A bottlenose dolphin, Tursiops sp., stranded on the coast of South Carolina, USA was found to be heavily infected in its intestine by tapeworms, which we identified molecularly. Sequencing of portions of the mitochondrial cytochrome c oxidase I (COI) and nuclear large subunit ribosomal RNA (28S rRNA) genes showed the cestodes to be Diphyllobothrium stemmacephalum, commonly known as a broad tapeworm. Infections of marine mammals by Diphyllobothrium have been previously reported in the Northwestern Atlantic Ocean, but only to genus level. Infection by tapeworms may be rare in dolphins in South Carolina, but because this species is zoonotic, its presence indicates the potential for an emerging public health concern.

This study provides a comprehensive analysis of the morphology and genetics of Raillietiella gigliolii, an endoparasitic pentastomid found in amphisbaenians. The research was based on specimens deposited in the Universidade Regional do Cariri (URCA), as well as newly collected individuals from the Brazilian Caatinga. Detailed morphological descriptions were carried out, including measurements of the hooks, cephalothorax, tail, buccal cadre, and the copulatory spicule in males. In parallel, the first molecular characterisation of this species was performed, targeting the mitochondrial COI gene (barcode region). All specimens exhibited consistent morphotypes, particularly in the shape of the hooks, with no observable variation between males and females, nor between individuals parasitising different hosts (Amphisbaena alba and A. vermicularis). Molecular analyses revealed a well-supported monophyletic clade, with no detectable genetic divergence among individuals, confirming both the morphological stability and genetic delimitation of the species. These findings support the recognition of R. gigliolii as a clearly delineated species, currently restricted to amphisbaenians, which does not exhibit significant morphological variability, in contrast to other congeners.

Malacological surveys were conducted in 2021 in the Kimpese region of Central Kongo Province, west of the Democratic Republic of Congo (DRC). Snail specimens were collected following a standardised protocol, identified using morphological and molecular methods, and tested for schistosome infection using a diagnostic PCR assay. Positive snail samples were sequenced to characterise the infecting schistosome species. Partial mitochondrial cytochrome c oxidase subunit 1 (COX1) gene sequences were used in phylogenetic analyses to explore the evolutionary position of these snail species within the broader African context. At least four intermediate snail hosts were identified: Bulinus truncatus, Bulinus forskalii, Biomphalaria pfeifferi, and a Biomphalaria species belonging to the Nilotic species complex (tentatively named Biomphalaria cf sudanica), of which the species identity needs to be confirmed. A total of 37 out of 1,196 snails (3.1%) tested positive for schistosome infection, with an infection prevalence of 7.4% for B. truncatus with Schistosoma haematobium and 1.5% for Biomphalaria spp. with Schistosoma mansoni. The S. mansoni sequence retrieved from these samples formed a basal clade relative to Zambian isolates, whereas S. haematobium grouped with the most frequently characterised haplotype cluster previously identified across mainland Africa. It is important to note that no animal schistosome species were identified in this study. Both the sequences from the snail hosts and the parasites represent novel contributions from the DRC. Additionally, the findings update the current knowledge of schistosomiasis transmission in the Kimpese region by providing insight into the phylogenetic placement, species diversity, and infection status of local snail populations.

Visceral larva migrans syndrome (VLM) is caused by L2 Toxocara canis. This parasitic disease is difficult to diagnose in humans, but specific antigen identification could allow for parasite detection. The aim of this study was to analyse antigens of different parasite developmental stages and observe their cross-reactions with antigens from other parasites to determine their importance in the diagnosis of VLM caused by T. canis. Sera from 14 children with cryptogenic epilepsy previously positive for T. canis were analysed via Western blot (WB) using T. canis excretion-secretion antigens (TESs) from distinct morphological parasite stages; cross-reactivity of these antigens with antigens from other parasites were evaluated. Children sera recognized antigens from L2 T. canis TES, mainly a protein of 24 kDa. Proteins in the medium- and high-molecular-weight ranges were also detected in the egg phase. In the adult phase, only 42.9% of analysed sera recognized a protein of high-molecular weight. Cross-reaction tests identified medium and high-molecular weight proteins, mainly from L2 of Ascaris lumbricoides and Gnathostoma binucleatum and adults of Ancylostoma caninum, but none of the proteins found had crossover with low-molecular weight proteins from Toxocara canis. Antigens in the larval morphological stage of T. canis TES were recognized in the highest percentage of the analysed sera; these antigens could be used to diagnose VLM.

