Dentition patterns and molecular diversity of Mastophorus muris (Gmelin, 1790) (Nematoda: Spiruroidea) support a host-associated subdivision.

Mastophorus muris (Gmelin, 1790) is a globally distributed parasitic nematode of broad range mammals. The taxonomy within the genus Mastophorus and the cryptic diversity among the genus are controversial among taxonomists. This study provides a detailed morphological description of M. muris from Mus musculus combined with a molecular phylogenetic approach. Moreover, descriptions and molecular data of M. muris from non-Mus rodents and wildcats complement our findings and together provide new insights into their taxonomy. The analysis of M. muris was based on light microscopy and scanning electron microscopy. The morphological description focused on the dentition pattern of the two trilobed pseudolabia. Additionally, we described the position of the vulva, arrangement of caudal pairs of papillae, spicules and measured specimens from both sexes and the eggs. For the molecular phylogenetic approach, we amplified the small subunit ribosomal RNA gene and the internal transcribed spacer, and the cytochrome c oxidase subunit 1. Mastophorus morphotypes based on dentition patterns and phylogenetic clustering indicate a subdivision of the genus in agreement with their host. We recognize two groups without a change to formal taxonomy: One group including those specimens infecting Mus musculus, and the second group including organisms infecting non-Mus rodents. Our genetic and morphological data shed light into the cryptic diversity within the genus Mastopohorus. We identified two host-associated groups of M. muris. The described morphotypes and genotypes of M. muris allow a consistent distinction between host-associated parasites.

Complete mitochondrial genome of Metathelazia capsulata (Pneumospiruridae) and comparison with other Spiruromorpha species.

Metathelazia capsulata (family Pneumospiruridae) is a lungworm parasitizing the bronchi and bronchioles, described in four species of wild carnivores. Very little molecular data are available on this nematode and none on other species of the Pneumospiruridae family. In this work, we describe for the first time the complete mitogenome (mitochondrial genome) of M. capsulata, being the first described of the family Pneumospiruridae. The mitogenome of M. capsulata has 13,659 bp in length, an A + T content of 79.2%. The mitogenome included 12 protein-coding genes (PCGs) (lacking the atp8 gene), 22 tRNA genes, 2 rRNA genes (all the genes are coded by the heavy strand), and an AT-rich region. The PCGs varied in size (232 bp-1645 bp). Only the tRNA-Trp has the standard cloverleaf secondary structure, while the other 21 do not. The AT-rich region, with a 90.5% A + T content and a length of 389 bp, is located between the cox3 and tRNA-Ala genes. Comparison with the mitogenomes of 29 species of Spiruromorpha infraorder, belonging to different families, demonstrates that M. capsulata mitogenome shared the common characteristics of most of them. The phylogeny constructions yielded phylogenies that were in agreement with the obtained previously by using sequences and gene order data of mitogenomes.

First record of molecular and pathological investigations of physalopterid larvae infection in northern palm squirrel Funambulus pennantii.

Around 100 reported species of Physaloptera commonly infect mammals, reptiles, birds, and amphibians. The identification of Physaloptera species solely on morphological characteristics is difficult, especially in the case of larval and congeneric infections. The present study is an attempt to identify molecularly and to perform phylogeny and pathology of natural Physaloptera larval infection in northern palm squirrels. The molecular confirmation of the recovered parasitic stages was performed by targeting the nuclear 18S rRNA gene sequence. Phylogenetic analysis and evolutionary divergence of the present study isolate with GenBank™ archived Physaloptera sequences were performed. The cysts (containing the larval stages) were subjected to histopathological examination. Morphological identification of the larval stages revealed the presence of pseudolabia, two spines, and a collar-like projection at the anterior end. Histopathology of the cysts revealed transverse sections of parasites in the lumen along with the thickened cystic wall, infiltration of mononuclear cells, fibrous tissue proliferation in the wall, and cellular debris in the cystic lumen. The molecularly confirmed and sequenced present study isolate was submitted to GenBank™ under the accession number LC706442. Blast analysis revealed 96.82-98.64% nucleotide homology of the present study isolate to the GenBank™ archived Physaloptera sequences. The isolate of the present study was monophyletic with Physaloptera sp. and P. praeputialis recovered from the cats of Haryana, India. Also, evolutionary divergence studies revealed no difference among these sequences. The present study evinced the most probable role of the northern palm squirrel Funambulus pennantii as an aberrant or second intermediate host for P. praeputialis.

