International journal for parasitology最新文献

{"title":"Innovating stomach fluke identification: An integrative approach combining Micro-CT imaging and molecular tools.","authors":"Ruben Schols, Arnaud Henrard, Jonathan Brecko, Aspire Mudavanhu, Emilie Goossens, Natascha Steffanie, Sarah Clegg, Maarten P M Vanhove, Tine Huyse","doi":"10.1016/j.ijpara.2025.05.002","DOIUrl":"https://doi.org/10.1016/j.ijpara.2025.05.002","url":null,"abstract":"<p><p>The rapid loss of biodiversity driven by anthropogenic pressures highlights the urgent need for improved species identification methods. Parasites, vital ecosystem regulators, are being lost at disproportionate rates, with amphistomes-a broadly distributed group of trematode parasites, infecting all major vertebrate groups-facing significant challenges. Many amphistome species remain undescribed, and reference sequences for known species are scarce, partly due to the reliance on labour-intensive identification methods, such as Scanning Electron Microscopy (SEM) and median sagittal sections. While sagittal sectioning is particularly informative for diagnostic traits, it is destructive, requires toxic chemicals, and demands specialized personnel. In this study, we evaluated micro-computed tomography (micro-CT) imaging as a non-destructive alternative for identifying three amphistome species, Gigantocotyle gigantocotyle (Brandes in Otto, 1896); Carmyerius aff. chabaudi van Strydonck, 1970; and Carmyerius aff. endopapillatus Dollfus, 1962, isolated from the common hippopotamus, Hippopotamus amphibius Linnaeus, 1758. By comparing micro-CT imaging with traditional sectioning, SEM and incorporating molecular barcoding, we reveal the need for a taxonomic revision of Carmyerius, focussed on identifying new diagnostic characters, to better reflect species boundaries. Moreover, the integrated taxonomic effort represented in this work uncovered evidence that C. aff. chabaudi is a new species record from the common hippopotamus. Additionally, we provide high-resolution images of the original type specimens of Carmyerius cruciformis (Leiper, 1910) and G. gigantocotyle and designate new lectotypes and paralectotypes. Our findings demonstrate that micro-CT imaging is a powerful, non-invasive tool for amphistome identification, facilitating access to fragile natural history collections and advancing integrative taxonomy.</p>","PeriodicalId":13725,"journal":{"name":"International journal for parasitology","volume":" ","pages":""},"PeriodicalIF":3.7,"publicationDate":"2025-05-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144132332","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":"CRISPR/Cas genome editing, functional genomics, and diagnostics for parasitic helminths.","authors":"Akito Koike, Paul J Brindley","doi":"10.1016/j.ijpara.2025.05.001","DOIUrl":"10.1016/j.ijpara.2025.05.001","url":null,"abstract":"<p><p>Functional genomics using CRISPR (Clustered Regulatory Interspaced Short Palindromic Repeats)/Cas (CRISPR-associated endonuclease)-based approaches has revolutionized biomedical sciences. Gene editing is also widespread in parasitology generally and its use is increasing in studies on helminths including flatworm and roundworm parasites. Here, we survey the progress, specifically with experimental CRISPR-facilitated functional genomics to investigate helminth biology and pathogenesis, and also with the burgeoning use of CRISPR-based methods to assist in diagnosis of helminth infections. We also provide an historical timeline of the introduction and uses of CRISPR in helminth species to date.</p>","PeriodicalId":13725,"journal":{"name":"International journal for parasitology","volume":" ","pages":""},"PeriodicalIF":3.7,"publicationDate":"2025-05-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143982244","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":"Identification of immunogenic proteins of Ascaris lung stage larvae through immunoproteomics: towards recombinant-based serodiagnostic assays for humans and pigs.","authors":"Sara Roose, Iris Peelaers, Evy Timmerman, Johnny Vlaminck, Delphi Van Haver, Daniel Dana, Zeleke Mekonnen, Simon Devos, Bruno Levecke, Peter Geldhof","doi":"10.1016/j.ijpara.2025.04.017","DOIUrl":"10.1016/j.ijpara.2025.04.017","url":null,"abstract":"<p><p>Soil-transmitted helminthiases are recognised by the World Health Organization as one of the 20 neglected tropical diseases, primarily affecting communities with socioeconomic disadvantages in tropical and subtropical regions. Of the four soil-transmitted helminths, Ascaris stands out as the most widespread, affecting more than 700 million people globally. Today, the diagnostic standard for ascariasis is based on microscopic examination of stool, which faces important limitations. Although serological diagnosis is a promising alternative, the current landscape of well-validated commercial serological diagnostics is sobering. An ELISA based