This retrospective study evaluated 29 free-living white-eared opossums (Didelphis albiventris) necropsied between 2022 and 2025. Among 19 adults, 13 (68.4%) presented intestinal remodeling associated with acanthocephalan (Oligacanthorhynchus microcephalus) attachment. Parasite burden was determined by counting attached individuals per animal, providing a measure of infection level. Macroscopically, firm nodules (3-11 mm) were observed, mainly in the jejunum, accompanied by luminal dilation and thinning of the intestinal wall. Histologically, the nodules involved mucosa, muscularis, and serosa, containing parasitic sections with necrosis, inflammatory infiltrate, and a thick collagenized capsule (mean 362 μm), with neovascularization; mineralization occurred in 36.4% cases. These findings demonstrate that O. microcephalus attachment induces focal chronic granulomatous inflammation and remodeling in D. albiventris. To our knowledge, this is the first detailed pathological and morphometric characterization of intestinal lesions caused by this parasite in this host species. Despite the retrospective design and relatively small sample size, the study provides novel insights into the dynamic progression of acanthocephalan-induced intestinal remodeling expanding comparative knowledge of acanthocephalan pathology in neotropical marsupials.

Biosecurity in aquaculture is essential to reduce disease burden and ensure sustainability. Piaractus mesopotamicus (pacu) is a key species in South American aquaculture, yet parasitic threats to its health remain understudied. We analyzed intestinal helminth and assessed their effects on the health of 34 farmed pacu reared in intensive and semi-intensive systems in Santa Fe, Argentina, using parasitological, hematological, and histopathological approaches. Three parasite taxa were identified: the digenean Dadaytrema oxycephala (∼65 % prevalence; mean abundance: ∼3 parasites/fish), the nematode Rondonia rondoni (3 % prevalence; one host with 119 parasites), and the acanthocephalan Echinorhynchus jucundus (100 % prevalence; mean abundance: ∼235 parasites/fish). E. jucundus caused macrocytic hypochromic anemia (low erythrocyte count and hemoglobin, high MCV) and severe intestinal lesions (muscle penetration and chronic inflammation). D. oxycephala had marginal hematological effects. Infestations likely originated in land-based ponds, where zooplankton hosts thrive in the absence of technical biosecurity measures. Despite the high parasite burden, infected fish maintained stable body condition, suggesting a degree of physiological tolerance. However, the risk of nutrient malabsorption and market rejection remains. We propose: (1) prevention measures such as ≥ 15-day quarantine, pond sterilization, zooplankton monitoring in semi-intensive systems, water quality control in intensive systems, and necropsy of samples in cases of low feed conversion; (2) corrective action via targeted anthelmintic treatment or culling during outbreaks (>50 parasites/gut). This study identifies E. jucundus as an emerging pathogenic parasite and highlights the need for tailored biosecurity protocols adapted to different production systems, promoting the sustainable culture of pacu.

Acanthocephala are known as thorny-headed worms and are common parasites in animals, but acanthocephaliasis in humans is rare, with limited medical literature available. Infections are acquired via direct ingestion of arthropod intermediate hosts. In this case report, a female toddler is evaluated for passage of a pseudosegmented worm in the stool, which was later identified as Moniliformis moniliformis She is treated with pyrantel pamoate with a resolution of worms in stool. This case report aims to expand knowledge surrounding infections by the Acanthocephala phylum and the nuances of identification and treatment.

The present report describes a case of acanthocephaliasis associated with necrotic enteritis in quetzals (Pharomachrus mocinno). Three juvenile quetzals exhibited depression, anorexia, ruffled feathers, and sudden death. They were submitted to the laboratory for examination. The birds had hatched and lived in captivity in an aviary in Mexico. Gross lesions observed were hemorrhagic, fibrinoid necrotic enteritis, with acanthocephalans adhered to the intestinal mucosa. The specimens were identified by parasitology, electronic microscopy, and molecular biology as Plagiorhynchus (Prosthorhynchus) sp. Lesions compatible with necrotic enteritis were also confirmed by isolation and genotyping of Clostridium perfringens type E. This is the first report of Plagiorhynchus (Prosthorhynchus) sp. in quetzals in captivity in Mexico. The findings in this manuscript suggest that this parasite could be a predisposing factor for necrotic enteritis as well as a risk component in the breeding programs and survival of this avian species in captivity.