Larvae of Spirocerca lupi and another spirurid species in the same dung beetles: notes on species identification.

Various dung beetle species of the family Scarabaeidae have been reported as intermediate hosts of Spirocerca lupi from different geographical locations, but there has been no data from south-east Asian countries. In the present study in Vietnam, by using morphological and molecular approaches, we identified the third-stage larvae of S. lupi for the first time in two dung beetle species, Catharsius molossus and Copris szechouanicus, adding them as new intermediate hosts of this nematode. In addition, both beetle species were infected with larvae of another spirurid nematode of Physocephalus sp. At large magnifications above 200×, these two spirurid larvae can be differentiated from each other by their body size (1880-2662 vs. 1417-1635 µm) and detailed morphological features of the anterior and posterior ends, such as the length of the buccal cavity, the position of the nerve ring and excretory pore, and tail characters. However, it is difficult to distinguish them at a lower magnification due to their minute size. Moreover, morphometric data of S. lupi larvae vary among reports and the body length may overlap with that of Physocephalus sp., thus, misidentification may occur, indicating the necessity of careful examination for accurate identification. The findings of the present study also supposed that larvae of S. lupi and more spirurid nematodes may be concurrently found in various dung beetle species, including C. molossus and C. szechouanicus, in other south-east Asian countries. Thus, more investigations in various countries should be conducted to identify spirurid larvae from dung beetles in order to fully understand their role as intermediate hosts of S. lupi and other spirurid nematodes.

Three new species of Ascarophis van Beneden, 1871 (Nematoda: Cystidicolidae) from deep-sea hydrothermal vent fishes of the Pacific Ocean.

Examinations of some deep-sea hydrothermal vent fishes from the western and eastern regions of the Pacific Ocean revealed the presence of three new species of Ascarophis van Beneden, 1871 (Nematoda: Cystidicolidae), all gastrointestinal parasites, namely: A. justinei n. sp. from Thermarces cerberus Rosenblatt & Cohen (type host) and Thermichthys hollisi Cohen, Rosemblatt & Moser (both Zoarcidae, Perciformes) and A. globuligera n. sp. from T. cerberus from the Northern East Pacific Rise, and A. monofilamentosa n. sp. from Pyrolicus manusanus Machida & Hashimoto (Zoarcidae, Perciformes) from the Manus Basin near Papua New Guinea. Specimens are described and illustrated based on light and scanning electron microscopical examinations. In addition to other morphological differences, all the three new species differ from each other by the structure of eggs: eggs bearing a lateral superficial swelling (A. globuligera n. sp.), eggs with one conspicuously long filament on one pole (A. monofilamentosa n. sp.) and eggs smooth, without any filaments or swellings (A. justinei n. sp.). The egg morphology of the two first-named species is unique within all species of Ascarophis, which indicates that all the three newly described species of Ascarophis are probably endemic to the respective hydrothermal vents as their fish hosts.

Redescription of the two most recorded Physaloptera (Nematoda: Physalopteridae) parasitizing lizards in the Americas: first step towards a robust species identification framework.

Despite being the two most recorded species of Physaloptera from lizards in the Americas, P. retusa and P. lutzi are either incompletely described or have accumulated inaccurate morphological data through the years. Here, we redescribe both species from Tropidurus torquatus in the State of Minas Gerais, Brazil, including evaluation of specimens from the Coleção Helmintológica do Instituto Oswaldo Cruz. In P. retusa, the presence and location of amphids, presence and pattern of porous areas on pseudolabia, detailed pattern of cuticular ornamentations on ventral surface of the caudal bursa, structure of cloacal labia, presence of dome-shaped elevation between the last pair of postcloacal papillae and location of phasmids in males, were revealed for the first time. Additional morphometric data are also provided. In P. lutzi, the detailed morphological analysis revealed for the first time, porous areas on pseudolabia, as well as presence of amphids, phasmids, and the detailed ornamentation and papillae arrangement on the male bursa. Also, the presence of an internal tripartite and an external triangular labial tooth in the specimens were observed to be constant, diverging from the assertions by other authors. Finally, in P. lutzi was possible to observe that deirids are consistently located close to muscular oesophagus base with excretory pore slightly posterior to it, and the vulva is always close to anal aperture. The present observations confirmed the validity of P. lutzi and strengthened its taxonomic diagnosis. An up-to-date list of records of both species is provided, including a brief discussion on their host spectrum and geographic range.

