International journal for parasitology最新文献

{"title":"Oocyst wall protein EtOWP6 is critical for sporocyst formation and developmental progression in Eimeria tenella.","authors":"Liushu Jia, Jinwen Wang, Qingjie Wang, Lu Wang, Shunhai Zhu, Qiping Zhao, Shanbo Wu, Wenqi Han, Jaiyu Bai, Fanghe Zhao, Yu Yu, Hongyu Han, Hui Dong","doi":"10.1016/j.ijpara.2026.104985","DOIUrl":"https://doi.org/10.1016/j.ijpara.2026.104985","url":null,"abstract":"<p><p>Transmission of apicomplexan parasites-including Eimeria, Toxoplasma, and Cryptosporidium-relies on the environmentally resilient oocyst wall, a bilayered structure whose integrity is maintained by cysteine-rich oocyst wall proteins (OWPs). Yet the functional roles of these conserved proteins remain poorly defined. Here, we characterize EtOWP6, a conserved OWP in Eimeria tenella, the causative agent of avian coccidiosis. Immunofluorescence reveals that EtOWP6 localizes specifically to wall-forming bodies and oocyst/sporocyst walls during sexual development. CRISPR/Cas9-mediated knockout demonstrates that EtOWP6 is essential for sporocyst formation, with deficient parasites exhibiting malformed sporocysts, developmental arrest in vitro, and an in vivo reduction in oocyst output exceeding 85%. The knockout strain is highly attenuated yet retains partial immunogenicity. Transcriptomic analysis reveals that EtOWP6 deletion induces widespread transcriptional reprogramming, disrupting genes critical for developmental regulation and oocyst wall biogenesis. Our findings establish EtOWP6 as a critical regulator coupling structural integrity with developmental progression in Eimeria, and more broadly, highlight OWPs as conserved targets for transmission-blocking interventions across apicomplexan parasites.</p>","PeriodicalId":13725,"journal":{"name":"International journal for parasitology","volume":" ","pages":"104985"},"PeriodicalIF":3.3,"publicationDate":"2026-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149206930","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Disruption of Parasite-Host Interaction Networks: the role of key hosts.","authors":"Nayara Yoshie Sano, Filipe Martins Santos","doi":"10.1016/j.ijpara.2026.104986","DOIUrl":"https://doi.org/10.1016/j.ijpara.2026.104986","url":null,"abstract":"<p><p>Biodiversity loss is a threat to ecosystems for potentially triggering cascades of extinctions that compromise the stability of ecological communities. Host-parasite interaction networks are particularly sensitive to host extinction and represent a significant portion of biodiversity. This study investigates the structural robustness of two distinct small mammal-parasite networks in the Neotropical region: (i) generalist protozoan parasites and (ii) specific nematode parasites. By using sequential host removal simulations based on centrality metrics (degree and betweenness) we compare the decay of parasite richness and network fragmentation with random extinction scenarios. Our results demonstrate that targeted removal of key hosts significantly accelerates network collapse compared to random loss (P < 0.001 in all scenarios), showing that network stability depends on a small number of highly connected species. The protozoan network proved more vulnerable to fragmentation, while the nematode network was more sensitive to the loss of parasite diversity when the most connected hosts were removed. These results highlight the importance of considering network structure and the topological roles of species in conservation strategies, as the loss of key hosts can have disproportionate consequences for maintaining parasite diversity and ecosystem integrity.</p>","PeriodicalId":13725,"journal":{"name":"International journal for parasitology","volume":" ","pages":"104986"},"PeriodicalIF":3.3,"publicationDate":"2026-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149193151","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Leishmania tarentolae as a potential disease-modifying agent in dogs infected with Leishmania infantum.","authors":"Jairo Alfonso Mendoza-Roldan, Sara Epis, Ilaria Varotto-Boccazzi, Mariaelisa Carbonara, Viviane Noll Louzada-Flores, Imad Bouzaidi Cheikhi, Giulia Maria Cattaneo, Claudio Bandi, Frederic Beugnet, Andrea Zatelli, Domenico Otranto","doi":"10.1016/j.ijpara.2026.104984","DOIUrl":"https://doi.org/10.1016/j.ijpara.2026.104984","url":null,"abstract":"<p><p>Canine leishmaniosis (CanL), by Leishmania infantum, is a global zoonotic disease with complex immune interactions. The non-pathogenic Leishmania tarentolae emerged as a candidate for immunoprophylaxis, yet in vivo evidence demonstrating natural cross-protection in dogs remains scarce. This experimental study evaluated the immunological and clinical outcomes of co-exposure to both parasites. Fourteen purposedly breed dogs were allocated into three