Helminth zoonoses remain a global problem to public health and the economy of many countries. Polymerase chain reaction-based techniques and sequencing have resolved many taxonomic issues and are now essential to understanding the epidemiology of helminth zoonotic infections and the ecology of the causative agents. This is clearly demonstrated from research on Echinococcus (echinococcosis) and Trichinella (trichinosis). Unfortunately, a variety of anthropogenic factors are worsening the problems caused by helminth zoonoses. These include cultural factors, urbanization and climate change. Wildlife plays an increasingly important role in the maintenance of many helminth zoonoses making surveillance and control increasingly difficult. The emergence or re-emergence of helminth zoonoses such as Ancylostoma ceylanicum, Toxocara, Dracunculus and Thelazia exacerbate an already discouraging scenario compounding the control of a group of long neglected diseases.

The evolution of helminth parasites has long been seen as an interplay between host resistance to infection and the parasite's capacity to bypass such resistance. However, there has recently been an increasing appreciation of the role of symbiotic microbes in the interaction of helminth parasites and their hosts. It is now clear that helminths have a different microbiome from the organisms they parasitize, and sometimes amid large variability, components of the microbiome are shared among different life stages or among populations of the parasite. Helminths have been shown to acquire microbes from their parent generations (vertical transmission) and from their surroundings (horizontal transmission). In this latter case, natural selection has been strongly linked to the fact that helminth-associated microbiota is not simply a random assemblage of the pool of microbes available from their organismal hosts or environments. Indeed, some helminth parasites and specific microbial taxa have evolved complex ecological relationships, ranging from obligate mutualism to reproductive manipulation of the helminth by associated microbes. However, our understanding is still very elementary regarding the net effect of all microbiome components in the eco-evolution of helminths and their interaction with hosts. In this non-exhaustible review, we focus on the bacterial microbiome associated with helminths (as opposed to the microbiome of their hosts) and highlight relevant concepts and key findings in bacterial transmission, ecological associations, and taxonomic and functional diversity of the bacteriome. We integrate the microbiome dimension in a discussion of the evolution of helminth parasites and identify fundamental knowledge gaps, finally suggesting research avenues for understanding the eco-evolutionary impacts of the microbiome in host–parasite interactions in light of new technological developments.

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.

The Mermithidae is a family of nematodes parasitic in many kinds of insects, spiders, leeches, crustaceans and other invertebrates throughout the world. While conducting an assay with entomopathogenic nematodes, we found Armadillidium vulgare (Crustacea: Isopoda) individuals to be infected with Agamermis sp., marking the fourth known discovery of a mermithid infection in the order Isopoda. In this work, we contribute with an 18S rDNA sequence of the isolated nematode and the morphological and morphometrical characterization of the juveniles.

More than 65 species of the genus Microcotyle Van Beneden & Hesse, 1863, have been described to date, most of them infecting Perciformes. Among the scorpaenoids (Perciformes, formerly Scorpaeniformes) the species of the genus Microcotyle parasitize sebastids and scorpaenids worldwide. In this study, we provide new morphological and molecular data for Microcotyle spp. in sebastids and scorpaenids from the Western Mediterranean and north-east Atlantic. Specimens of Helicolenus dactylopterus (Delaroche, 1809) (n = 107) and Scorpaena spp. (n = 107) were examined and their microcotylid specimens morphologically and molecularly characterized. Microcotyle merche n. sp. ex H. dactylopterus and specimens of Microcotyle algeriensis Ayadi, Gey, Justine & Tazerouti, 2016 from a new host and locality (Scorpaena scrofa from the north-east Atlantic) are herein described. Both species are phylogenetically close, but their morphology is markedly different mostly because the anterior lobe of the haptor present in other Microcotyle species is almost absent in M. algeriensis. Findings of M. merche n. sp. in the Mediterranean also excludes the presence of Microcotyle sebastis in this sea, encouraging the review of the exceptionally large host range and geographical distribution of this species.

