Circadian rhythms are timekeeping mechanisms responsible for an array of biological processes. Disruption of such cycles can detrimentally affect animal health. Circadian rhythms are critical in the co-evolution of host–parasite systems, as synchronization of parasite rhythms to the host can influence infection dynamics and transmission potential. This study examines the circadian rhythms in behaviour and activity of a model fish species (Poecilia reticulata) in isolation and in shoals, both when uninfected and infected with an ectoparasite (Gyrodactylus turnbulli). Additionally, the rhythmical variance of parasite activity under different light conditions as well as rhythmical variance in parasite transmissibility was explored. Overall, infection alters the circadian rhythm of fish, causing nocturnal restlessness. Increased activity of gyrodactylids on the host's skin at night could potentially contribute to this elevated host activity. Whilst migration of gyrodactylids across the host's skin may have caused irritation to the host resulting in nocturnal restlessness, the disruption in guppy activity rhythm caused by the expression of host innate immunity cannot be excluded. We discuss the wider repercussions such behavioural responses to infection have for host health, the implications for animal behaviour studies of diurnal species as well as the application of chronotherapeutic approaches to aquaculture.

Schistosomiasis, a parasite infectious disease caused by Schistosoma japonicum, often leads to egg granuloma and fibrosis due to the inflammatory reaction triggered by egg antigens released in the host liver. This study focuses on the role of the egg antigens CP1412 protein of S. japonicum (SjCP1412) with RNase activity in promoting liver fibrosis. In this study, the recombinant egg ribonuclease SjCP1412, which had RNase activity, was successfully prepared. By analysing the serum of the population, it has been proven that the anti-SjCP1412 IgG in the serum of patients with advanced schistosomiasis was moderately correlated with liver fibrosis, and SjCP1412 may be an important antigen associated with liver fibrosis in schistosomiasis. In vitro, the rSjCP1412 protein induced the human liver cancer cell line Hep G2 and liver sinusoidal endothelial cells apoptosis and necrosis and the release of proinflammatory damage-associated molecular patterns (DAMPs). In mice infected with schistosomes, rSjCP1412 immunization or antibody neutralization of SjCP1412 activity significantly reduced cell apoptosis and necroptosis in liver tissue, thereby reducing inflammation and liver fibrosis. In summary, the SjCP1412 protein plays a crucial role in promoting liver fibrosis during schistosomiasis through mediating the liver cells apoptosis and necroptosis to release DAMPs inducing an inflammatory reaction. Blocking SjCP1412 activity could inhibit its proapoptotic and necrotic effects and alleviate hepatic fibrosis. These findings suggest that SjCP1412 may be served as a promising drug target for managing liver fibrosis in schistosomiasis japonica.

Parasitic gastrointestinal nematodes pose significant health risks to humans, livestock, and companion animals, and their control relies heavily on the use of anthelmintic drugs. Overuse of these drugs has led to the emergence of resistant nematode populations. Herein, a naturally occurring isolate (referred to as BCR) of the dog hookworm, Ancylostoma caninum, that is resistant to 3 major classes of anthelmintics is characterized. Various drug assays were used to determine the resistance of BCR to thiabendazole, ivermectin, moxidectin and pyrantel pamoate. When compared to a drug-susceptible isolate of A. caninum, BCR was shown to be significantly resistant to all 4 of the drugs tested. Multiple single nucleotide polymorphisms have been shown to impart benzimidazole resistance, including the F167Y mutation in the β-tubulin isotype 1 gene, which was confirmed to be present in BCR through molecular analysis. The frequency of the resistant allele in BCR was 76.3% following its first passage in the lab, which represented an increase from approximately 50% in the founding hookworm population. A second, recently described mutation in codon 134 (Q134H) was also detected at lower frequency in the BCR population. Additionally, BCR exhibits an altered larval activation phenotype compared to the susceptible isolate, suggesting differences in the signalling pathways involved in the activation process which may be associated with resistance. Further characterization of this isolate will provide insights into the mechanisms of resistance to macrocyclic lactones and tetrahydropyrimidine anthelmintics.

The most common equine tapeworm, Anoplocephala perfoliata, has often been neglected amongst molecular investigations and has been faced with limited treatment options. However, the recent release of a transcriptome dataset has now provided opportunities for in-depth analysis of A. perfoliata protein expression. Here, global, and sub-proteomic approaches were utilized to provide a comprehensive characterization of the A. perfoliata soluble glutathione transferases (GST) (ApGST). Utilizing both bioinformatics and gel-based proteomics, GeLC and 2D-SDS PAGE, the A. perfoliata ‘GST-ome’ was observed to be dominated with Mu class GST representatives. In addition, both Sigma and Omega class GSTs were identified, albeit to a lesser extent and absent from affinity chromatography approaches. Moreover, 51 ApGSTs were localized across somatic (47 GSTs), extracellular vesicles (EVs) (Whole: 1 GST, Surface: 2 GSTs) and EV depleted excretory secretory product (ESP) (9 GSTs) proteomes. In related helminths, GSTs have shown promise as novel anthelmintic or vaccine targets for improved helminth control. Thus, provides potential targets for understanding A. perfoliata novel infection mechanisms, host–parasite relationships and anthelmintic treatments.