Acanthocephaliasis is a zoonotic parasitic infection of vertebrates. The phylum Acanthocephala contains nearly 1500 acanthocephalan species. The Archiacanthocephala class is observed in terrestrial habitats and usually has a large, spineless trunk. Acanthocephalans are parasitic worms that use insects as intermediate hosts in their two-host life cycles. Insects, millipedes, and crustaceans in terrestrial areas serve as intermediate hosts and birds and mammals as definitive hosts. Acanthocephalans collected from the red fox (Vulpes vulpes) found dead on the road to Sarıkamış-Kars in 1995 and stored in formaldehyde were kept in Ondokuz Mays University Faculty of Veterinary Medicine, Veterinary Parasitology Laboratory Museum until 2023 after our parasitological study found an infected red fox with Pachysentis sp. This study provides the anatomy of the acanthocephalans and the laboratory practice necessary for a good and reliable diagnosis. This study reports a new species, Pachysentis sp., of acanthocephalan (thorny-headed worm) found in red foxes for Türkiye. On the basis of relevant articles, we have created a key to Acanthocephala species occurring in mammals.

The tambaqui (Colossoma macropomum) is a species of great economic importance for fish farming in the Brazilian Amazon, and acanthocephaliasis caused by Neoechinorhynchus buttnerae (Golvan 1956) represents an obstacle to its production due to it causing severe morphological damage to the intestinal mucosa, thus impairing the absorption of nutrients and causing weight loss in the fish. Therefore, the establishment of in vitro protocols for evaluation of anthelmintic drugs is the first step to development of effective measures for in vivo control of this endoparasite. The present study evaluated the in vitro survival of N. buttnerae maintained in Eagle's minimum essential medium under different culture conditions. Three assays were carried out to evaluate whether temperature, supplementation with the antibiotics penicillin and streptomycin, and culture medium replacement or no replacement would influence the motility and morphology of the acanthocephalans. The results of the Kaplan-Meier analysis indicated that the use of culture in minimum essential medium together with penicillin and streptomycin prolonged the parasite's survival when kept at temperatures of 24 °C or 28 °C. We describe herein for first time an alternative protocol that is ideal for the in vitro culture of N. buttnerae. As such, this protocol ensures greater reliability in further in vitro studies with N. buttnerae.

Acanthocephalans of the order Polymorphida mainly parasitic in birds and mammals, are of veterinary, medical and economic importance. However, the evolutionary relationships of its 3 families (Centrorhynchidae, Polymorphidae and Plagiorhynchidae) remain under debate. Additionally, some species of Polymorphida (i.e. Bolbosoma spp. and Corynosoma spp.) are recognized as zoonotic parasites, associated with human acanthocephaliasis, but the mitochondrial genomes for representatives of Bolbosoma and Corynosoma have not been reported so far. In the present study, the complete mitochondrial genomes B. nipponicum and C. villosum (Acanthocephala: Polymorphidae) are reported for the first time, which are 14 296 and 14 241 bp in length, respectively, and both contain 36 genes [including 12 PCGs, 22 tRNA genes and 2 rRNA genes] and 2 non-coding regions (NCR1 and NCR2). The gene arrangement of some tRNAs in the mitogenomes of B. nipponicum and C. villosum differs from that found in all other acanthocephalans, except Polymorphus minutus. Phylogenetic results based on concatenated amino acid (AA) sequences of the 12 protein-coding genes (PCGs) strongly supported that the family Polymorphidae is a sister to the Centrorhynchidae rather than the Plagiorhynchidae, and also confirmed the sister relationship of the genera Bolbosoma and Corynosoma in the Polymorphidae based on the mitogenomic data for the first time. Our present findings further clarified the phylogenetic relationships of the 3 families Plagiorhynchidae, Centrorhynchidae and Polymorphidae, enriched the mitogenome data of the phylum Acanthocephala (especially the order Polymorphida), and provided the resource of genetic data for diagnosing these 2 pathogenic parasites of human acanthocephaliasis.

This study reports a new case of acanthocephalan (thorny-headed worm) eggs in a coprolite from Bonneville Estates Rockshelter in eastern Nevada and uses archaeological and ethnographic data to better understand long-term relationships between people and acanthocephalans. Acanthocephalans are parasitic worms that use arthropods as intermediate hosts in their multi-host life cycles. Though acanthocephaliasis is rare among humans today, cases have increased in the last decade, and the discovery of acanthocephalan eggs in coprolites from archaeological sites in the Great Basin suggests a deep, shared history. At Bonneville Estates Rockshelter, 9 acanthocephalan eggs were recovered using a modified rehydration-homogenization-micro-sieving protocol on a coprolite that was radiocarbon dated to 6,040 ± 60 14C BP (7,160-6,730 cal BP), pushing back the oldest evidence of human acanthocephalan infection by 3 millennia. Researchers have proposed that the paleoepidemiology of acanthocephalans may relate to subsistence practices due to overlap in locations of infection and areas where insects are part of traditional foodways. This paper considers the paleoepidemiology of acanthocephalan infection through the first combined review of paleoparasitological, ethnographic, and archaeological records in western North America. Ethnographic and archaeological records support the hypothesis that archaeological cases of human acanthocephaliasis may be linked to entomophagy. Additional parasitological analyses are advised to determine whether this distribution is the result of dietary practices, host ecology, taphonomic issues, sampling biases, or a combination of factors.