Slugs are important agricultural pests causing yearly yield losses. However, parasitizing helminths potentially could affect the size of the slug population. Here, a survey of terrestrial slug-parasitic helminths (nematodes and trematodes) was conducted for the first time in Sweden. In total, 268 terrestrial slugs were collected from 27 agricultural field edges in three seasons over 2020 and 2021 and dissected for presence of helminth parasites. Slugs belonging to the genus Arion were molecularly identified by mitochondrial DNA cytochrome c oxidase subunit I (COI) while parasites were identified using ribosomal RNA (18S). Overall, 13% of the collected slugs had helminth parasites and the likelihood of a slug being parasitized was highest in autumn. Slugs identified as Arion vulgaris were more likely to be parasitized than native slug species. The prevalence of nematodes and trematodes were similar; the dominant species found were Alloionema appendiculatum and Brachylaima thompsoni, respectively. This is the first record of the presence of these two species in Sweden.

Next generation sequencing technologies have facilitated a shift from a few targeted loci in population genetic studies to whole genome approaches. Here, we review the types of questions and inferences regarding the population biology and evolution of parasitic helminths being addressed within the field of population genomics. Topics include parabiome, hybridization, population structure, loci under selection and linkage mapping. We highlight various advances, and note the current trends in the field, particularly a focus on human-related parasites despite the inherent biodiversity of helminth species. We conclude by advocating for a broader application of population genomics to reflect the taxonomic and life history breadth displayed by helminth parasites. As such, our basic knowledge about helminth population biology and evolution would be enhanced while the diversity of helminths in itself would facilitate population genomic comparative studies to address broader ecological and evolutionary concepts.

Dirofilaria repens is a zoonotic mosquito-borne filarioid that parasitizes in the subcutaneous tissues of carnivores, that has been incriminated in the great majority of human dirofilariasis cases reported throughout the Old World. From the Republic of Uzbekistan, recent data showed that this parasite is endemic in domestic and wild carnivores. In contrast, information regarding human infection is scarce and mostly outdated, with a single case report being published during the last decades. The present paper reports a case of recurrent autochthonous infection with D. repens in a patient living in the rural area of the Sirdaryo Region of Uzbekistan and having no international travel history. The first diagnosis was in 2019, when the patient presented with what was suspected to be a tumour of the left breast. Three years later, in 2022, she presented for a consultation after experiencing redness, occasional swelling and persistent itching in the umbilical region of the abdomen. The ultrasound indicated the presence of a living, motile nematode. Following anthelmintic therapy, the parasite was surgically removed and identified as a female D. repens. The present report highlights the possibility of human re-infection with D. repens and further underlines the necessity of raising public awareness and implementing of solid control strategies in carnivores.

Adult specimens of Andracantha gravida (Alegret, 1941) were recorded from the intestines of the double-crested cormorant Nannopterum auritus (Lesson) (type host) and brown pelican Pelecanus occidentalis L. in two localities from Mexico: Celestún, Yucatan (south-eastern) and Punta Piedra, Tamaulipas (north-eastern). The specimens of A. gravida are morphologically characterized by having a pipe-shaped body without swellings, the absence of small trunk spines between the two fields of spines on the foretrunk and a cylindrical proboscis with 14–16 rows of 10–12 hooks per row. Newly generated partial sequences of the mitochondrial cytochrome c oxidase subunit 1 (cox1) gene were generated from adult isolates of A. gravida from Mexico and compared with one sequence of A. gravida and with sequences of other polymorphid acanthocephalans available in GenBank. Phylogenetic analyses based on maximum likelihood and Bayesian inference methods of the cox1 dataset placed all the species of Andracantha in a single clade, with weak support. The analyses of the cox1 dataset placed Andracantha sigma Presswell, García-Varela & Smales, 2018, as sister to the clade formed by A. gravida, Andracantha phalacrocoracis (Yamaguti, 1939), Andracantha leucocarboi Presswell, García-Varela & Smales, 2018 and an unidentified species of Andracantha from Japan. The newly generated cox1 sequences of A. gravida from piscivorous birds of Mexico formed a strongly supported clade with the published sequence of A. gravida from the double-crested cormorant from the south-eastern coast of Mexico. The intraspecific genetic divergence among isolates identified as A. gravida ranged from 0.0% to 2.2%. A cox1 haplotype network inferred with 14 sequences revealed the presence of nine haplotypes, two of which were shared between the populations of piscivorous birds from the north-eastern and south-eastern coasts of Mexico and seven of which were unique. The fixation index between the populations from north-eastern and south-eastern Mexico was low (0.06949), which suggests genetic flow. This can be explained by the migration patterns of the brown pelican and the double-crested cormorant along the coasts of the Gulf of Mexico.