on homogenate from Ascaris suum lung stage larvae (AsLungL3-ELISA) showed significant potential to inform human and veterinary prevention and control programs against ascariasis. Therefore, this study aimed to identify the immunogenic proteins in Ascaris lung stage larval homogenate and investigate the antibody response towards recombinantly expressed versions of these proteins. Given the potential of recombinant-based assays for both human and veterinary applications, the study encompasses experiments involving both humans and pigs. First, immuno-affinity purifications were coupled with liquid chromatography-tandem mass spectrometry, resulting in three lists of immunogenic proteins (for children, adults, and pigs). As a proof of concept, four promising immunogenic proteins (polyprotein ABA-1, paramyosin, apolipophorin and an S60 ribosomal protein) were recombinantly produced in Escherichia coli and the antibody response against these recombinants was evaluated using ELISA. While the results for pigs were inconclusive due to non-specific binding of antibodies, the findings for potential human serodiagnostic applications detecting IgG4 appeared promising. For both polyprotein ABA-1 and paramyosin, a notable difference in OD values was observed between children and adults who were AsLungL3-ELISA negative and positive. In conclusion, this study is a steppingstone towards the development of new serodiagnostic assays and demonstrates that recombinant protein production offers an efficient method to produce diagnostic Ascaris antigens without requiring pig studies.</p>","PeriodicalId":13725,"journal":{"name":"International journal for parasitology","volume":" ","pages":""},"PeriodicalIF":3.7,"publicationDate":"2025-05-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144016380","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":"Are there 16 species of brown dog ticks? Phylogenies from 60 entire mitochondrial genomes and 162 cox1 sequences reveal 16 species-level clades in the Rhipicephalus (Rhipicephalus) sanguineus group☆☆.","authors":"Samuel Kelava, Ryo Nakao, Ben J Mans, Mingeun Cho, Kynan B T Mateo, Dmitry A Apanaskevich, Renfu Shao, Alexander W Gofton, Ernest J M Teo, Takuya Ito, Dayana Barker, Stephen C Barker","doi":"10.1016/j.ijpara.2025.04.016","DOIUrl":"https://doi.org/10.1016/j.ijpara.2025.04.016","url":null,"abstract":"<p><p>The Rhipicephalus sanguineus group, the brown dog ticks, are cosmopolitan and doubtless the most important ticks of domestic dogs, clinically and economically. Despite four decades of taxonomic enquiry with nucleotide sequences and morphology, the taxonomy of the R. sanguineus group is confused, even chaotic. We provide 13 new mitochondrial (mt) genomes and internal transcribed spacer 2 (ITS2) sequences from nine localities in Australia, Israel and Japan. We inferred phylogenetic trees from 10 mt protein-coding genes (9,514 bp), as well as partial cox1, ITS2, 12S, and 16S rRNA genes, to resolve to common clades the >2,000 nucleotide sequences in GenBank from the R. sanguineus group. Then we applied three species delimitation protocols to 60 entire mt genomes (ca. 15,000 bp) and 162 partial cox1 sequences (472 bp): Automatic Barcode Gap discovery, Assemble Species by Automatic Partitioning, and Poisson Tree Process. We considered pairwise genetic differences and Tamura-Nei genetic distances among 60 entire mt genomes and 162 partial cox1 sequences. We found 16 species-level clades (clades A to P) that we hypothesise represent at least 16 species in the R. sanguineus group. These clades had intra-clade differences of <3.8% (entire mt genomes) and <5.1% (partial cox1) whereas the inter-clade differences were >7.7% (entire mt genomes) and >4.5% (partial cox1). We assigned the species names Rhipicephalus linnaei (Audouin, 1826), Rhipicephalus rutilus (Koch, 1844), Rhipicephalus secundus (Feldman-Muhsam, 1952) and R. sanguineus (Latreille, 1806) to clades A, C, D, and K, respectively. And we hypothesise that the names Rhipicephalus camicasi (Morel, Mouchet & Rodhain, 1976), Rhipicephalus turanicus (Pomerantsev, 1940), Rhipicephalus guilhoni (Morel & Vassilades, 1963), Rhipicephalus sulcatus (Neumann, 1908), Rhipicephalus rossicus (Yakimov & Kol-Yakimova, 1911), Rhipicephalus pumilio (Schulze, 1935) and Rhipicephalus pusillus (Gil Collado, 1936) apply to clades B, E, H, J, M, N and O, respectively. The newly described Rhipicephalus hibericus (Millán, Rodriguez-Pastor & Estrada-Peña, 2024) was genetically indistinguishable from R. sanguineus in clade K and thus is a synonym of R. sanguineus. We could not assign names to clades F (USA, Hungary), I (India, Pakistan), L (Nigeria), G (China, Kazakhstan), and P (Cameroon): some or all of these five clades may be new species in the R. sanguineus group. Our haplotype network of partial mt genes (cox1, cytb and nad2) revealed much genetic similarity among geographically distant populations of R. linnaei. This indicates recent dispersal, likely originating in Africa or the Middle East, since African populations were more genetically diverse than populations in other parts of the world.