Comorbid early esophageal cancer and Gongylonema pulchrum infection: a case report.

BACKGROUND: Gongylonema pulchrum is a zoonotic parasite rarely found in humans. To date, there have been no reports on the carcinogenic properties of G. pulchrum, and there are few reports overall on the relationship between esophageal cancer and parasites. CASE PRESENTATION: This report describes the first case of esophageal gongylonemiasis coexisting with early esophageal cancer. The patient had no high-risk factors for esophageal cancer, such as smoking, flushing after drinking, or tumor history. We speculate the existence of unknown links between esophageal cancer and parasitic infection in this patient. DISCUSSION AND CONCLUSIONS: We report the first case of a human presenting both esophageal G. pulchrum infection and esophageal squamous cell carcinoma with the hope that it may provide evidence for a new hypothesis of tumorigenesis.

First report of molecular and phylogenetic analysis of Physaloptera praeputialis in naturally infected stray cats from India.

Nematodes of the genus Physaloptera are globally distributed and infect a multitude of hosts. Their life cycle involves orthopterans and coleopterans as intermediate hosts. The morphological characters alone are inadequate to detect and differentiate Physaloptera spp. from its congeners. Moreover, molecular studies are limited to compare them precisely. The present communication reports the first molecular phylogenetic characterization of feline Physaloptera spp. from India based on mitochondrial cytochrome c oxidase subunit 1 (COX1) and small subunit ribosomal DNA (18S rDNA). The nematodes were first isolated from the stomach of adult stray cats during necropsy examination. Based on the gross and microscopic characters, the worms were identified as P. praeputialis. Morphological identification was further confirmed through PCR targeting the barcode region of the mitochondrial cytochrome c oxidase subunit I (MT-COI) gene, using nematode-specific primers cocktail followed by species specific primers targeting partial COX1 and 18S rRNA genes. Generated sequences were submitted in NCBI GenBank (MW517846, MW410927, MW411349), and phylogenetic trees were constructed using the maximum likelihood method. When compared with other sequences of Physaloptera species across the globe, the present isolates showed 85.6-97.7% and 97.3-99% nucleotide homology based on COX1 and 18S rRNA gene, respectively. BLASTn analysis revealed a strong identity to other Physaloptera spp., and the phylogenetic tree placed all Physaloptera spp. in the same cluster. This study again indicates the usefulness of molecular techniques to substantiate the identity of species that may lack adequate descriptions and impart new insight for the potentially overlooked significance of P. praeputialis infections in felines.

Molecular phylogenetic study in Spirocercidae (Nematoda) with description of a new species Spirobakerus sagittalis sp. nov. in wild canid Cerdocyon thous from Brazil.

The nematode family Spirocercidae Chitwood and Wehr, 1932, comprises three subfamilies, Spirocercinae Chitwood and Wehr, 1932; Ascaropsinae Alicata and McIntosh, 1933; and Mastophorinae Quentin, 1970, which occur worldwide. Spirocercids infect canids and can cause severe illness. The crab-eating fox, Cerdocyon thous (Linnaeus, 1766), is a canid that inhabits most of South America, including Brazil and is a host for several parasitic worms, in particular, nematodes. However, few reports or genetic data are available on the spirocercids found in this host. In the present study, we describe a new species of Spirobakerus Chabaud and Bain 1981, from the intestine of two crab-eating foxes from two different biomes in Brazil. Spirobakerus sagittalis sp. nov. presents a) unequal spicules, with a long, thin left spicule with a lanceolated shape at the tip; b) a pair of sessile papillae and a median unpaired papillae located anteriorly of the cloaca, and c) a tuft without spines at the tip of the tail in females. The molecular phylogenetic analysis indicated that S. sagittalis sp. nov. is basal to the other species of the subfamily Ascaropsinae, which was not recovered as monophyletic. Our phylogenies also indicated that Spirocercidae is paraphyletic, given that Mastophorinae did not group with Ascaropsinae and Spirocercinae. We provide the first molecular data on the genus Spirobakerus and expand the molecular database of the spirocercids. However, further studies, including the sequences of other spirocercid taxa, are still needed to infer the relationships within this family more accurately.

