ITS-2 rDNA sequencing of Gnathostoma species (Nematoda) and elucidation of the species causing human gnathostomiasis in the Americas

Distinct biogeographical patterns in snail gastrointestinal tract bacterial communities compared with sediment and water

The factors that influence the distribution of bacterial community composition are not well understood. The role of geographical patterns, which suggest limited dispersal, is still a topic of debate. Bacteria associated with hosts face unique dispersal challenges as they often rely on their hosts, which provide specific environments for their symbionts. In this study, we examined the effect of biogeographic distances on the bacterial diversity and composition of bacterial communities in the gastrointestinal tract of Ampullaceana balthica. We compared the effects on the host-associated bacterial community to those on bacterial communities in water and sediment. This comparison was made using 16S ribosomal RNA gene sequencing. We found that the bacterial communities we sampled in Estonia, Denmark, and Northern Germany varied between water, sediment, and the gastrointestinal tract. They also varied between countries within each substrate. This indicates that the type of substrate is a dominant factor in determining bacterial community composition. We separately analyzed the turnover rates of water, sediment, and gastrointestinal bacterial communities over increasing geographic distances. We observed that the turnover rate was lower for gastrointestinal bacterial communities compared to water bacterial communities. This implies that the composition of gastrointestinal bacteria remains relatively stable over distances, while water bacterial communities exhibit greater variability. However, the gastrointestinal tract had the lowest percentage of country-specific amplicon sequence variants, suggesting bacterial colonization from local bacterial communities. Since the overlap between the water and gastrointestinal tract was highest, it appears that the gastrointestinal bacterial community is colonized by the water bacterial community. Our study confirmed that biogeographical patterns in host-associated communities differ from those in water and sediment bacterial communities. These host-associated communities consist of numerous facultative symbionts derived from the water bacterial community.

Next step in Monachacantiana (Montagu, 1803) phylogeography: northern French and Dutch populations (Eupulmonata, Stylommatophora, Hygromiidae)

Features of shell and genitalia as well as nucleotide sequences of selected mitochondrial and nuclear genes of specimens of Monachacantiana from ten northern French and two Dutch populations were compared with the same features of British and Italian populations. They were found to be very similar to populations previously identified as belonging to the CAN-1 lineage of M.cantiana. This confirms previous suggestions that M.cantiana was introduced to western Europe (England, France and the Netherlands) in historical times.

Canine Schistosomiasis in the West Coast: Heterobilharzia americana in Two Natural Intermediate Hosts Found in the Colorado River, California

The emergence of infectious diseases presents a significant global health, economic, and security risk. Climate change can unexpectedly lead to the spread of pathogens, vectors, or hosts into new areas, contributing to the rise of infectious diseases. Surveillance plays a crucial role in monitoring disease trends and implementing control strategies. In this study, we document the first discovery of Heterobilharzia americana, a parasitic schistosome of mammals and its intermediate hosts Galba cubensis and Galba humilis along the banks of the Colorado River in California. We conducted multiple samplings of snails from various locations in the region with a previous history of canine schistosomiasis. Nucleotide sequencing of the multiple regions of the snails' and parasites' DNA revealed the coexistence of G. cubensis and G. humilis, both infected with H. americana. Phylogenetic analyses further validate the presence of H. americana in California, suggesting a wider distribution than previously reported. Our findings have implications for public health, veterinary medicine, and biodiversity conservation, contributing to developing effective control strategies to prevent the spread of this emerging infectious disease.

Possible zoonotic implications of the discovery of the advanced third stage larva of Gnathostoma turgidum (Spirurida: Gnathostomatidae) in a Mexican fish species

Gnathostomiasis in humans is acquired by consumption of any infected second intermediate host or paratenic host. This includes amphibians, snakes and poultry as well as fish. In this work we report for the first time in Mexico the presence of an AdvL3 of Gnathostoma turgidum in the musculature of a wild fish (Gobiomorus dormitor, which also acts as intermediate host for the larvae of G. binucleatum and G. lamothei), from the Papaloapan River, Veracruz; previously, larvae of G. turgidum had only been recorded in amphibians in Mexico and in wild swamp eels from Tampa, Florida, USA. The larva found is extremely small (approximately 1,500 by 140 microns in length and width, respectively), and was obtained by artificial digestion with pepsin after examining the musculature against the light between two glass plates, a method by which it went unnoticed. Our finding of an AdvL3 in this fish, together with a previous molecular phylogenetic analysis revealing that the five species involved in human infections do not nest in the same clade, suggest that all species in the genus are potentially zoonotic. In this context, we strongly recommend the identification of larvae extracted from human patients at specific level, in order to know the role played by the 3 species distributed in Mexico in human cases of gnathostomiasis.

Distinct stages of the intestinal bacterial community of Ampullaceana balthica after salinization

Environmental disturbances influence bacterial community structure and functioning. To investigate the effect of environmental disturbance caused by changes in salinity on host-protected bacterial communities, we analyzed the microbiome within the gastrointestinal tract of Ampullaceana balthica in different salinities. A. balthica is a benthic gastropod found in fresh- and mesohaline waters. Whereas the total energy reserves of A. balthica were unaffected by an increase of salinity to 3, a high mortality rate was detected after a shift from freshwater to salinity 6 suggesting a major disruption of energy homeostasis. The shift to salinity 6 also caused a change in the gastrointestinal bacterial community composition. At salinity 3, the bacterial community composition of different host individuals was related either to the freshwater or salinity 6 gastrointestinal bacterial community, indicating an ambivalent nature of salinity 3. Since salinity 3 represents the range where aquatic gastropods are able to regulate their osmolarity, this may be an important tipping point during salinization. The change in the intestinal microbiome was uncoupled from the change in the water bacterial community and unrelated to the food source microbiome. Our study shows that environmental disturbance caused by salinity acts also on the host-protected microbiome. In light of the sea-level rise, our findings indicate that salinization of the near-shore freshwater bodies will cause changes in organisms' intestinal microbiomes if a critical salinity threshold (presumably ∼3) is exceeded.