</p>","PeriodicalId":13725,"journal":{"name":"International journal for parasitology","volume":" ","pages":""},"PeriodicalIF":3.7,"publicationDate":"2025-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143982241","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":"Contrasting effects of body condition on ectoparasite abundance in a social bat: different roles of season and host sex.","authors":"Áron Péter, Boróka Beke, Zoltán László, Sándor Hornok, Attila D Sándor","doi":"10.1016/j.ijpara.2025.04.015","DOIUrl":"https://doi.org/10.1016/j.ijpara.2025.04.015","url":null,"abstract":"<p><p>Understanding the interplay between host species ecology and parasite dynamics is crucial for comprehending disease transmission patterns, population structures, and ecosystem health. In most host-parasite systems, host body condition is of primary importance in ectoparasite host choice. Bats were considered an exception, as previously several studies suggested that bat ectoparasites showed no or minimal dependence on host body condition. We investigated the relationships between host condition and ectoparasite abundance in multiple populations of European bent-winged bats (Miniopterus schreibersii) and their arthropod ectoparasites (mites, nycteribiid bat flies and ixodid ticks). We found weak correlations between individual host condition and combined ectoparasite abundance, with seasonal fluctuations in both, and a single seasonal peak in parasite abundance. However, when treated individually, single ectoparasite groups showed contrasting answers to changes in body condition. Body condition had a significant positive effect on wing mite abundance and a significant negative effect on the prevalence and intensity of nycteribiid bat flies, overall with no effect on tick infestation. These responses moreover showed also seasonal differences, highly correlating with the life-stages of the two host's sexes. Our long-term, large-scale study of European bent-winged bats and their arthropod ectoparasites was able to detect major influences exerted by hosts' body condition on ectoparasites' host choice. Here we showed that bat populations undergo dynamic changes in their body condition during the active period of their annual cycle, with ectoparasites evolved to differentially exploit peaks or troughs of these changes.</p>","PeriodicalId":13725,"journal":{"name":"International journal for parasitology","volume":" ","pages":""},"PeriodicalIF":3.7,"publicationDate":"2025-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143997798","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":"In the face of fear: the success of encounters between digenean cercariae and an intermediate target host under predation pressure.","authors":"Anna Stanicka, Zuzanna Dlouhy, Anna Cichy, Elżbieta Żbikowska, Łukasz Jermacz","doi":"10.1016/j.ijpara.2025.04.012","DOIUrl":"https://doi.org/10.1016/j.ijpara.2025.04.012","url":null,"abstract":"<p><p>Predation is one of the most potent factors shaping relationships between organisms with different trophic levels. The interaction is an evolutionary arms race, where early detection of the other side often holds the key to success. Preying on the free-living parasite larvae is a valid and underestimated factor affecting parasite infection dynamics. Our study aimed to investigate whether often dominant invertebrates in aquatic ecosystems, gammarids, induce a significant reduction in host-parasite encounters, taking into account the influence of the presence of additional chemical signals from top predators (fish) and the parasite prey \"age\" on the possible dilution effect. The study is based on a model involving representatives of native (Gammarus jazdzewskii) and invasive (Pontogammarus robustoides) gammarids as consumers and two species of free-living parasite larvae, echinostome cercariae (Echinoparyphium aconiatum and Molinella anceps), as prey. The invasive gammarid species modified E. aconiatum success more significantly than the native one. However, a dilution effect was detected exclusively for P. robustoides, utilising freshly released cercariae and the absence of additional stressors (fish kairomones in the water). In contrast, the presence of both gammarid species usually significantly reduced the success of parasite transmission. The presence of fish cues or the differences in the post-emergence \"age\" of cercariae only affected treatments with the invasive P. robustoides. Our results suggest that the strength of predation's impact on the cercarial dilution effect can be modelled depending on the attractiveness of the prey. Additionally, this study potentially provides the first evidence of the influence of \"enemy scent\" on the strategy adopted by free-living larval trematodes, where a trade-off between cercarial age and anti-predator strategy was observed. Moreover, the study discusses how investigations conducted solely using freshly released cercariae may provide an incomplete or distorted picture of what is happening in the environment.