Gastrointestinal nematodes in two galliform birds from South Africa: patterns associated with host sex and age.

Parasite ecology has recently focused on elucidating patterns and processes that shape helminth communities in avian hosts. However, helminths parasitizing gamebirds are still poorly understood. Here we describe the gastrointestinal nematode fauna of Swainson's spurfowl, Pternistis swainsonii (Phasianidae) and helmeted guineafowl, Numida meleagris (Numididae), collected at three and four localities, respectively, in South Africa and analyze the prevalence, mean abundance and diversity of their helminth communities. Eleven nematode species were collected from spurfowl, which had a mean number of nematode species per host of 3.01 ± 0.18, whereas guineafowl harboured 15 nematode species, with a mean number of nematode species per host of 3.93 ± 0.12. Focusing on the most prevalent species, we also asked if host sex and/or age were associated with infracommunity structure with regard to nematode counts and species richness, as well as the species and taxonomic composition of infracommunities. While pooling data of nematode species masked the influence of host characteristics on helminth communities, analysis of individual nematode species revealed a number of patterns. In particular, adult female bias was seen in Tetrameres swainsonii in spurfowl and in Allodapa dentigera and Gongylonema congolense in guineafowl; Acuaria gruveli reached higher numbers in adult spurfowl than in juveniles, and helminth infracommunities in juvenile male guineafowl were more species rich than those in adult males. Combined, our results suggest that helminth communities of spurfowl and guineafowl are associated with a complex interplay of numerous factors, including host characteristics, parasite traits and environmental conditions.

Gastric Physaloptera Infection in 27 Dogs (1997-2019).

Infection with the stomach worm Physaloptera spp. in dogs can cause chronic vomiting, although the diagnosis is often difficult owing to a low worm burden, single-sex infections, a failure to produce ova, or ova that are of greater density than solutions routinely used for qualitative fecal flotation. A retrospective evaluation was performed of 27 dogs that had gastric Physaloptera spp. infection confirmed endoscopically. In 23 of 27 dogs (85.2%), chronic vomiting was the chief complaint, and Physaloptera was an incidental finding in 3 dogs with esophageal or gastric foreign bodies. The worm burden was low (1-3 worms) in 21 dogs (77.8%), but 2 dogs were infected with large numbers (>50 worms). Prior therapy with routine doses of anthelmintics was ineffective in eight dogs prior to endoscopy. A higher dose and longer duration of fenbendazole in combination with pyrantel pamoate is recommended for treatment of suspected or confirmed infections. Reinfection is common in some dogs and should not be viewed as treatment failure.

Haematobium irritans and Haematobium titillans as potential vectors of Parabronema skrjabini in camels (Camelus bactrianus) in Inner Mongolia, China.

Parabronema skrjabini is one of the most harmful nematodes to camels and is responsible for economic losses in animal husbandry industry. There is an urgent need for in-depth studies of potential vectors of the nematode due to its scant regarding information. As previous studies indicated that flies may be the vectors of P. skrjabini, we captured flies in the main camel-producing areas of Inner Mongolia. After autopsy of the specimens of two species of horn flies, we observed the morphology of the suspected nematode larvae found in them. Internal transcribed spacer ribosomal-DNA gene sequences were considered the best candidate to confirm the species of the larvae found. Our results showed that the homology compared with P. skrjabini was 99.5% in GenBank. Subsequently, we preliminarily identified two species of horn flies through morphological observation and then sequenced the mitochondrial-DNA-gene cytochrome oxidase subunit I obtained from two species of horn flies, with 100 and 99.2% similarity to sequences deposited in GenBank, respectively. Thus, we identified Haematobia titillans and Haematobia irritans and provided evidence for their potential role as vectors of parabronemosis. Our study provides reference for future research on the life history of the nematode and the vectors of parabronemosis.

Ascarophisnema hoiae n. sp. (Nematoda: Cystidicolidae), from the stomach of the trumpeter whiting, Sillago maculata Quoy & Gaimard (Perciformes: Sillaginidae) from Moreton Bay, Queensland, Australia.