Aprocta bainae Mutafchiev & Kinsella sp. nov, collected from the orbits of a flammulated owl, Psiloscops flammeolus (Kaup) (Strigiformes: Strigidae), from Montana, USA is described based on light and scanning electron microscopies. Additionally, fragments of 18S and 12S rRNA genes of the new species are provided. Based on the molecular data of the 18S gene, A. bainae n. sp. was included in a monophyletic clade of the genus Aprocta. Aprocta ophthalmophaga Stossich, 1902 and Aprocta colaptidis Schuurmans-Stekhoven, 1950 are considered species inquirendae. Aprocta colaptidis Schuurmans-Stekhoven, 1951, a homonym of A. colaptidis Schuurmans-Stekhoven, 1950, is considered a species incertae sedis.

Understanding the stock structure of a commercial species is essential for sustainable management. Failure to do so can lead to the depletion of regional sub-populations, erosion of genetic diversity, and ecosystem services loss. Plaice, Pleuronectes platessa, is a commercially exploited species inhabiting the continental shelf around Iceland. Despite a tagging study providing support for strong spawning site and feeding ground fidelity, and otolith microstructure analysis revealing local population structure, plaice is managed as a single stock in Icelandic waters. Here, we describe and quantify the parasite fauna of plaice and assess the potential of parasites as biological tags for stock identification of plaice in Icelandic waters. A total of 82 plaice were sampled from different geographical locations (north and south) and seasons (summer and winter) in Iceland. Our sampling identified 11 parasites, five of which are new parasite records for plaice in Icelandic waters: the trematodes Zoogonoides viviparus (adults) and Rhipidocotyle sp. (metacercariae), and the nematodes Contracaecum osculatum (larvae), Dichelyne sp. (adults), and Hysterothylacium aduncum (larvae and adults). Additionally, we recovered metacercariae of the trematode genus Apatemon, which has not been recorded previously from plaice. Two parasites were identified as potential biological tags for stock identification – namely, the nematode Anisakis simplex and the trematode Z. viviparus. Our findings support a complex stock structure for plaice in Icelandic waters and the need for an integrative strategy to stock identification to provide fine spatial scale data required to inform fisheries managers.

Neodiplostomum vaucheri Dubois, 1983 is a digenean trematode originally described from the intestine of the woolly false vampire bat, Chrotopterus auritus (Peters, 1856), in the northwestern Peruvian Amazon. Decades later, it was also reported from the fringe-lipped bat, Trachops cirrhosis (Spix, 1823), in Ecuador. During a helminthological survey of phyllostomid bats at the Kawsay Biological Station in Madre de Dios, southeastern Peruvian Amazonia, specimens of Neodiplostomum Railliet, 1919 were recovered from the intestine of T. cirrhosus. Morphological comparisons with the holotype confirmed these specimens as conspecific with N. vaucheri. Phylogenetic inference supported the morphological identification, recovering the Peruvian isolate with an N. vaucheri isolate from another South American region within the same clade, with strong support (ML = 90; BI = 0.9587). The observed genetic divergence (4.47% under the Kimura two-parameter model and 4.27% based on uncorrected p-distances) in the partial cox1 sequence may indicate cryptic diversity, as previously noted in congeners. This represents the first integrative characterization of a digenean from a bat host in Peru, contributing to our understanding of parasite diversity in neotropical chiropterans. Furthermore, the use of third-generation sequencing technology (Oxford Nanopore) proved effective for generating reliable partial gene sequences, underscoring its applicability in molecular helminthology.

Trichinellosis is a global foodborne zoonotic disease. Numerous drugs used in its treatment exhibit inadequate absorption and diminished efficacy against encysted larvae in muscle tissue. Therefore, there is a need for innovative therapeutic agents to treat trichinellosis. Allium sativum (A. sativum), commonly known as garlic, is a bulbous plant that has been historically utilized in the treatment of various ailments. Currently, there is a paucity of data regarding the in vivo efficacy of A. sativum against trichinellosis. This study assessed the antiparasitic, anti-inflammatory, and antiapoptotic effects of A. sativum in murine models, independently or in conjunction with albendazole (ABZ), against the intestinal and muscular stages of trichinellosis. Fifty mice were equally categorized into five groups: negative control, positive control, ABZ, A. sativum, and a combination of ABZ and A. sativum. The effectiveness of the examined drugs was assessed through parasitological, biochemical, histological, and immunohistochemical methodologies. A. sativum resulted in a significant reduction of adult counts by 39.7% and larval counts by 54.4%. The inflammatory cellular infiltrate in the intestine and muscle was significantly reduced. In mice treated with A. sativum, serum levels of IFN-γ exhibited a significant increase, accompanied by a rise in Bcl-2 expression and a notable decrease in COX-2 expression. In conclusion, A. sativum demonstrates potential as a therapeutic agent for treating experimental trichinellosis, particularly during the muscle phase of the disease. It may serve as a safe promising therapy for trichinellosis.