Two new pseudocryptic species in the medium-sized common European land snails, Fruticicola Held, 1838; as a result of phylogeographic analysis of Fruticicola fruticum (O. F. Müller, 1774) (Gastropoda: Helicoidea: Camaenidae)

Fruticicola fruticum (O. F. Müller, 1774), a medium-sized helicoid snail in the Bradybaenidae, has a wide range in Europe, reaching from the Urals and the Caucasus to the Balkans, and from the southern part of Scandinavia, through Central Europe to eastern and central France and northern Italy. There are numerous studies on its distribution, biology, life cycle, etc., but little is known about the genetic diversity of this taxon. Here, we studied the phylogeny and phylogeography of F. fruticum using two mitochondrial markers: cytochrome oxidase subunit I (COI) and 16S ribosomal RNA (16S); and four nuclear markers: 18S ribosomal RNA (18S), 28S ribosomal RNA (28S), internal transcribed spacer (ITS-2), and histone 3 (H3). The study was based on 59 populations sampled across the range. Whereas nuclear markers showed little differentiation, phylogenetic analysis of COI sequences clearly confirmed the distinctness of the European Fruticicola and Asian Bradybaena (p-distance 0.229). Within Fruticicola 54 haplotypes were detected, haplotype diversity (Hd) = 0.973±0.006, nucleotide diversity (π) = 0.137±0.005. ABGD and PTP delimitation analyzes distinguished eight mOTUs. Two sequences (our mOTU C) from Russia were published in the GenBank as two distinct species: F. schrenckii and F. transbaicalia. Seven further mOTUs identified in our study formed three distinct lineages, regarded as species. The first (mOTU A and mOTU B), represented by 40 populations, occupies a wide range across northern and central Europe, extending east to Ukraine and south to northern Croatia (mOTU B). It encompasses the type locality of F. fruticum, and can be recognized as F. fruticum sensu stricto. Another lineage (mOTU D and mOTU E), represented by six populations in central Romania, appears to form another species. Both mOTUs were found together in one population. A third lineage, containing mOTUs F, G and H, represented by 14 populations, was distributed across the Balkans from N.E. Croatia to Bulgaria. p-distances between the three species ranged from 0.172 to 0.219, and between all the mOTUs, pooled together, from 0.172 to 0.258. The highest genetic diversity was found in species 3 (0.112) and the lowest in species 1 (0.025), despite its largest geographic distribution. Pairwise p-distances, Tamura 3-parameter distances, composite likelihood distances, as well as the coancestry coefficient F_ST, calculated for all populations pooled together were significantly associated with geographic distance, but this was not the case within each of these three species. The significant association for all populations reflected high diversity between the species coupled with high geographic distances between their populations, not the character of intraspecies diversity. With a few exceptions, there hold a rather infinite island model with low migration. AMOVA detected 78% of the variance between the three species, 18% among populations within the species, and only 3.6% within the populations. The low genetic diversity of widespread F. fruticum s. stricto, compared with much higher diversity of two narrowly distributed newly found species of Fruticicola, may reflect the rapid spread of the former into previously uninhabitable regions, while the latter were able to maintain populations in glacial refugia. The estimated time of divergence between the three species, 1.7-2.19 mya, suggests their ancestors' isolation in southern European refugia during the lower Pleistocene, the Gelasian/Calabrian. There was no clear association of variation in shell morphology and lineage or mOTU identity; on external characters, these species are semicryptic, subtle differences in reproductive anatomy among them were found.

Development and Validation of Novel PCR Assays for the Diagnosis of Bovine Stephanofilariasis and Detection of Stephanofilaria sp. Nematodes in Vector Flies

Background: Stephanofilaria spp. nematodes are associated with cutaneous lesions in cattle and other livestock and mammalian wildlife species. In Australia, Haematobia irritans exigua, commonly known as buffalo fly (BF) transmits a well-described but presently unnamed species of Stephanofilaria, which has been speculatively implicated in the aetiology of BF lesions. The sensitivity of current techniques for detecting Stephanofilaria spp. in skin lesions and vector species is low, and there is no genomic sequence for any member of the genus Stephanofilaria currently available in sequence databases. Methods: To develop molecular assays for the detection of the Australian Stephanofilaria sp., skin biopsies were collected from freshly slaughtered cattle with typical lesions near the medial canthus. Adult nematodes and microfilariae were isolated from the biopsies using a saline recovery technique. The nematodes were morphologically identified as Stephanofilaria sp. by scanning electron microscopy. DNA was extracted and the internal transcribed spacer 2 (ITS2) region of rDNA, and the cytochrome c oxidase subunit 1 (cox1) region of mtDNA was amplified and sequenced. Stephanofilaria sp. specific polymerase chain reaction (PCR) and qPCR assays (SYBR Green^® and TaqMan™) were developed and optimised from the novel ITS2 sequence obtained. The specificity of each assay was confirmed by testing against nematode species Onchocerca gibsoni and Dirofilaria immitis, as well as host (bovine) and BF DNA. Results: Scanning electron microscopy of the anterior and posterior ends of isolated nematodes confirmed Stephanofilaria sp. A phylogenetic analysis of the cox1 sequence demonstrated that this species is most closely related to Thelazia callipaeda, a parasitic nematode that is a common cause of thelaziasis (or eyeworm infestation) in humans, dogs, and cats. Both conventional and qPCR assays specifically amplified DNA from Stephanofilaria sp. Conventional PCR, TaqMan™, and SYBR Green^® assays were shown to detect 1 ng, 1 pg, and 100 fg of Stephanofilaria DNA, respectively. Both qPCR assays detected DNA from single Stephanofilaria microfilaria. Conclusion: Molecular diagnostic assays developed in this study showed high specificity and sensitivity for Stephanofilaria sp. DNA. The availability of an accurate and sensitive PCR assay for Stephanofilaria will assist in determining its role in the pathogenesis of cattle skin lesions, as well as in understanding its epidemiological dynamics. This assay may also have application for use in epidemiological studies with other species of Stephanofilaria, most particularly closely related S. stilesi, but this will require confirmation.

Proteomics of Gnathostomiasis: A Way Forward for Diagnosis and Treatment Development

Gnathostoma spinigerum is the most common cause of gnathostomiasis in humans. It has a complex life cycle, which requires two intermediate hosts and a definitive host, and poses a high risk for zoonosis. Definitive prognosis of gnathostomiasis relies mainly on the isolation of advanced-stage larvae (aL3), which is very challenging especially if the aL3 is sequestered in difficult-to-reach organs. There is also a lack of a confirmatory diagnostic test for gnathostomiasis. With the ongoing advancement of proteomics, a potential diagnostic approach is underway using immunoproteomics and immunodiagnostics. In addition to this, the employment of mass spectrometry could further elucidate not only understanding the biology of the parasite but also determining potential targets of prospective drugs and vaccines. This article reports the past, present, and future application of proteomics in the study of gnathostomiasis.

An Unusual Case of Gastric Gnathostomiasis Caused by Gnathostoma spinigerum Confirmed by Video Gastroscopy and Morphological and Molecular Identification

Human gnathostomiasis is a harmful foodborne parasitic infection caused by nematodes of the genus Gnathostoma. Here, we report an unusual case of gastric gnathostomiasis seen in a hospital in Thailand along with the clinical characteristics, treatment, and outcome. A 39-year-old man presented with complaints of epigastric pain, dizziness, and history of passing dark, tarry stools for 2 days. The patient had a history of consuming raw freshwater fish. Supplementary differential diagnosis was performed via rapid serological testing, and presence of the causative agent was confirmed based on video gastroscopy, morphology of the removed parasite, and molecular identification. After its surgical removal from the stomach, the parasite was morphologically identified as Gnathostoma species. Molecular identification was performed via DNA extraction from the recovered worm, and amplification and sequencing of the second internal transcribed spacer (ITS2) region and partial cytochrome c oxidase subunit I (cox1) gene. The ITS2 and cox1 sequences were consistent with those of Gnathostoma spinigerum. Clinicians in endemic areas should therefore be aware of the rare clinical manifestations and use of supplementary serological tests to facilitate early diagnosis and treatment of gastric gnathostomiasis.