</p>","PeriodicalId":13725,"journal":{"name":"International journal for parasitology","volume":" ","pages":""},"PeriodicalIF":3.7,"publicationDate":"2025-04-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144006545","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":"Zoonotic Echinococcus granulosus sensu lato genotypes G6 and G7: new insights from the global mitogenome analysis.","authors":"Anti Biedermann, Teivi Laurimäe, Liina Anijalg, Laura Kamenetzky, Silvia V Soriano, Nora Pierangeli, Lorena E Lazzarini, Gérald Umhang, Bolor Bold, Chimedtseren Bayasgalan, Jacek Karamon, Małgorzata Samorek-Pieróg, Sami Simsek, Figen Celik, Majid F Harandi, Saeid Nasibi, Naunain Mehmood, Oleg Chihai, Adriano Casulli, Urmas Saarma","doi":"10.1016/j.ijpara.2025.04.014","DOIUrl":"https://doi.org/10.1016/j.ijpara.2025.04.014","url":null,"abstract":"<p><p>Cystic echinococcosis is a severe zoonotic disease caused by different species and genotypes belonging to the Echinococcus granulosus sensu lato (s.l.) complex. Among these, genotypes G6 and G7 are the second most common cause of human cystic echinococcosis. One of the very first steps towards understanding the epidemiology of G6 and G7 is to study their genetic and host diversity, population structure and phylogenetic relationships. For this, we sequenced near-complete mitochondrial genomes (12,850-12,856 bp) of 72 new G6 and G7 samples from eight countries and six host species, including humans. By adding 103 sequences from previous studies, the total dataset for further analyses comprised of 175 sequences from 20 countries and seven host species. This is the most comprehensive global mitogenome study of Echinococcus granulosus s.l. G6 and G7 to date. The results of this work revealed: (i) a new divergent haplogroup G6b from Mongolia; (ii) the subdivision of genotype G6 into two major haplogroups: G6a (the nominal haplogroup) and G6b (the Mongolian haplogroup); (iii) highly divergent haplotypes of G6 and G7; (iv) the first molecularly confirmed findings of genotype G7 in camel; (v) genotype G7 in sheep - a rare species for G7; (vi) the importance of using long DNA sequences in phylogenetic analysis.</p>","PeriodicalId":13725,"journal":{"name":"International journal for parasitology","volume":" ","pages":""},"PeriodicalIF":3.7,"publicationDate":"2025-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144021943","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":"Alba protein-mediated gene and protein regulation in protozoan parasites.","authors":"Meghan E Zadow, Christopher A MacRaild, Darren J Creek, Danny W Wilson","doi":"10.1016/j.ijpara.2025.04.013","DOIUrl":"https://doi.org/10.1016/j.ijpara.2025.04.013","url":null,"abstract":"<p><p>The success of protozoan parasites relies heavily on regulation of gene and protein expression to facilitate their persistence in harsh and often changing environments. These parasites display biology that is highly divergent from model eukaryotes, unfortunately leaving our understanding of these parasites' critical regulatory mechanisms incomplete. Alba proteins, a highly diverse group of DNA/RNA-binding proteins, are found across all domains of life and it has become increasingly apparent that these proteins play key regulatory roles in many protozoan parasite species including Plasmodium, Leishmania, Toxoplasma, and Trypanosoma. This review focusses on a subset of clinically relevant protozoan parasites and highlights the key biological processes known to have Alba protein involvement in these organisms including parasite development, survival, and virulence. In order to gain greater insight into these proteins, we also undertook a bioinformatic exploration of their protein sequences, leading us to identify previously unreported C-terminal Alba domain motifs and propose annotations for several currently unannotated protozoan Alba-like proteins. This collation of information allows us to observe common themes in Alba protein function across this group of parasites while also identifying areas of opportunity for further study.