The superfamily Diplostomoidea Poirier, 1886 is a large, globally distributed group of digeneans characterized by the presence of a unique holdfast organ and parasitic in most major groups of vertebrates (birds, mammals, reptiles, fishes) as definitive hosts. A number of diplostomoideans are associated with diseases in their intermediate and, more rarely, definitive hosts. Prior to this work and upon the recent synonymization of the Brauninidae Wolf, 1903, the Diplostomoidea included 5 families: Bolbocephalodidae Strand, 1935; Cyathocotylidae Mühling, 1896; Diplostomidae Poirier, 1886; Proterodiplostomidae Dubois, 1936; and Strigeidae Railliet, 1919. The separation of these families was based primarily on the structure and shape of prosoma and holdfast organ as well as the presence/absence of cirrus sac and paraprostate. More rarely, distinguishing among families was based on life cycles and types of larval stages, excretory system or even host specificity. However, due to the inconsistent nature of most of morphological and biological characters across the Diplostomoidea and nearly universal lack of agreement on their relative value, the systematic history of the group has been extremely tumultuous, and none of many classification systems proposed over the last 140 years has become broadly accepted or supported by phylogenetic analyses. Extensive molecular phylogenetic studies of the Diplostomoidea in the last 15 years helped to partly improve the classification system and resolve multiple taxonomic questions. Notably, practically all molecular phylogenies have clearly demonstrated non-monophyly of the two largest families, the Diplostomidae and the Strigeidae and indicated it as systematic problem. We provide a brief overview of the history and current state of knowledge of diplostomoidean systematics and re-evaluate the classification system of the Diplostomoidea based on morphological and molecular evidence. We propose changes in the classification system that reconciles the traditional morphological and life cycle data with molecular phylogenies. The major element of the proposed classification system is the synonymization of the families Proterodiplostomidae and Strigeidae with the Diplostomidae as the only feasible way to resolve the problem of consistent non-monophyly of the latter two families and provide stability to the classification system.

The interaction of helminth infections with type 2 diabetes (T2D) has been a major area of research in the past few years. This paper, therefore, focuses on the systematic review of the effects of helminthic infections on metabolism and immune regulation related to T2D, with mechanisms through which both direct and indirect effects are mediated. Specifically, the possible therapeutic role of helminths in T2D management, probably mediated through the modulation of host metabolic pathways and immune responses, is of special interest. This paper discusses the current possibilities for translating helminth therapy from basic laboratory research to clinical application, as well as existing and future challenges. Although preliminary studies suggest the potential for helminth therapy for T2D patients, their safety and efficacy still need to be confirmed by larger-scale clinical studies.

Cryphodera guangdongensis n. sp. was collected from the soil and roots of Schima superba in Guangdong province, China. The new species is characterised by having a nearly spherical female, with dimensions of length × width = 532.3 (423.8–675.3) × 295.6 (160.0–381.2) μm, stylet length of 35.7 (31.1–42.1) μm, protruding vulval lips, a vulval slit measuring 54.2 (47.4–58.9) μm, an area between the vulva and anus that is flat to concave, and a vulva–anus distance 49.3 (41.1–57.6) μm. The male features two lip annules, a stylet length of 31.7 (27.4–34.8) μm and basal knobs that are slightly projecting anteriorly, while lateral field is areolated with three incisures and spicules length of 27.1 (23.7–31.0) μm. The second stage juvenile is characterised by a body length of 506.1 (441.8–564.4) μm long, two to three lip annules, a stylet length 31.2 (29.7–33.2) μm which is well developed, basal knobs projecting anteriorly, a lateral field that is areolate with three incisures, and a narrow rounded tail measuring 63.2 (54.2–71.3) μm long, with a hyaline region of 35.6 (27.4–56.6) μm long that is longer than the stylet. Based on morphology and morphometrics, the new species is closely related to C. sinensis and C. japonicum within the genus Cryphodera. The phylogenetic trees constructed based on the ITS-rRNA, 28S-rRNA D2–D3 region, and the partial COI gene sequences indicate that the new species clusters with other Cryphodera species but maintains in a separated subgroup. A key to the species of the genus Cryphodera is also provided in this study.

