as an intermediate host. We applied DNA barcoding and morphometric analysis to differentiate cystacanth larvae from G. lacustris sampled from 17 Albertan water bodies. We slide-mounted specimens and measured morphological traits relating to proboscis hooks. We sequenced the standard DNA barcoding region of the mitochondrial cytochrome c oxidase subunit I gene (COI). Morphometric analysis suggested that the acanthocephalans we collected belonged to four morphologically different groups that keyed to Polymorphus contortus (Bremser, 1821) Travassos, 1926; P. marilis Van Cleave, 1939; P. paradoxus Connel et Corner, 1957; and P. strumosoides (Lundström, 1942) Amin, 2013. Our Bayesian tree based on COI sequences generally corroborated the morphological results and supported that the specimens assigned to P. cf. contortus and P. cf. strumosoides belong to two distinct species. In contrast, the Bayesian tree showed that specimens of P. cf. marilis were nested as a cluster within the P. cf. paradoxus clade. Similarly, small pairwise genetic distance (< 2%) between specimens identified as P. cf. contortus and P. cf. strumosoides suggests that they are conspecific. Future studies should use morphology and sequence data from adult acanthocephalans to assess the taxonomic identity of the cystacanth-based Polymorphus taxa. Our study is the first to provide genetic information for the four Polymorphus taxa and emphasizes the importance of applying multiple approaches to differentiate parasite species.

A human corneal ulcer caused by Thelazia callipaeda in Southwest China: case report.

In this study, we describe a rare human case with corneal ulcer caused by thelaziosis in a 69-year-old man in Southwest China. A male nematode was discovered and removed from the patient's right eye with a long spicule and further identified by sequencing mitochondrial cox1 gene. The ophthalmologic and molecular biological evidence demonstrates the corneal ulcer caused by T. callipaeda infection, which is mainly distributed in Asian and European countries. Most T. callipaeda infections are emerged in the conjunctiva, leading to conjunctivitis. To the best knowledge of the authors, corneal ulcers caused by T. callipaeda have not been reported yet.

Morphological and molecular identification of Hysterothylacium larvae (Nematoda: Raphidascarididae) in marine fish from Tunisian Mediterranean coasts.

The taxonomy of Hysterothylacium genus in Mediterranean waters remains incomplete and unresolved. The aim of the current study was to investigate the morphological and molecular identification of selected species of Hysterothylacium larvae in marine fish from the Tunisian Mediterranean coasts. A total of 192 marine fish samples were examined. In total, thirty-seven third-stage larvae of Hysterothylacium were morphologically identified as Hysterothylacium type V. In the present study, representatives of this type from the Mediterranean Sea were genetically characterized for the first time by sequencing the rDNA ITS (ITS1-5.8S-ITS2) regions and mtDNA cox2 gene. This study represents the first report of Hysterothylacium type V from the Mediterranean Sea. We also report Mullus barbatus, M. surmuletus, and Pagellus erythrinus as new hosts for this larval type. Based upon molecular and phylogenetic analyses considering the rDNA ITS regions, the Hysterothylacium type V described here was classified as a new genotype, named Genotype B. The valid genetic data of the described Hysterothylacium type V in the present study can be used to establish the phylogenetic relationships among Hysterothylacium species from the Mediterranean Sea and worldwide for future research.

Cell-type-specific promoters for C. elegans glia.

Glia shape the development and function of the C. elegans nervous system, especially its sense organs and central neuropil (nerve ring). Cell-type-specific promoters allow investigators to label or manipulate individual glial cell types, and therefore provide a key tool for deciphering glial function. In this technical resource, we compare the specificity, brightness, and consistency of cell-type-specific promoters for C. elegans glia. We identify a set of promoters for the study of seven glial cell types (F16F9.3, amphid and phasmid sheath glia; F11C7.2, amphid sheath glia only; grl-2, amphid and phasmid socket glia; hlh-17, cephalic (CEP) sheath glia; and grl-18, inner labial (IL) socket glia) as well as a pan-glial promoter (mir-228). We compare these promoters to promoters that are expressed more variably in combinations of glial cell types (delm-1 and itx-1). We note that the expression of some promoters depends on external conditions or the internal state of the organism, such as developmental stage, suggesting glial plasticity. Finally, we demonstrate an approach for prospectively identifying cell-type-specific glial promoters using existing single-cell sequencing data, and we use this approach to identify two novel promoters specific to IL socket glia (col-53 and col-177).

ROS regulation of RAS and vulva development in Caenorhabditis elegans.