The occurrence and clinical importance of infectious stage of Echinocephalus (Nematoda: Gnathostomidae) larvae in selected Australian edible fish

Cases of gnathostomiasis, an infection caused by consuming infected seafood, have been reported in Australia. However, doubt exists over the validity of these diagnoses as there are no reports of Gnathostoma spp. in Australian teleost fish. Also, the diagnoses in human cases were based on a serological test developed in Thailand. The specificity and sensitivity of this test in non-endemic areas are uncertain. Interestingly, parasites belonging to the genus Echinocephalus, which morphologically are very similar to Gnathostomum, are commonly found in Australian fish and shellfish and can potentially infect humans. The aim of this study was to determine the occurrence of these zoonotic nematodes within commercial fish and to characterise nematode larvae in order to provide insights into the specific identity of the potential causative agents of gnathostomiasis in Australia. Six edible fish species (n = 163) were examined. Gnathostomid-type larvae were found only in Acanthopagrus australis and Rhabdosargus sarba. Detailed examination and sequence data suggested parasite larvae belonged to the genus Echinocephalus. Further investigation of the occurrence of zoonotic nematodes within marine environments and observation of their spatial and temporal patterns will help raise awareness of the significance of this food safety issue within global fishing industries and health sectors. The accurate identification of zoonotic nematodes is a key component of disease surveillance and control. This information can also be used to develop specific and sensitive diagnostic test.

Molecular, Morphological, and Spatial Study of Galba schirazensis (Pulmonata, Lymnaeidae) from Southeastern Iran

Background:

Snails of the genus Galba are the intermediate hosts of Fasciola species, the etiological agents of liver fluke disease, fascioliasis. A genetically different but morphologically very similar species in the genus, G. schirazensis, is sympatrically distributed with G. truncatula in some regions of the world. We aimed to investigate the occurrence of G. schirazensis in Kerman province, Iran and to characterize genetically G. schirazensis specimens from southeast Iran.

Methods:

Field-collected snails from four localities in Jiroft, Bam and Faryab, Kerman province, southeastern Iran were studied. Hydrological variables including temperature and pH were recorded for each habitat. Each specimen was identified using morphological as well as conchological characteristics. Genetic characterization was performed using PCR-sequencing followed by phylogenetic analyses on nuclear ITS2 as well as mitochondrial cox1 gene fragments. MaxEnt software was used to predict the most appropriate ecological niches for the targeted species.

Results:

G. schirazensis was found in 4 out of 28 locations. One ITS2 and two cox1 haplotypes were detected among G. schirazensis populations from the four localities. Habitat study showed that G. schirazensis thrives in habitats with alkaline pH. G.schirazensis from South America were clustered with specimens from Bam, Kerman, Iran; however, north Iranian isolates of G. schirazensis were strongly correlated with specimens from Jiroft and Faryab. MaxEnt model for the most appropriate ecological niches of the targeted species predicted environmental suitability for this species in western Africa as well as coastal areas in north and southwestern Africa.

Conclusion:

G. schirazensis is frequently present in southern areas of Kerman Province. At least two genetically different haplotypes are present in southeastern Iran.

Human gnathostomiasis: a neglected food-borne zoonosis

BACKGROUND

Human gnathostomiasis is a food-borne zoonosis. Its etiological agents are the third-stage larvae of Gnathostoma spp. Human gnathostomiasis is often reported in developing countries, but it is also an emerging disease in developed countries in non-endemic areas. The recent surge in cases of human gnathostomiasis is mainly due to the increasing consumption of raw freshwater fish, amphibians, and reptiles.

METHODS

This article reviews the literature on Gnathostoma spp. and the disease that these parasites cause in humans. We review the literature on the life cycle and pathogenesis of these parasites, the clinical features, epidemiology, diagnosis, treatment, control, and new molecular findings on human gnathostomiasis, and social-ecological factors related to the transmission of this disease.

CONCLUSIONS

The information presented provides an impetus for studying the parasite biology and host immunity. It is urgently needed to develop a quick and sensitive diagnosis and to develop an effective regimen for the management and control of human gnathostomiasis.

Systematics and geographical distribution of Galba species, a group of cryptic and worldwide freshwater snails

Cryptic species can present a significant challenge to the application of systematic and biogeographic principles, especially if they are invasive or transmit parasites or pathogens. Detecting cryptic species requires a pluralistic approach in which molecular markers facilitate the detection of coherent taxonomic units that can then be analyzed using various traits (e.g., internal morphology) and crosses. In asexual or self-fertilizing species, the latter criteria are of limited use. We studied a group of cryptic freshwater snails (genus Galba) from the family Lymnaeidae that have invaded almost all continents, reproducing mainly by self-fertilization and transmitting liver flukes to humans and livestock. We aim to clarify the systematics, distribution, and phylogeny of these species with an integrative approach that includes morphology, molecular markers, wide-scale sampling across America, and data retrieved from GenBank (to include Old World samples). Our phylogenetic analysis suggests that the genus Galba originated ca. 22 Myr ago and today comprises six species or species complexes. Four of them show an elongated-shell cryptic phenotype and exhibit wide variation in their genetic diversity, geographic distribution, and invasiveness. The remaining two species have more geographically restricted distributions and exhibit a globose-shell cryptic phenotype, most likely phylogenetically derived from the elongated one. We emphasize that no Galba species should be identified without molecular markers. We also discuss several hypotheses that can explain the origin of cryptic species in Galba, such as convergence and morphological stasis.

Assessing the diversity and distribution of potential intermediate hosts snails for urogenital schistosomiasis: Bulinus spp. (Gastropoda: Planorbidae) of Lake Victoria

BACKGROUND

The Lake Victoria basin is one of the most persistent hotspots of schistosomiasis in Africa, the intestinal form of the disease being studied more often than the urogenital form. Most schistosomiasis studies have been directed to Schistosoma mansoni and their corresponding intermediate snail hosts of the genus Biomphalaria, while neglecting S. haematobium and their intermediate snail hosts of the genus Bulinus. In the present study, we used DNA sequences from part of the cytochrome c oxidase subunit 1 (cox1) gene and the internal transcribed spacer 2 (ITS2) region to investigate Bulinus populations obtained from a longitudinal survey in Lake Victoria and neighbouring systems during 2010-2019.

METHODS

Sequences were obtained to (i) determine specimen identities, diversity and phylogenetic positions, (ii) reconstruct phylogeographical affinities, and (iii) determine the population structure to discuss the results and their implications for the transmission and epidemiology of urogenital schistosomiasis in Lake Victoria.

RESULTS

Phylogenies, species delimitation methods (SDMs) and statistical parsimony networks revealed the presence of two main groups of Bulinus species occurring in Lake Victoria; B. truncatus/B. tropicus complex with three species (B. truncatus, B. tropicus and Bulinus sp. 1), dominating the lake proper, and a B. africanus group, prevalent in banks and marshes. Although a total of 47 cox1 haplotypes, were detected within and outside Lake Victoria, there was limited haplotype sharing (only Haplotype 6 was shared between populations from Lake Victoria open waters and neighbouring aquatic systems) - an indication that haplotypes are specific to habitats.