The nematodes isolated from three species of Chanodichthys were completely consistent with the morphological description of Rhabdochona coronacauda. We provide new morphometric data for R. coronacauda, which slightly differ from those of the original description. For the first time, we performed a phylogenetic analysis by using both primary (linear) and secondary (folded structures) sequences of the complete 18S rRNA gene for three superfamilies of Spiruromorpha. The interspecific genetic distances within the genus Rhabdochona were 0.13%–3.06% between 18 species. Rhabdochona coronacauda was sister to a sub-group consisting of the type species R. denudata, R. hospeti, R. hellichi, and R. turkestanica. The secondary structures reconstructed for 35 species of three superfamilies from the order Spiruromorpha comprised 16 conformations of the region including helix 39 and expansion segment 9, and two conformations of helix 17. Helix 39 can be used to differentiate single species or separate species groups of Rhabdochona. The structures of helix 39 in both Rhabdochonidae and Cystidicolidae with Salmonema had an identical 39a domain but differed in the 39b domain and expansion segment 9. In addition, the structure of the helix 39–expansion segment 9 domain within and between families of different superfamilies and their resolution on the phylogenetic tree in combination did not correspond to the accepted classification of spiruromorph nematodes. Helix 17 did not differ within Rhabdochona, or between Rhabdochonidae and Cystidicolidae. At the superfamily level, helix 17 can distinguish Thelazioidea, Spiruroidea, and Habronematoidea from Rhabdochonidae, and Cystidicolidae from Spirocercidae, Thelaziidae, and Pneumospiruridae.

A variety of larvae and parthenitae of trematodes have been detected in gastropods in the intertidal zone in Japan. However, because of the difficulty associated with the morphological identification of these stages, they have rarely been identified to the species or higher taxonomic levels. In this study, trematodes of these stages were sampled from intertidal gastropods in the Japanese coastal regions and were identified to the species, genus, or family levels morphologically and molecularly to elucidate or predict their life cycles. Investigation of 17 gastropod species (682 individuals in total) from 14 localities led to the detection of trematodes in 47 individuals belonging to six snail species. The infected gastropods were morphologically identified as Nipponacmea fuscoviridis, Monodonta confusa, Trochus sacellum, Batillaria attramentaria, Littorina brevicula, and Purpuradusta gracilis. Our molecular analyses revealed that sporocysts, rediae, and metacercariae from the gastropods were divided into 14 species belonging to nine families: Philophthalmidae, Fellodistomidae, Gymnophallidae, Lepocreadiidae, Heterophyidae, Opisthorchiidae, Notocotylidae, Microphallidae, and Opecoelidae. These trematodes were thought to use fishes, octopuses, seabirds, and marine mammals as their definitive hosts. Marine organisms such as jellyfishes, crustaceans, and fishes are also thought to act as the second intermediate and paratenic hosts of few present trematode species. As for the other trematode species, DNA barcodes of trematodes from various marine organisms will also illuminate the life cycles in future.

Echinococcus equinus is a parasitic cestode primarily maintained within an equine-canine life cycle, with horses, donkeys, mules, and other ungulates serving as intermediate hosts. Although E. equinus has historically been considered non-zoonotic, recent molecular studies suggest that this assumption may need to be reevaluated. This study aimed to investigate the presence and molecular characterization of E. equinus in equids from Türkiye. A retrospective analysis of 52 equine necropsies performed between 2020 and 2025 identified hydatid cysts in one Arabian horse and two donkeys. Gross and histopathological examination confirmed the presence of hydatid cysts in the liver and lungs, exhibiting characteristic structural features. Molecular identification was conducted through PCR amplification targeting the mitochondrial cytochrome c oxidase subunit 1 (mt-CO1) gene, with all positive samples confirmed as E. equinus through sequence analysis. Phylogenetic analysis demonstrated a close relationship between the obtained sequences and reference E. equinus strains from other geographic regions. These findings provide the molecular confirmation of E. equinus in equids from Türkiye and underscore the need for targeted surveillance to better understand its distribution, transmission, and zoonotic relevance, especially considering the first confirmed human case reported in the country in 2021.