In this study, a new dactylogyrid species is described from the gills of two ariid fish species of the Brazilian coast, Genidens barbus and Genidens genidens, by combining morphological characters with partial 18S rDNA sequences. The new species can be distinguished from its congeners by the following morphological characteristics: a male copulatory organ (MCO), a coiled tubular shaft of around one counterclockwise ring, base with a sclerotized cap; MCO with tapered distal region; a T-shaped accessory piece; a vagina, a cup-shaped vaginal vestibule, slightly sclerotized; and a pharynx comprising a muscular, glandular bulb. Supplementary taxonomic data for Chauhanellus velum from Sciades couma (type-host) are also presented and new 18S rDNA sequences of Chauhanellus spp. from other ariid fish from South America are provided. Phylogenetic analyses based on partial 18S rDNA gene sequences placed Chauhanellus riograndinensis n. sp. and Chauhanellus velum as two early divergent lineages within Chauhanellus from South America. Finally, a way to test the monophyly of Chauhanellus and Hamatopeduncularia is also discussed, which may be useful for future studies.

Given their sheer cumulative biomass and ubiquitous presence, parasites are increasingly recognized as essential components of most food webs. Beyond their influence as consumers of host tissue, many parasites also have free-living infectious stages that may be ingested by non-host organisms, with implications for energy and nutrient transfer, as well as for pathogen transmission and infectious disease dynamics. This has been particularly well-documented for the cercaria free-living stage of digenean trematode parasites within the Phylum Platyhelminthes. Here, we aim to synthesize the current state of knowledge regarding cercariae consumption by examining: (a) approaches for studying cercariae consumption; (b) the range of consumers and trematode prey documented thus far; (c) factors influencing the likelihood of cercariae consumption; (d) consequences of cercariae consumption for individual predators (e.g. their viability as a food source); and (e) implications of cercariae consumption for entire communities and ecosystems (e.g. transmission, nutrient cycling and influences on other prey). We detected 121 unique consumer-by-cercaria combinations that spanned 60 species of consumer and 35 trematode species. Meaningful reductions in transmission were seen for 31 of 36 combinations that considered this; however, separate studies with the same cercaria and consumer sometimes showed different results. Along with addressing knowledge gaps and suggesting future research directions, we highlight how the conceptual and empirical approaches discussed here for consumption of cercariae are relevant for the infectious stages of other parasites and pathogens, illustrating the use of cercariae as a model system to help advance our knowledge regarding the general importance of parasite consumption.

The world's biodiversity is in peril. The major threats to biodiversity globally are habitat change, overexploitation, climate change, invasive species and pollution. Not only do these stressors impact free-living organisms, but they affect parasitic ones as well. Herein, this perspective examines the potential consequences of these anthropogenic perturbations on helminth populations and communities, with emphasis on significant developments over the past decade. Furthermore, several case studies are examined in more detail for each of these threats to biodiversity. While effects are widespread and diverse, for the most part all these environmental stressors have negative effects on parasite populations and communities. Those parasites with complex life cycles that are trophically transmitted are often more at risk, although larval parasites with a wide host spectrum, and directly transmitted ectoparasites, appear less threatened and may even benefit. However, differential effects on hosts and parasites, on parasite life cycle stages and on host–parasite interactions made specific predictions difficult and context-dependent. Experimental laboratory and mesocosm studies on specific parasites that test effects on the different life cycle stages, hosts and host–parasite interactions, permitting the determination of net effects of an environmental stressor, yield insightful and sometimes counterintuitive results, although they remain a simplification of real-world complexity. Recent advances in the use of parasites as bioindicators of effects also are discussed.