groups: Group 1 (G1) and Group 2 (G2) were previously exposed to L. tarentolae, then challenged with L. infantum intravenously (G1) or intradermally (G2). Group 3 (G3) served as unimmunized L. infantum-infected control group, with three dogs challenged intravenously and two intradermally. Animals were longitudinally monitored for 13.5 months through clinical, molecular and serological assessments. While prior exposure to L. tarentolae did not confer sterilizing immunity against L. infantum, differences in clinicopathological and immunological parameters were observed among experimental groups. Unimmunized controls (G3) developed higher UPC values during the later stages of the study, whereas pre-exposed dogs (G1 and G2) generally showed lower UPC values, although considerable inter-individual variability was observed. The intravenous challenge group (G1) developed high parasite burdens, hyperglobulinemia, and inflammatory alterations, whereas intradermally challenged group (G2) showed comparatively lower parasite burdens and fewer clinicopathological alterations. Additionally, in vitro stimulation with L. infantum, on peripheral blood monocytic cells from pre-immunized dogs, revealed a cytokine profile characterized by intermittent pro-inflammatory activation and variable regulatory interleukin-10 expression (IL-10). Overall, this is the first study detailing the longitudinal clinicopathological and immunological profile of L. infantum infection in the canine model, which suggests that prior exposure to L. tarentolae may influence the subsequent course of L. infantum. Hence, further studies are advocated to investigate the potential disease-modifying effect herein observed.</p>","PeriodicalId":13725,"journal":{"name":"International journal for parasitology","volume":" ","pages":"104984"},"PeriodicalIF":3.3,"publicationDate":"2026-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149181704","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The spatial proteome of Eimeria tenella provides a high-resolution view of proteins localised to key invasion organelles","authors":"E. Attree,&nbsp;K. Barylyuk,&nbsp;C. Noonan,&nbsp;E. Einarsson,&nbsp;V. Marugan-Hernandez,&nbsp;O. Gundogdu,&nbsp;D. Blake,&nbsp;F. Tomley,&nbsp;R.F. Waller,&nbsp;D. Xia","doi":"10.1016/j.ijpara.2026.104878","DOIUrl":"10.1016/j.ijpara.2026.104878","url":null,"abstract":"<div><div><em>Eimeria tenella</em> is one of the most prevalent species of <em>Eimeria</em> that infects chickens causing coccidiosis, an enteric disease estimated to cost the poultry industry over £10.4 billion globally per year. The <em>E. tenella</em> genome contains ∼7268 protein-coding genes, almost half of which are annotated as hypothetical with no known function. In this study we investigated the localisation of <em>E. tenella</em> sporozite proteins using Hyperplexed Localisation of Organelle Proteins by Isotope Tagging (hyperLOPIT) combined with Bayesian machine learning. We assigned 722 identified proteins with previously unknown localisation to one of 12 subcellular niches at ≥0.99 confidence, substantially expanding the known proteome of this invasive parasite stage. These included 49 and 70 proteins assigned to the invasion-related microneme and rhoptry organelles respectively. Importantly, we observed distinct separation of previously described surface antigen (SAG) A and B proteins into separate subcellular niches including one (SAGB) within the micronemes, suggestive of functional divergence between these two SAG sub-families and highlighting a potential mechanism contributing to virulence. Furthermore, our spatial map provides vital functional context for hypothetical proteins, notably assigning a highly conserved ortholog of the <em>T. gondii</em> SPATR (secreted protein with an altered thrombospondin repeat) to the microneme, supporting its shared role in apicomplexan host cell invasion. This spatial proteome provides a valuable resource to the research community, revealing complex evolutionary divergences of key protein subfamilies. These create opportunities to further our understanding of parasite pathogenicity, identify vaccine candidates and enable comparative evolutionary and biological analyses across diverse apicomplexan parasites that impact human, livestock and wider animal welfare.