CONCLUSIONS

The Bulinus fauna of Lake Victoria consists of at least B. truncatus, B. tropicus, Bulinus sp. 1 (B. trigonus?) and B. ugandae. The occurrence and wide distribution of Bulinus species in Lake Victoria potentially implies the occurrence of urogenital schistosomiasis in communities living along the shores and on islands of the lake who depend solely on the lake for their livelihood. More in-depth studies are needed to obtain a better picture of the extent of the disease in the Lake Victoria basin.

Impact of Salinity on the Gastrointestinal Bacterial Community of Theodoxus fluviatilis

Differences in salinity are boundaries that act as barriers for the dispersal of most aquatic organisms. This creates distinctive biota in freshwater and brackish water (mesohaline) environments. To test how saline boundaries influence the diversity and composition of host-associated microbiota, we analyzed the microbiome within the digestive tract of Theodoxus fluviatilis, an organism able to cross the freshwater and mesohaline boundary. Alpha-diversity measures of the microbiome in freshwater and brackish water were not significantly different. However, the composition of the bacterial community within freshwater T. fluviatilis differed significantly compared with mesohaline T. fluviatilis and typical bacteria could be determined for the freshwater and the mesohaline digestive tract microbiome. An artificial increase in salinity surrounding these freshwater snails resulted in a strong change in the bacterial community and typical marine bacteria became more pronounced in the digestive tract microbiome of freshwater T. fluviatilis. However, the composition of the digestive tract microbiome in freshwater snails did not converge to that found within mesohaline snails. Within mesohaline snails, no cardinal change was found after either an increase or decrease in salinity. In all samples, Pseudomonas, Pirellula, Flavobacterium, Limnohabitans, and Acinetobacter were among the most abundant bacteria. These bacterial genera were largely unaffected by changes in environmental conditions. As permanent residents in T. fluviatilis, they may support the digestion of the algal food in the digestive tract. Our results show that freshwater and mesohaline water host-associated microbiomes respond differently to changes in salinity. Therefore, the salinization of coastal freshwater environments due to a rise in sea level can influence the gut microbiome and its functions with currently unknown consequences for, e.g., nutritional physiology of the host.

Molecular Identification of the Etiological Agent of Human Gnathostomiasis in an Endemic Area of Mexico

Human gnathostomiasis, which is endemic in Mexico, is a worldwide health concern. It is mainly caused by the consumption of raw or insufficiently cooked fish containing the advanced third-stage larvae (AL3A) of Gnathostoma species. The diagnosis of gnathostomiasis is based on epidemiological surveys and immunological diagnostic tests. When a larva is recovered, the species can be identified by molecular techniques. Polymerase chain reaction (PCR) amplification of the second internal transcription spacer (ITS-2) is useful to identify nematode species, including Gnathostoma species. This study aims to develop a duplex-PCR amplification method of the ITS-2 region to differentiate between the Gnathostoma binucleatum and G. turgidum parasites that coexist in the same endemic area, as well as to identify the Gnathostoma larvae recovered from the biopsies of two gnathostomiasis patients from Sinaloa, Mexico. The duplex PCR established based on the ITS-2 sequence showed that the length of the amplicons was 321 bp for G. binucleatum and 226 bp for G. turgidum. The amplicons from the AL3A of both patients were 321 bp. Furthermore, the length and composition of these amplicons were identical to those deposited in GenBank as G. binucleatum (accession No. JF919679), corroborating our previous morphological finding that G. binucleatum is the etiological agent for human gnathostomiasis in the endemic area of Sinaloa, Mexico.

Cryptic intermediate snail host of the liver fluke Fasciola hepatica in Africa

BACKGROUND

Snails such as Galba truncatula are hosts for trematode flukes causing fascioliasis, a zoonosis that is a major public health problem. Galba truncatula has recently been shown to be a cryptic species complex. African populations of Galba spp. are not yet studied using molecular assessments and is imperative to do so and reconstruct the centre of origin of Galba and to understand when and by what means it may have colonized the highlands of Africa and to what extent humans might have been involved in that process.

METHODS

Samples from all known sub-ranges throughout Africa and new samples from Europe and Asia were obtained. We used a combination of two mitochondrial (cox1 and 16S) and one nuclear (ITS2) markers and phylogenetic, divergence time estimates and phylogeographical methods to determine the identity and biogeographical affinities. We also reconstructed the colonization history including the likely mode of dispersal and tested for the presence of cryptic Galba species in Africa.

RESULTS

Galba truncatula is restricted to the Palaearctic region of the continent, namely Morocco. All sub-Saharan populations proved to be a distinct species according to the phylogenetic analyses and genetic distance. We propose to use the existing name Galba mweruensis (Connolly, 1929) for this species which is morphologically indistinguishable from the other two species hitherto known to occur in northern Africa, i.e. G. truncatula and G. schirazensis. Sub-tropical Africa has been colonized only once in either the Pliocene and possibly Miocene. Diversification within G. mweruensis is dated to the Plio-Pleistocene and thus human-mediated dispersal can be ruled out for the initial colonization of the isolated mountain ranges. There are potentially even more cryptic species in high altitude areas of Africa as outlined by the distinctness of the population found at the top of Mt. Elgon, Uganda.

CONCLUSIONS

From a novel genetic inspection of available African material, a hitherto neglected distinct species, G. mweruensis, now appears a major host of F. hepatica throughout sub-Saharan Africa. A closer examination of trematode parasites hosted by this species is needed in order to understand transmission patterns in highlands throughout eastern and southern Africa. We encourage future studies to inspect other high altitudes areas in Africa in light of parasites of either veterinary or medical importance.

Morphological and molecular characteristics of adult worms of Gnathostoma Owen, 1836 (Nematoda) collected from domestic pigs in Dien Bien Province, northern Vietnam

Gnathostomes are of interest because of their unique appearance and medical importance. Among 13 valid species of the genus Gnathostoma Owen, 1836 (Nematoda: Spirurida), two species, G. doloresi Tubangui, 1925 and G. hispidum Fedtschenko, 1872, are parasites of pigs but their larvae can infect humans to cause gnathostomiasis. In this study, we collected adults of Gnathostoma sp. from the stomach of domestic pigs (Sus scrofa domesticus Linnaeus) from Dien Bien Province, northern Vietnam. Morphologically, nematodes found here are most similar to G. doloresi with a slight difference in the spicules of males. In contrast, they are genetically distinct from G. doloresi and other species of Gnathostoma in both ITS2 and cox1 sequences. The findings of the present study suggest that specimens of Gnathostoma sp. found in Dien Bien are likely a new species and emphasise the need of further studies on the taxonomy and phylogenetic relationship of species of Gnathostoma. Special attention should also be paid to swine and human gnathostomiasis in Dien Bien Province, Vietnam and the neighbouring areas of China and Laos.