</p>","PeriodicalId":13725,"journal":{"name":"International journal for parasitology","volume":" ","pages":""},"PeriodicalIF":3.7,"publicationDate":"2025-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143970551","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":"Evolution of antigenic diversity in the zoonotic multi-host parasite Schistosoma japonicum: implications for vaccine design.","authors":"Daniel A J Parsons, Anthony J Walker, Aidan M Emery, Fiona Allan, Da-Bing Lu, Joanne P Webster, Scott P Lawton","doi":"10.1016/j.ijpara.2025.04.004","DOIUrl":"https://doi.org/10.1016/j.ijpara.2025.04.004","url":null,"abstract":"<p><p>The multi-host zoonotic transmission of the blood fluke Schistosoma japonicum is complex, presenting challenges for China's schistosomiasis elimination strategy. How multi-host transmission impacts the genetic diversity of S. japonicum populations is poorly understood and the extent of Schistosoma japonicum antigen coding gene (SjACG) variability remains unknown despite the implications for parasite survival, vaccine development and disease control. To address this, we sequenced the host-interacting domains of three functionally significant SjACGs previously identified as promising vaccine targets (tetraspanin 23 (TSP-23), venom allergen-like protein 7 (VAL-7), and tegument allergen-like protein 1 (TAL-1)) from FTA-archived S. japonicum miracidia sampled from natural infections amongst different definitive host species in mainland China. This work represents the first known analysis of SjACG variation among different host species. SjACGs were genetically diverse across host species, with 10-20 SjACG haplotypes identified from 60 to 81 sequences. Host-derived immune selection pressures may be driving this variation, impacting antigen protein structure, function, and antigenic propensity. Antigen haplotypes were broadly shared across host species, supporting prior suggestions of gene flow and underscoring the importance of zoonotic transmission in disseminating diversity. Some host adaptation was inferred through identification of host species-specific variation. Parasites sampled from humans displayed the greatest overall diversity of SjACGs, and humans shared haplotypes with all other host species. SjACG diversification appears to have occurred rapidly, and before modern humans arrived in China (∼1.7-0.66 million years ago (MYA)), suggesting that animal hosts have been important in the evolutionary history of these antigens. Collectively, the results expand our understanding of the impact of zoonotic transmission on the co-evolutionary processes driving antigenic variability and provide possible evidence of adaptive molecular evolution of certain antigen haplotypes to specific host species. Our findings have implications for the development of anti-schistosome vaccines and, ultimately, for control of zoonotic schistosomiasis.</p>","PeriodicalId":13725,"journal":{"name":"International journal for parasitology","volume":" ","pages":""},"PeriodicalIF":3.7,"publicationDate":"2025-04-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144007209","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":"Effect of parasite infections on fish body condition: a systematic review and meta-analysis.","authors":"Ryota Hasegawa, Robert Poulin","doi":"10.1016/j.ijpara.2025.03.002","DOIUrl":"https://doi.org/10.1016/j.ijpara.2025.03.002","url":null,"abstract":"<p><p>Using host body condition indices (BCIs) based on the relationship between host body mass and length is a general and pervasive approach to assess the negative effects of parasites on host health. Although many researchers, especially fish biologists and fisheries managers, commonly utilize BCIs, the overall general patterns among BCI - infection relationships remain unclear. Here, we first systematically reviewed 985 fish BCI - infection relationships from 216 publications and investigated the factors affecting the strength and directionality of effects in BCI - infection relationships. We specifically predicted that the BCI measure used, parasite taxonomic group, and the infection measure used would influence the observed effect size and directionality of BCI - infection relationships. We found that most studies were heavily biased towards specific BCI measures such as Fulton's BCI and Relative BCI. Furthermore, studies using Fulton's BCI were more likely to report significant results compared with those using other BCI measures, suggesting that index choice could lead to an overestimation of the negative effects of parasites. Our meta-regressions uncovered that the use of parasite intensity as an infection measure and studies based on experimental rather than natural infections were more likely to report significant negative effects, however there were no differences among parasite taxonomic groups. Surprisingly, many studies, especially field studies, did not report significant negative correlations between BCI and infection, contrary to widespread expectations among researchers that parasites would negatively affect fish health. We discuss potential mechanisms underlying these results. Finally, we make several recommendations for the use of BCI - infection relationships in future studies.</p>","PeriodicalId":13725,"journal":{"name":"International journal for parasitology","volume":" ","pages":""},"PeriodicalIF":3.7,"publicationDate":"2025-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143964239","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}