Members of the genus Strigea Abildgaard, 1790 are endoparasites of birds distributed worldwide. Adults of an undescribed species of the genus Strigea were collected from the intestines of two hawk species (Rupornis magnirostris and Accipiter coperii). Other species identified as Parastrigea macrobursa that were described in Argentina were also recovered from two hawk species (Buteogallus urubitinga and Buteogallus anthracinus) in three localities along the coasts of Mexico. Specimens of the two species were sequenced for three molecular markers, the internal transcribed spacers locus (ITS1-5.8S rDNA- ITS2) and the domains D1–D3 from the large subunit from nuclear ribosomal DNA and the cytochrome c oxidase subunit 1 from mitochondrial DNA. The newly sequenced specimens were aligned with other strigeids sequences downloaded from GenBank. Maximum likelihood and Bayesian analyses inferred with each molecular marker revealed that our specimens of Strigea sp. formed an independent lineage, which is recognized herein as a new species, Strigea magnirostris n. sp., representing the first species in Mexico and the 16th in the Neotropical region. Morphologically, the new species is distinguished from other congeneric species from the Americas by having an oral sucker with several papillae around it, well-developed pseudosuckers (118–248 μm), a tegument covered with tiny spines, a larger cone genital (193–361 × 296–637) and a larger copulatory bursa (247–531 × 468–784). Our phylogenetic analyses revealed that P. macrobursa is not closely related to other members of the genus Parastrigea and is nested within Strigea, suggesting that P. macrobursa should be transferred to Strigea to form Strigea macrobursa n. comb., expanding its distribution range from Mexico to Argentina. Finally, the analyses also revealed that the taxonomy and systematics of Strigea should be re-evaluated, combining morphological and molecular characteristics.

Currently, no effective treatment is available for trichinellosis, a zoonotic parasitic disease caused by infection with the genus Trichinella. Kaempferol (KPF), a dietary flavonoid, has been documented to have anti-parasitic effects and various medicinal uses. Thus, this study aimed to investigate the efficacy of KPF in preventing and treating the intestinal and muscular phases of trichinellosis in mice compared with albendazole (ABZ). To achieve this, mice were divided into six groups: negative control; positive control; KPF prophylaxis; KPF treatment; ABZ treatment; and a combination of ABZ and KPF. Parasitological, histopathological and immunohistochemical evaluations were conducted to assess the effectiveness of the treatments. The parasitological assessment involved counting small intestinal adult worms and encysted muscle larvae. Additionally, the histopathological evaluation used the haematoxylin and eosin staining method for intestinal and muscular sections and picrosirius red stain for muscular sections. Moreover, the immunohistochemical expression of the intestinal NOD-like receptor-pyrin domain containing 3 (NLRP3) was evaluated. The group treated with combined drugs demonstrated a statistically significant reduction in the count of adults and encysted larvae (P < 0.05), a remarkable improvement in the inflammation of the intestines and muscles and a decrease in the thickness of the larvae's capsular layer. Additionally, the highest reduction in NLRP3 expression was observed in this group. Based on this study, KPF shows promise as an anti-trichinellosis medication that, when taken with ABZ, has a synergistic impact by modulating inflammation and larval capsule formation.

Ancylostoma caninum is the most common nematode parasite of dogs in the United States. The present study aimed to describe the molecular epidemiology of A. caninum isolates from the central and eastern states of the United States using the partial mitochondrial cytochrome oxidase (cox1) gene and to compare them with those reported globally. We isolated eggs from faecal samples of dogs and characterized each isolate based on cox1 sequences. A total of 60 samples originating from Kansas, Iowa, New York, Florida and Massachusetts were included. 25 haplotypes were identified in the United States dataset with high haplotype diversity (0.904). Sequence data were compared to sequences from other world regions available in GenBank. Global haplotype analysis demonstrated 35 haplotypes with a haplotype diversity of 0.931. Phylogenetic and network analysis provide evidence for the existence of moderate geographical structuring of A. caninum haplotypes. Our results provide an updated summary of A. caninum haplotypes and data for neutral genetic markers with utility for tracking hookworm populations. Sequences have been deposited in GenBank (ON980650–ON980674). Further studies of isolates from other regions are essential to understand the genetic diversity of this parasite.