Reactive oxygen species (ROS) are signalling molecules whose study in intact organisms has been hampered by their potential toxicity. This has prevented a full understanding of their role in organismal processes such as development, aging and disease. In Caenorhabditis elegans, the development of the vulva is regulated by a signalling cascade that includes LET-60ras (homologue of mammalian Ras), MPK-1 (ERK1/2) and LIN-1 (an ETS transcription factor). We show that both mitochondrial and cytoplasmic ROS act on a gain-of-function (gf) mutant of the LET-60ras protein through a redox-sensitive cysteine (C118) previously identified in mammals. We show that the prooxidant paraquat as well as isp-1, nuo-6 and sod-2 mutants, which increase mitochondrial ROS, inhibit the activity of LET-60rasgf on vulval development. In contrast, the antioxidant NAC and loss of sod-1, both of which decrease cytoplasmic H202, enhance the activity of LET-60rasgf. CRISPR replacement of C118 with a non-oxidizable serine (C118S) stimulates LET-60rasgf activity, whereas replacement of C118 with aspartate (C118D), which mimics a strongly oxidised cysteine, inhibits LET-60rasgf. These data strongly suggest that C118 is oxidized by cytoplasmic H202 generated from dismutation of mitochondrial and/or cytoplasmic superoxide, and that this oxidation inhibits LET-60ras. This contrasts with results in cultured mammalian cells where it is mostly nitric oxide, which is not found in worms, that oxidizes C118 and activates Ras. Interestingly, PQ, NAC and the C118S mutation do not act on the phosphorylation of MPK-1, suggesting that oxidation of LET-60ras acts on an as yet uncharacterized MPK-1-independent pathway. We also show that elevated cytoplasmic superoxide promotes vulva formation independently of C118 of LET-60ras and downstream of LIN-1. Finally, we uncover a role for the NADPH oxidases (BLI-3 and DUOX-2) and their redox-sensitive activator CED-10rac in stimulating vulva development. Thus, there are at least three genetically separable pathways by which ROS regulates vulval development.

Taenia asiatica: Historical overview of taeniasis and cysticercosis with molecular characterization.

Asian Taenia is a human-infecting Taenia tapeworm known as Taenia asiatica following morphological examination of adult and larval stages of the tapeworm by Eom and Rim (1993). The life cycle of T. asiatica differs from that of T. saginata in its intermediate host (pigs versus cattle) as well as in the infected organs (liver versus muscle). T. asiatica can be differentiated from T. solium and T. saginata by examination of morphological characteristics such as the scolex, mature and gravid proglottids in the adult stage, and the scolex and bladder surface in the larval stage. T. asiatica has been identified in Korea, Taiwan, the Philippines, China, Thailand, Indonesia, Vietnam, Japan, Lao PDR, Nepal and India. The molecular tools employed for T. asiatica identification have been developed to differentiate T. asiatica from other human-infecting Taenia tapeworms based on genetic information such as nucleotide sequence of mitochondrial genes, nuclear ribosomal genes and nuclear genes that lead to development of the subsequent molecular techniques, such as PCR-RFLP, PCR-RAPD, BESST-base, LAMP and qPCR. Investigation of the phylogenetic relationships among human Taenia species revealed that T. asiatica is a sister species with T. saginata, which is genetically more similar than other Taenia species in terms of the nucleotide sequences of cox1, nad1 and 28S rDNA. The mitochondrial genomes of human Taenia tapeworms comprise 13,703bp (T. asiatica), 13,670bp (T. saginata) and 13,709bp (T. solium), and contain 36 genes including 12 protein-coding genes, 2 ribosomal RNAs (rRNAs, a small and a large subunit), and 22 transfer RNAs (tRNAs). Sequence differences in the full genome of T. asiatica and T. saginata mitochondria is 4.6%, while T. solium differs by 11%. Hox gene orthology in T. asiatica was established by comparative analysis with Platyhelminthes Hox genes. T. asiatica Hox revealed six Hox orthologs including two lab/Hox1, two Hox3, one Dfd/Hox4 and one Lox/Lox4. Hybridization between T. asiatica and T. saginata was definitely observed in these species which are sympatrically endemic in the regions of Korea, Thailand, China and Lao PDR. Comparative analyses of T. asiatica, T. saginata and T. solium genomes were also reported with genome features. Taenia asiaticus nomen novum was proposed for T. asiaticaEom and Rim, 1993 which is a homonym of T. asiatica Linstow, 1901 (Davaineidae).

Schistosoma species detection by environmental DNA assays in African freshwaters.

BACKGROUND: Schistosomiasis is a neglected tropical parasitic disease associated with severe pathology, mortality and economic loss worldwide. Programs for disease control may benefit from specific and sensitive diagnostic methods to detect Schistosoma trematodes in aquatic environments. Here we report the development of novel environmental DNA (eDNA) qPCR assays for the presence of the human-infecting species Schistosoma mansoni, S. haematobium and S. japonicum. METHODOLOGY/PRINCIPAL FINDINGS: We first tested the specificity of the assays across the three species using genomic DNA preparations which showed successful amplification of target sequences with no cross amplification between the three focal species. In addition, we evaluated the specificity of the assays using synthetic DNA of multiple Schistosoma species, and demonstrated a high overall specificity; however, S. japonicum and S. haematobium assays showed cross-species amplification with very closely-related species. We next tested the effectiveness of the S. mansoni assay using eDNA samples from aquaria containing infected host gastropods, with the target species revealed as present in all infected aquaria. Finally, we evaluated the effectiveness of the S. mansoni and S. haematobium assays using eDNA samples from eight discrete natural freshwater sites in Tanzania, and demonstrated strong correspondence between infection status established using eDNA and conventional assays of parasite prevalence in host snails. CONCLUSIONS/SIGNIFICANCE: Collectively, our results suggest that eDNA monitoring is able to detect schistosomes in freshwater bodies, but refinement of the field sampling, storage and assay methods are likely to optimise its performance. We anticipate that environmental DNA-based approaches will help to inform epidemiological studies and contribute to efforts to control and eliminate schistosomiasis in endemic areas.