Ascarophisnema hoiae n. sp. (Nematoda: Cystidicolidae) is described from the stomach of the trumpeter whiting, Sillago maculata Quoy & Gaimard (Perciformes: Sillaginidae) from Moreton Bay, Queensland, Australia. It differs morphologically from the only other valid congener, A. tridentatum Moravec & Justine, 2010 in the shape of the sub-labium and in the lengths of the spicules and the morphology of their distal tips (bifid). It represents the first record of this genus from Australia and appears to be highly oioxenous, having been found only in this host species among 133 other species of fish examined at the same locality.

New insights into the tetrameric family of the Fur metalloregulators.

The ferric uptake regulator (Fur) belongs to the family of the metal-responsive transcriptional regulators. Fur is a global regulator found in all proteobacteria. It controls the transcription of a wide variety of genes involved in iron metabolism but also in oxidative stress or virulence factor synthesis. As a general view, Fur proteins were considered to be dimeric proteins both in solution and when bound to DNA. However, our recent data demonstrate that Fur proteins can be classified into two subfamilies, according to their quaternary structure. The group of dimers is represented by E. coli, V. cholerae and Y. pestis Fur and the group of highly stable tetramers by P. aeruginosa and F. tularensis Fur. Here, another tetrameric structure of a PaFur mutant containing manganese and zinc metal ions is described. Through biochemical, structural and computational studies, we have deciphered the important structural characteristics of the tetramers and studied the main interactions responsible for their strength. Potential or mean force calculations for tetramer formation have been determinant to quantify these interactions. Moreover calculations allow us to propose that some conserved residues prevent the tetramerization in the subfamily of dimeric Fur.

Taxonomic status of Rhabdochona ictaluri (Nematoda: Rhabdochonidae) based on molecular and morphological evidence.

The genus Rhabdochona includes more than 100 species infecting freshwater fishes in all zoogeographical regions of the world. In Mexico, 12 nominal species of Rhabdochona have been recorded. Of these, Rhabdochona ictaluri was originally described as a parasite of endemic catfishes of the family Ictaluridae; however, the species was later considered on morphological grounds as a junior synonym of Rhabdochona kidderi. In this study, newly sampled specimens of R. ictaluri were obtained from the type host and type locality and were used to perform a detailed morphological analysis and molecular phylogenetic inferences through one mitochondrial and two nuclear genes; data were used in an integrative taxonomy context to test the taxonomic status of R. ictaluri. This approach proved to be very useful to confirm the validity of this species, and robust species limits were established between these two putative species considering morphology, molecular data, host association, and biogeography.

A new species of Physaloptera (Nematoda: Spirurida) from Proechimys gardneri (Rodentia: Echimyidae) from the Amazon rainforest and molecular phylogenetic analyses of the genus.

Nematodes of the genus Physaloptera are globally distributed and more than 100 species are known. Their life cycle involves insects, including beetles, cockroaches and crickets, as intermediate hosts. This study describes a new species of Physaloptera and reports molecular phylogenetic analyses to determine its relationships within the family Physalopteridae. Physaloptera amazonica n. sp. is described from the stomach of the caviomorph rodent Proechimys gardneri collected in the Amazon rainforest in the state of Acre, Brazil. The species is characterized by the male having the first and second pair of sessile papillae asymmetrically placed, lacking a median papilla-like protuberance between the third pairs of sessile papillae, differentiated by size and shape of the spicules, while females have four uterine branches. For both nuclear 18S rRNA and MT-CO1 gene-based phylogenies, we recovered Turgida sequences forming a clade nested within Physaloptera, thus making Physaloptera paraphyletic to the exclusion of Turgida, suggesting that the latter may have evolved from the former monodelphic ancestral state to a derived polydelphic state, or that some species of Physaloptera may belong to different genera. Relationships between most taxa within Physaloptera were poorly resolved in our phylogenies, producing multifurcations or a star phylogeny. The star-like pattern may be attributed to evolutionary processes where past simultaneous species diversification events took place. Physaloptera amazonica n. sp. formed an independent lineage, separately from the other species of Physaloptera, thus supporting the status of a new species. However, all molecular data suggested a closer relationship with other Neotropical species. In conclusion, we added a new species to this already largely diverse genus Physaloptera, bringing new insights to its phylogenetic relationships. Further analyses, adding more species and markers, should provide a better understanding of the evolutionary history of physalopterids.