Metacercariae of Diplostomum spp. are widespread fish parasites. In this study we obtained the first data on infection of Bullhead Cottus koshewnikowi with these larvae in five rivers of northern Europe (Finland and Russia) using molecular and morphological description. Three Diplostomum spp. were revealed in the eyes of bullheads. Diplostomum spathaceum and D. mergi Lineage 3 sensu Georgieva et al. (2013) were found in the lens, while Diplostomum sp. Lineage 6 sensu Blasco-Costa et al. (2014) was found in the retina. We obtained molecular data on these three species and provided morphological characteristics of the latter two species. Partial sequences of the cytochrome c oxidase subunit 1 (cox1) and ITS1-5.8S-ITS2 were amplified for 20 isolates. Using molecular data, we ascertained the species identification and obtained new information on the life cycles of D. mergi Lineage 3 and Diplostomum sp. Lineage 6. Partial cox1 sequences were used to assess the haplotype diversity of D. mergi Lineage 3 and Diplostomum sp. Lineage 6 in the study area. Discriminant analysis showed that D. mergi Lineage 3 was morphometrically close both to the species of the lens complex (D. mergi Lineage 2, D. mergi, D. nordmanni, and D. parviventosum) and to the species from the retina (D. pungiti, D. volvens). Dimensions of Diplostomum gobiorum lay far outside the confidence interval of D. mergi Lineage 3. Our molecular and morphological data and the new information about the hosts and the distribution of these parasites are a crucial step towards elucidating the diversity and life cycles of these important parasites. The data on the infection of bullheads in the River Utsjoki (a tributary of the River Teno, Finland) with metacercariae of Diplostomum spp. offer some insights into the relationships between the introduced host and the native parasites. Infection of bullheads, which are considered invasive in the Teno River system, with metacercariae of Diplostomum spp. may lead to increased infection levels in resident fish.

A novel entomopathogenic nematode (EPN) species, Steinernema tarimense n. sp., was isolated from soil samples collected in a Populus euphratica forest located in Yuli County within the Tarim Basin of Xinjiang, China. Integrated morphological and molecular analyses consistently place S. tarimense n. sp. within the ‘kushidai-clade’. The infective juvenile (IJ) of new species is characterized by a body length of 674–1010 μm, excretory pore located 53–80 μm from anterior end, nerve ring positioned 85–131 μm from anterior end, pharynx base situated 111–162 μm from anterior end, a tail length of 41–56 μm, and the ratios D% = 42.0–66.6, E% = 116.2–184.4, and H% = 25.5–45.1. The first-generation male of the new species is characterized by a curved spicule length of 61–89 μm, gubernaculum length of 41–58 μm, and ratios D% = 36.8–66.2, SW% = 117.0–206.1, and GS% = 54.8–82.0. Additionally, the tail of first-generation female is conoid with a minute mucron. Phylogenetic analyses of ITS, 28S, and mt12S sequences demonstrated that the three isolates of S. tarimense n. sp. are conspecific and form a sister clade to members of the ‘kushidai-clade’ including S. akhursti, S. anantnagense, S. kushidai, and S. populi. Notably, the IJs of the new species exhibited faster development at 25°C compared to other Steinernema species. This represents the first described of an indigenous EPN species from Xinjiang, suggesting its potential as a novel biocontrol agent against local pests.

Cystic echinococcosis (CE) is a significant zoonotic helminthic disease with considerable public health and economic impact in endemic regions. We aimed to analyse the climatic and environmental factors affecting the human CE cases in North Khorasan Province, northeast Iran. Using a geographic information system, we map the addresses of 316 hospitalised CE patients from 2012 to 2022 and examined the influence of climatic variables, altitude, and land cover on CE case distribution. Data were analysed using logistic regression models. Most patients were female (58.9%) and aged 21–60 years (67.4%), with liver involvement being the most common (57.3%). The multivariate model identified urban settings, irrigated and dry farms, soil temperature, and humidity as the most important geoclimatic determinants, respectively. In contrast, gardens, moderate and excellent rangelands, minimum, maximum, and mean air temperatures, and rainfall were only found to be significant factors in univariate models. High-risk areas for CE include urban and suburban regions, surrounding fields, and pastures where stray dogs and wild canids roam, livestock husbandries are present, and residents consume unsanitised vegetables. Additionally, areas with lower soil and weather temperatures and higher humidity conditions that may enhance the survival of E. granulosus eggs dispersed by canids were identified as high-risk zones. Health managers can use these findings to prioritise control programs and allocate limited resources to these areas, ultimately reducing the future incidence of CE.