</div></div>","PeriodicalId":13725,"journal":{"name":"International journal for parasitology","volume":"56 10","pages":"Article 104878"},"PeriodicalIF":3.3,"publicationDate":"2026-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147856355","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Maternal vaccination with gamete-related antigens of Cystoisospora suis reduces clinical effects and oocyst excretion in an experimental model of suckling piglet coccidiosis","authors":"Anja Joachim,&nbsp;Teresa Cruz-Bustos,&nbsp;Anna S. Feix,&nbsp;Bärbel Ruttkowski,&nbsp;Lukas Schwarz","doi":"10.1016/j.ijpara.2026.104868","DOIUrl":"10.1016/j.ijpara.2026.104868","url":null,"abstract":"<div><div>The protozoan parasite <em>Cystoisospora suis</em> (Order Coccidia) is a major cause of gastrointestinal disease in suckling piglets, resulting in significant economic losses to the pig industry due to diarrhea, weight loss and increased susceptibility to secondary infections. Current control strategies are limited and rely primarily on strict hygiene measures and the use of toltrazuril, and reports on resistance against this drug in <em>C. suis</em> have been reported. To address the urgent need for alternative control measures, this study investigated maternal vaccination as an approach to confer passive immunity to piglets. We evaluated the immunogenicity and protective efficacy of a recombinant vaccine containing three antigens from the sexual stages of <em>C. suis</em>: CsTyRP, CsOWP1 and CsHAP2. Sows were vaccinated three times prior to parturition and antibody transfer to piglets via colostrum and the outcome of experimental infections of piglets with <em>C. suis</em> on the third day of life were assessed in comparison to an adjuvant-only (sham vaccinated) control group. Vaccinated sows developed significant antibody titers which were successfully transferred to their offspring. Piglets from vaccinated sows showed a significant reduction in oocyst shedding and improved weight gain compared to controls. We here provide the first evidence that a recombinant vaccine effectively reduces the clinical impact of <em>C. suis</em> in neonatal piglets and lays the groundwork for the development of sustainable vaccination strategies against mammalian coccidiosis.</div></div>","PeriodicalId":13725,"journal":{"name":"International journal for parasitology","volume":"56 10","pages":"Article 104868"},"PeriodicalIF":3.3,"publicationDate":"2026-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147837448","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Recommendations for sustainable control of cattle tick, Rhipicephalus (Boophilus) microplus (Canestrini, 1887) in Latin America and the Caribbean","authors":"G.A. Sabatini,&nbsp;F.A. Borges,&nbsp;L.M. Costa-Junior,&nbsp;U. Cuore,&nbsp;A.A. Cutolo,&nbsp;C.A. Fiel,&nbsp;N.N. Jonsson,&nbsp;W.D.Z Lopes,&nbsp;S. López-Osorio,&nbsp;J.R. Martins,&nbsp;M. Molento,&nbsp;C.M.O. Monteiro,&nbsp;N. Morel,&nbsp;S. Nava,&nbsp;P. Parodi,&nbsp;M. Pulido,&nbsp;J. Reck,&nbsp;D.S. Rodrigues,&nbsp;R.I. Rodriguez-Vivas","doi":"10.1016/j.ijpara.2026.104869","DOIUrl":"10.1016/j.ijpara.2026.104869","url":null,"abstract":"<div><div>The control of the cattle tick, <em>Rhipicephalus (Boophilus) microplus</em>, is an ongoing challenge for cattle producers in tropical and sub-tropical regions around the world. It is a robust parasite that transmits potentially fatal pathogens and can cause substantial damage to cattle in its own right. With a high fecundity and a life cycle with an off-host, free-living phase that can extend to around one year, <em>R. microplus</em> has a demonstrated capacity to both, evade treatment with acaricides and to acquire resistance to acaricides. The aim of this article is to design current best practice recommendations for control of <em>R. microplus</em> for Latin American environments, based on empirical and theoretical studies available in the literature, and on the field experiences of the authors. To help control program designers ensure that all critical factors are considered, a five-pointed approach to control is recommended: (1) Treat with the right product; (2) Treat using the right dose; (3) Treat the right animals; (4) Treat at the right time; (5) Use non-acaricidal methods. Consideration of each of these points should enable control of ticks consistent with three pillars of sustainable parasite control: (1) ensuring environmental and human safety; (2) enhancing the production of high-quality, high welfare animal products; and (3) preserving the financial viability of cattle farms.</div></div>","PeriodicalId":13725,"journal":{"name":"International journal for parasitology","volume":"56 10","pages":"Article 104869"},"PeriodicalIF":3.3,"publicationDate":"2026-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147837495","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Early prediction of declining health associated with helminth infection in small ruminants using accelerometers and machine learning","authors":"Axel X. Montout,&nbsp;Ranjeet S. Bhamber,&nbsp;Nlingisisi D. Babayani,&nbsp;Eric R. Morgan,&nbsp;Christos C. Ioannou,&nbsp;Thomas H. Terrill,&nbsp;Jan A. van Wyk,&nbsp;Tilo Burghardt,&nbsp;Andrew W. Dowsey","doi":"10.1016/j.ijpara.2026.104867","DOIUrl":"10.1016/j.ijpara.2026.104867","url":null,"abstract":"<div><div>Assessment of the health