Diversity of Rhabdochona mexicana (Nematoda: Rhabdochonidae), a parasite of Astyanax spp. (Characidae) in Mexico and Guatemala, using mitochondrial and nuclear genes, with the description of a new species.

Among fish parasitic nematodes Rhabdochona is one of the most speciose genera, with c. 100 species. Twelve congeneric species occur in Mexican freshwater fishes, in a region located between the Nearctic and Neotropical biogeographical regions. Host association and biogeographical history have determined the high species richness of Rhabdochona in Mexico. One of these species, Rhabdochona mexicana, is highly specific to the characid genus Astyanax. Characids are a group of freshwater fish with Neotropical affinity. In this paper, we explore the genetic diversity of R. mexicana through samples obtained from populations of Astyanax spp. across river basins of Mexico and Guatemala. Sequences of one mitochondrial and two ribosomal genes were obtained from 38 individuals and analysed using Maximum Likelihood and Bayesian Inference analysis. Phylogenetic analyses using cox1, and a concatenated alignment of 18S + 28S + cox1 recovered two genetic lineages. One of them corresponded with R. mexicana sensu stricto; this lineage included three reciprocally monophyletic subgroups; the other lineage was highly divergent and represented a putative candidate species. A detailed morphological study was conducted to corroborate the molecular findings. We describe a new species herein and discuss the implications of using molecular tools to increase our knowledge about the diversity of a speciose genus such as Rhabdochona.

First case of human Gongylonema pulchrum infection in Slovenia.

Nematodes of the genus Gongylonema infect a wide range of mammals worldwide but are only sporadically reported in humans. We describe a case of human infection with Gongylonema pulchrum in a 41-year-old man. The patient extracted the nematode from the submucosa under his tongue and correctly self-diagnosed the infection with the help of the Google search engine. In the laboratory, the collected nematode was confirmed as G. pulchrum microscopically by morphological analysis and genetically by amplifying and sequencing the parasite's rDNA. This is the first report of human G. pulchrum infection in Slovenia.

Helminth community and host dynamics in northern bobwhites from the Rolling Plains Ecoregion, U.S.A.

One hundred and sixty-one northern bobwhites (Colinus virginianus; hereafter 'bobwhite') were examined from the Rolling Plains ecoregion of Texas and western Oklahoma from 2011 to 2013. Complete necropsies yielded 13 species, of which two are new host (Gongylonema phasianella) and region (Eucoleus contortus) records and three (Dispharynx nasuta, Tetrameres pattersoni and Oxyspirura petrowi) are known to cause morbidity and mortality. Of the species found, Aulonocephalus pennula commonly occurred, Oxyspirura petrowi was intermediate in prevalence, and the remaining species were rare. Species richness was similar compared to studies from the southeastern U.S., but higher than studies from the same region. In addition, 12 of the 13 species were heteroxenous helminths, supporting the theory that heteroxenous helminths in semi-arid regions are more successful than monoxenous helminths. Prevalence and abundance of A. pennula and O. petrowi were higher in adult bobwhites than in juveniles. Abundance of A. pennula and O. petrowi was higher at southern locations compared to northern locations in the study area. Our study is the first to provide a current assessment of the bobwhite helminth community across the Rolling Plains ecoregion of the U.S.

Helminth parasites of Mabuya arajara Rebouças-Spieker, 1981 (Lacertilia: Mabuyidae) from Chapada do Araripe, northeastern Brazil.

We provide data on the helminth fauna from the digestive tract of the lizard Mabuya arajara Rebouças-Spieker, 1981 from Chapada do Araripe, northeastern Brazil. Seventy one of the 127 lizards examined (56%) were infected with four nematode species: Physalopteroides venancioi and Physaloptera sp. (Physalopteridae), Strongyluris oscari (Heterakidae), and Parapharyngodon alvarengai (Pharyngodonidae), the latter being the component species (prevalence 53.5%; mean intensity of infection 3.37 ± 2.0; discrepancy index D = 0.69). The helminth P. alvarengai infected M. arajara throughout the year and showed increased infection rates in July, at the beginning of the dry season. In addition to the relationship with seasonality, lizards with greater body length and/or body mass were more infected. Relationships between number of parasites and body mass and with the sexes of lizards, on the other hand, were not found. Mabuya arajara represents a new host for these nematodes. This study contributes to the knowledge of the helminth fauna associated with the digestive tract of lizards from South America and the Caatinga domain.