Haemonchus contortus is a parasitic nematode that causes significant economic losses in ruminant livestock worldwide. In this study, we assessed the global genetic diversity and population structure of H. contortus using mitochondrial COX1 and ribosomal ITS2 sequences retrieved from the NCBI GenBank database. In total, 324 haplotypes of the COX1 and 72 haplotypes of the ITS2 were identified. The haplotype diversity values were all higher than 0.5, and the nucleotide diversity values were higher than 0.005. The Tajima’s D value for COX1 (−1.65634) was higher than that for ITS2 (−2.60400). Fu’s Fs, Fu and Li’s D (FLD), and Fu and Li’s F (FLF) values also showed high negative values, indicating a high probability of future population growth. In addition, the high fixation index (FST) value suggests significant genetic differentiation among populations. The haplotype networks of H. contortus populations based on COX1 sequences revealed clear geographic clustering, whereas ITS2 sequences showed more haplotype admixture across regions. The results of phylogenetic analyses were consistent with the haplotype networks. These findings highlighted that H. contortus populations exhibit significant genetic variation and are undergoing rapid population expansion, with clear genetic differences across geographic regions. This study established critical baseline data for future molecular epidemiology studies, which could guide region-specific parasite surveillance and targeted control strategies, thus helping to mitigate the risk of cross-border parasite transmission and drug resistance.

Fasciolosis, a parasitic disease of ruminants, poses significant economic and animal-health challenges in Algeria. This study aimed to assess spatial, temporal, and species-specific patterns of fasciolosis prevalence across diverse agro-climatic zones and to estimate associated economic losses. Between 2013 and 2023, eight wilayas El-Tarf, Skikda, Jijel (Region I), Blida, Mila (Region II), and M’Sila, Medea, Laghouat (Region III) were surveyed. Systematic postmortem inspections of 1,569,392 animals (349,176 cattle; 982,669 sheep; 235,639 goats; 1,882 camels; 26 horses) were performed by qualified veterinarians, with liver and bile-duct examination for Fasciola. Data on region, species, year, and season were analyzed in R 4.4.0 using ANOVA, Kruskal–Wallis, Tukey’s post hoc tests, and principal component analysis (PCA). Economic losses were calculated from condemned liver weights in Blida, Laghouat, and Jijel, converted to USD. PCA distinguished three regional prevalence profiles, with PC1 (77.7% variance) separating overall prevalence levels. Region I exhibited the highest mean prevalence (2.47%), peaking at 3.54% in 2018 – significantly greater than Region II (1.39%) and Region III (1.96%) (p < 0.01). Cattle showed the greatest infection rate (mean 4.14%), significantly higher than sheep (1.32%; p < 0.001) and goats (0.25%; p < 0.001), while horses and camels remained uninfected. Seasonal analysis revealed highest prevalence in autumn and winter (≈2.1%) versus spring (≈1.5%). Economic losses totaled USD 10.6 million in Blida, USD 1.0 million in Laghouat, and USD 142.2 million in Jijel over the study period. Targeted control strategies, adapted to regional and seasonal risk patterns, are essential. Future work should investigate environmental and management factors driving regional differences and evaluate cost-effective interventions to mitigate fasciolosis impact in Algerian livestock.

Kalicephalus (Molin, 1861) comprises 33 species of gastrointestinal snake and lizard parasites with a cosmopolitan distribution, with seven taxa occurring in the Neotropical realm. In the present study, we describe Kalicephalus atroxi n. sp., found parasitising the snake Bothrops atrox, from the Eastern Amazon in the State of Amapá, North of Brazil. We used an integrative approach that included light microscopy, scanning electron microscopy, and sequencing of the internal transcribed spacer 1 (ITS1) region to describe Kalicephalus atroxi n. sp. The new species has a buccal capsule characteristic of the genus, a slight cuticular inflation in the cephalic region. The females have an amphidelphic reproductive system, a vulva with prominent lips, and a long tail, tapering posteriorly. The males have long and alate spicules, and the copulatory bursa is lobed with dorsal rays with distinct morphology compared to their congeners. Molecular analyses and phylogenetic reconstructions cluster the new species into a well-supported clade with K. costatus costatus, from Chironius fuscus, from the same locality in northern Brazil. Kalicephalus atroxi n. sp. is the eighth species of the genus in the Neotropics, the seventh in Brazil, the second described parasitising B. atrox in Brazil, and the first species of snake nematode described in the State of Amapá.