Human acanthocephaliasis is a rare parasitic zoonosis mainly caused by acanthocephalans belonging to the genera Acanthocephalus, Bolbosoma, Corynosoma, Macracanthorhynchus, and Moniliformis. In the present paper, the juveniles of Bolbosoma nipponicum Yamaguti, 1939 collected from the northern fur seal Callorhinus ursinus (Linnaeus) (Mammalia: Carnivora) in Alaska, USA were precisely identified based on morphological characters and genetic data. Their detailed morphology was studied using light and, for the first time, scanning electron microscopy. The molecular characterization of the nuclear genes [small ribosomal subunit (18S) and large ribosomal subunit (28S)] and the mitochondrial cytochrome c oxidase subunit 1 (cox1) sequence data of B. nipponicum are provided for the first time. Moreover, in order to clarify the phylogenetic relationships of the genus Bolbosoma and the other genera in the family Polymorphidae, phylogenetic analyses were performed integrating different nuclear (18S + ITS+28S) and mitochondrial (cox1) sequence data using maximum likelihood (ML) and Bayesian inference (BI). The phylogenetic results showed that Bolbosoma has a sister relationship with Corynosoma, and also revealed that Southwellina is sister to Ibirhynchus + Hexaglandula. Our molecular phylogeny also indicated a possible host-switch pattern during the evolution of the polymorphid acanthocephalans. The ancestors of polymorphid acanthocephalans seem to have originally parasitized fish-eating waterfowl in continental habitats, then extended to fish-eating marine birds in brackish water and marine habitats, and finally, opportunistically infected the marine mammals.

In the present study, a new species of the genus Moniliformis species is described taxonomically in the mitochondrial genomic context. The parasite was found in a plateau zokor captured in a high-altitude area of Xiahe County of Gansu Province, China. The mitochondrial (mt) genome length of this new species was 14,066 bp comprising 36 genes and 2 additional non-coding regions (SNR and LNR), without atp8. The molecular phylogeny inferred by the cytochrome c oxidase subunit I gene (cox1) and the18S ribosomal RNA gene (18S rDNA) sequences showed that the parasite as a sister species to other Moniliformis spp. and was named Moniliformis sp. XH-2020. The phylogeny of the concatenated amino acid sequences of the 12 protein-coding genes (PCGs) showed Moniliformis sp. XH-2020 in the same cluster as Macracanthorhynchus hirudinaceus and Oncicola luehei confirming the cox1 and 18S rDNA phylogenetic inference. In addition, the entire mt genome sequenced in this study represents the first in the order Moniliformida, providing molecular material for further study of the phylogeny of the class Archiacanthocephala. Moreover, the species of this class, use arthropods as intermediate hosts and mammals as definitive hosts and are agents of acanthocephaliasis, a zoonosis in humans. Therefore, this study not only expands the host range among potential wild animal hosts for Archiacanthocephalans which is of great ecological and evolutionary significance but also has important significance for the research of zoonotic parasitic diseases.

Acanthocephala is a phylum of parasitic pseudocoelomates that infect a wide range of vertebrate and invertebrate hosts and can cause zoonotic infections in humans. The zoologic literature is quite rich and diverse; however, the human-centric literature is sparse, with sporadic reports over the past 70 years. Causal agents of acanthocephaliasis in humans are reviewed as well as their biology and life cycle. This review provides the first consolidated and summarized report of human cases of acanthocephaliasis based on English language publications, including epidemiology, clinical presentation, treatment, and diagnosis and identification.

From 12 May 2013 to 29 May 2013, the Gull-billed Tern (Gelochelidon nilotica) colony at the San Diego Bay National Wildlife Refuge, California, US, experienced a mass die-off of at least 92 adults, representing 71-92% of the breeding population on the US west coast. Cause of death was determined to be peritonitis due to perforations of the intestine by a large quantity of acanthocephala (Profilicollis [=Polymorphus] altmani). This is a unique report of P. altmani infecting G. nilotica, and a report of a great impact to a tern population in southern California. Mole crabs (Emerita analoga), the intermediate host for P. altmani and a major component of the Gull-billed Tern diet in San Diego, were found in the stomachs of necropsied terns along with cystacanths, and are the presumed source of the parasite infection. The tern's dietary reliance upon mole crabs likely amplified parasite transmission and infection. We suggest additional research to determine factors that influence parasite infection of intermediate and definitive hosts, particularly mole crabs, given that they are a vital resource for migrating birds within the coastal zone.