status of individual animals is a key step in the timely and targeted treatment of infections, which is critical in the fight to slow the development of anthelmintic and antimicrobial resistance. The FAMACHA scoring system has been used successfully to detect anaemia caused by infection with the parasitic nematode <em>Haemonchus contortus</em> in small ruminants and is an effective way to identify individuals in need of treatment. However, assessing FAMACHA is labour-intensive and costly<strong>,</strong> as individuals must be manually examined at frequent intervals. Here, accelerometers were used to measure the individual activity of extensively grazing small ruminants (sheep and goats) exposed to natural <em>Haemonchus contortus</em> worm infection in southern Africa<strong>,</strong> over long time scales (13 + months). When combined with machine learning, this activity data can predict poorer health (increases in FAMACHA score) in sheep with an area under the receiver operating characteristic curve (AUC) of 82.7%, as well as to identify animals that fail to respond to treatment with AUC of 66.4%. We demonstrate that these classifiers remain robust over time, and that interpretation of their trained results reveals that poorer health, such as that resulting from haemonchosis, significantly affects the night-time activity levels, more so than that of the daytime. Our study thus reveals that low-cost biologgers can exploit behavioural patterns to detect subtle changes in animal health and enable timely and targeted intervention. This has real potential to improve economic outcomes and animal welfare, as well as to limit the use of anthelmintic drugs and diminish selective pressures on anthelmintic resistance in both commercial and resource-poor communal farming.</div></div>","PeriodicalId":13725,"journal":{"name":"International journal for parasitology","volume":"56 10","pages":"Article 104867"},"PeriodicalIF":3.3,"publicationDate":"2026-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147814658","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Comparative proteomics reveals a conserved core of tegumental proteins in parasitic flatworms","authors":"Inés Guarnaschelli,&nbsp;Analía Lima,&nbsp;Rafael Velazco,&nbsp;Monika Bergmann,&nbsp;Matías Preza,&nbsp;Javier Calvelo,&nbsp;Marcela Cucher,&nbsp;Mara Cecilia Rosenzvit,&nbsp;Klaus Brehm,&nbsp;Andrés Iriarte,&nbsp;Uriel Koziol","doi":"10.1016/j.ijpara.2026.104963","DOIUrl":"10.1016/j.ijpara.2026.104963","url":null,"abstract":"<div><div>Parasitic flatworms, including cestodes and trematodes, are covered by a specialized syncytial tegument that mediates nutrient uptake and host–parasite interactions. While the tegument of trematodes has been extensively characterized, its molecular composition in cestodes remains largely unknown. In this work, we performed a comparative proteomic analysis of the tegument of three cestode species, including larval and adult stages: <em>Hymenolepis microstoma</em>, <em>Mesocestoides corti</em> (syn. <em>M. vogae</em>) and the human pathogen <em>Echinococcus multilocularis</em>. Using stringent enrichment criteria relative to whole-worm extracts, we identified hundreds of tegument-enriched proteins in each species. Comparative analyses revealed a conserved core of tegumental proteins shared among all three species, including members of the Tegument Allergen-Like (TAL) family, vesicular trafficking components and calcium-sensing proteins, and identified candidates for nutrient uptake activities such as glucose and nucleoside transporters. Further comparative analyses revealed a set of shared tegumental proteins with the trematode <em>Schistosoma mansoni</em>, including conserved proteins that are specific to parasitic flatworms, supporting the existence of a conserved ancestral tegumental proteome. Finally, we confirmed tegumental expression of several genes in <em>H. microstoma</em> and <em>E. multilocularis</em>, and demonstrated regionally restricted gene expression among tegumental cytons, suggesting functional specialization within the syncytial tegument. Altogether, these results reveal an evolutionarily conserved composition of the tegument of parasitic flatworms, providing a foundation for future work targeting this critical host–parasite interface.