Some serology assays demonstrated useful for post-treatment monitoring of Strongyloides stercoralis infection. Serology frequently has low specificity, which might be improved by the use of recombinant antigens. The Strongy Detect ELISA is based on 2 recombinant antigens (SsIR and NIE) and proved good accuracy. Aim of this study was to evaluate the performance of this test for the post-treatment monitoring of strongyloidiasis. We tested 38 paired sera, with matched fecal tests results, stored in our biobank and originating from a randomized controlled trial. At baseline, all patients tested positive for at least 1 fecal assay among PCR, direct stool microscopy and agar plate culture. Patients were re-tested with both serology and fecal assays 12 months after treatment. Primary outcome was the relative reduction in optical density (OD) between baseline and follow up. We observed that about 95% samples showed a reduction between pre and post-treatment OD, with a median relative reduction of 93.9% (IQR 77.3%–98.1%). In conclusion, the test proved reliable for post-treatment monitoring. However, some technical issues, including that the threshold for positivity has not be predefined, and that a substantial number of samples showed overflow signals, need to be fixed to permit use in routine practice.

A 30 years long data series on the infection dynamics of European eel (Anguilla anguilla L.) with the non-native invasive nematode Anguillicola crassus Kuwahara, Niimi & Hagaki, 1974 is presented. Parasite burden was evaluated for 30 years in inland and coastal waters in Mecklenburg-Western Pomerania from 1991 to 2020. The total prevalence, mean intensity and damage status of the swim bladders were very high during the first decade (1991–2000), and significantly decreased in both marine and freshwater eel populations in the following decades (2001–2010, 2011–2020). The parasite intensity of eels in coastal waters was significantly lower compared with the freshwater systems (61.3% vs 79.5% in the first decade), indicating the vulnerability of the parasites to brackish water conditions and the fact that the life cycle of A. crassus cannot be completed under high saline conditions. Eel caught in the western part of the Baltic Sea (west of Darss sill) had the lowest mean infection (51.8% in first decade) compared to the eastern part with 63.8%. Thus, besides different infection patterns caused by the environmental conditions, a temporal trend towards a reduced parasite intensity and a more balanced parasite–host relationship developed in the 30 years of interaction after the first invasion. Possible reasons and mechanisms for the observed trends in parasite–host interactions are discussed.

Trematodes of the family Allocreadiidae are primarily found in the intestines of freshwater fishes around the world. The family includes 15 genera and c. 130 species. The last 2 decades have witnessed an increase in the genetic library of its species. Molecular data have been crucial for species delimitation and species description within Allocreadiidae and for understanding their evolutionary and biogeographical history and classification. Here, the mitogenomes of 3 species of allocreadiids were obtained using high throughput sequencing methods. Mitogenomes were compared with other members of the order Plagiorchiida to determine their molecular composition, gene rearrangement and phylogenetic interrelationships. The complete circular mitogenomes of Allocreadium lobatum, Creptotrematina aguirrepequenoi and Wallinia mexicana were 14 424, 13 769 and 13 924 bp long respectively, comprising 12 protein-coding genes, 22 transfer RNA genes, 2 ribosomal RNA genes and 2 non-coding regions. Gene arrangements were identical to other Xiphidiatan trematodes. Phylogenetic analyses using the mitogenomes revealed Allocreadiidae as a monophyletic group closely related to other members of the suborder Xiphidiata; A. lobatum was yielded as the sister taxon of C. aguirrepequenoi + W. mexicana. Our study increases the complete mitochondrial genome library of trematodes and strengthens our understanding of the phylogenetic relationships and classification of this parasite group.

Dermoergasilus madagascarensis n. sp. is described from the gills of Paretroplus polyactis, an endemic cichlid fish in Madagascar, using a combined morphological (light microscopy and SEM) and molecular approach (partial 18S rDNA, 28S rDNA, and COI sequences). The new species is characterized mainly by possessing: (i) roughly pentagonal cephalosome; (ii) antennal endopodal segments covered with slightly inflated membrane; (iii) maxillule bearing 2 equally long outer setae and a minute inner seta; (iv) interpodal sternites of swimming legs ornamented with 3–4 rows of spinules; (v) genital segment and first abdominal somite both barrel-shaped; and (vi) a caudal ramus projecting into a digitiform process with inconspicuous terminal seta and bearing 3 terminal setae. The obtained DNA sequences of Malagasy species represent the first molecular data for species of Dermoergasilus. The 28S rDNA phylogeny showed the affiliation of D. madagascarensis n. sp. to Ergasilidae and its sister relationship with cosmopolitan Ergasilus sieboldi von Nordmann, 1832. The first checklist for all species of Dermoergasilus is provided.

Little is known about the life cycle and mode of transmission of Dientamoeba fragilis. Recently it was suggested that fecal–oral transmission of cysts may play a role in the transmission of D. fragilis. In order to establish an infection, D. fragilis is required to remain viable when exposed to the pH of the stomach. In this study, we investigated the ability of cultured trophozoites to withstand the extremes of pH. We provide evidence that trophozoites of D. fragilis are vulnerable to highly acidic conditions. We also investigated further the ultrastructure of D. fragilis cysts obtained from mice and rats by transmission electron microscopy. These studies of cysts showed a clear cyst wall surrounding an encysted parasite. The cyst wall was double layered with an outer fibrillar layer and an inner layer enclosing the parasite. Hydrogenosomes, endoplasmic reticulum and nuclei were present in the cysts. Pelta-axostyle structures, costa and axonemes were identifiable and internal flagellar axonemes were present. This study therefore provides additional novel details and knowledge of the ultrastructure of the cyst stage of D. fragilis.