Transcriptome and excretory-secretory proteome of infective-stage larvae of the nematode Gnathostoma spinigerum reveal potential immunodiagnostic targets for development

Background: Gnathostoma spinigerum is a harmful parasitic nematode that causes severe morbidity and mortality in humans and animals. Effective drugs and vaccines and reliable diagnostic methods are needed to prevent and control the associated diseases; however, the lack of genome, transcriptome, and proteome databases remains a major limitation. In this study, transcriptomic and secretomic analyses of advanced third-stage larvae of G. spinigerum (aL3Gs) were performed using next-generation sequencing, bioinformatics, and proteomics. Results: An analysis that incorporated transcriptome and bioinformatics data to predict excretory–secretory proteins (ESPs) classified 171 and 292 proteins into classical and non-classical secretory groups, respectively. Proteins with proteolytic (metalloprotease), cell signaling regulatory (i.e., kinases and phosphatase), and metabolic regulatory function (i.e., glucose and lipid metabolism) were significantly upregulated in the transcriptome and secretome. A two-dimensional (2D) immunomic analysis of aL3Gs-ESPs with G. spinigerum-infected human sera and related helminthiases suggested that the serine protease inhibitor (serpin) was a promising antigenic target for the further development of gnathostomiasis immunodiagnostic methods. Conclusions: The transcriptome and excretory–secretory proteome of aL3Gs can facilitate an understanding of the basic molecular biology of the parasite and identifying multiple associated factors, possibly promoting the discovery of novel drugs and vaccines. The 2D-immunomic analysis identified serpin, a protein secreted from aL3Gs, as an interesting candidate for immunodiagnosis that warrants immediate evaluation and validation.

Exploring Monacha cantiana (Montagu, 1803) phylogeography: cryptic lineages and new insights into the origin of the English populations (Eupulmonata, Stylommatophora, Hygromiidae)

Molecular analysis of nucleotide sequences of mitochondrial cytochrome oxidase subunit 1 (COI) and 16S ribosomal DNA (16SrDNA) as well as nuclear histone 3 (H3) and internal transcribed spacer 2 of rDNA (ITS2) gene fragments together with morphological analysis of shell and genitalia features showed that English, French and Italian populations usually assigned to Monacha cantiana consist of four distinct lineages (CAN-1, CAN-2, CAN-3, CAN-4). One of these lineages (CAN-1) included most of the UK (five sites) and Italian (five sites) populations examined. Three other lineages represented populations from two sites in northern Italy (CAN-2), three sites in northern Italy and Austria (CAN-3), and two sites in south-eastern France (CAN-4). The taxonomic and nomenclatural setting is only currently available for lineages CAN-1 and CAN-4; a definitive frame for the other two requires much more research. The lineage CAN-1 corresponds to the true M. cantiana (Montagu, 1803) because it is the only one that includes topotypical English populations. The relationships and genetic distances support the hypothesis of the Italian origin of this lineage which was probably introduced to England by the Romans. The lineage CAN-4 is attributed to M. cemenelea (Risso, 1826), for which a neotype has been designated and deposited. Its diagnostic sequences of COI, 16SrDNA, H3 and ITS2 genes have also been deposited in GenBank. Molecular and morphological (shell and genitalia) features showed that M. parumcincta (Rossmässler, 1834) is a distinct taxon from the M. cantiana lineages.

Gnathostomiasis: an emerging infectious disease relevant to all dermatologists

Gnathostomiasis is a parasitic infection caused by the third larval stage of nematodes of the genus Gnathostoma. The disease is endemic in some countries around the world. In the American continent, the majority of cases is concentrated in Mexico, Ecuador, and Peru. However, due to increasing traveling either at the intercontinental or intracontinental level, the disease is seen each time more frequently in tourists. Furthermore, countries, such as Brazil, that have never been considered endemic are reporting autochthonous cases. The disease usually presents as a deep-seated or slightly superficial migratory nodule in patients with history of eating raw fish, in the form of ceviche, sushi, or sashimi. Along with the clinical presentation, diagnostic criteria include either blood or tissue eosinophilia. In most instances, these criteria are enough for the attending physician to institute therapy. Chances of finding the parasite are low, unless the biopsy is taken from a very specific area that develops after antiparasitic treatment is started. The potential of other organ involvement with more serious consequences should always be kept in mind.

Molecular and morphological characterization of the cercariae of Lecithodendrium linstowi (Dollfus, 1931), a trematode of bats, and incrimination of the first intermediate snail host, Radix balthica

Lecithodendrium linstowi is one of the most prevalent and abundant trematodes of bats, but the larval stages and intermediate hosts have not been identified. We present the first molecular and morphological characterization of the cercariae of L. linstowi based on a phylogenetic analysis of partial fragments of LSU and ITS2 rDNA. The first intermediate host was incriminated as Radix balthica by DNA barcoding using cox1 and ITS2 sequences, although the snail morphologically resembled Radix peregra, emphasizing the requirement for molecular identification of lymnaeids as important intermediate hosts of medical and veterinary impact. The application of molecular data in this study has enabled linkage of life cycle stages and accurate incrimination of the first intermediate host.

Histopathological changes in the liver and stomach of Didelphis virginiana (Didelphimorphia: Didelphidae) during natural infection with Gnathostoma turgidum (Nematoda: Gnathostomidae)

Gnathostoma turgidum is a nematode parasite that exploits the stomach of Virginian opossums, Didelphis virginiana, in Latin America. The opossum is the definitive host of G. turgidum in the wild. Intrahepatic growth and maturation of the parasite, subsequent migration to the stomach and spontaneous expulsion are common. However, the histopathological lesions caused by G. turgidum are poorly described. A better understanding of the life cycle of this parasite and the pathological changes in natural host-parasite interactions could help to clarify the progression of human infections caused by Gnathostoma binucleatum. The aim of this work was to study morphological changes in the liver and stomach of D. virginiana during natural infection and adult worm expulsion. Three opossums naturally infected with G. turgidum were captured from an endemic area of gnathostomosis. Three uninfected opossums captured from a non-endemic area were used as controls. The opossums were sacrificed at different stages of infection (March, May and December), and a histopathological study of their livers and stomachs was conducted. Injuries in livers were observed by histopathology - areas of necrosis and collagen septa were identified. Parasites caused nodules with necrosis on the periphery of lesions, and collagen fibres were also observed in stomachs. Collagen septa may be caused by antigenic remains of the parasite. Further immunological studies are necessary to verify that stimulation is caused by these factors.

Fish-borne nematodiases in South America: neglected emerging diseases

Fish-borne zoonotic nematodes may infect humans when fish or squid are ingested raw or inadequately cooked. Human infections may have serious consequences, including the unexpected deaths of infected people. This kind of disease is poorly known in general, and the characteristics of such infections in South American countries as a whole have never been assessed. In this paper the present status of fish-borne nematodiases in humans in South American countries is characterized. Potentially zoonotic nematode species are very common in both freshwater and marine fish in South America. Reports of human infections have only been found in some countries, and their incidence (especially with anisakids and Gnathostoma spp.) varies from country to country. Apparently they are more abundant in countries with strong traditions of eating raw fish, and are more frequent on the western coast of South America. So far fish-borne nematodes have been reported in Argentina, Brazil, Chile, Colombia, Ecuador and Peru. In recent years, cases of human infection have appeared in probably underestimated numbers. People need to be clearly informed about risky feeding habits, and physicians need to learn more about zoonotic diseases.