</div></div>","PeriodicalId":13725,"journal":{"name":"International journal for parasitology","volume":"56 10","pages":"Article 104963"},"PeriodicalIF":3.3,"publicationDate":"2026-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148880366","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The development and validation of long-read ITS-1/5.8S/ITS-2 nemabiome metabarcoding for ovine gastrointestinal nematodes using Oxford Nanopore Technologies (ONT) sequencing","authors":"Eléonore Charrier,&nbsp;Rebecca Chen,&nbsp;Elizabeth Redman,&nbsp;Sawsan Ammar,&nbsp;Camila Meira,&nbsp;Camila Queiroz,&nbsp;John S. Gilleard","doi":"10.1016/j.ijpara.2026.104850","DOIUrl":"10.1016/j.ijpara.2026.104850","url":null,"abstract":"<div><div>Internal Transcribed Spacer ITS-2 rRNA nemabiome metabarcoding is increasingly used to characterize gastrointestinal nematode (GIN) communities. While powerful, current approaches have some limitations in their flexibility and applicability to smaller-scale studies and diagnostic use. The short read lengths provided by the Illumina platform may lack discriminatory power for some closely related species and also pose a challenge for new marker selection and primer design. To address these challenges, we have developed ITS-1/5.8S/ITS-2 rRNA Oxford Nanopore Technologies (ONT) long-read metabarcoding for ovine gastrointestinal nematodes. Samples from two previous field studies, from UK and western Canadian sheep farms were used. ITS-1/5.8S/ITS-2 long-read metabarcoding showed strong concordance with prior ITS-2 data for the major GIN species in both datasets, with minor discrepancies for some low abundance taxa mainly due to differences in reference sequence database representation.</div><div>We also used the PrimerTC tool to design a new primer pair, EC1 and EC2, to minimize the amplification of off-target fungal sequences derived from fecal DNA and maximize the nematode sequence read depth when ONT ITS-1/5.8S/ITS-2 metabarcoding was applied directly to ovine fecal stool DNA.</div><div>In summary, ITS-1/5.8S/ITS-2 ONT long-read nemabiome metabarcoding showed good agreement with ITS-2 metabarcoding and the use of primer pair EC1/EC2 should make the approach more tolerant of fecal contamination of parasite material, with the potential for direct application to ovine fecal DNA. Overall, these new developments should make nemabiome metabarcoding more accessible, discriminating, and flexible for both research and diagnostic applications.</div></div>","PeriodicalId":13725,"journal":{"name":"International journal for parasitology","volume":"56 10","pages":"Article 104850"},"PeriodicalIF":3.3,"publicationDate":"2026-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147716556","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"From pathology to phylogeny: Highly rearranged mitochondrial genome of the emerging testudine intranuclear coccidium","authors":"Peihang Hong,&nbsp;Kana Matsumoto,&nbsp;Hisashi Yoshimura,&nbsp;Sijia Yu,&nbsp;Yen-Chi Chang,&nbsp;Hau-You Tzeng,&nbsp;Tzu-Chun Chou,&nbsp;Hsin-Yu Lin,&nbsp;Tung Yee Shiu,&nbsp;Ryotaro Suzuki,&nbsp;Tetsuya Tanabe,&nbsp;Makoto Haritani,&nbsp;Shyun Chou,&nbsp;Toshihiro Tokiwa,&nbsp;Masami Yamamoto","doi":"10.1016/j.ijpara.2026.104855","DOIUrl":"10.1016/j.ijpara.2026.104855","url":null,"abstract":"<div><div>The testudine intranuclear coccidium (TINC) is an emerging, globally significant apicomplexan pathogen responsible for severe multisystemic disease in captive chelonians. In this study, samples were obtained from deceased captive Sri Lankan star tortoise (<em>Geochelone elegans</em>) in Taiwan and leopard tortoises (<em>Stigmochelys pardalis</em>) in Japan for comprehensive pathological and molecular analysis. Histopathological examination of three cases confirmed systemic infection characterized by intranuclear inclusions within epithelial cells of multiple organs, with lesions ranging from widespread coagulative necrosis to degenerative changes. Transmission electron microscopy further identified multiple intranuclear developmental stages, including trophozoites, meronts, and gamonts. Utilizing Oxford Nanopore long-read sequencing, we present the first complete mitochondrial genome of TINC, which exhibits a novel and highly rearranged architecture divergent from conserved patterns in the family Eimeriidae, featuring flanking direct and inverted repeats not previously reported in this family. Phylogenetic reconstructions using both 18S ribosomal RNA gene and concatenated mitochondrial protein-coding genes consistently place TINC within a robust, distinct clade situated between the families Eimeriidae and Sarcocystidae. Comparative sequence analysis of the partial cytochrome <em>c</em> oxidase subunit 1 gene confirmed genetic identity across TINC from different cases. These integrated pathological and genomic results define TINC as a genetically distinct lineage with unique molecular features, providing critical data for its taxonomic revision and new insights into mitochondrial genome evolution at the interface of two major apicomplexan families.</div></div>","PeriodicalId":13725,"journal":{"name":"International journal for parasitology","volume":"56 10","pages":"Article 104855"},"PeriodicalIF":3.3,"publicationDate":"2026-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147770299","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}