In this paper we re-describe Trichuris muris based on morphological data following isolation from two commensal rodent species, Mus musculus from Mexico and Rattus rattus from Argentina. Furthermore, we provide a molecular characterization based on mitochondrial (cytochrome c oxidase subunit 1 mitochondrial gene) and nuclear (internal transcribed spacer 2 region) markers in order to support the taxonomic identification of the studied specimens of T. muris from M. musculus. We distinguished T. muris from 29 species of Trichuris found in American rodents based on morphological and biometrical features, such as the presence of a spicular tube, length of spicule, size of proximal and distal cloacal tube and non-protrusive vulva. We suggest that spicular tube patterns can be used to classify Trichuris species in three groups. Considering that the diagnosis among the species of this genus is mainly based on morphometry, this proposal represents a relevant contribution. We provide molecular studies on two markers, making this the first contribution for T. muris in the Americas. This study makes an important contribution to the integrative taxonomy of cosmopolitan nematode species, and its correct determination from the parasitological study of commensal rodents.

The spirurid nematode Thubunaea schukurovi Annaev, 1973 (Physalopteridae) is redescribed by means of light microscopy and scanning electron microscopy from Ablepharus chernovi collected in Çamlıyayla, Turkey. This is the first record of the species from this host and the first record of the genus Thubunaea from Turkey. The taxonomic status of the species of the genus Thubunaea from the Palaeacrtic and Indomalayan realms is reviewed based on their original morphological descriptions; as a result, Thubunaea dessetae Barus & Tenora, 1976, a parasite of Saara hardwickii (Gray) (Agamidae) in Afghanistan, is transferred to the genus Pseudabbreviata as Pseudabbreviata dessetae (Barus & Tenora, 1976) n. comb. Several species described in India, that is, Thubunaea singhi Deshmukh, 1969 and Thubunaea brooki Deshmukh, 1969, both from Hemidactylus brookii Gray (Gekkonidae), and Thubunaea aurangabadensis Deshmukh, 1969 and Thubunaea syedi Deshmukh, 1969, both from Hemidactylus giganteus Stoliczka, are considered members of the genus Physalopteroides; therefore, the following new combinations are proposed: Physalopteroides singhi, Physalopteroides brooki, Physalopteroides aurangabadensis and Physalopteroides syedi. Thubunaea hemidactylae Oshmarin & Demshin, 1972 from Hemidactylus frenatus Duméril & Bibron in Vietnam is considered a member of the genus Physalopteroides as P. hemidactylae (Oshmarin & Demshin, 1972) n. comb.

Gyrodactylus sprostonae Ling, 1962 is a highly invasive parasite reported across freshwater environments of the northern hemisphere. The taxon was originally described from Carassius auratus (Linnaeus, 1758) and Cyprinus carpio Linnaeus, 1758 in China. This parasite has never been reported in Africa or the southern hemisphere. Recently, this taxon was collected from an indigenous yellowfish, Labeobarbus aeneus (Burchell, 1822), in the Vaal River, South Africa. The present study includes the conclusive identification of the gyrodactylid parasites collected from L. aeneus, including additional taxonomic data, using microscopy and molecular techniques. Microscopy included light microscopy (LM) of whole worms and scanning electron microscopy (SEM) of isolated haptoral sclerites. Additionally, morphometric data were obtained from SEM and compared to that generated using LM. For molecular analysis, the internal transcribed spacer (ITS) region of rDNA was amplified and phylogenetic topologies constructed. The specimens were morphometrically and genetically highly similar to other data for G. sprostonae. Additional point-to-point measurements and ITS rDNA sequences were generated for the taxon, contributing to the morphometric and molecular data for G. sprostonae. The study also includes the first study of the isolated haptoral sclerites of the taxon using SEM, with similar morphometric results to LM. This is the first record of G. sprostonae in the southern hemisphere and from a new, indigenous African host, L. aeneus, indicating host switching to smallmouth yellowfish. Furthermore, these results expand on the knowledge of the distribution of invasive parasites in South Africa, as well as Gyrodactylus species diversity in Africa.