Is Galba schirazensis (Mollusca, Gastropoda) an intermediate host of Fasciola hepatica (Trematoda, Digenea) in Ecuador?

Fasciolosis is a widely distributed disease in livestock in South America but knowledge about the epidemiology and the intermediate hosts is relatively scarce in Ecuador. For three months, lymnaeid snails were sampled (n = 1482) in Pichincha Province at two sites located in a highly endemic area. Snails were identified (based on morphology and ITS-2 sequences) and the infection status was established through microscopic dissection and a multiplex polymerase chain reaction (PCR)-based technique. Techniques based on morphology were not useful to accurately name the collected snail species. Comparison with available DNA sequences showed that a single snail species was collected, Galba schirazensis. Live rediae were observed in 1.75% (26/1482) and Fasciola sp. DNA was detected in 6% (89/1482) of collected snails. The COX-1 region permitted identification of the parasite as Fasciola hepatica. The relative sensitivity and specificity of the microscope study, compared to PCR results, were 25.84% and 99.78%, respectively. The mean size of the snails recorded positive for F. hepatica through crushing and microscopy was significantly higher than the mean size of negative snails, but there was no such difference in PCR-positive snails. The role of G. schirazensis as an intermediate host of F. hepatica in Ecuador is discussed and the hypothesis of an adaptation of the parasite to this invasive snail is proposed. For the first time, an epidemiological survey based on molecular biology-based techniques assessed the possible role of lymnaeid snails in the epidemiology of fasciolosis in Ecuador.

Origin and diversification of Lake Ohrid's endemic acroloxid limpets: the role of geography and ecology

BACKGROUND

Ancient Lake Ohrid, located on the Albania-Macedonia border, is the most biodiverse freshwater lake in Europe. However, the processes that gave rise to its extraordinary endemic biodiversity, particularly in the species-rich gastropods, are still poorly understood. A suitable model taxon to study speciation processes in Lake Ohrid is the pulmonate snail genus Acroloxus, which comprises two morphologically distinct and ecologically (vertically) separated endemic species. Using a multilocus phylogenetic framework of Acroloxus limpets from the Euro-Mediterranean subregion, together with molecular-clock and phylogeographic analyses of Ohrid taxa, we aimed to infer their geographic origin and the timing of colonization as well as the role of geography and ecology in intra-lacustrine diversification.

RESULTS

In contrast to most other endemic invertebrate groups in Lake Ohrid, the phylogenetic relationships of the endemic Ohrid Acroloxus species indicate that the Balkan region probably did not serve as their ancestral area. The inferred monophyly and estimated divergence times further suggest that these freshwater limpets colonized the lake only once and that the onset of intra-lacustrine diversification coincides with the time when the lake reached deep-water conditions ca 1.3 Mya. However, the difference in vertical distribution of these two ecologically distinct species is not reflected in the phylogeographic pattern observed. Instead, western and eastern populations are genetically more distinct, suggesting a horizontal structure.

CONCLUSIONS

We conclude that both geography and ecology have played a role in the intra-lacustrine speciation process. Given the distinct morphology (sculptured vs. smooth shell) and ecology (littoral vs. sublittoral), and the timing of intra-lacustrine diversification inferred, we propose that the onset of deep-water conditions initially triggered ecological speciation. Subsequent geographic processes then gave rise to the phylogeographic patterns observed today. However, the generally weak genetic differentiation observed suggests incipient speciation, which might be explained by the comparatively young age of the lake system and thus the relatively recent onset of intra-lacustrine diversification.

Cross-Reactivity Pattern of Asian and American Human Gnathostomiasis in Western Blot Assays Using Crude Antigens Prepared from Gnathostoma spinigerum and Gnathostoma binucleatum Third-Stage Larvae

Gnathostomiasis is a zoonotic parasitosis endemic in many Asian and some Latin American countries. Most human infections are caused by Gnathostoma spinigerum in Asia and Gnathostoma binucleatum in the Americas, and recently, imported cases have been increasing among travelers returning from endemic regions. Confirmation of the clinical diagnosis relies largely on serologic tests, with a G. spinigerum-antigen-based immunoblot currently being the diagnostic method of choice. However, we repeatedly experienced that sera from patients with clinically suspected American gnathostomiasis gave negative results in this assay. Therefore, we used homologous methods to prepare G. spinigerum- and G. binucleatum-antigen-based immunoblot assays, and evaluated the cross-reactivity of the two assays. The results show incomplete cross-reactivity between the two assays: the G. spinigerum-antigen-based immunoblot apparently only detects Asian gnathostomiasis caused by G. spinigerum, whereas the G. binucleatum-antigen-based immunoblot is apparently capable of detecting American as well as Asian gnathostomiasis.

Effect of Fascioloides magna (Digenea) on fecundity, shell height, and survival rate of Pseudosuccinea columella (Lymnaeidae)

Infection with Fascioloides magna (Digenea) causes serious damage to liver tissue in definitive hosts represented by ruminants, especially cervids. The distribution of F. magna includes the indigenous areas in North America, and the areas to which F. magna was introduced-Central Europe, Southeast Europe, and Italy. The North American intermediate host of F. magna, the freshwater snail Pseudosuccinea columella (Lymnaeidae), is an invasive species recorded in South America, the Caribbean, Africa, Australia, and west and Southeast Europe. In Europe, Galba truncatula is the snail serving for transmission, but P. columella has potential to become here a new intermediate host of F. magna. Little is known about interactions between F. magna and P. columella. In this study, the susceptibility of P. columella (Oregon, USA) to the infection by a single miracidium of the Czech strain of F. magna and the influence of F. magna on snail fecundity, shell height, and survival were evaluated. The data show that the Oregon strain of P. columella is a highly suitable host for the Czech strain of F. magna, with the infection rate of 74 %. In addition, a negative effect on survival rate of infected snails was recorded only in the late phase of infection. The infection was accompanied by a major reduction in egg mass production and by a decrease in the number of eggs per egg mass. The shell height of infected snails did not significantly differ from that in unexposed controls.

Gnathostomiasis: An Emerging Infection of Raw Fish Consumers in Gnathostoma Nematode-Endemic and Nonendemic Countries

BACKGROUND

Gnathostomiasis, a helminthic infection commonly reported in Southeast Asia and Latin America, may follow consumption of raw seafood infected with muscle-encysted larvae of Gnathostoma species nematodes. As a result of increasingly exotic tastes for local ethnic dishes, including raw seafood, some regions outside of gnathostome-endemic areas import live species for raw consumption. This may facilitate imported human gnathostomiasis or potentially the establishment of this zoonosis in formerly nonendemic regions. Traveling to a gnathostome-endemic area is no longer a criterion for diagnosis. The objectives of this review are to enhance clinician awareness of this infection by describing the behavioral risk factors for its acquisition, life-cycle, clinical manifestations, diagnosis, management, and prevention.

METHODS

Internet search engines were queried with the key medical subject heading words. Case reports, case series, epidemiological investigations, and laboratory studies were reviewed; high risk behaviors for gnathostomiasis were identified; and human cases were stratified as cutaneous gnathostomiasis, visceral gnathostomiasis, neurognathostomiasis, and ocular gnathostomiasis.

RESULTS

The greatest risk factors for gnathostomiasis included the consumption of raw freshwater seafood dishes in endemic regions and the consumption of raw imported or domestic seafood dishes in households and ethnic restaurants in many nonendemic regions.

CONCLUSIONS

Gnathostomiasis is no longer a disease of returning travelers, and autochthonous cases may be anticipated to increase as a result of the importation of live Gnathostoma-infected species and the potential establishment of regional zoonoses of Gnathostoma-infected wild species. Since the eradication of gnathostomiasis is unlikely given the global distribution of Gnathostoma nematodes, the only effective preventive strategy is to educate persons in endemic and nonendemic areas that fish, eels, frogs, snakes, and birds must be cooked thoroughly first before eating and not eaten raw or marinated. The onset of migratory subcutaneous swellings with hyper-eosinophilia weeks to months after consuming raw seafood should provoke suspicion of gnathostomiasis.

Unravelling the riddle of Radix: DNA barcoding for species identification of freshwater snail intermediate hosts of zoonotic digeneans and estimating their inter-population evolutionary relationships

Radix spp. are intermediate host snails for digenean parasites of medical and veterinary importance. Within this genus, species differentiation using shell and internal organ morphology can result in erroneous species identification, causing problems when trying to understand the population biology of Radix. In the present study, DNA barcoding, using cox1 and ITS2 sequences, identified populations of Radix auricularia and Radix balthica from specimens originally morphologically identified as Radix peregra from the UK. Assessment of cox1 and ITS2 as species identification markers showed that, although both markers differentiated species, cox1 possessed greater molecular diversity and higher phylogenetic resolution. Cox1 also proved useful for gaining insights into the evolutionary relationships of Radix species populations. Phylogenetic analysis and haplotype networks of cox1 indicated that R. auricularia appeared to have invaded the UK several times; some haplotypes forming a distinct UK specific clade, whilst others are more akin to those found on mainland Europe. This was in contrast to relationships between R. balthica populations, which had low molecular diversity and no distinct UK specific haplotypes, suggesting recent and multiple invasions from mainland Europe. Molecular techniques therefore appear to be crucial for distinguishing Radix spp., particularly using cox1. This barcoding marker also enables the population biology of Radix spp. to be explored, and is invaluable for monitoring the epidemiology of fluke diseases especially in the light of emerging diseases and food security.

Helminths of three species of opossums (Mammalia, Didelphidae) from Mexico

From August 2011 to November 2013, 68 opossums (8 Didelphis sp., 40 Didelphisvirginiana, 15 Didelphismarsupialis, and 5 Philanderopossum) were collected in 18 localities from 12 Mexican states. A total of 12,188 helminths representing 21 taxa were identified (6 trematodes, 2 cestodes, 3 acanthocephalans and 10 nematodes). Sixty-six new locality records, 9 new host records, and one species, the trematode Brachylaimadidelphus, is added to the composition of the helminth fauna of the opossums in Mexico. These data, in conjunction with previous records, bring the number of taxa parasitizing the Mexican terrestrial marsupials to 41. Among these species, we recognized a group of helminths typical of didelphids in other parts of the Americas. This group is constituted by the trematode Rhopaliascoronatus, the acanthocephalan Oligacanthorhynchusmicrocephalus and the nematodes Cruziatentaculata, Gnathostomaturgidum, and Turgidaturgida. In general, the helminth fauna of each didelphid species showed a stable taxonomic composition with respect to previously sampled sites. This situation suggests that the rate of accumulation of helminth species in the inventory of these 3 species of terrestrial marsupials in the Neotropical portion of Mexico is decreasing; however, new samplings in the Nearctic portion of this country will probably increase the richness of the helminthological inventory of this group of mammals.

Three Human Gnathostomiasis Cases in Thailand with Molecular Identification of Causative Parasite Species

Human gnathostomiasis is one of the important food-borne parasitic zoonoses. The disease is caused by a spirurid roundworm of the genus Gnathostoma. Here, we describe three parasitological confirmed cases of human gnathostomiasis, caused by Gnathostoma spinigerum, in a hospital in Thailand during 2004-2012. Clinical characteristics, treatment, and outcome of cases were revealed. Parasites were accidentally recovered from patients and morphologically identified as Gnathostoma species. Confirmed diagnosis and identification of causative parasite species was made by DNA extraction of the recovered worms, followed by a polymerase chain reaction (PCR) of the second internal transcribed spacer region (ITS2) of DNA and the partial cytochrome c oxidase subunit 1 (cox-1) gene. Sequences corresponding to ITS2 and cox-1 were similar to G. spinigerum. To our knowledge, this study represents the first molecular confirmation that recovered G. spinigerum is a causative agent of human infection in Thailand.

Gnathostoma spinigerum in live Asian swamp eels (Monopterus spp.) from food markets and wild populations, United States

In Southeast Asia, swamp eels (Synbranchidae: Monopterus spp.) are a common source of human gnathostomiasis, a foodborne zoonosis caused by advanced third-stage larvae (AL3) of Gnathostoma spp. nematodes. Live Asian swamp eels are imported to US ethnic food markets, and wild populations exist in several states. To determine whether these eels are infected, we examined 47 eels from markets and 67 wild-caught specimens. Nematodes were identified by morphologic features and ribosomal intergenic transcribed spacer-2 gene sequencing. Thirteen (27.7%) M. cuchia eels from markets were infected with 36 live G. spinigerum AL3: 21 (58.3%) in liver; 7 (19.4%) in muscle; 5 (13.8%) in gastrointestinal tract, and 3 (8.3%) in kidneys. Three (4.5%) wild-caught M. albus eels were infected with 5 G. turgidum AL3 in muscle, and 1 G. lamothei AL3 was found in a kidney (both North American spp.). Imported live eels are a potential source of human gnathostomiasis in the United States.

Pathological and parasitological traits in experimentally infected cats with Gnathostoma binucleatum (Spirurida: Gnathostomatidae)

This study aims to describe some of the unknown pathological and parasitological traits of experimental feline gnathostomosis. Thirteen female cats were orally inoculated with 30 advanced third-stage Gnathostoma binucleatum larvae and were euthanized at various post-infection (p.i.) periods. Clinically, the cats presented with nausea, vomiting, abdominal pain and other nonspecific signs. None of the cats shed eggs in their fecal matter. One cat, euthanized at 6 months p.i., developed a fibrous vascular nodule 2-3 cm in diameter within its gastric wall. The nodule contained caverns filled with mucous and bloody fluid as well as a juvenile worm. The histological characteristics of the nodule were observed, and the morphology of the juvenile worm was revealed using scanning electron microscopy. Another cat, euthanized at 10 months p.i., was found to have a larva within its diaphragm. Infected cats developed increased antibody titers against antigens of G. binucleatum adults and larvae beginning in the first month p.i., and these titers were maintained until the end of the experiment, suggesting the presence of undetected migrating larvae. The low number of cats with parasites and poor development of the parasites found suggest that cats have a low susceptibility to infection by G. binucleatum and cast doubt on the importance of domestic cats in maintaining the biological cycle of this parasite in nature.

Sequence analysis in partial genes of five isolates of Angiostrongylus cantonensis from Taiwan and biological comparison in infectivity and pathogenicity between two strains

Angiostrongylus cantonensis is the most common infectious agent causing eosinophilic meningitis and is present in Taiwan, Thailand and the Pacific islands. Clinical symptoms vary within different endemic regions, and their severity is probably dependent on the number of ingested parasites and the diversity among strains. The experimentally definitive host is the rat, and non-permissive hosts are certain mammals such as humans and mice. In this study, the partial gene sequences of two A. cantonensis strains isolated from five different regions in Taiwan were selected and molecularly analyzed. The internal transcribed spacer gene and cytochrome-c oxidase subunit I gene sequences of the Hualien (H) strain of A. cantonensis differed from those of the Pingtung (P) strain and the other three strains by 19% and 11%, respectively. We analyzed the infectivity, fecundity, and development of the H and P strain in rats and host pathogenicity in mice inoculated with both strains. The number of the emerged first-stage larvae, adult recovery, and average length of adults in Sprague-Dawley rats significantly differed between rats inoculated with the H and P strain. Young adult recovery, average length of young adults, eosinophil counts in the cerebrospinal fluid (CSF), glutathione peroxidase concentration, levels of reactive oxygen species as well as malondialdehyde concentration in the CSF, and the survival of mice significantly differed between BALB/c mice inoculated with the H and P strain. The H strain of A. cantonensis had lower infectivity, delayed fecundity, and poor development in rats, and caused milder pathology and lower mortality in mice than the P strain. These data clearly indicate that the H strain of A. cantonensis is a pathogenically distinct strain with lower infectivity to its definitive host, and causing mild pathogenic symptoms to its non-permissive host.

New insight in lymnaeid snails (Mollusca, Gastropoda) as intermediate hosts of Fasciola hepatica (Trematoda, Digenea) in Belgium and Luxembourg

BACKGROUND

The present study aims to assess the epidemiological role of different lymnaeid snails as intermediate hosts of the liver fluke Fasciola hepatica in Belgium and Luxembourg.

METHODS

During summer 2008, 7103 lymnaeid snails were collected from 125 ponds distributed in 5 clusters each including 25 ponds. Each cluster was located in a different biogeographic area of Belgium and Luxembourg. In addition, snails were also collected in sixteen other biotopes considered as temporary wet areas. These snails were identified as Galba truncatula (n = 2474) (the main intermediate host of F. hepatica in Europe) and Radix sp. (n = 4629). Moreover, several biological and non-biological variables were also recorded from the different biotopes. DNA was extracted from each snail collected using Chelex® technique. DNA samples were screened through a multiplex PCR that amplifies lymnaeid internal transcribed spacer 2 gene sequences (500-600 bp) (acting as an internal control) and a 124 bp fragment of repetitive DNA from Fasciola sp.

RESULTS

Lymnaeid snails were found in 75 biotopes (53.2%). Thirty individuals of G. truncatula (1.31%) and 7 of Radix sp. (0.16%) were found to be positive for Fasciola sp. The seven positive Radix sp. snails all belonged to the species R. balthica (Linnaeus, 1758). Classification and regression tree analysis were performed in order to better understand links and relative importance of the different recorded factors. One of the best explanatory variables for the presence/absence of the different snail species seems to be the geographic location, whereas for the infection status of the snails no obvious relationship was linked to the presence of cattle.

CONCLUSIONS

Epidemiological implications of these findings and particularly the role of R. balthica as an alternative intermediate host in Belgium and Luxembourg were discussed.

Highland cattle and Radix labiata, the hosts of Fascioloides magna

Background

Fascioloides magna is a pathogenic fluke introduced to Europe ca 140 years ago. As it is spreading over the continent, new intermediate and definitive hosts might be involved in transmission of the parasite. In Europe, several studies reported potential new intermediate snail hosts (Radix spp.) for F. magna, and also several cases of fascioloidosis of wild and domestic animals were published. However, the data based on molecular and histological analyses confirming these findings remained unreported. This study aims to refer to unique findings of F. magna in European snails and domestic animals (the first observation in the Czech Republic in the last 30 years) and demonstrate the use of molecular techniques in determination of F. magna.

Results

Two snails of R. labiata naturally infected with F. magna were found; mature cercariae and daughter rediae were observed. Maturity of cercariae was checked by histological methods, however, their ability to encyst was not confirmed. Co-infection of F. magna and Fasciola hepatica in the liver of two highland cattle bulls was proved. Adult fasciolid flukes producing eggs were found in the liver pseudocysts (F. magna) and the bile ducts (F. hepatica). Identification of intermediate hosts, intramolluscan stages, adult flukes and eggs was performed by sequencing the ITS2 region. Connection of F. magna pseudocysts with the gut (via the bile ducts) was not confirmed by means of histological and coprological examinations.

Conclusions

For the first time, Radix labiata was confirmed as the snail host for F. magna under natural conditions and, together with the finding of F. magna infection in cattle, we can expect further transmission of F. magna from wildlife to livestock in localities shared by these hosts.

Evaluation of the antigenic similarities of adult-worm extracts from threeGnathostomaspecies, using sera from Mexican and Japanese patients withGnathostomainfections

The antigenic similarities of adult-worm extracts of Gnathostoma spinigerum, G. hispidum and G. doloresi, all of which are important food-borne parasites causing larva migrans in humans, were evaluated. The 40 sera used came from gnathostomiasis cases in Mexico, where G. binucleatum is endemic, or in Japan, where G. doloresi predominates. When used as the fixed antigens in microplate-ELISA, the adult-worm extracts from the three different species of Gnathostoma were found to have equal binding capacity to the Gnathostoma-specific IgG antibodies in the sera of the Mexican and Japanese patients. The correlation coefficients for the optical densities seen in the ELISA, between any two of the three Gnathostoma extracts, were all >0.900. The dose-response curves produced when four sera were tested, in the microplate-ELISA, against the three different Gnathostoma extracts were nearly identical, indicating that the antigens in each of the extracts had similar avidity. Furthermore, the results of competitive-inhibition ELISA indicated that the antigenic specificities of the three extracts were almost identical. An antigen of 40 kDa, which SDS-PAGE and immunoblot analysis revealed to be present in all three extracts, was recognized by the sera from the gnathostomiasis cases. When the sera were investigated by dot-blot ELISA, they also gave similar results whichever extract was used as the antigen source. It appears that, in the serodiagnosis of gnathostomiasis by microplate- or dot-ELISA, each of the three adult-worm extracts would be equally useful, regardless of the causative species of Gnathostoma.